Image coding method, image coding apparatus, image decoding method and image decoding apparatus
A decoding method decodes last position information indicating horizontal and vertical positions of a last non-zero coefficient in a predetermined order within a current block to be decoded, the current block including plural coefficients. The decoding includes obtaining a bitstream including first, second, third and fourth partial signals, in this order, performing first arithmetic decoding on the first and the third partial signals respectively to obtain decoded first and decoded third partial signals, performing second arithmetic decoding on the second and the fourth partial signals respectively to obtain decoded second and decoded fourth partial signals, the second arithmetic decoding being different from the first arithmetic decoding, deriving a horizontal component of the last position information from the decoded first and decoded third partial signals, and deriving a vertical component of the last position information from the decoded second and decoded fourth partial signals.
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This application is a continuation of co-pending U.S. application Ser. No. 13/669,690, filed Nov. 6, 2012, which is claims the benefit of U.S. Provisional Patent Application No. 61/556,406 filed on Nov. 7, 2011, the disclosures of which are expressly incorporated herein by reference in its entireties.
FIELDThe present disclosure relates to an image coding technique and an image decoding technique for arithmetic coding or arithmetic decoding.
BACKGROUNDApplications for providing services via the Internet (e.g., video-conference, digital video broadcast, and Video on Demand services including video content streaming) are increasing. These applications rely on transmission of video data. When the applications transmit video data, most video data is transmitted via a conventional transmission path having a limited bandwidth. Furthermore, when the applications record video data, most video data is recorded on a conventional recording medium having a limited capacity. To transmit video data via the conventional transmission path or record video data on the conventional recording medium, it is indispensable to compress or reduce the data amount of the video data.
In view of this, many video coding standards have been developed to compress video data. These video coding standards are, for example, ITU-T standards denoted as H.26x and ISO/IEC standards denoted as MPEG-x. Currently, the latest and most advanced video coding standard is the standard denoted as H.264/MPEG-4 AVC (see Non Patent Literature 1 and Non Patent Literature 2).
The coding approach underlying most of these video coding standards is based on prediction coding that includes the following main steps of (a) to (d): (a) Divide each video frame into blocks each having pixels to compress data of the video frame on a block-by-block basis. (b) Predict each block based on previously coded video data to identify temporal and spatial redundancy. (c) Subtract the predicted data from the video data to remove the identified redundancy. (d) Compress remaining data (residual blocks) by Fourier transform, quantization, and entropy coding.
As for the step (a), the current video coding standard provides different prediction modes depending on a macroblock to be predicted. According to most of the video coding standards, motion estimation and motion compensation are used for predicting video data based on a previously coded and decoded frame (inter frame prediction). Alternatively, block data may be extrapolated from an adjacent block of the same frame (intra frame prediction).
In the step (d), quantized coefficients included in a current block to be coded are scanned in a predetermined order (scan order). Then, information (SignificantFlag) indicating whether the scanned coefficients are zero coefficients or non-zero coefficients (e.g., binary information (symbol) indicating a non-zero coefficient as 1 and a zero coefficient as 0) is coded.
Furthermore, information (last position information) indicating the position of the last non-zero coefficient in the scan order is binarized, arithmetically coded, and arithmetically decoded.
CITATION LIST Non Patent Literature[Non Patent Literature 1]
ITU-T Recommendation H.264 “Advanced video coding for generic audiovisual services”, March 2010.
[Non Patent Literature 2]
JCT-VC “WD4: Working Draft 4 of High-Efficiency Video Coding”, JCTVC-F803, July 2011.
SUMMARY Technical ProblemHowever, there is a demand for the conventional technique to achieve more efficient arithmetic coding and arithmetic decoding of the last position information.
In view of this, one non-limiting and exemplary embodiment provides an image coding method which allows efficient arithmetic coding and arithmetic decoding of the last position information.
Solution to ProblemAn image coding method according to an aspect of the present disclosure is an image coding method for coding last position information indicating a horizontal position and a vertical position of a last non-zero coefficient in a predetermined order in a current block to be coded, the image coding method including: binarizing a first component and a second component to generate a first binary signal and a second binary signal, respectively, the first component being one of a horizontal component and a vertical component which are included in the last position information, and the second component being the other of the horizontal component and the vertical component; coding a first partial signal and a second partial signal by first arithmetic coding, and coding a third partial signal and a fourth partial signal by second arithmetic coding different from the first arithmetic coding, the first partial signal being a part of the first binary signal, the second partial signal being a part of the second binary signal, the third partial signal being another part of the first binary signal, and the fourth partial signal being another part of the second binary signal; and placing the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal in a bit stream, wherein in the placing, (i) the coded second partial signal is placed next to the coded first partial signal, or (ii) the coded fourth partial signal is placed next to the coded third partial signal.
It is to be noted that this general aspect may be implemented using a system, an apparatus, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or any combination of systems, apparatuses, integrated circuits, computer programs, or computer-readable recording media.
Advantageous EffectsWith the image coding method according to an aspect of the present disclosure, it is possible to arithmetically code and arithmetically decode the last position information efficiently.
These and other objects, advantages and features of the disclosure will become apparent from the following description thereof taken in conjunction with the accompanying drawings that illustrate a specific embodiment of the present disclosure.
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(Underlying Knowledge Forming Basis of the Present Disclosure)
The inventors have found the following matter regarding the arithmetic coding and arithmetic decoding of the last position information described in the “Background” section.
It is to be noted that in the following description, the last position information indicates a horizontal position and a vertical position of the last non-zero coefficient in a predetermined order in a current block. Here, the last position information includes a horizontal component (hereinafter referred to as “X component”) and a vertical component (hereinafter referred to as “Y component”). The X component indicates a horizontal position in the current block. The Y component indicates a vertical position in the current block.
The image decoding apparatus 1000 obtains a bit stream BS which includes the last position information. Then, the image decoding apparatus 1000 inputs the bit stream BS to the first decoding unit 1001, the second decoding unit 1002, and the decoding control unit 1003.
The decoding control unit 1003 manages whether each signal in the obtained bit stream BS is the X component or the Y component of the last position information.
The first decoding unit 1001 arithmetically decodes a prefix part of the X component of the last position information included in the bit stream BS (S1001). More specifically, the first decoding unit 1001 decodes the prefix part of the X component by context adaptive binary arithmetic decoding. Here, the prefix part is a part of a binary signal of the X component or the Y component, which is coded by context adaptive binary arithmetic coding.
Next, the first decoding unit 1001 determines whether or not the binary signal of the X component includes a suffix part (S1002). The suffix part is a part of the binary signal of the X component or the Y component, which is coded by bypass coding.
The prefix part and the suffix part are determined according to each value (hereinafter referred also to as “last value”) of the X component and the Y component as shown in
More specifically, when the size of a transform block (hereinafter referred to as “transform size”) is 4×4, for example, the binary signal of the X component includes the prefix part only and does not include the suffix part regardless of the last value as shown in
In the case where the transform size is 8×8, for example, the first decoding unit 1001 determines that the decoded binary signal of the X component does not include the suffix part when any of binary symbol values up to the binary symbol value of the 4th bit of the binary signal of the X component is “1” as shown in
In the case where the transform size is 16×16, for example, the first decoding unit 1001 determines that the decoded binary signal of the X component does not include the suffix part when any of the binary symbol values up to the binary symbol value of the 8th bit of the binary signal of the X component is “1” as shown in
In the case where the transform size is 32×32, for example, the first decoding unit 1001 determines that the decoded binary signal of the X component does not include the suffix part when any of binary symbol values up to the binary symbol value of the 16th bit of the binary signal of the X component is “1” as shown in
Here, when the binary signal of the X component includes the suffix part (Yes in S1002), the second decoding unit 1002 arithmetically decodes the suffix part having a predetermined, fixed bit length (S1003). More specifically, the second decoding unit 1002 arithmetically decodes the suffix part of the X component by bypass decoding. On the other hand, when the binary signal of the X component does not include the suffix part (No in S1002), the decoding process for the suffix part is skipped.
The reconstructing unit 1004 reconstructs the X component of the last position information using the prefix part and the suffix part which have been decoded (S1004). More specifically, when the binary signal of the X component includes the suffix part, the reconstructing unit 1004 reconstructs the X component by debinarizing the binary signal including the decoded prefix part and suffix part. On the other hand, when the binary signal of the X component does not include the suffix part, the reconstructing unit 1004 reconstructs the X component by debinarizing the binary signal including the decoded prefix part.
Next, the first decoding unit 1001 arithmetically decodes the prefix part of the Y component of the last position information as in Step S1001 (S1005). After that, the first decoding unit 1001 determines whether or not the binary signal of the Y component includes the suffix part as in Step S1002 (S1006).
Here, when the binary signal of the Y component includes the suffix part (Yes in S1006), the second decoding unit 1002 arithmetically decodes the suffix part having a predetermined fixed length as in Step S1003 (S1007). On the other hand, when the binary signal of the Y component does not include the suffix part (No in S1006), the decoding process for the suffix part is skipped.
Lastly, the reconstructing unit 1004 reconstructs the Y component of the last position information as in Step S1004 (S1008). More specifically, when the binary signal of the Y component includes the suffix part, the reconstructing unit 1004 reconstructs the Y component by debinarizing the binary signal including the decoded prefix part and suffix part. On the other hand, when the binary signal of the Y component does not include the suffix part, the reconstructing unit 1004 reconstructs the Y component by debinarizing the binary signal including the decoded prefix part.
This is the manner in which the X component and the Y component included in the last position information are reconstructed.
Next, variable-length coding and variable-length decoding will be described. H.264 employs context adaptive binary arithmetic coding (CABAC) as one of variable-length coding methods. The prefix part is coded by CABAC. In contrast, the suffix part is coded by bypass coding, which is arithmetic coding in which a fixed probability (e.g., “0.5”) is used. Hereinafter, context adaptive binary arithmetic decoding and bypass decoding will be described using
With the arithmetic decoding, first, context (ctxIdx) is inputted which is determined based on the signal type of a current signal to be decoded.
Next, the following process is performed in Step S2001.
First, qCodIRangeIdx is calculated from a first parameter codIRange indicating a current state of arithmetic decoding. Furthermore, pStateIdx is obtained which is a state value corresponding to ctxIdx. Then, codIRangeLPS corresponding to the two values (qCodIRangeIdx and pStateIdx) is obtained by reference to a table (rangeTableLPS).
It is to be noted that codIRangeLPS indicates a state of arithmetic decoding when LPS has occurred in a state of arithmetic decoding indicated by the first parameter codIRange. LPS specifies one of the symbols “0” and “1” which has a lower probability of occurrence.
Furthermore, a value obtained by subtracting the above-mentioned codIRangeLPS from the current codIRange is set to codIRange.
Next, in Step S2002, a comparison is made between codIRange and a second parameter codIOffset which indicates a state of arithmetic decoding.
Here, when codIOffset is greater than or equal to codIRange (Yes in S2002), the following process is performed in Step S2003.
First, it is determined that LPS has occurred, and a value different from vaIMPS (“0” when vaIMPS=1, and “1” when vaIMPS=0) is set to binVal that is a decoding output value. vaIMPS indicates a specific value of MPS (“0” or “1”). MPS specifies one of the binary symbol values “0” and “1” which has a higher probability of occurrence.
Furthermore, a value obtained by subtracting codIRange from the current codIOffset is set to the second parameter codIOffset that indicates a state of arithmetic decoding. Furthermore, the value of codIRangeLPS which has been set in Step S2001 is set to the first parameter codIRange that indicates a state of arithmetic decoding.
Next, in Step S2005, whether or not the value of pStateIdx is “0” is determined.
Here, when the value of pStateIdx is “0” (Yes in S2005), it means that the probability of LPS is greater than the probability of MPS. Thus, the value of vaIMPS is switched over (i.e., “0” is set when vaIMPS=1, and “1” is set when vaIMPS=0) (Step S2006). On the other hand, when the value of pStateIdx is not “0” (No in S2005), the value of pStateIdx is updated based on a transform table transIdxLPS that is referred to when LPS occurs (Step S2007).
Furthermore, when codIOffset is smaller than codIRange (No in S2002), it is determined that MPS has occurred. Thus, vaIMPS is set to binVal that is a decoding output value, and the value of pStateIdx is updated based on a transform table transIdxMPS that is referred to when MPS occurs (Step S2004).
Lastly, normalization (RenormD) is performed (Step S2008), and the arithmetic decoding finishes.
As shown above, with the context adaptive binary arithmetic decoding, multiple probabilities of symbol occurrence, which are probabilities of occurrence of binary symbols, are held in association with context indices. The contexts are switched according to a condition (e.g., value of an adjacent block), and thus, it is necessary to maintain the processing order.
First, the second parameter codIOffset that indicates a current state of arithmetic decoding is left-shifted (doubled). Furthermore, one bit is read out from the bit stream, and when the read-out bit is “1”, 1 is added to codIOffset (Step S3001).
Next, when codIOffset is greater than or equal to the first parameter codIRange that indicates a state of arithmetic decoding (Yes in S3002), “1” is set to binVal that is a decoding output value, and a value obtained by subtracting codIRange from the current codIOffset is set to codIOffset (Step S3003). On the other hand, when codIOffset is smaller than the first parameter codIRange that indicates a state of arithmetic decoding (No in S3002), “0” is set to binVal that is a decoding output value (Step S3004).
When the first parameter codIRange that indicates a state of arithmetic decoding has become smaller than 0x100 (in base 16: 256 (in base 10)) (Yes in S4001), codIRange is left-shifted (doubled). Furthermore, the second parameter codIOffset that indicates a state of arithmetic decoding is left-shifted (doubled). Moreover, one bit is read out from the bit stream, and when the read-out bit is “1”, 1 is added to codIOffset (Step S4002).
When codIRange eventually reaches 256 or greater by this process in Step S4002 (No in S4001), the normalization finishes.
This is the manner in which the arithmetic decoding is performed.
However, with the above underlying knowledge, the X component and the Y component included in the last position information are decoded in sequence. That is to say, the X component and the Y component are placed one after the other in the bit stream. Therefore, when the last position information is to be arithmetically decoded, context adaptive binary arithmetic decoding and bypass decoding are alternately performed. This means that switching between the arithmetic decoding methods occurs many times, which hinders efficient arithmetic decoding of the last position information.
In view of the foregoing, an image coding method according to an aspect of the present disclosure is an image coding method for coding last position information indicating a horizontal position and a vertical position of a last non-zero coefficient in a predetermined order in a current block to be coded, the image coding method including: binarizing a first component and a second component to generate a first binary signal and a second binary signal, respectively, the first component being one of a horizontal component and a vertical component which are included in the last position information, and the second component being the other of the horizontal component and the vertical component; coding a first partial signal and a second partial signal by first arithmetic coding, and coding a third partial signal and a fourth partial signal by second arithmetic coding different from the first arithmetic coding, the first partial signal being a part of the first binary signal, the second partial signal being a part of the second binary signal, the third partial signal being another part of the first binary signal, and the fourth partial signal being another part of the second binary signal; and placing the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal in a bit stream, wherein in the placing, (i) the coded second partial signal is placed next to the coded first partial signal, or (ii) the coded fourth partial signal is placed next to the coded third partial signal.
With this, in the bit stream, a coded partial signal is followed by a partial signal which has been coded by the same arithmetic coding as the preceding partial signal. Thus, when the arithmetically coded last position information is decoded, it is possible to reduce the number of times the arithmetic decoding methods are switched as compared to the case where the partial signals arithmetically coded by different methods are alternately placed. In other words, it is possible to output a bit stream from which the last position information can be efficiently decoded.
For example, the first arithmetic coding may be context adaptive binary arithmetic coding in which a variable probability updated based on a coded signal is used, and in the placing, the coded second partial signal may be placed next to the coded first partial signal.
With this, context adaptive binary arithmetic coding can be used as the first arithmetic coding. This makes it possible to output a bit stream from which two coded partial signals can be efficiently decoded in series by context adaptive binary arithmetic decoding.
For example, the second arithmetic coding may be bypass coding in which a fixed probability is used, and in the placing, the coded fourth partial signal may be placed next to the coded third partial signal.
With this, bypass coding can be used as the first arithmetic coding. It is to be noted that bypass decoding makes parallel processing easier because the variable probability is not used. This makes it possible to output a bit stream from which two coded partial signals can be efficiently decoded in series or in parallel by bypass decoding.
For example, the first arithmetic coding may be context adaptive binary arithmetic coding in which a variable probability updated based on a coded signal is used, the second arithmetic coding may be bypass coding in which a fixed probability is used, and in the placing, the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal may be placed in the bit stream in the following order: the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal. With this, two partial signals coded by bypass coding can be placed next to two partial signals coded by context adaptive binary arithmetic coding. This makes it possible to further reduce the number of times the arithmetic decoding methods are switched when the last position information is decoded. In other words, it is possible to output a bit stream from which the last position information can be more efficiently decoded.
For example, the first arithmetic coding may be context adaptive binary arithmetic coding in which a variable probability updated based on a coded signal is used, the second arithmetic coding may be bypass coding in which a fixed probability is used, and in the placing, the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal may be placed in the bit stream in the following order: the coded first partial signal, the coded second partial signal, the coded fourth partial signal, and the coded third partial signal.
With this, two partial signals coded by bypass coding can be placed next to two partial signals coded by context adaptive binary arithmetic coding. This makes it possible to further reduce the number of times the arithmetic decoding methods are switched when the last position information is decoded. In other words, it is possible to output a bit stream from which the last position information can be more efficiently decoded.
Furthermore, with this, the coded fourth partial signal is placed next to the coded second partial signal, which makes it possible to output a bit stream from which the second binary signal can be obtained by a series of decoding processes.
For example, the image coding method may further include: switching a coding process to either a first coding process compliant with a first standard or a second coding process compliant with a second standard; and adding, to the bit stream, identification information indicating either the first standard or the second standard with which the coding process switched to is compliant, wherein when the coding process is switched to the first coding process, the binarizing, the coding, and the placing may be performed as the first coding process.
This makes it possible to switch between the first coding process compliant with the first standard and the second coding process compliant with the second standard.
Furthermore, an image decoding method according to an aspect of the present disclosure is an image decoding method for decoding last position information indicating a horizontal position and a vertical position of a last non-zero coefficient in a predetermined order in a current block to be decoded, the image decoding method including: decoding, by first arithmetic decoding, a coded first partial signal and a coded second partial signal which are included in a bit stream, and decoding, by second arithmetic decoding different from the first arithmetic decoding, a coded third partial signal and a coded fourth partial signal which are included in the bit stream; and reconstructing a first component by debinarizing a first binary signal which includes the decoded first partial signal and the decoded third partial signal, and reconstructing a second component by debinarizing a second binary signal which includes the decoded second partial signal and the decoded fourth partial signal, the first component being one of a horizontal component and a vertical component which are included in the last position information, and the second component being the other of the horizontal component and the vertical component, wherein in the bit stream, (i) the coded second partial signal is placed next to the coded first partial signal, or (ii) the coded fourth partial signal is placed next to the coded third partial signal.
With this, the last position information can be reconstructed by decoding of the bit stream in which a coded partial signal is followed by a partial signal which has been coded by the same arithmetic coding as the preceding partial signal. This makes it possible to reduce the number of times the arithmetic decoding methods are switched as compared to the case of decoding a bit stream in which the partial signals arithmetically coded by different methods are alternately placed. In other words, the last position information can be efficiently decoded.
For example, in the bit stream, the coded second partial signal may be placed next to the coded first partial signal, and the first arithmetic decoding may be context adaptive binary arithmetic decoding in which a variable probability updated based on a decoded signal is used.
With this, context adaptive binary arithmetic decoding can be used as the first arithmetic decoding. This makes it possible to efficiently decode two coded partial signals in series by context adaptive binary arithmetic decoding.
For example, in the bit stream, the coded fourth partial signal may be placed next to the coded third partial signal, and the second arithmetic decoding may be bypass decoding in which a fixed probability is used.
With this, bypass decoding can be used as the first arithmetic decoding. It is to be noted that bypass decoding makes parallel processing easier because the variable probability is not used. This makes it possible to efficiently decode two coded partial signals in series or in parallel by bypass decoding.
For example, the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal may be placed in the bit stream in the following order: the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal, the first arithmetic decoding may be context adaptive binary arithmetic decoding in which a variable probability updated based on a decoded signal is used, and the second arithmetic decoding may be bypass decoding in which a fixed probability is used.
With this, it is possible to decode the bit stream in which two partial signals coded by bypass coding are placed next to two partial signals coded by context adaptive binary arithmetic coding. This makes it possible to further reduce the number of times the arithmetic decoding methods are switched when the last position information is decoded, thereby allowing more efficient decoding of the last position information.
For example, the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal may be placed in the bit stream in the following order: the coded first partial signal, the coded second partial signal, the coded fourth partial signal, and the coded third partial signal, the first arithmetic decoding may be context adaptive binary arithmetic decoding in which a variable probability updated based on a decoded signal is used, and the second arithmetic decoding may be bypass decoding in which a fixed probability is used.
With this, it is possible to decode the bit stream in which two partial signals coded by bypass coding are placed next to two partial signals coded by context adaptive binary arithmetic coding. This makes it possible to further reduce the number of times the arithmetic decoding methods are switched when the last position information is decoded, thereby allowing more efficient decoding of the last position information.
Furthermore, with this, the bit stream is coded in which the coded fourth partial signal is placed next to the coded second partial signal, thereby allowing the second binary signal to be obtained by a series of decoding processes.
For example, the image decoding method may further include switching a decoding process to either a first decoding process compliant with a first standard or a second decoding process compliant with a second standard, according to identification information which is added to the bit stream and indicates either the first standard or the second standard, wherein when the decoding process is switched to the first decoding process, the decoding and the reconstructing may be performed as the first decoding process.
This makes it possible to switch between the first decoding process compliant with the first standard and the second decoding process compliant with the second standard.
It is to be noted that these general and specific aspects may be implemented using a system, an apparatus, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or any combination of systems, apparatuses, integrated circuits, computer programs, or computer-readable recording media.
Hereinafter, embodiments will be described in detail using the drawings.
It is to be noted that each of the embodiments described below shows a general or specific example. The numerical values, shapes, materials, structural elements, the arrangement and connection of the structural elements, steps, the processing order of the steps etc., shown in the following embodiments are mere examples, and are therefore not intended to limit the scope of the Claims. Furthermore, among the structural elements in the following embodiments, structural elements not recited in any one of the independent claims representing the most generic concepts are described as arbitrary structural elements.
(Embodiment 1)
As shown in
The image decoding apparatus 100 obtains a bit stream BS which includes the coded last position information.
It is to be noted that in some cases the bit stream BS does not include the coded third partial signal or does not include the coded fourth partial signal. For example, the bit stream BS does not include the coded third partial signal or does not include the coded fourth partial signal when a block to be decoded is smaller than a predetermined size, or when the value (last value) of a first component or a second component included in the last position information is smaller than a predetermined value.
Each of the coded first partial signal and the coded second partial signal corresponds to a prefix part which has been coded by context adaptive binary arithmetic coding, for example. Each of the coded third partial signal and the coded fourth partial signal corresponds to a suffix part which has been coded by bypass coding, for example.
Here, in the bit stream BS, the coded second partial signal is placed next to the coded first partial signal, or, the coded fourth partial signal is placed next to the coded third partial signal.
More specifically, in the bit stream BS, the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal are placed in the following order: the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal, for example. Furthermore, in the bit stream BS, the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal may be placed in the following order: the coded first partial signal, the coded second partial signal, the coded fourth partial signal, and the coded third partial signal, for example.
The first decoding unit 101 decodes the coded first partial signal and the coded second partial signal by first arithmetic decoding. The first arithmetic decoding is context adaptive binary arithmetic decoding in which a variable probability updated based on a decoded signal is used, for example. In this case, the first decoding unit 101 decodes the coded first partial signal and the coded second partial signal by context adaptive binary arithmetic decoding. It is to be noted that the first arithmetic decoding need not be context adaptive binary arithmetic decoding.
The second decoding unit 102 decodes the coded third partial signal and the coded fourth partial signal by second arithmetic decoding. For example, the second arithmetic decoding is bypass decoding in which a fixed probability is used. In this case, the second decoding unit 102 decodes the coded third partial signal and the coded fourth partial signal by bypass decoding. In doing so, the second decoding unit 102 may decode the coded third partial signal and the coded fourth partial signal in parallel.
It is to be noted that the second arithmetic decoding need not be bypass decoding. More specifically, it is sufficient as long as the first arithmetic decoding and the second arithmetic decoding are different.
The decoding control unit 103 manages, for each part of the bit stream BS, whether the part is the X component or the Y component of the last position information. It is to be noted that the decoding control unit 103 need not be included in the arithmetic decoding unit 110. That is to say, the image decoding apparatus 100 need not include the decoding control unit 103. In this case, it is sufficient as long as the first decoding unit 101 and the second decoding unit 102 manage the X component and the Y component.
The reconstructing unit 104 reconstructs the first component that is one of the horizontal component and the vertical component included in the last position information, by debinarizing a first binary signal which includes the first partial signal and the third partial signal. Furthermore, the reconstructing unit 104 reconstructs the second component that is the other of the horizontal component and the vertical component included in the last position information, by debinarizing a second binary signal which includes the second partial signal and the fourth partial signal.
Next, using
Hereinafter, it is assumed that the first component is the X component and the second component is the Y component. It is also assumed that each of the first partial signal and the second partial signal is the prefix part and each of the third partial signal and the fourth partial signal is the suffix part. Furthermore, it is assumed that the suffix flag of the X component and the suffix flag of the Y component are set “OFF” as the default value. It is to be noted that the suffix flag is an internal flag indicating whether or not the binary signal of its corresponding component of the last position information includes the suffix part.
First, the first decoding unit 101 decodes, from the bit stream BS, the coded prefix part of the X component by context adaptive binary arithmetic decoding (S101). For example, the first decoding unit 101 arithmetically decodes the coded prefix part on a one bit-by-one bit basis until a predetermined maximum length is reached or until “1” is decoded.
Next, the first decoding unit 101 determines whether or not the binary signal of the X component includes the suffix part (S102).
For example, the first decoding unit 101 determines that the binary signal of the X component includes the suffix part when the prefix part has the predetermined maximum length and the binary symbol values included in the prefix part are all “0”.
It is to be noted that the maximum length of the prefix part is predetermined according to the transform size, for example. For example, the maximum length of the prefix part is determined in the manner shown in
Here, when the binary signal of the X component includes the suffix part (Yes in S102), the first decoding unit 101 sets the suffix flag of the X component “ON” (S103). On the other hand, when the binary signal of the X component does not include the suffix part (No in S102), the first decoding unit 101 does not set the suffix flag of the X component “ON”. In other words, the suffix flag of the X component remains “OFF”, which is the default value. It is to be noted that the first decoding unit 101 may set the suffix flag of the X component “OFF” here.
Next, the first decoding unit 101 decodes, by context adaptive binary arithmetic decoding, the coded prefix part of the Y component placed next to the coded prefix part of the X component (S104). More specifically, the first decoding unit 101 decodes the prefix part of the Y component in the same manner as the decoding of the prefix part of the X component.
After that, the first decoding unit 101 determines whether or not the binary signal of the Y component includes the suffix part (S105). More specifically, the first decoding unit 101 determines whether or not the binary signal of the Y component includes the suffix part in the same manner as the determination as to whether or not the binary signal of the X component includes the suffix part.
Here, when the binary signal of the Y component includes the suffix part (Yes in S105), the first decoding unit 101 sets the suffix flag of the Y component “ON” (S106). On the other hand, when the binary signal of the Y component does not include the suffix part (No in S105), the first decoding unit 101 does not set the suffix flag of the Y component “ON”.
Next, the second decoding unit 102 determines whether or not the suffix flag of the X component is set “ON” (S107). Here, when the suffix flag of the X component is set “ON” (Yes in S107), the second decoding unit 102 decodes, by bypass decoding, the coded suffix part of the X component placed next to the coded prefix part of the Y component (S108). On the other hand. when the suffix flag of the X component is not set “ON” (No in S107), Step S108 is skipped.
The reconstructing unit 104 reconstructs the X component of the last position information by debinarizing the binary signal of the X component which includes both the prefix part and the suffix part or which includes the prefix part only (S109). For example, when the value of the X component is binarized as shown in
Next, the second decoding unit 102 determines whether or not the suffix flag of the Y component is set “ON” (S110). Here, when the suffix flag of the Y component is set “ON” (Yes in S110), the second decoding unit 102 decodes, by bypass decoding, the coded suffix part of the Y component placed next to the coded suffix part of the X component or placed next to the coded prefix part of the Y component (S111). On the other hand, when the suffix flag of the Y component is not set “ON” (No in S110), Step S111 is skipped.
Lastly, the reconstructing unit 104 reconstructs the Y component of the last position information by debinarizing the binary signal of the Y component which includes both the prefix part and the suffix part or which includes the prefix part only (S112).
It is to be noted that although the second decoding unit 102 in
Next, the following describes the case where the prefix part and the suffix part of each component are placed in the bit stream in an order different from that in
As for
First, the first decoding unit 101 decodes the coded prefix part of the X component by context adaptive binary arithmetic decoding (S101). Then, the first decoding unit 101 determines whether or not the binary signal of the X component includes the suffix part (S102).
Here, when the binary signal of the X component includes the suffix part (Yes in S102), the first decoding unit 101 sets the suffix flag of the X component “ON” (S103). On the other hand, when the binary signal of the X component does not include the suffix part (No in S102), the first decoding unit 101 does not set the suffix flag of the X component “ON”.
Next, the first decoding unit 101 decodes, by context adaptive binary arithmetic decoding, the coded prefix part of the Y component placed next to the coded prefix part of the X component (S104). Then, the first decoding unit 101 determines whether or not the binary signal of the Y component includes the suffix part (S105).
Here, when the binary signal of the Y component includes the suffix part (Yes in S105), the second decoding unit 102 decodes, by bypass decoding, the coded suffix part of the Y component placed next to the coded prefix part of the Y component (S111). On the other hand, when the binary signal of the Y component does not include the suffix part (No in S105), Step S111 is skipped.
Next, the reconstructing unit 104 reconstructs the Y component of the last position information by debinarizing the binary signal of the Y component which includes both the prefix part and the suffix part or which includes the prefix part only (S112).
After that, the second decoding unit 102 determines whether or not the suffix flag of the X component is set “ON” (S107). Here, when the suffix flag of the X component is set “ON” (Yes in S107), the second decoding unit 102 decodes, by bypass decoding, the coded suffix part of the X component placed next to the coded prefix part or suffix part of the Y component (S108). On the other hand, when the suffix flag of the X component is not set “ON” (No in S107), Step S108 is skipped.
Lastly, the reconstructing unit 104 reconstructs the X component of the last position information by debinarizing the binary signal of the X component which includes both the prefix part and the suffix part or which includes the prefix part only (S109).
By consecutively decoding the prefix part and the suffix part of the Y component in the above-described manner, it is possible to reconstruct the Y component without holding, in a memory, information indicating whether or not the binary signal of the Y component includes the suffix part (here, the suffix flag of the Y component). This reduces the capacity required of the memory.
It is to be noted that in the flowcharts shown in
Next, the following describes an example of the decoding process on the coded suffix parts of the X component and the Y component (S108 and Sill). Described here is the case where the suffix parts are binarized by Golomb-Rice coding.
With the Golomb-Rice coding, the length of each suffix part is not fixed. The suffix part can be divided into two parts, the first half and the second half.
The second half is a fixed-length part having a length indicated by a rice parameter (hereinafter referred to as “RP”).
The first half can be represented by: “1” that increases in the unit of a number representable by 2 to the RPth power (2RP) (e.g., in the unit of “4” when RP is “2”); and “0” that is set at the last bit position. More specifically, when RP is “2”, the length of the first half increases by 1 bit for each unit of 2 to the RPth power as follows: 0, 0, 0, 0, 10, 10, 10, 10, 110, 110, 110, 110, . . . .
It is to be noted that here, the amount of information to be represented by the suffix part is known, and thus it is possible to omit the last “0” of the first half when the first half has the maximum length. For example, when RP is “2” and the maximum amount of information is “12”, the first half can be represented by any one of 0, 0, 0, 0, 10, 10, 10, 10, 11, 11, 11, and 11. By omitting the last “0” of the first half in this manner, the coding amount of the binary signal can be reduced by 1 bit.
The maximum amount of information can be represented by the difference between the length in the transform size and the length of the prefix part. This reduces redundant bit(s).
It is sufficient as long as RP is predetermined according to the transform size as shown in
The following describes, using
First, the second decoding unit 102 sets an RP value (S201). More specifically, the second decoding unit 102 refers to a predetermined table, for example, to set the RP value. The predetermined table in this case is a table shown in
It is to be noted that the second decoding unit 102 may set the RP value without referring to the table. The setting of the RP value will be described later in detail using
Next, the second decoding unit 102 sets a Max value (S202). Here, the Max value indicates the maximum value of the length of the first half of the Golomb-Rice code. More specifically, the Max value indicates the shortest length of the binary signal that can represent a value obtained by subtracting the maximum length of the prefix part from the maximum value of the last value. Thus, the second decoding unit 102 derives the Max value by (i) subtracting the length of the prefix part from the maximum value of the last value and (ii) dividing the resultant value by 2 to the RPth power or performing a right shift operation on the resultant value by RP bit(s).
It is to be noted that the maximum length of the prefix part may be varied according to the transform size as shown in
Next, the second decoding unit 102 decodes, from the bit stream BS, a signal corresponding to 1 bit of the Golomb-Rice code by bypass decoding, and increments the count value (default is “0”) by 1 (S203).
Here, when the decoded signal corresponding to 1 bit is “0” (Yes in S204), the decoding of the first half of the Golomb-Rice code finishes, and the process proceeds to Step S206.
On the other hand, when the decoded signal is not “0” (when the decoded signal is “1”) (No in S204), it is determined whether or not the count value is equal to the Max value (S205). Here, when the count value is not equal to the Max value (No in S205), the process returns to Step S203. More specifically, the second decoding unit 102 decodes a signal corresponding to the next 1 bit of the Golomb-Rice code by bypass decoding.
On the other hand, when the count value is equal to the Max value (Yes in S205), the decoding of the first half of the suffix part finishes, and the process proceeds to Step S206.
Next, the second decoding unit 102 decodes the second half of the Golomb-Rice code (a binary signal having a fixed length of RP bit(s)) by bypass decoding (S206).
Lastly, the second decoding unit 102 reconstructs the value represented by Golomb-Rice coding (S207). Here, the value is reconstructed by adding up the second half of the Golomb-Rice code and a value obtained by shifting, to the left by the RP bit(s), a value obtained by subtracting 1 from the value represented by the first half of the Golomb-Rice code.
It is to be noted that in some cases the value of the binary signal of the second half is binarized in the form of a reversed value. In such cases, the second decoding unit 102 performs the reconstruction with this reverse taken into account. It is to be noted that it is sufficient as long as the decoding apparatus and the coding apparatus determine in advance whether or not the value of the binary signal is to be reversed. Neither the coding efficiency nor the processing load is affected regardless of whether or not the value of the binary signal is reversed.
Next, the following describes, using
First, the second decoding unit 102 obtains the transform size (S301). Then, the second decoding unit 102 refers to a table as shown in
Furthermore, the second decoding unit 102 refers to a table as shown in
First, the second decoding unit 102 obtains prediction information (S311). The prediction information is information related to prediction of a transform block which is a current block to be decoded. For example, the prediction information indicates whether the transform block is to be decoded by intra prediction or inter prediction. Furthermore, for example, the prediction information may be information indicating a prediction direction in intra prediction.
Next, the second decoding unit 102 determines the RP value based on the prediction information (S312). For example, it is known that in the case of inter prediction, there are generally less high frequency components than in intra prediction. Thus, when the prediction information indicates inter prediction, it is sufficient as long as the second decoding unit 102 determines such an RP value that allows the X component and the Y component having small values to be represented by short binary signals. More specifically, when the prediction information indicates inter prediction, it is sufficient as long as the second decoding unit 102 determines an RP value smaller than an RP value determined when the prediction information indicates intra prediction.
Furthermore, when the direction of intra prediction is the horizontal direction, it is generally expected that the Y component of the last position information is smaller than the X component. In view of this, when the prediction direction of intra prediction is the horizontal direction, it is sufficient as long as the second decoding unit 102 determines, as the RP value of the Y component, an RP value smaller than the RP value of the X component. It is to be noted that when the prediction direction of intra prediction is the vertical direction, it is sufficient as long as the second decoding unit 102 determines, as the RP value of the X component, an RP value smaller than the RP value of the Y component.
Lastly, the second decoding unit 102 determines the maximum length of the prefix part based on the prediction information (S313).
As described above, the second decoding unit 102 can vary the code length of the binary signal according to the prediction information, and thus, the coding efficiency can be increased.
First, the second decoding unit 102 obtains statistical information (S321). The statistical information is, for example, information on statistics of the length of the binary signal of the X component or the Y component included in the last position information of a previously decoded block.
Next, the second decoding unit 102 determines the RP value based on the statistical information (S322). Lastly, the second decoding unit 102 determines the maximum length of the prefix part based on the statistical information (S323).
As described above, the second decoding unit 102 can vary the code length of the binary signal according to the statistical information, and thus, the coding efficiency can be further increased.
First, the second decoding unit 102 obtains a previously-decoded one of the X component and the Y component (S331). For example, the second decoding unit 102 obtains a previously-decoded X component when decoding a coded Y component. Furthermore, for example, the second decoding unit 102 may obtain a previously-decoded Y component when decoding a coded X component.
Then, the second decoding unit 102 determines, using the previously-decoded one of the X component and the Y component, the RP value of the other, yet-to-be-decoded one of the X component and the Y component (S332). Generally, it is likely that the X component and the Y component have the same or similar values. Therefore, when the value of a previously-decoded X component is smaller than a certain value (e.g., half the transform size), for example, the second decoding unit 102 determines, as the RP value of the Y component, a value smaller than the RP value of the X component.
Lastly, the second decoding unit 102 determines, using the previously-decoded one of the X component and the Y component, the maximum length of the prefix part of the other, yet-to-be-decoded one of the X component and the Y component (S333).
As described above, the second decoding unit 102 can vary the code length of the binary signal according to a previously-decoded one of the X component and the Y component, and thus, the coding efficiency can be further increased.
It is to be noted that the methods of determining the RP value and the maximum length of the prefix part shown in
Moreover, the second decoding unit 102 may determine the maximum length of the prefix part in the same manner as the RP value. It is to be noted that when the values of the X component and the Y component are predicted to be large, it is sufficient as long as the second decoding unit 102 determines the maximum length of the prefix part to be shorter than when the X component and the Y component are predicted to be small. This further increases the coding efficiency.
Next, the following describes, using
The part (a) of
Here, one might consider arithmetically decoding the last position information in parallel in order to increase the processing speed of the arithmetic decoding. However, since the prefix part is decoded by context adaptive binary arithmetic decoding, it is difficult to perform arithmetic decoding in parallel. To be more specific, a variable probability (probability of symbol occurrence) which is updated based on a coded signal is used in the arithmetic decoding of the prefix part. This means that it is necessary to successively read and update the probability of symbol occurrence. Therefore, it is difficult to parallelize the arithmetic decoding of the prefix part.
On the other hand, it is relatively easy to parallelize the arithmetic decoding of the suffix part because the suffix part is decoded by bypass decoding. To be more specific, the variable probability updated based on a coded signal is not used in the arithmetic decoding of the suffix part, but a fixed probability (probability of symbol occurrence) is used. Therefore, it is relatively easy to parallelize the arithmetic decoding of the suffix part.
In view of this, the arithmetic decoding of the suffix part may be parallelized bitwise as shown in the part (b) of
Moreover, when the process is to be further parallelized, information related to the suffix part may be obtained from the bit stream BS, and the arithmetic decoding of the suffix part may start before context adaptive binary arithmetic decoding is completed, as shown in the part (c) of
The part (a) of
The part (b) of
As described above, the image decoding apparatus 100 according to Embodiment 1 can efficiently decode the last position information.
More specifically, the image decoding apparatus 100 can reconstruct the last position information by decoding the bit stream in which the coded binary signals of the X component and the Y component included in the last position information are placed after being classified into a group for context adaptive binary arithmetic decoding and a group for bypass decoding. This allows the image decoding apparatus 100 to reduce the number of times the arithmetic decoding methods are switched. Moreover, the image decoding apparatus 100 can arithmetically decode the coded last position information at high speed because it is possible to group partial signals that are to be decoded by bypass decoding, which can be performed in parallel.
To be more specific, the image decoding apparatus 100 can reconstruct the last position information by decoding the bit stream in which a coded partial signal (e.g., the suffix part of the X component) is followed by a partial signal (e.g., the suffix part of the Y component) which has been coded by the same arithmetic coding as the preceding partial signal. Thus, the image decoding apparatus 100 can reduce the number of times the arithmetic decoding methods are switched and efficiently decode the last position information as compared to the case of decoding a bit stream in which partial signals which have been arithmetically coded by different methods are alternately placed.
It is to be noted that the RP values and the maximum lengths of the prefix part shown in
It is to be noted that each of the structural elements in the present embodiment may be configured in the form of an exclusive hardware product, or may be implemented by executing a software program suitable for the structural element. Each structural element may be implemented by means of a program executing unit, such as a CPU or a processor, reading and executing the software program recorded on a recording medium such as a hard disk or a semiconductor memory. Here, the software program for implementing the image decoding apparatus according to the present embodiment is a program described below.
This program causes a computer to execute an image decoding method for decoding last position information indicating a horizontal position and a vertical position of a last non-zero coefficient in a predetermined order in a current block to be decoded, the image decoding method including: decoding, by first arithmetic decoding, a coded first partial signal and a coded second partial signal which are included in a bit stream, and decoding, by second arithmetic decoding different from the first arithmetic decoding, a coded third partial signal and a coded fourth partial signal which are included in the bit stream; and reconstructing a first component by debinarizing a first binary signal which includes the decoded first partial signal and the decoded third partial signal, and reconstructing a second component by debinarizing a second binary signal which includes the decoded second partial signal and the decoded fourth partial signal, the first component being one of a horizontal component and a vertical component which are included in the last position information, and the second component being the other of the horizontal component and the vertical component, wherein in the bit stream, (i) the coded second partial signal is placed next to the coded first partial signal, or (ii) the coded fourth partial signal is placed next to the coded third partial signal.
(Variation of Embodiment 1)
The image decoding apparatus 100 according to Embodiment 1 may be included in an image decoding apparatus below.
The image decoding apparatus 200 decodes coded image data generated by compression coding. For example, the image decoding apparatus 200 receives coded image data on a block-by-block basis as a current signal to be decoded. The image decoding apparatus 200 performs variable-length decoding, inverse quantization, and inverse transform on the received current signal to reconstruct image data.
As shown in
The entropy decoding unit 210 performs variable-length decoding on an input signal (bit stream) to reconstruct quantized coefficients. Here, the input signal is a current signal to be decoded and corresponds to data on a block-by-block basis of the coded image data. The coded image data includes the coded last position information. Furthermore, the entropy decoding unit 210 obtains motion data from the input signal and outputs the motion data to the motion compensation unit 260.
It is to be noted that the image decoding apparatus 100 according to Embodiment 1 corresponds to part of the entropy decoding unit 210. That is to say, the entropy decoding unit 210 decodes the coded last position information.
The inverse quantization and inverse transform unit 220 performs inverse quantization on the quantized coefficients reconstructed by the entropy decoding unit 210, to reconstruct transform coefficients. Then, the inverse quantization and inverse transform unit 220 performs inverse transform on the transform coefficients to reconstruct a prediction error.
The adder 225 adds the prediction error and a prediction signal to generate a decoded image.
The deblocking filter 230 applies a deblocking filter to the decoded image. The resultant decoded image is outputted as a decoded signal.
The memory 240 is a memory for storing a reference image used in motion compensation. More specifically, the memory 240 stores the decoded image to which the deblocking filter has been applied.
The intra prediction unit 250 performs intra prediction to generate a prediction signal (intra prediction signal). More specifically, the intra prediction unit 250 generates an intra prediction signal by performing intra prediction by reference to an image neighboring the current block to be decoded (input signal) in the decoded image generated by the adder 225.
The motion compensation unit 260 performs motion compensation based on the motion data outputted by the entropy decoding unit 210, to generate a prediction signal (inter prediction signal).
The intra/inter switch 270 selects either the intra prediction signal or the inter prediction signal, and outputs the selected signal to the adder 225 as the prediction signal.
With the above configuration, the image decoding apparatus 200 decodes the coded image data generated by compression coding.
(Embodiment 2)
The following describes an image coding apparatus according to Embodiment 2 using the drawings.
It is to be noted that the first component is one of the horizontal component and the vertical component, and the second component is the other of the horizontal component and the vertical component.
As shown in
The binarizing unit 310 binarizes the first component and the second component included in the last position information, to generate the first binary signal and the second binary signal.
The first coding unit 321 codes, by first arithmetic coding, the first partial signal that is a part of the first binary signal and the second partial signal that is a part of the second binary signal. The first arithmetic coding is, for example, context adaptive binary arithmetic coding in which a variable probability updated based on a coded signal is used. It is to be noted that the first arithmetic coding need not be context adaptive binary arithmetic coding.
The second coding unit 322 codes, by second arithmetic coding different from the first arithmetic coding, the third partial signal that is another part of the first binary signal and the fourth partial signal that is another part of the second binary signal. The second arithmetic coding is, for example, bypass coding in which a fixed probability is used. It is to be noted that the second arithmetic coding need not be bypass coding. That is to say, it is sufficient as long as the first arithmetic coding and the second arithmetic coding are different.
The coding control unit 323 manages which one of the first to fourth partial signals is the signal received by the arithmetic coding unit 320. It is to be noted that the coding control unit 323 need not be included in the arithmetic coding unit 320. That is to say, the image coding apparatus 300 need not include the coding control unit 323.
The placing unit 330 places, in a bit stream, the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal. Here, the placing unit 330 places the coded second partial signal next to the coded first partial signal, or places the coded fourth partial signal next to the coded third partial signal.
More specifically, the placing unit 330 may place, for example, the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal in the bit stream in the following order: the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal. Furthermore, the placing unit 330 may place, for example, the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal in the bit stream in the following order: the coded first partial signal, the coded second partial signal, the coded fourth partial signal, and the coded third partial signal.
Next, using
Hereinafter, it is assumed that the first component is the X component and the second component is the Y component. It is also assumed that each of the first partial signal and the second partial signal is the prefix part and each of the third partial signal and the fourth partial signal is the suffix part. Furthermore, it is assumed that the suffix flag of the X component and the suffix flag of the Y component are set “OFF” as the default value. It is to be noted that the suffix flag is an internal flag indicating whether or not the binary signal of its corresponding component of the last position information includes the suffix part.
First, the binarizing unit 310 binarizes each of the X component and the Y component of the last position information (S401). More specifically, the binarizing unit 310 binarizes each of the X component and the Y component (last values) as shown in
Next, the first coding unit 321 codes, by context adaptive binary arithmetic coding, the prefix part of the X component included in the last position information (S402).
Context adaptive binary arithmetic coding is coding corresponding to context adaptive binary arithmetic decoding shown in
Next, the first coding unit 321 determines whether or not the binary signal of the X component includes the suffix part (S403). More specifically, the first coding unit 321 determines whether or not the binary signal of the X component includes the suffix part in the same manner as in Step S102 in
Here, when the binary signal of the X component includes the suffix part (Yes in S403), the first coding unit 321 sets the suffix flag of the X component “ON” (S404). On the other hand, when the binary signal of the X component does not include the suffix part (No in S403), the first coding unit 321 does not set the suffix flag of the X component “ON”. In other words, the suffix flag of the X component remains “OFF”. It is to be noted that the first coding unit 321 may set the suffix flag of the X component “OFF” here.
Next, the first coding unit 321 codes, by context adaptive binary arithmetic coding, the prefix part of the Y component included in the last position information (S405). After that, the first coding unit 321 determines whether or not the binary signal of the Y component includes the suffix part (S406).
Here, when the binary signal of the Y component includes the suffix part (Yes in S406), the first coding unit 321 sets the suffix flag of the Y component “ON” (S407). On the other hand, when the binary signal of the Y component does not include the suffix part (No in S406), the first coding unit 321 does not set the suffix flag of the Y component “ON”.
Next, the second coding unit 322 determines whether or not the suffix flag of the X component is set “ON” (S408). Here, when the suffix flag of the X component is set “ON” (Yes in S408), the second coding unit 322 codes the suffix part of the X component by bypass coding (S409). On the other hand, when the suffix flag of the X component is not set “ON” (No in S408), Step S409 is skipped.
The second coding unit 322 determines whether or not the suffix flag of the Y component is set “ON” (S410). Here, when the suffix flag of the Y component is set “ON” (Yes in S410), the second coding unit 322 codes the suffix part of the Y component by bypass coding (S411). On the other hand, when the suffix flag of the Y component is not set “ON” (No in S410). Step S411 is skipped.
Lastly, the placing unit 330 places, in the bit stream BS, the coded prefix part of the X component, the coded prefix part of the Y component, the coded suffix part of the X component, and the coded suffix part of the Y component in this order (S412). Here, the placing unit 330 places, in the bit stream BS, the prefix part and the suffix part of each component in the order in which they have been coded.
Next, the following describes the case where the prefix part and the suffix part of each component are placed in the bit stream in an order different from
First, the binarizing unit 310 binarizes each of the X component and the Y component of the last position information (S401). Next, the first coding unit 321 codes, by context adaptive binary arithmetic coding, the prefix part of the X component included in the last position information (S402).
Next, the first coding unit 321 determines whether or not the binary signal of the X component includes the suffix part (S403). Here, when the binary signal of the X component includes the suffix part (Yes in S403), the first coding unit 321 sets the suffix flag of the X component “ON” (S404). On the other hand, when the binary signal of the X component does not include the suffix part (No in S403), the first coding unit 321 does not set the suffix flag of the X component “ON”.
Then, the first coding unit 321 codes the prefix part of the Y component by context adaptive binary arithmetic coding (S405). After that, the first coding unit 321 determines whether or not the binary signal of the Y component includes the suffix part (S406).
Here, when the binary signal of the Y component includes the suffix part (Yes in S406), the second coding unit 322 codes the suffix part of the Y component by bypass coding (S411). On the other hand, when the binary signal of the Y component does not include the suffix part (No in S406), Step S411 is skipped.
Next, the second coding unit 322 determines whether or not the suffix flag of the X component is set “ON” (S408). Here, when the suffix flag of the X component is set “ON” (Yes in S408), the second coding unit 322 codes the suffix part of the X component by bypass coding (S409). On the other hand, when the suffix flag of the X component is not set “ON” (No in S408), Step S409 is skipped.
Lastly, the placing unit 330 places, in the bit stream BS, the coded prefix part of the X component, the coded prefix part of the Y component, the coded suffix part of the Y component, and the coded suffix part of the X component in this order (S512). Here, the placing unit 330 places, in the bit stream BS, the prefix part and the suffix part of each component in the order in which they have been coded.
By consecutively coding the prefix part and the suffix part of the Y component in the above-described manner, it is possible to code the binary signal of the Y component without holding, in a memory, information indicating whether or not the binary signal of the Y component includes the suffix part (the suffix flag of the Y component in
It is to be noted that in the flowcharts shown in
Next, using
When the prefix part is shorter than the maximum length of the prefix part, the first coding unit 321 codes, by context adaptive binary arithmetic coding, as many “0” as the number indicated by the value of the X component. Lastly, the first coding unit 321 codes “1” by context adaptive binary arithmetic coding. In this case, the binary signal of the X component does not include the suffix part, and thus the coding of the X component finishes here.
On the other hand, when the prefix part is longer than the maximum length of the prefix part, the first coding unit 321 codes, by context adaptive binary arithmetic coding, as many “0” as the number of the maximum length.
Next, the second coding unit 322 codes the first half of the suffix part. More specifically, the second coding unit 322 adds “1” to the first half in the unit of the number representable by 2 to the RPth power (e.g., in the unit of “4” when RP is “2”), codes the resultant value, and lastly codes “0”.
That is to say, when the value of the X component is greater than or equal to 4 and less than 8, the second coding unit 322 only codes “0” as the first half. When the value of the X component is greater than or equal to 8 and less than 12, the second coding unit 322 codes “10” as the first half. When the value of the X component is greater than or equal to 12 and less than 16, the second coding unit 322 codes “110” as the first half.
It is to be noted that in the example of
Next, the second coding unit 322 codes the second half of the suffix part. The second half is a fixed-length part having a length indicated by the RP value. In the example of
It is to be noted that even in
As described above, with the image coding apparatus 300 according to the present embodiment, in a bit stream, a coded partial signal (e.g., the suffix part of the X component) is followed by a partial signal (e.g., the suffix part of the Y component) which has been coded by the same arithmetic coding as the preceding partial signal. Thus, when the arithmetically coded last position information is decoded, it is possible to reduce the number of times the arithmetic decoding methods are switched as compared to the case where the partial signals arithmetically coded by different methods are alternately placed. That is to say, the image coding apparatus 300 can output a bit stream from which the last position information can be efficiently decoded.
It is to be noted that each of the structural elements in the present embodiment may be configured in the form of an exclusive hardware product, or may be implemented by executing a software program suitable for the structural element. Each structural element may be implemented by means of a program executing unit, such as a CPU or a processor, reading and executing the software program recorded on a recording medium such as a hard disk or a semiconductor memory. Here, the software program for implementing the image coding apparatus according to the present embodiment is a program described below.
This program causes a computer to execute an image coding method for coding last position information indicating a horizontal position and a vertical position of a last non-zero coefficient in a predetermined order in a current block to be coded, the image coding method including: binarizing a first component and a second component to generate a first binary signal and a second binary signal, respectively, the first component being one of a horizontal component and a vertical component which are included in the last position information, and the second component being the other of the horizontal component and the vertical component; coding a first partial signal and a second partial signal by first arithmetic coding, and coding a third partial signal and a fourth partial signal by second arithmetic coding different from the first arithmetic coding, the first partial signal being a part of the first binary signal, the second partial signal being a part of the second binary signal, the third partial signal being another part of the first binary signal, and the fourth partial signal being another part of the second binary signal; and placing the coded first partial signal, the coded second partial signal, the coded third partial signal, and the coded fourth partial signal in a bit stream, wherein in the placing, (i) the coded second partial signal is placed next to the coded first partial signal, or (ii) the coded fourth partial signal is placed next to the coded third partial signal.
(Variation of Embodiment 2)
The image coding apparatus 300 according to Embodiment 2 may be included in an image coding apparatus below.
The image coding apparatus 400 performs compression coding on image data. For example, the image coding apparatus 400 receives the image data on a block-by-block basis as an input signal. The image coding apparatus 400 performs transform, quantization, and variable-length coding on the input signal to generate a coded signal (bit stream).
As shown in
The subtractor 405 calculates a difference between the input signal and the prediction signal as a prediction error.
The transform and quantization unit 410 transforms the prediction error in the spatial domain to generate transform coefficients in the frequency domain. For example, the transform and quantization unit 410 performs discrete cosine transform (DCT) on the prediction error to generate the transform coefficients. Furthermore, the transform and quantization unit 410 quantizes the transform coefficients to generate quantized coefficients.
The entropy coding unit 420 performs variable-length coding on the quantized coefficients to generate a coded signal. Furthermore, the entropy coding unit 420 codes motion data (e.g., motion vector) detected by the motion estimation unit 470, to output the coded signal with the motion data included therein.
It is to be noted that the image coding apparatus 300 according to Embodiment 2 corresponds to part of the entropy coding unit 420. That is to say, the entropy coding unit 420 codes the last position information.
The inverse quantization and inverse transform unit 430 performs inverse quantization on the quantized coefficients to reconstruct transform coefficients. Furthermore, the inverse quantization and inverse transform unit 430 performs inverse transform on the reconstructed transform coefficients to reconstruct a prediction error. It is to be noted that the reconstructed prediction error lacks information due to the quantization and thus is not the same as the prediction error generated by the subtractor 405. In other words, the reconstructed prediction error contains a quantization error.
The adder 435 adds up the reconstructed prediction error and a prediction signal to generate a local decoded image.
The deblocking filter 440 applies a deblocking filter to the local decoded image.
The memory 450 is a memory for storing a reference image used in motion compensation. More specifically, the memory 450 stores the local decoded image to which the deblocking filter has been applied.
The intra prediction unit 460 performs intra prediction to generate a prediction signal (intra prediction signal). More specifically, the intra prediction unit 460 generates an intra prediction signal by performing intra prediction by reference to an image neighboring the current block to be coded (input signal) in the local decoded image generated by the adder 435.
The motion estimation unit 470 detects motion data (e.g., motion vector) between the input signal and the reference image stored in the memory 450.
The motion compensation unit 480 performs motion compensation based on the motion data to generate a prediction signal (inter prediction signal).
The intra/inter switch 490 selects either the intra prediction signal or the inter prediction signal, and outputs the selected signal to the subtractor 405 and the adder 435 as the prediction signal.
With the above configuration, the image coding apparatus 400 performs compression coding on the image data.
Although only some exemplary embodiments have been described above, the scope of the Claims of the present application is not limited to these embodiments. Those skilled in the art will readily appreciate that various modifications may be made in these exemplary embodiments and that other embodiments may be obtained by arbitrarily combining the structural elements of the embodiments without materially departing from the novel teachings and advantages of the subject matter recited in the appended Claims. Accordingly, all such modifications and other embodiments are included in the present disclosure.
For example, although each embodiment above has specifically described the decoding or coding of the last position information, it is also possible to decode and code the X component and the Y component of a motion vector in the same manner as that described above. More specifically, it is possible to perform coding and decoding without buffering information indicating whether or not the suffix part of the Y component is present, by placing a bypass-coded part including the suffix part of the Y component and a positive/negative code and a bypass-coded part including the suffix part of the X component and a positive/negative code next to the prefix part of the X component (context-adaptive-coded part) and the prefix part of the Y component (context-adaptive-coded part). It is to be noted that the details of motion vector information are described in detail in Non Patent Literature 1 and thus a description thereof is omitted here.
Furthermore, although the suffix part is binarized by Golomb-Rice coding in each embodiment above, the suffix part may be binarized with a different method. For example, the suffix part may be binarized with a fixed length as shown in
Moreover, the method of binarizing the X component and the Y component in each embodiment above is a mere example, and they may be binarized with a different binarizing method. For example, in
Furthermore, although each embodiment above has shown the example where (i) the prefix part of the X component, the prefix part of the Y component, the suffix part of the X component, and the suffix part of the Y component are placed in this order or (ii) the prefix part of the X component, the prefix part of the Y component, the suffix part of the Y component, and the suffix part of the X component are placed in this order, the placing order of these prefix and suffix parts is not limited to this example. For example, the prefix part of the Y component and the prefix part of the X component may be placed in this order.
(Embodiment 3)
The processing described in each of embodiments can be simply implemented in an independent computer system, by recording, in a recording medium, a program for implementing the configurations of the moving picture coding method (image coding method) and the moving picture decoding method (image decoding method) described in each of embodiments. The recording media may be any recording media as long as the program can be recorded, such as a magnetic disk, an optical disk, a magnetic optical disk, an IC card, and a semiconductor memory.
Hereinafter, the applications to the moving picture coding method (image coding method) and the moving picture decoding method (image decoding method) described in each of embodiments and systems using thereof will be described. The system has a feature of having an image coding and decoding apparatus that includes an image coding apparatus using the image coding method and an image decoding apparatus using the image decoding method. Other configurations in the system can be changed as appropriate depending on the cases.
The content providing system ex100 is connected to devices, such as a computer ex111, a personal digital assistant (PDA) ex112, a camera ex113, a cellular phone ex114 and a game machine ex115, via the Internet ex101, an Internet service provider ex102, a telephone network ex104, as well as the base stations ex106 to ex110, respectively.
However, the configuration of the content providing system ex100 is not limited to the configuration shown in
The camera ex113, such as a digital video camera, is capable of capturing video. A camera ex116, such as a digital camera, is capable of capturing both still images and video. Furthermore, the cellular phone ex114 may be the one that meets any of the standards such as Global System for Mobile Communications (GSM) (registered trademark), Code Division Multiple Access (CDMA), Wideband-Code Division Multiple Access (W-CDMA), Long Term Evolution (LTE), and High Speed Packet Access (HSPA). Alternatively, the cellular phone ex114 may be a Personal Handyphone System (PHS).
In the content providing system ex100, a streaming server ex103 is connected to the camera ex113 and others via the telephone network ex104 and the base station ex109, which enables distribution of images of a live show and others. In such a distribution, a content (for example, video of a music live show) captured by the user using the camera ex113 is coded as described above in each of embodiments (i.e., the camera functions as the image coding apparatus according to an aspect of the present disclosure), and the coded content is transmitted to the streaming server ex103. On the other hand, the streaming server ex103 carries out stream distribution of the transmitted content data to the clients upon their requests. The clients include the computer ex111, the PDA ex112, the camera ex113, the cellular phone ex114, and the game machine ex115 that are capable of decoding the above-mentioned coded data. Each of the devices that have received the distributed data decodes and reproduces the coded data (i.e., functions as the image decoding apparatus according to an aspect of the present disclosure).
The captured data may be coded by the camera ex113 or the streaming server ex103 that transmits the data, or the coding processes may be shared between the camera ex113 and the streaming server ex103. Similarly, the distributed data may be decoded by the clients or the streaming server ex103, or the decoding processes may be shared between the clients and the streaming server ex103. Furthermore, the data of the still images and video captured by not only the camera ex113 but also the camera ex116 may be transmitted to the streaming server ex103 through the computer ex111. The coding processes may be performed by the camera ex116, the computer ex111, or the streaming server ex103, or shared among them.
Furthermore, the coding and decoding processes may be performed by an LSI ex500 generally included in each of the computer ex111 and the devices. The LSI ex500 may be configured of a single chip or a plurality of chips. Software for coding and decoding video may be integrated into some type of a recording medium (such as a CD-ROM, a flexible disk, and a hard disk) that is readable by the computer ex111 and others, and the coding and decoding processes may be performed using the software. Furthermore, when the cellular phone ex114 is equipped with a camera, the video data obtained by the camera may be transmitted. The video data is data coded by the LSI ex500 included in the cellular phone ex114.
Furthermore, the streaming server ex103 may be composed of servers and computers, and may decentralize data and process the decentralized data, record, or distribute data.
As described above, the clients may receive and reproduce the coded data in the content providing system ex100. In other words, the clients can receive and decode information transmitted by the user, and reproduce the decoded data in real time in the content providing system ex100, so that the user who does not have any particular right and equipment can implement personal broadcasting.
Aside from the example of the content providing system ex100, at least one of the moving picture coding apparatus (image coding apparatus) and the moving picture decoding apparatus (image decoding apparatus) described in each of embodiments may be implemented in a digital broadcasting system ex200 illustrated in
Furthermore, a reader/recorder ex218 (i) reads and decodes the multiplexed data recorded on a recording medium ex215, such as a DVD and a BD, or (i) codes video signals in the recording medium ex215, and in some cases, writes data obtained by multiplexing an audio signal on the coded data. The reader/recorder ex218 can include the moving picture decoding apparatus or the moving picture coding apparatus as shown in each of embodiments. In this case, the reproduced video signals are displayed on the monitor ex219, and can be reproduced by another device or system using the recording medium ex215 on which the multiplexed data is recorded. It is also possible to implement the moving picture decoding apparatus in the set top box ex217 connected to the cable ex203 for a cable television or to the antenna ex204 for satellite and/or terrestrial broadcasting, so as to display the video signals on the monitor ex219 of the television ex300. The moving picture decoding apparatus may be implemented not in the set top box but in the television ex300.
The television ex300 further includes: a signal processing unit ex306 including an audio signal processing unit ex304 and a video signal processing unit ex305 that decode audio data and video data and code audio data and video data, respectively (which function as the image coding apparatus and the image decoding apparatus according to the aspects of the present disclosure); and an output unit ex309 including a speaker ex307 that provides the decoded audio signal, and a display unit ex308 that displays the decoded video signal, such as a display. Furthermore, the television ex300 includes an interface unit ex317 including an operation input unit ex312 that receives an input of a user operation. Furthermore, the television ex300 includes a control unit ex310 that controls overall each constituent element of the television ex300, and a power supply circuit unit ex311 that supplies power to each of the elements. Other than the operation input unit ex312, the interface unit ex317 may include: a bridge ex313 that is connected to an external device, such as the reader/recorder ex218; a slot unit ex314 for enabling attachment of the recording medium ex216, such as an SD card; a driver ex315 to be connected to an external recording medium, such as a hard disk; and a modem ex316 to be connected to a telephone network. Here, the recording medium ex216 can electrically record information using a non-volatile/volatile semiconductor memory element for storage. The constituent elements of the television ex300 are connected to each other through a synchronous bus.
First, the configuration in which the television ex300 decodes multiplexed data obtained from outside through the antenna ex204 and others and reproduces the decoded data will be described. In the television ex300, upon a user operation through a remote controller ex220 and others, the multiplexing/demultiplexing unit ex303 demultiplexes the multiplexed data demodulated by the modulation/demodulation unit ex302, under control of the control unit ex310 including a CPU. Furthermore, the audio signal processing unit ex304 decodes the demultiplexed audio data, and the video signal processing unit ex305 decodes the demultiplexed video data, using the decoding method described in each of embodiments, in the television ex300. The output unit ex309 provides the decoded video signal and audio signal outside, respectively. When the output unit ex309 provides the video signal and the audio signal, the signals may be temporarily stored in buffers ex318 and ex319, and others so that the signals are reproduced in synchronization with each other. Furthermore, the television ex300 may read multiplexed data not through a broadcast and others but from the recording media ex215 and ex216, such as a magnetic disk, an optical disk, and a SD card. Next, a configuration in which the television ex300 codes an audio signal and a video signal, and transmits the data outside or writes the data on a recording medium will be described. In the television ex300, upon a user operation through the remote controller ex220 and others, the audio signal processing unit ex304 codes an audio signal, and the video signal processing unit ex305 codes a video signal, under control of the control unit ex310 using the coding method described in each of embodiments. The multiplexing/demultiplexing unit ex303 multiplexes the coded video signal and audio signal, and provides the resulting signal outside. When the multiplexing/demultiplexing unit ex303 multiplexes the video signal and the audio signal, the signals may be temporarily stored in the buffers ex320 and ex321, and others so that the signals are reproduced in synchronization with each other. Here, the buffers ex318, ex319, ex320, and ex321 may be plural as illustrated, or at least one buffer may be shared in the television ex300. Furthermore, data may be stored in a buffer so that the system overflow and underflow may be avoided between the modulation/demodulation unit ex302 and the multiplexing/demultiplexing unit ex303, for example.
Furthermore, the television ex300 may include a configuration for receiving an AV input from a microphone or a camera other than the configuration for obtaining audio and video data from a broadcast or a recording medium, and may code the obtained data. Although the television ex300 can code, multiplex, and provide outside data in the description, it may be capable of only receiving, decoding, and providing outside data but not the coding, multiplexing, and providing outside data.
Furthermore, when the reader/recorder ex218 reads or writes multiplexed data from or on a recording medium, one of the television ex300 and the reader/recorder ex218 may decode or code the multiplexed data, and the television ex300 and the reader/recorder ex218 may share the decoding or coding.
As an example,
Although the optical head ex401 irradiates a laser spot in the description, it may perform high-density recording using near field light.
Although an optical disk having a layer, such as a DVD and a BD is described as an example in the description, the optical disk is not limited to such, and may be an optical disk having a multilayer structure and capable of being recorded on a part other than the surface. Furthermore, the optical disk may have a structure for multidimensional recording/reproduction, such as recording of information using light of colors with different wavelengths in the same portion of the optical disk and for recording information having different layers from various angles.
Furthermore, a car ex210 having an antenna ex205 can receive data from the satellite ex202 and others, and reproduce video on a display device such as a car navigation system ex211 set in the car ex210, in the digital broadcasting system ex200. Here, a configuration of the car navigation system ex211 will be a configuration, for example, including a GPS receiving unit from the configuration illustrated in
Next, an example of a configuration of the cellular phone ex114 will be described with reference to
When a call-end key or a power key is turned ON by a user's operation, the power supply circuit unit ex361 supplies the respective units with power from a battery pack so as to activate the cell phone ex114.
In the cellular phone ex114, the audio signal processing unit ex354 converts the audio signals collected by the audio input unit ex356 in voice conversation mode into digital audio signals under the control of the main control unit ex360 including a CPU, ROM, and RAM. Then, the modulation/demodulation unit ex352 performs spread spectrum processing on the digital audio signals, and the transmitting and receiving unit ex351 performs digital-to-analog conversion and frequency conversion on the data, so as to transmit the resulting data via the antenna ex350. Also, in the cellular phone ex114, the transmitting and receiving unit ex351 amplifies the data received by the antenna ex350 in voice conversation mode and performs frequency conversion and the analog-to-digital conversion on the data. Then, the modulation/demodulation unit ex352 performs inverse spread spectrum processing on the data, and the audio signal processing unit ex354 converts it into analog audio signals, so as to output them via the audio output unit ex357.
Furthermore, when an e-mail in data communication mode is transmitted, text data of the e-mail inputted by operating the operation key unit ex366 and others of the main body is sent out to the main control unit ex360 via the operation input control unit ex362. The main control unit ex360 causes the modulation/demodulation unit ex352 to perform spread spectrum processing on the text data, and the transmitting and receiving unit ex351 performs the digital-to-analog conversion and the frequency conversion on the resulting data to transmit the data to the base station ex110 via the antenna ex350. When an e-mail is received, processing that is approximately inverse to the processing for transmitting an e-mail is performed on the received data, and the resulting data is provided to the display unit ex358.
When video, still images, or video and audio in data communication mode is or are transmitted, the video signal processing unit ex355 compresses and codes video signals supplied from the camera unit ex365 using the moving picture coding method shown in each of embodiments (i.e., functions as the image coding apparatus according to the aspect of the present disclosure), and transmits the coded video data to the multiplexing/demultiplexing unit ex353. In contrast, during when the camera unit ex365 captures video, still images, and others, the audio signal processing unit ex354 codes audio signals collected by the audio input unit ex356, and transmits the coded audio data to the multiplexing/demultiplexing unit cx353.
The multiplexing/demultiplexing unit ex353 multiplexes the coded video data supplied from the video signal processing unit ex355 and the coded audio data supplied from the audio signal processing unit ex354, using a predetermined method. Then, the modulation/demodulation unit (modulation/demodulation circuit unit) ex352 performs spread spectrum processing on the multiplexed data, and the transmitting and receiving unit ex351 performs digital-to-analog conversion and frequency conversion on the data so as to transmit the resulting data via the antenna ex350.
When receiving data of a video file which is linked to a Web page and others in data communication mode or when receiving an e-mail with video and/or audio attached, in order to decode the multiplexed data received via the antenna ex350, the multiplexing/demultiplexing unit ex353 demultiplexes the multiplexed data into a video data bit stream and an audio data bit stream, and supplies the video signal processing unit ex355 with the coded video data and the audio signal processing unit ex354 with the coded audio data, through the synchronous bus ex370. The video signal processing unit ex355 decodes the video signal using a moving picture decoding method corresponding to the moving picture coding method shown in each of embodiments (i.e., functions as the image decoding apparatus according to the aspect of the present disclosure), and then the display unit ex358 displays, for instance, the video and still images included in the video file linked to the Web page via the LCD control unit ex359. Furthermore, the audio signal processing unit ex354 decodes the audio signal, and the audio output unit ex357 provides the audio.
Furthermore, similarly to the television ex300, a terminal such as the cellular phone ex114 probably have 3 types of implementation configurations including not only (i) a transmitting and receiving terminal including both a coding apparatus and a decoding apparatus, but also (ii) a transmitting terminal including only a coding apparatus and (iii) a receiving terminal including only a decoding apparatus. Although the digital broadcasting system ex200 receives and transmits the multiplexed data obtained by multiplexing audio data onto video data in the description, the multiplexed data may be data obtained by multiplexing not audio data but character data related to video onto video data, and may be not multiplexed data but video data itself.
As such, the moving picture coding method and the moving picture decoding method in each of embodiments can be used in any of the devices and systems described. Thus, the advantages described in each of embodiments can be obtained.
Furthermore, the present disclosure is not limited to embodiments, and various modifications and revisions are possible without departing from the scope of the present disclosure.
(Embodiment 4)
Video data can be generated by switching, as necessary, between (i) the moving picture coding method or the moving picture coding apparatus shown in each of embodiments and (ii) a moving picture coding method or a moving picture coding apparatus in conformity with a different standard, such as MPEG-2, MPEG-4 AVC, and VC-1.
Here, when a plurality of video data that conforms to the different standards is generated and is then decoded, the decoding methods need to be selected to conform to the different standards. However, since to which standard each of the plurality of the video data to be decoded conforms cannot be detected, there is a problem that an appropriate decoding method cannot be selected.
In order to solve the problem, multiplexed data obtained by multiplexing audio data and others onto video data has a structure including identification information indicating to which standard the video data conforms. The specific structure of the multiplexed data including the video data generated in the moving picture coding method and by the moving picture coding apparatus shown in each of embodiments will be hereinafter described. The multiplexed data is a digital stream in the MPEG-2 Transport Stream format.
Each stream included in the multiplexed data is identified by PID. For example, 0x1011 is allocated to the video stream to be used for video of a movie, 0x1100 to 0x111F are allocated to the audio streams, 0x1200 to 0x121F are allocated to the presentation graphics streams, 0x1400 to 0x141F are allocated to the interactive graphics streams, 0x1B00 to 0x1B1F are allocated to the video streams to be used for secondary video of the movie, and 0x1A00 to 0x1A1F are allocated to the audio streams to be used for the secondary audio to be mixed with the primary audio.
Each of the TS packets included in the multiplexed data includes not only streams of audio, video, subtitles and others, but also a Program Association Table (PAT), a Program Map Table (PMT), and a Program Clock Reference (PCR). The PAT shows what a PID in a PMT used in the multiplexed data indicates, and a PID of the PAT itself is registered as zero. The PMT stores PIDs of the streams of video, audio, subtitles and others included in the multiplexed data, and attribute information of the streams corresponding to the PIDs. The PMT also has various descriptors relating to the multiplexed data. The descriptors have information such as copy control information showing whether copying of the multiplexed data is permitted or not. The PCR stores STC time information corresponding to an ATS showing when the PCR packet is transferred to a decoder, in order to achieve synchronization between an Arrival Time Clock (ATC) that is a time axis of ATSs, and an System Time Clock (STC) that is a time axis of PTSs and DTSs.
When the multiplexed data is recorded on a recording medium and others, it is recorded together with multiplexed data information files.
Each of the multiplexed data information files is management information of the multiplexed data as shown in
As illustrated in
As shown in
In the present embodiment, the multiplexed data to be used is of a stream type included in the PMT. Furthermore, when the multiplexed data is recorded on a recording medium, the video stream attribute information included in the multiplexed data information is used. More specifically, the moving picture coding method or the moving picture coding apparatus described in each of embodiments includes a step or a unit for allocating unique information indicating video data generated by the moving picture coding method or the moving picture coding apparatus in each of embodiments, to the stream type included in the PMT or the video stream attribute information. With the configuration, the video data generated by the moving picture coding method or the moving picture coding apparatus described in each of embodiments can be distinguished from video data that conforms to another standard.
Furthermore,
As such, allocating a new unique value to the stream type or the video stream attribute information enables determination whether or not the moving picture decoding method or the moving picture decoding apparatus that is described in each of embodiments can perform decoding. Even when multiplexed data that conforms to a different standard is input, an appropriate decoding method or apparatus can be selected. Thus, it becomes possible to decode information without any error. Furthermore, the moving picture coding method or apparatus, or the moving picture decoding method or apparatus in the present embodiment can be used in the devices and systems described above.
(Embodiment 5)
Each of the moving picture coding method, the moving picture coding apparatus, the moving picture decoding method, and the moving picture decoding apparatus in each of embodiments is typically achieved in the form of an integrated circuit or a Large Scale Integrated (LSI) circuit. As an example of the LSI,
For example, when coding is performed, the LSI ex500 receives an AV signal from a microphone ex117, a camera ex113, and others through an AV 10 ex509 under control of a control unit ex501 including a CPU ex502, a memory controller ex503, a stream controller ex504, and a driving frequency control unit ex512. The received AV signal is temporarily stored in an external memory ex511, such as an SDRAM. Under control of the control unit ex501, the stored data is segmented into data portions according to the processing amount and speed to be transmitted to a signal processing unit ex507. Then, the signal processing unit ex507 codes an audio signal and/or a video signal. Here, the coding of the video signal is the coding described in each of embodiments. Furthermore, the signal processing unit ex507 sometimes multiplexes the coded audio data and the coded video data, and a stream 10 ex506 provides the multiplexed data outside. The provided multiplexed data is transmitted to the base station ex107, or written on the recording medium ex215. When data sets are multiplexed, the data should be temporarily stored in the buffer ex508 so that the data sets are synchronized with each other.
Although the memory ex511 is an element outside the LSI ex500, it may be included in the LSI ex500. The buffer ex508 is not limited to one buffer, but may be composed of buffers. Furthermore, the LSI ex500 may be made into one chip or a plurality of chips.
Furthermore, although the control unit ex501 includes the CPU ex502, the memory controller ex503, the stream controller ex504, the driving frequency control unit ex512, the configuration of the control unit ex501 is not limited to such. For example, the signal processing unit ex507 may further include a CPU. Inclusion of another CPU in the signal processing unit ex507 can improve the processing speed. Furthermore, as another example, the CPU ex502 may serve as or be a part of the signal processing unit ex507, and, for example, may include an audio signal processing unit. In such a case, the control unit ex501 includes the signal processing unit ex507 or the CPU ex502 including a part of the signal processing unit ex507.
The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.
Moreover, ways to achieve integration are not limited to the LSI, and a special circuit or a general purpose processor and so forth can also achieve the integration. Field Programmable Gate Array (FPGA) that can be programmed after manufacturing LSIs or a reconfigurable processor that allows re-configuration of the connection or configuration of an LSI can be used for the same purpose.
In the future, with advancement in semiconductor technology, a brand-new technology may replace LSI. The functional blocks can be integrated using such a technology. The possibility is that the present disclosure is applied to biotechnology.
(Embodiment 6)
When video data generated in the moving picture coding method or by the moving picture coding apparatus described in each of embodiments is decoded, compared to when video data that conforms to a conventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1 is decoded, the processing amount probably increases. Thus, the LSI ex500 needs to be set to a driving frequency higher than that of the CPU ex502 to be used when video data in conformity with the conventional standard is decoded. However, when the driving frequency is set higher, there is a problem that the power consumption increases.
In order to solve the problem, the moving picture decoding apparatus, such as the television ex300 and the LSI ex500 is configured to determine to which standard the video data conforms, and switch between the driving frequencies according to the determined standard.
More specifically, the driving frequency switching unit ex803 includes the CPU ex502 and the driving frequency control unit ex512 in
Furthermore, along with the switching of the driving frequencies, the power conservation effect can be improved by changing the voltage to be applied to the LSI ex500 or an apparatus including the LSI ex500. For example, when the driving frequency is set lower, the voltage to be applied to the LSI ex500 or the apparatus including the LSI ex500 is probably set to a voltage lower than that in the case where the driving frequency is set higher.
Furthermore, when the processing amount for decoding is larger, the driving frequency may be set higher, and when the processing amount for decoding is smaller, the driving frequency may be set lower as the method for setting the driving frequency. Thus, the setting method is not limited to the ones described above. For example, when the processing amount for decoding video data in conformity with MPEG-4 AVC is larger than the processing amount for decoding video data generated by the moving picture coding method and the moving picture coding apparatus described in each of embodiments, the driving frequency is probably set in reverse order to the setting described above.
Furthermore, the method for setting the driving frequency is not limited to the method for setting the driving frequency lower. For example, when the identification information indicates that the video data is generated by the moving picture coding method and the moving picture coding apparatus described in each of embodiments, the voltage to be applied to the LSI ex500 or the apparatus including the LSI ex500 is probably set higher. When the identification information indicates that the video data conforms to the conventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1, the voltage to be applied to the LSI ex500 or the apparatus including the LSI ex500 is probably set lower. As another example, when the identification information indicates that the video data is generated by the moving picture coding method and the moving picture coding apparatus described in each of embodiments, the driving of the CPU ex502 does not probably have to be suspended. When the identification information indicates that the video data conforms to the conventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1, the driving of the CPU ex502 is probably suspended at a given time because the CPU ex502 has extra processing capacity. Even when the identification information indicates that the video data is generated by the moving picture coding method and the moving picture coding apparatus described in each of embodiments, in the case where the CPU ex502 has extra processing capacity, the driving of the CPU ex502 is probably suspended at a given time. In such a case, the suspending time is probably set shorter than that in the case where when the identification information indicates that the video data conforms to the conventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1.
Accordingly, the power conservation effect can be improved by switching between the driving frequencies in accordance with the standard to which the video data conforms. Furthermore, when the LSI ex500 or the apparatus including the LSI ex500 is driven using a battery, the battery life can be extended with the power conservation effect.
(Embodiment 7)
There are cases where a plurality of video data that conforms to different standards, is provided to the devices and systems, such as a television and a cellular phone. In order to enable decoding the plurality of video data that conforms to the different standards, the signal processing unit ex507 of the LSI ex500 needs to conform to the different standards. However, the problems of increase in the scale of the circuit of the LSI ex500 and increase in the cost arise with the individual use of the signal processing units ex507 that conform to the respective standards.
In order to solve the problem, what is conceived is a configuration in which the decoding processing unit for implementing the moving picture decoding method described in each of embodiments and the decoding processing unit that conforms to the conventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1 are partly shared. Ex900 in
Furthermore, ex1000 in
As such, reducing the scale of the circuit of an LSI and reducing the cost are possible by sharing the decoding processing unit for the processing to be shared between the moving picture decoding method according to the aspect of the present disclosure and the moving picture decoding method in conformity with the conventional standard.
Industrial Applicability
The image coding apparatus and the image decoding apparatus according to an aspect of the present disclosure are applicable to television receivers, digital video recorders, car navigation systems, mobile phones, digital cameras, or digital video cameras, for example.
Claims
1. A decoding method for decoding last position information indicating a horizontal position and a vertical position of a last non-zero coefficient in a predetermined order within a current block to be decoded, the current block being included in a picture and including a plurality of coefficients, the decoding method comprising:
- obtaining a bitstream including a first partial signal, a second partial signal, a third partial signal, and a fourth partial signal, in this order;
- performing first arithmetic decoding on the first partial signal and the third second partial signal respectively to obtain a decoded first partial signal and a decoded third second partial signal, the first arithmetic decoding being context adaptive arithmetic decoding using a variable probability that is updated based on decoded last position information of a decoded block different from the current block;
- generating a first flag that indicates when the decoded first partial signal is greater than or equal to a predetermined value;
- generating a second flag that indicates when the decoded second partial signal is greater than or equal to the predetermined value;
- when the first flag is generated, performing second arithmetic decoding on the second third partial signal, and when the second flag is generated, performing second arithmetic decoding on the fourth partial signal, respectively, to obtain a decoded second third partial signal and a decoded fourth partial signal, the second arithmetic decoding being bypass decoding without using a fixed variable probability;
- deriving a horizontal component of the last position information indicating the horizontal position of the non-zero coefficient from the decoded first partial signal and the decoded third partial signal; and
- deriving a vertical component of the last position information indicating the vertical position of the non-zero coefficient from the decoded second partial signal and the decoded fourth partial signal; and
- reconstructing the horizontal component of the last position information and the vertical component of the last position information to provide decoded last position information for the current block in the picture.
2. A decoding apparatus which decodes last position information indicating a horizontal position and a vertical position of a last non-zero coefficient in a predetermined order within a current block to be decoded, the current block being included in a picture and including a plurality of coefficients, the decoding apparatus comprising:
- electrical processing circuitry; and
- storage coupled to the electrical processing circuitry;
- wherein the electrical processing circuitry, which includes one or more processors and one or more integrated circuits, is configured to perform the following using the storage: obtaining a bitstream including a first partial signal, a second partial signal, a third partial signal, and a fourth partial signal, in this order; performing first arithmetic decoding on the first partial signal and the third second partial signal respectively to obtain a decoded first partial signal and a decoded third second partial signal; generating a first flag that indicates when the decoded first partial signal is greater than or equal to a predetermined value; generating a second flag that indicates when the decoded second partial signal is greater than or equal to the predetermined value; when the first flag is generated, performing second arithmetic decoding on the second third partial signal and when the second flag is generated, performing second arithmetic decoding on the fourth partial signal, respectively, to obtain a decoded second third partial signal and a decoded fourth partial signal, the second arithmetic decoding being different from the first arithmetic decoding; deriving a horizontal component of the last position information indicating the horizontal position of the non-zero coefficient from the decoded first partial signal and the decoded third partial signal; and deriving a vertical component of the last position information indicating the vertical position of the non-zero coefficient from the decoded second partial signal and the decoded fourth partial signal.
3. A decoding apparatus which decodes last position information indicating a horizontal position and a vertical position of a last non-zero coefficient in a predetermined order within a current block to be decoded, the current block being included in a picture and including a plurality of coefficients, the decoding apparatus comprising:
- an obtainer configured to obtain a bitstream including a first partial signal, a second partial signal, a third partial signal, and a fourth partial signal, in this order;
- an arithmetic decoder configured to: perform a first arithmetic decoding on the first partial signal and the third second partial signal respectively to obtain a decoded first partial signal and a decoded third second partial signal; and generate a first flag that indicates when the decoded first partial signal is greater than or equal to a predetermined value; generate a second flag that indicates when the decoded second partial signal is greater than or equal to the predetermined value; when the first flag is generated, perform a second arithmetic decoding on the second third partial signal and when the second flag is generated, perform second arithmetic decoding on the fourth partial signal respectively to obtain a decoded second third partial signal and a decoded fourth partial signal, the second arithmetic decoding being different from the first arithmetic decoding; and
- a deriver configured to: derive a horizontal component of the last non-zero coefficient indicting the horizontal position of the non-zero coefficient from the decoded first partial signal and the decoded third partial signal; and derive a vertical component of the last non-zero coefficient indicting the vertical position of the non-zero coefficient from the decoded second partial signal and the decoded fourth partial signal.
4. A non-transitory computer-readable recording medium, having a computer program recorded thereon, for causing the a computer to execute the a decoding method according to claim 1, the decoding method comprising:
- obtaining a bitstream including a first partial signal, a second partial signal, a third partial signal, and a fourth partial signal, in this order;
- performing first arithmetic decoding on the first partial signal and the second partial signal respectively to obtain a decoded first partial signal and a decoded second partial signal, the first arithmetic decoding being context adaptive arithmetic decoding using a variable probability that is updated based on decoded last position information of a decoded block different from the current block;
- generating a first flag that indicates when the decoded first partial signal is greater than or equal to a predetermined value;
- generating a second flag that indicates when the decoded second partial signal is greater than or equal to the predetermined value;
- when the first flag is generated, performing second arithmetic decoding on the third partial signal, and when the second flag is generated, performing second arithmetic decoding on the fourth partial signal, respectively, to obtain a decoded third partial signal and a decoded fourth partial signal, the second arithmetic decoding being bypass decoding without using a variable probability;
- deriving a horizontal component of the last position information indicating the horizontal position of the non-zero coefficient from the decoded first partial signal and the decoded third partial signal;
- deriving a vertical component of the last position information indicating the vertical position of the non-zero coefficient from the decoded second partial signal and the decoded fourth partial signal; and
- reconstructing the horizontal component of the last position information and the vertical component of the last position information to provide decoded last position information for the current block in the picture.
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Type: Grant
Filed: Sep 29, 2016
Date of Patent: Nov 12, 2019
Assignee: SUN PATENT TRUST (New York, NY)
Inventors: Hisao Sasai (Osaka), Takahiro Nishi (Nara), Youji Shibahara (Tokyo), Toshiyasu Sugio (Osaka), Kyoko Tanikawa (Osaka), Toru Matsunobu (Osaka), Kengo Terada (Osaka)
Primary Examiner: Joseph R Pokrzywa
Application Number: 15/279,658
International Classification: G06K 9/36 (20060101); G06T 9/00 (20060101); H04N 19/184 (20140101); H04N 19/593 (20140101); H04N 19/159 (20140101);