Abstract: The demultiplexing apparatus 200 comprises a data obtainment unit 210 operable to obtain the MP4 file data 100, a decoding unit 213 operable to demultiplex the MP4 file data 100 obtained by the data obtainment unit 210 into pairs of a moov 110 and a mdat 110 and pairs of a moof 130 and a mdat 140, and decode those pairs pair by pair, a content duration specification unit 211a operable to specify the content total duration based on the content total duration information contained in the moov 110 of the MP4 file data 100 obtained by the data obtainment unit 210 and a playback unit 214 operable to display content total duration specified by the content duration specification unit 211a.

Abstract: A packet compressor 12 operates under a reliable mode or an optimistic mode. A mode determination unit 31 counts the number of ACK packets or NACK packets received by a unit time X by an ACK/NACK packet receiver 14. When the counted number of NACK packets is larger than a predetermined value Y, the mode determination unit 31 switches the operation mode of the packet compressor 12 to the reliable mode. When the counted number of ACK packets is larger than a predetermined value Z, the mode determination unit 31 switches the operation mode of the packet compressor 12 to the optimistic mode.

Abstract: A packet compressor 12 operates under a reliable mode or an optimistic mode. A mode determination unit 31 counts the number of ACK packets or NACK packets received by a unit time X by an ACK/NACK packet receiver 14. When the counted number of NACK packets is larger than a predetermined value Y, the mode determination unit 31 switches the operation mode of the packet compressor 12 to the reliable mode. When the counted number of ACK packets is larger than a predetermined value Z, the mode determination unit 31 switches the operation mode of the packet compressor 12 to the optimistic mode.

Abstract: A picture counter 205 counts and outputs the number of pictures input from the beginning of communication. A coding controlling section 206 outputs coding scheme information for controlling a coding apparatus to perform intra-coding when a counted value on the picture counter 205 is equal to or less than a predetermined value (N), and outputs coding scheme information for motion compensation prediction scheme when the counted value is more than N. Moreover, when the counted value is equal to and less than (N?1), the coding controlling section 206 outputs a signal for controlling a quantization section 210 to make the value of a quantization parameter large to the quantization section 210, and when the counted value is N, the coding controlling section 206 outputs a signal for controlling the quantization section 210 to make the quantization parameter small to the quantization section 210.

Abstract: In a header decompression apparatus 709, a header decompressor 703 refers to reference information stored in a reference information manager 707 to decompress a compressed header of a packet received by a packet receiver 704. An error detector 702 detects a CRC error in the packet with its header decompressed by the packet receiver 704, and outputs only a correct packet. A successive error counter 705 counts the number of successive errors detected by the error detector 702. A successive decompression success counter 706 counts the number of decompression successes that successively appear. By referring to these counted numbers, an update request unit 708 transmits an update request to a transmitting side as required. A reference information manager 707 manages the reference information for header decompression. With this structure, the header decompression apparatus can request update of the reference information based on the state of the error.

Abstract: When an RTP packet generating section outputs a retransmission request signal to a compression method selecting section, the compression method selecting section compares a sequence number of a retransmission packet with a sequence number of context stored in a buffer. When the sequence number of the retransmission packet is smaller than the sequence number of the context, the compression method selecting section selects, as a header of the retransmission packet, a header which is decompressed not referring to reference information and is not used in updating the reference information in a communicating party.

Abstract: When an update request signal is output from update request signal receiver 108 to compression scheme selector 201, compression scheme selector 201 selects UPDATE_FULLHEADER. However, compression method selector 201, within an RTT after selecting an UPDATE_FULLHEADER, does not select an UPDATE_FULLHEADER again. That is, within an RTT after transmitting an UPDATE_FULLHEADER a packet transmitting apparatus does not transmit an UPDATE_FULLHEADER even upon receiving an update request signal, and selects NON_UPDATE or UPDATE as usual.

Abstract: The present invention relates to a code amount control apparatus and code amount control method that changes a code amount of an image to a predetermined value for a short processing time. A determining section (352) compares a generated code amount output from a coding section (310) with a designated code amount and determines whether the code amount of encoded data encoded by the coding section (310) is larger than the designated code amount. A linear line deciding section (354) decides a linear line (namely, linear function) of a square of the generated code amount and a reciprocal of a parameter from a predetermined fixed point, the square of the generated code amount output from the coding section (310) and the reciprocal of the parameter output from a parameter calculating section (320) on two-dimensional coordinates. A modified parameter calculating section (356) calculates a modified parameter corresponding to the designated code amount from the decided linear line (linear function).

Abstract: Update request signal generator 107 generates an update request signal when an NG signal is output from CRC section 104 a predetermined number of times, continuously. More specifically, update request signal generator 107 comprises a counter that counts the number of times errors are detected, increments the counter by 1 every time an NG signal is output from CRC section 104, and resets the counter when an OK signal is output from CRC section 104 or every time the value on the counter reaches a predetermined number of times. Then, update request signal generator 107 generates an update request signal when the value on the counter reaches the predetermined number of times.

Abstract: When an error is detected in a received header, in estimating reference information while assuming an error in a packet receiving interval, a header is decompressed using at least one value of another candidate sequence numbers used in correcting an erroneous sequence number, corresponding to a time that elapses between previously receiving a packet correctly and receiving a current packet and to the packet receiving internal. It is thereby possible to increase a possibility of estimating the reference information correctly and suppress the number of discarded packets at a receiving side, while suppressing increases in introduced processing amount in data transmission with header compression.

Abstract: Method, transmitter and system for transmitting compressed header data in a packet stream from a transmitter to a receiver, the header data including a header data item, wherein the method comprises estimating a time period needed for performing a re-initialization process for reinitializing a value of said header data item, determining a time for starting the re-initialization process, the determined time being based on the estimated time period and starting the re-initialization process at the determined time.

Abstract: The present invention provides a variable-length encoding and decoding apparatus which, when an overlap of a variable-length code and a synchronizing word is generated on a bit stream due to a transmission error or the like in the variable-length encoding and decoding apparatus of an image compression bit stream, can exactly detect the synchronizing word and a state where the overlap is generated.

Abstract: A file creating device 201 includes (1) a data input unit 202 that receives audio data from outside and outputs digital audio data, (2) an encoding unit 203 that encodes the digital audio data, creates one access unit by putting together encoded samples so as to keep the size of all the access units same in a byte unit, and outputs the access units to a file output unit 205, (3) a format creating unit 204 that acquires format information from the encoding unit 203, creates header information of an MP4 file, and outputs the header information to the file output unit 205, and (4) the file output unit 205 that creates an access unit train by multiplexing the access units acquired from the encoding unit 203, and outputs the MP4 file by combining the access unit train and the header information acquired from the format creating unit 204.

Abstract: A data reproduction apparatus comprises a data request unit for requesting a server to transmit data; a reception buffer for holding received data; a control unit for detecting the beginning position of AV data, and instructing a decoding unit to start decoding of the AV data when the amount of data stored in the reception buffer has reached a set value after detection of the beginning position position; a decoding unit for decoding the AV data stored in the reception buffer; a clock circuit for outputting a clock signal; and a display unit for displaying the decoded data. Since the AV data of the size required for data reproduction can be reliably pre-buffered when receiving the data, stable data reproduction can be carried out.

Abstract: SN examine section 101 monitors transmission data by way of monitoring an SN per packet, compares the SN in a packet that is to be transmitted with the SN in an immediately preceding packet, and outputs the comparison result to CID selection section 102 with transmission data. CID selection section 102 selects a CID based on the comparison result output from SN examination section 101 and appends the CID to the transmission data, and outputs the transmission data to header compression section 104. CRC bit calculation section 103 calculates a CRC bit from the header information. Header compression section 104 determines on a header compression format, compresses a header that contains an SN and a CRC bit, and connects the header with transmission data and transmit this to transmission section 106. Transmission packet storing section 105 that stores transmitted packets.

Abstract: When a received packet contains static information and a CRC section 104 detects an error, the static information alone will be read from a buffer 106 and replace the static information of the received packet. A header reproduction section 107 once again reproduces a header, and upon this reproduced header the CRC section 104 performs CRC. If a bit error is detected, the received packet will be discarded. If no error is detected, determining that the bit error was in the static information portion in the header of the received packet, the packet in which the static information has been replaced will be output as a received packet.

Abstract: A data communication system capable of eliminating the retransmission of useless data that is too late for the playback time at the receiving side, and, accordingly, capable of eliminating the wasteful utilization of transmission band. In the system, round-trip time RTT of a packet between the server (data transmitting apparatus) 100 and the terminal apparatus (data receiving apparatus) 200 is calculated, and only when the sum of the round-trip time RTT and present time is less than the playback time of the packet, retransmission request for lost packet which has high priority is made.

Abstract: Received packets are preserved in a receiving buffer 102; a playback decision section 103 decides whether the preserved packets are in time for the playback time or not; the playback orders and the preservation addresses of the preserved packets which have been decided to be in time are memorized in a pointer 104 for playback; the preserved packets are read and played back according to the pointer 104 for playback. And, the playback orders and the preservation addresses of the preserved packets are memorized in a pointer 106 for preservation; and a media conversion section 107 reads the preserved packets according to the pointer 106 for preservation, and memorizes them after conversion into packets with a form by which the packets may be memorized in a preservation memory 108.

Abstract: An output controller 104 outputs coded data included in a packet arrived later than reproduction and display timing designated by a timestamp to a decoding section 105 together with coded data included in a packet designated by a timestamp next to the above timestamp. The decoding section 105 first decodes coded data included in the packet arrived later and updates the reproduced image that is one earlier than the above decoded reproduced image to the above decoded reproduced image, then decoding coded data included in the packet arrived before reproduction and display timing designated by the timestamp.

Abstract: In a bit counter 214, an amount of codes included in one transmission unit is counted; in a significance decision section 217, the amount of codes counted in the bit counter 214 is divided by the number of coded macroblocks included in the one transmission unit to calculate an average amount of codes per one coded macroblocks; and in a threshold comparing section 220, the significance of the pertinent transmission unit is decided by comparing the average amount of codes to the calculated threshold based on a frame rate and a bit rate.