Abstract: A block transform-based digital media codec has a signaling scheme and bitstream syntax to flexibly signal that truncation of less significant information bits of transform coefficients coded as an optional layer of the bitstream has been performed adaptively per region or tile of the image.

Abstract: Techniques and tools for encoding and decoding a block of frequency coefficients are presented. An encoder selects a scan order from multiple available scan orders and then applies the selected scan order to a two-dimensional matrix of transform coefficients, grouping non-zero values of the frequency coefficients together in a one-dimensional string. The encoder entropy encodes the one-dimensional string of coefficient values according to a multi-level nested set representation. In decoding, a decoder entropy decodes the one-dimensional string of coefficient values from the multi-level nested set representation. The decoder selects the scan order from among multiple available scan orders and then reorders the coefficients back into a two-dimensional matrix using the selected scan order.

Abstract: Techniques and tools for switching distortion metrics during motion estimation are described. For example, a video encoder determines a distortion metric selection criterion for motion estimation. The criterion can be based on initial results of the motion estimation. To evaluate the criterion, the encoder can compare the criterion to a threshold that depends on a current quantization parameter. The encoder selects between multiple available distortion metrics, which can include a sample-domain distortion metric (e.g., SAD) and a transform-domain distortion metric (e.g., SAHD). The encoder uses the selected distortion metric in the motion estimation. Selectively switching between SAD and SAHD provides rate-distortion performance superior to using only SAD or only SAHD. Moreover, due to the lower complexity of SAD, the computational complexity of motion estimation with SAD-SAHD switching is typically less than motion estimation that always uses SAHD.

Abstract: A decoder processes a first bitstream element (e.g., a pull-down flag) in a first syntax layer (e.g., sequence layer or entry point layer) above frame layer in a bitstream for a video sequence, the bitstream comprising encoded source video having a source type (e.g., progressive or interlace). The decoder processes frame data in a second syntax layer (e.g., frame layer) of the bitstream for a frame (such as an interlaced frame or progressive frame, depending on source type, or a skipped frame) in the video sequence. The first bitstream element indicates whether a repeat-picture element (e.g., a repeat-frame element or a repeat field-element) is present or absent in the frame data in the second syntax layer.

Abstract: Filter taps for filters are specified by filter coefficient parameters. The filter taps are greater in number than the coefficient parameters from which the filter taps are calculated. For example, two coefficient parameters are used to specify a four-tap filter. Filter information can be signaled in a bitstream, such as by signaling one or more family parameters for a filter family and, for each filter in a family, signaling one or more filter tap parameters from which filter taps can be derived. Family parameters can include a number of filters parameter, a resolution parameter, a scaling bits parameter, and/or a full integer position filter present parameter that indicates whether or not the filters include an integer position filter. Filter parameters can be signaled and used to determine coefficient parameters from which filter taps are calculated.

Abstract: A video codec efficiently signals that a frame is identical to its reference frame, such that separate coding of its picture content is skipped. Information that a frame is skipped is represented jointly in a coding table of a frame coding type element for bit rate efficiency in signaling. Further, the video codec signals the picture type (e.g., progressive or interlaced) of skipped frames, which permits different repeat padding methods to be applied according to the picture type.

Abstract: Techniques and tools are described for compensating for rounding when estimating sample-domain distortion in the transform domain. For example, a video encoder estimates pixel-domain distortion in the transform domain for a block of transform coefficients after compensating for rounding in the DC coefficient of the block. In this way, the video encoder improves the accuracy of pixel-domain distortion estimation but retains the computational advantages of performing the estimation in the transform domain. Rounding compensation includes, for example, looking up an index (from a de-quantized transform coefficient) in a rounding offset table to determine a rounding offset, then adjusting the coefficient by the offset. Other techniques and tools described herein are directed to creating rounding offset tables and encoders that make encoding decisions after considering rounding effects that occur after an inverse frequency transform on de-quantized transform coefficient values.

Abstract: Techniques and tools are described for flexible range reduction of samples of video. For example, an encoder signals a first set of one or more syntax elements for range reduction of luma samples and signals a second set of one or more syntax elements for range reduction of chroma samples. The encoder selectively scales down the luma samples and chroma samples in a manner consistent with the first syntax element(s) and second syntax element(s), respectively. Or, an encoder signals range reduction syntax element(s) in an entry point header for an entry point segment, where the syntax element(s) apply to pictures in the entry point segment. If range reduction is used for the pictures, the encoder scales down samples of the pictures. Otherwise, the encoder skips the scaling down. A decoder performs corresponding parsing and scaling up operations.

Abstract: Techniques and tools are described for compensating for rounding when estimating sample-domain distortion in the transform domain. For example, a video encoder estimates pixel-domain distortion in the transform domain for a block of transform coefficients after compensating for rounding in the DC coefficient of the block. In this way, the video encoder improves the accuracy of pixel-domain distortion estimation but retains the computational advantages of performing the estimation in the transform domain. Rounding compensation includes, for example, looking up an index (from a de-quantized transform coefficient) in a rounding offset table to determine a rounding offset, then adjusting the coefficient by the offset. Other techniques and tools described herein are directed to creating rounding offset tables and encoders that make encoding decisions after considering rounding effects that occur after an inverse frequency transform on de-quantized transform coefficient values.

Abstract: Rules for the signaling and interpretation of chroma position are described. One rule, called the short rule, defines fifteen discrete chroma centering positions and corresponding four-bit syntax element. Another rule, called the extended rule, defines 81 discrete chroma centering positions and corresponding seven-bit syntax elements. A described method includes receiving digital media data at a digital media encoder, determining chroma position information for the received digital media data, and representing the chroma position information with one or more syntax elements in an encoded bitstream. The one or more syntax elements are operable to communicate the chroma position information to a digital media decoder. The chroma position information facilitates an image rotation or flip.

Abstract: Techniques and tools are described for flexible range reduction of samples of video. For example, an encoder signals a first set of one or more syntax elements for range reduction of luma samples and signals a second set of one or more syntax elements for range reduction of chroma samples. The encoder selectively scales down the luma samples and chroma samples in a manner consistent with the first syntax element(s) and second syntax element(s), respectively. Or, an encoder signals range reduction syntax element(s) in an entry point header for an entry point segment, where the syntax element(s) apply to pictures in the entry point segment. If range reduction is used for the pictures, the encoder scales down samples of the pictures. Otherwise, the encoder skips the scaling down. A decoder performs corresponding parsing and scaling up operations.

Abstract: Techniques and tools for intensity compensation for interlaced forward-predicted fields are described. For example, a video decoder receives and decodes a variable length code that indicates which of two reference fields for an interlaced forward-predicted field use intensity compensation (e.g., both, only the first, or only the second). The decoder performs intensity compensation on each of the two reference fields that uses intensity compensation. A video encoder performs corresponding intensity estimation/compensation and signaling.

Abstract: A decoder receives an entry point header comprising plural control parameters for an entry point segment corresponding to the entry point header. The entry point header is in an entry point layer of a bitstream comprising plural layers. The decoder decodes the entry point header. The plural control parameters can include various combinations of control parameters such as a pan scan on/off parameter, a reference frame distance on/off parameter, a loop filtering on/off parameter, a fast chroma motion compensation on/off parameter, an extended range motion vector on/off parameter, a variable sized transform on/off parameter, an overlapped transform on/off parameter, a quantization decision parameter, and an extended differential motion vector coding on/off parameter, a broken link parameter, a closed entry parameter, one or more coded picture size parameters, one or more range mapping parameters, a hypothetical reference decoder buffer parameter, and/or other parameter(s).

Abstract: A decoder receives a field start code for an entry point key frame. The field start code indicates a second coded interlaced video field in the entry point key frame following a first coded interlaced video field in the entry point key frame and indicates a point to begin decoding of the second coded interlaced video field. The first coded interlaced video field is a predicted field, and the second coded interlaced video field is an intra-coded field. The decoder decodes the second field without decoding the first field. The field start code can be followed by a field header. The decoder can receive a frame header for the entry point key frame. The frame header may comprise a syntax element indicating a frame coding mode for the entry point key frame and/or a syntax element indicating field types for the first and second coded interlaced video fields.

Abstract: Techniques and tools for coding/decoding of digital video, and in particular, for determining, signaling and detecting entry points in video streams are described. Techniques and tools described herein are used to embed entry point indicator information in the bitstream that receivers, editing systems, insertion systems, and other systems can use to detect valid entry points in compressed video.

Abstract: Embodiments for implementing a speech recognition system that includes a speech classifier ensemble are disclosed. In accordance with one embodiment, the speech recognition system includes a classifier ensemble to convert feature vectors that represent a speech vector into log probability sets. The classifier ensemble includes a plurality of classifiers. The speech recognition system includes a decoder ensemble to transform the log probability sets into output symbol sequences. The speech recognition system further includes a query component to retrieve one or more speech utterances from a speech database using the output symbol sequences.

Abstract: Described tools and techniques relate to signaling for DC coefficients at small quantization step sizes. The techniques and tools can be used in combination or independently. For example, a tool such as a video encoder or decoder processes a VLC that indicates a DC differential for a DC coefficient, a FLC that indicates a value refinement for the DC differential, and a third code that indicates the sign for the DC differential. Even with the small quantization step sizes, the tool uses a VLC table with DC differentials for DC coefficients above the small quantization step sizes. The FLCs for DC differentials have lengths that vary depending on quantization step size.

Abstract: Described tools and techniques relate to signaling for DC coefficients at small quantization step sizes. The techniques and tools can be used in combination or independently. For example, a tool such as a video encoder or decoder processes a VLC that indicates a DC differential for a DC coefficient, a FLC that indicates a value refinement for the DC differential, and a third code that indicates the sign for the DC differential. Even with the small quantization step sizes, the tool uses a VLC table with DC differentials for DC coefficients above the small quantization step sizes. The FLCs for DC differentials have lengths that vary depending on quantization step size.

Abstract: Entropy coding and decoding techniques are described, which may be implemented separately or in combination. For example, a video encoder uses two-layer run level coding to reduce bitrate for frequency transform coefficients in a quick and efficient manner, and a video decoder uses corresponding two-layer run level decoding. This two-layer coding/decoding can be generalized to more than two layers of run level coding/decoding. The video encoder and decoder exploit common patterns in run level information to reduce code table size and create opportunities for early termination of decoding. Using zoned Huffman code tables helps limit overall table size while still providing a level of adaptivity in encoding and decoding. Using embedded Huffman code tables allows the encoder and decoder to reuse codes for 8×8, 8×4, 4×8, and 4×4 blocks.

Abstract: A method is described for efficiently determining total end-to-end distortion of a pre-compressed data stream, such as video streams or other media streams, at the time of delivery over a lossy-network, and for providing adaptive error-resilient delivery schemes based on distortion estimates. The methods can be utilized with single or multilayer packet streams and are particularly well suited for video streams. By way of example, distortion estimates are performed by generating side-information at the time of data stream compression, wherein the side-information is used in conjunction with information about the network status to determine an estimated distortion for the group of packets when the data stream is transported over the network to a destination end. This estimation may be utilized within described resiliency techniques in which the error correction mechanism is selected in response to the estimated distortion, which may be additionally refined in reference to cost factors.