Abstract: A video codec provides efficient repeat padding of hybrid video sequences having arbitrary video resolution. The video codec repeat pads to expand the active content of pictures in the video sequence out to meet an adaptive vertical macroblock alignment restriction that varies by picture type. For progressive type pictures, the video codec repeats the last row or horizontal boundary edge of the active content. For interlaced type pictures, the video coded repeats the last two rows (last row of each interlaced field) of the active content. This repeat padding differing by picture type provides a better prediction (lower prediction error residual) for macroblocks in following predicted frames whose motion vector points into the padded region.

Abstract: At high bit rates, the reconstruction error of compressed video is generally proportional to the squared value of quantization step size, such that full quantization step size increments at high bit rates can lead to significant change in the reconstruction error and/or bit rate of the compressed video. A video codec uses fractional increments of quantization step size at high bit rates to permit a more continuous variation of quality and/or bit rate as the quantization scale changes. For high bit rate scenarios, the bit stream syntax includes an additional syntax element to specify fractional step increments (e.g., half step) of the normal quantizer scale step sizes.

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: An encoder/decoder obtains pixel data from one or more field lines associated with a first block in an interlaced frame coded picture comprising plural macroblocks each having an equal number of top and bottom field lines. The encoder/decoder obtains pixel data from one or more field lines associated with a second block and performs in-loop deblocking filtering across a boundary. The in-loop deblocking filtering comprises filter operations performed on pixel data from field lines of same polarity only. In another aspect, an encoder/decoder obtains transform size information for plural blocks of macroblock, obtains field/frame type information for the macroblock and selects one or more boundaries for in-loop deblocking based at least in part on the transform size information and the field/frame type information. In-loop deblocking can be performed on horizontal block boundaries prior to vertical block boundaries.

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: In one aspect, for a first interlaced video frame in a video sequence, a decoder decodes a bitplane signaled at frame layer for the first interlaced video frame. The bitplane represents field/frame transform types for plural macroblocks of the first interlaced video frame. For a second interlaced video frame in the video sequence, for each of at least one but not all of plural macroblocks of the second interlaced video frame, the decoder processes a per macroblock field/frame transform type bit signaled at macroblock layer. An encoder performs corresponding encoding.

Abstract: Techniques and tools for code table selection and joint coding/decoding of macroblock mode information for macroblocks of interlaced forward-predicted frames are described. For example, a video decoder decodes a variable length code that jointly signals macroblock mode information for a motion-compensated macroblock. The jointly signaled information includes a macroblock type, whether a coded block pattern is present or absent, and whether motion vector data is present or absent for the motion-compensated macroblock. A video encoder performs corresponding encoding.

Abstract: In one aspect, an encoder/decoder selects a bitplane mode from a group of plural available bitplane modes, and processes a bitplane according to the selected bitplane mode, wherein the bitplane indicates AC prediction status information for plural macroblocks of a video picture. In another aspect, an encoder encodes a bitplane that indicates AC prediction status information for plural macroblocks of a video picture and signals the encoded bitplane. In another aspect, a decoder receives an encoded bitplane and decodes the bitplane, wherein the bitplane indicates AC prediction status information for plural macroblocks of a video picture.

Abstract: In one aspect, an encoder/decoder receives information for four field motion vectors for a macroblock in an interlaced frame-coded, forward-predicted picture and processes the macroblock using the four field motion vectors. In another aspect, an encoder/decoder determines a number of valid candidate motion vectors and calculates a field motion vector predictor. The encoder/decoder does not perform a median operation on the valid candidates if there are less than three of them. In another aspect, an encoder/decoder determines valid candidates, determines field polarities for the valid candidates, and calculates a motion vector predictor based on the field polarities. In another aspect, an encoder/decoder determines one or more valid candidates, determines a field polarity for each individual valid candidate, allocates each individual valid candidate to one of two sets (e.g.

Abstract: A digital media content (e.g., image, video, audio, etc.) encoder/decoder employs a spatially varying parameter to condition the application of an overlap pre-process and post-process to adjacent transform block edges for the spatial-domain lapped transform. This conditional application of the lapped transform to sub-blocks of the digital media can be signaled on an edge, block, macro-block or other granularity. Further, a restriction on use of the conditional lapped transform based on a frame-level quantization or other bit-rate related parameter minimizes the signaling overhead impact at low bit-rates of coding.

Abstract: A video encoder/decoder implements a lapped transform by applying an overlap filter in the spatial or transform domains to transform blocks. For interlace frames whose alternating scan lines are temporally displaced, the encoder/decoder imposes a limitation on application of the overlap filter to exclude horizontal block edges between adjacent transform blocks. This limitation can be imposed in both implementations where the overlap transform is applied across all blocks of an image, as well as implementations in which the lapped transform is conditionally applied on a spatially varying basis across the image.

Abstract: A decoder decodes skipped macroblocks of an interlaced frame. Skipped macroblocks use exactly one motion vector and have no motion vector differential information, and lack residual information. The skipped macroblock signal indicates one-motion-vector coding. The skipped macroblock signal can be a compressed bitplane (in a selected bitplane coding mode) sent at frame layer in a bitstream, or an individual bit sent at macroblock layer. In another aspect, an encoder jointly encodes motion compensation type and field/frame coding type for a macroblock in an interlaced P-frame. The encoder also can jointly encode other information for the macroblock (e.g., the presence of a differential motion vector). A decoder decodes a joint code (e.g., a variable length code in a variable length code table) to obtain both motion compensation type and field/frame coding type (and potentially other information) for the macroblock.

Abstract: Techniques and tools for hybrid motion vector prediction for interlaced forward-predicted fields are described. For example, a video decoder determines an initial motion vector predictor for a motion vector of an interlaced forward-predicted field. The decoder then checks a variation condition based at least in part on a predictor polarity selection (e.g., same or opposite), the initial motion vector predictor, and neighbor motion vectors. If the variation condition is satisfied, the decoder uses one of the neighbor motion vectors as a final motion vector predictor. Otherwise, the decoder uses the initial motion vector predictor as the final motion vector predictor. A video encoder performs corresponding processing.

Abstract: A video encoder/decoder utilizes a bistream syntax that provides an independently decodable, partial picture unit, which may be in the form of a unit containing one or more contiguous rows of macroblocks (called a slice). This slice layer provides a flexible combination of error-resilience and compression efficiency. The slice layer encodes an efficient addressing mechanism (e.g., a syntax element specifying a beginning macroblock row of the slice layer), as well as an efficient mechanism to optionally retransmit picture header information. The slice layer provides decoding and reconstruction independence by disabling all forms of prediction, overlap and loop-filtering across slice-boundaries. This permits a slice coded in intra-mode to be reconstructed error-free, irrespective of errors in other regions of the picture.

Abstract: Techniques and tools for using motion vector block patterns in video encoding and decoding are described. In general, a motion vector block pattern signals the presence or absence of motion vector data for a macroblock with multiple motion vectors. For example, a video decoder decodes variable length codes that represent motion vector block patterns. Each motion vector block pattern has one bit per corresponding luminance motion vector of a macroblock with multiple luminance motion vectors, where the one bit indicates whether or not motion vector data for the corresponding luminance motion vector is signaled. A video encoder performs corresponding encoding.

Abstract: Techniques and tools for escape mode code resizing are described. For example, a video decoder receives encoded information (e.g., runs, levels) for transform coefficients of blocks. For at least some of the encoded information, the decoder decodes in an escape mode for which codes have sizes signaled on a sub-frame basis (e.g., on a per-interlaced field basis in a video frame, or on a per-slice basis in a video frame). A video encoder performs corresponding encoding and signaling.

Abstract: Techniques and tools for bitstream-controlled filtering are described. For example, a video encoder puts control information into a bitstream for encoded video. A video decoder decodes the encoded video and, according to the control information, performs post-processing filtering on the decoded video with a de-ringing and/or de-blocking filter. Typically, a content author specifies the control information to the encoder. The control information itself is post-processing filter levels, filter selections, and/or some other type of information. In the bitstream, the control information is specified for a sequence, scene, frame, region within a frame, or at some other syntax level.

Abstract: A decoder receives luma motion vector information for plural luma motion vectors for a macroblock (e.g., a 4:2:0 macroblock). The decoder derives a chroma motion vector for each of the plural luma motion vectors by performing at least one calculation on the luma motion vector information, maintaining a 1:1 ratio of chroma motion vectors to luma motion vectors for the macroblock. For example, the decoder receives four luma (frame or field) motion vectors for a macroblock and derives four chroma motion vectors for the macroblock. The deriving can comprise sub-sampling and/or rounding (e.g., using a field-based rounding table).

Abstract: With adaptive multiple quantization, a video or other digital media codec can adaptively select among multiple quantizers to apply to transform coefficients based on content or bit rate constraints, so as to improve quality through rate-distortion optimization. The switch in quantizers can be signaled at the sequence level or frame level of the bitstream syntax, or can be implicitly specified in the syntax.

Abstract: Techniques and tools are described for decoding video data having samples that have been scaled in the spatial domain. For example, a decoder receives a bit stream that includes coded video data for a current frame. The decoder processes at least one syntax element (e.g., sequence layer flag, frame layer flag) that indicates whether the current frame should be scaled up in value in a spatial domain. If so, then the samples for the current frame are scaled up in value in the spatial domain. As another example, for a reference frame used in motion compensation for a current frame, a decoder scales samples of the reference frame so the range of the reference frame matches the range of the current frame.