Abstract: This disclosure relates to techniques for reducing a cost of coding prediction information in video coding. Video blocks in a generalized P/B (GPB) frame are encoded using up to two motion vectors calculated from reference pictures in two separate reference picture lists that are identical. Video blocks of a GPB frame may, therefore, be encoded using a bidirectional prediction mode with a first motion vector from a reference picture in a first reference picture list and a second motion vector from the same or substantially similar reference picture in a second reference picture list. The techniques include jointly coding the first and second motion vectors for a video block of a GPB frame. The techniques include coding the first motion vector relative to a first motion predictor generated from a motion vector of a neighboring block, and coding the second motion vector relative to the first motion vector.

Abstract: This disclosure relates to techniques for reducing a cost of coding prediction information in video coding. Video blocks in a generalized P/B (GPB) frame are encoded using up to two motion vectors calculated from reference pictures in two separate reference picture lists that are identical. When one of the reference picture lists is preferred over the other reference picture list, the preferred reference picture list may be used for unidirectional prediction, by default. When a GPB frame is enabled such that the first and second reference picture lists are identical, either of the first and second reference picture lists may be used for unidirectional prediction. The techniques include coding one or more syntax elements indicating that a video block is coded using one of the unidirectional prediction mode with respect to a reference picture in a reference picture list and the bidirectional prediction mode using less than two bits.

Abstract: This disclosure describes techniques for mitigating rounding errors in a fixed-point transform associated with video coding by applying a variable localized bit-depth increase at the transform. More specifically, the techniques include selecting a constant value based on a size of a fixed-point transform in a video coding device and applying a variable localized bit-depth increase at the transform with a value equal to the constant value. Applying the variable localized bit-depth increase includes left-shifting a transform input signal by a number of bits equal to the constant value before the fixed-point transform, and right-shifting a transform output signal by a number of bits equal to the constant value after the fixed-point transform. The constant value is selected from a plurality of constant values stored on the video coding device. Each of the constant values is pre-calculated for one of a plurality of different transform sizes supported by the video coding.

Abstract: In one example, an apparatus for encoding video data includes a video encoder configured to scan a two-dimensional block of transform coefficients to produce a one-dimensional vector of the transform coefficients, determine values indicative of whether the transform coefficients in the one-dimensional vector are significant; and entropy encode at least one of the values using a context model selected based on at least a percentage of significant coefficients in a predetermined number of the values encoded before the at least one of the values.

Abstract: In one example, an apparatus for encoding video data includes a video encoder configured to select an intra-prediction mode to use to encode a block of video data, determine whether the block includes a sub-block of a size for which multiple transforms are possible based on the size of the sub-block and the selected intra-prediction mode, when the block includes the sub-block of the size for which multiple transforms are possible based on the size of the sub-block and the selected intra-prediction mode, select one of the multiple possible transforms, transform the sub-block using the selected one of the multiple possible transforms, and provide an indication of the selected one of the multiple possible transforms for the size of the block.

Abstract: In one example, an apparatus for encoding video data includes a video encoder configured to calculate a residual block for a block of video data based on a predicted block formed using an intra-prediction mode, and transform the residual block using a transform mapped from the intra-prediction mode. In another example, an apparatus includes video encoder configured to receive an indication of a first intra-prediction mode in a first set of intra-prediction modes for a block of video data, determine a second intra-prediction mode from a second set of intra-prediction modes, smaller than the first set of intra-prediction modes, to which the first intra-prediction mode is mapped, determine a directional transform to which the second intra-prediction mode is mapped, and apply the directional transform to residual data of the block.

Abstract: An asymmetric frame of a coded video bitstream may include a first resolution picture of a left view and a reduced resolution picture of a right view, where the left and right views form a stereo view pair for three-dimensional video playback. In addition, the reduced resolution frame may be predicted relative to a picture of the left view. In one example, an apparatus includes a video encoder configured to encode a first picture of a first view of a scene to produce an encoded picture with a first resolution, encode at least a portion of a second picture of a second view of the scene relative to a reference picture of the first view to produce an encoded picture with a reduced resolution relative to the first resolution, and output the encoded first resolution picture and the encoded reduced resolution picture in a common bitstream.

Abstract: A video block syntax element indicates whether all of the partitions of a video block are predicted based on a same reference list and no greater than quarter-pixel accuracy is used. If the video block syntax element is set, partition-level signaling of the reference lists is avoided. If the video block syntax element is not set, partition-level signaling of the reference lists occurs. If the video block syntax element is set, partition-level syntax elements may be used for each of the partitions of the video block, wherein the partition-level syntax elements each identify one of the reference lists and motion vector accuracy for a given one of the partitions.

Abstract: A video encoder may encode video data by adaptively selecting between one-eighth-pixel and one-quarter-pixel precision motion vectors, and signal the selected precision. In one example, an apparatus includes a video encoder to encode a block of video data using a one-eighth-pixel precision motion vector when use of the one-eighth-pixel precision motion vector is determined to be preferable for the block over a one-quarter-pixel precision motion vector, and to generate a signal value indicative of the use of the one-eighth-pixel precision motion vector for the block, and an output interface to output the encoded block and the signal value. A video decoder may be configured to receive the signal value and the encoded block, analyze the signal value to determine whether the block was encoded using one-eighth-pixel precision or one-quarter-pixel precision, and decode the block based on the determination.

Abstract: In one example, an apparatus includes a video encoder configured to partition a block of video data into a first partition and a second partition using a geometric motion partition line, calculate a slope value and a y-intercept value of the geometric motion partition line, wherein the slope value and the y-intercept value comprise integer values, calculate a mask indicative of pixels of the block in the first partition and pixels of the block in the second partition, encode the first partition and the second partition based on the mask, and output the encoded first partition, the encoded second partition, the slope value, and the y-intercept value. This may allow for a fixed point implementation. A video decoder may receive the slope and y-intercept values to calculate the mask and decode the block based on the mask.

Abstract: In one example, an apparatus includes a video encoder configured to partition a block of video data into a first partition and a second partition using a geometric motion partition line, determine a first motion vector for the first partition and a second motion vector for the second partition, encode the first motion vector based on a first motion predictor selected from motion vectors for blocks neighboring the first partition, encode the second motion vector based on a second motion predictor selected from motion vectors for blocks neighboring the second partition, wherein the blocks neighboring the second partition are determined independently of the blocks neighboring the first partition, and output the encoded first and second motion vectors. A video decoder may similarly decode the motion vectors based on determining the first and second motion predictors for the first and second partitions.

Abstract: A video coding unit may be configured to encode or decode chrominance blocks of video data by reusing motion vectors for corresponding luminance blocks. A motion vector may have greater precision for chrominance blocks than luminance blocks, due to downsampling of chrominance blocks relative to corresponding luminance blocks. The video coding unit may interpolate values for a reference chrominance block by selecting interpolation filters based on the position of the pixel position pointed to by the motion vector. For example, a luminance motion vector may have one-quarter-pixel precision and a chrominance motion vector may have one-eighth-pixel precision. There may be interpolation filters associated with the quarter-pixel precisions. The video coding unit may use interpolation filters either corresponding to the pixel position or neighboring pixel positions to interpolate a value for the pixel position pointed to by the motion vector.

Abstract: In one example, an apparatus includes a video encoder configured to partition a block of video data into a first partition and a second partition using a geometric motion partition line, calculate a prediction value of a pixel in a transition region of the block using a filter that applies a value for at least one neighboring pixel from the first partition and a value for at least one neighboring pixel from the second partition, calculate a residual value of the pixel in the transition region of the block based on the prediction value of the pixel in the transition region, and output the residual value of the pixel. In one example, a video decoder may use a similar filter to decode an the encoded block after receiving the residual value for the encoded block, and using a definition of the geometric motion partition line.

Abstract: In one example, an apparatus includes a video encoder configured to partition a block of video data into a first geometric partition and a second geometric partition using a geometric motion partition line, wherein the block comprises N×N pixels, divide the block of video data into four equally-sized, non-overlapping (N/2)×(N/2) sub-blocks, and encode at least one of the sub-blocks through which the geometric motion partition line passes using a transform size smaller than (N/2)×(N/2). The video encoder may determine transform sizes for the sub-blocks based on whether the geometric motion partition line passes through the sub-blocks. In one example, a video decoder may inverse transform the sub-blocks, and may determine transform sizes for the sub-blocks based on whether the geometric motion partition line passes through the sub-blocks.

Abstract: A video coder may utilize large macroblocks having more than 16×16 pixels. Syntax for the large macroblocks may define whether a bitstream includes large macroblocks, such as superblocks having 64×64 pixels or bigblocks having 32×32 pixels. The syntax may be included in a slice header or a sequence parameter set. The large macroblocks may also be encoded according to a large macroblock syntax. The bitstream may further include syntax data that indicates a level value based on whether the bitstream includes any of the large macroblocks, for example, as a smallest-sized luminance prediction block. A decoder may use the level value to determine whether the decoder is capable of decoding the bitstream.

Abstract: Some embodiments comprise a method of decoding a video bitstream that include receiving a first layer of data and a second layer of data, combining the received first layer data and the received second layer data, and decoding the combined data. Also, a method of video encoding that includes selecting data for encoding in a first layer and a second layer so as to allow decoding of the data in a single combined layer, and encoding the selected data in the first layer and in the second layer by encoding a coefficient in the first layer and encoding a differential refinement to the first layer coefficient in the second layer.

Abstract: Methods and apparatus for efficient encoding multimedia data, such as live video streams are disclosed. The multimedia data is pre-encoded into multiple layers and characteristics of the pre-encoded data are determined. Based at least in part on the determined characteristics, the multimedia data is encoded into multiple layers.

Abstract: Source and destination video devices may use data structures that signal details of an operation point for an MPEG-2 (Motion Picture Experts Group) System bitstream. In one example, an apparatus includes a multiplexer that constructs a data structure corresponding to a multiview video coding (MVC) operation point of an MPEG-2 (Motion Picture Experts Group) System standard bitstream, wherein the data structure signals a rendering capability value that describes a rendering capability to be satisfied by a receiving device to use the MVC operation point, a decoding capability value that describes a decoding capability to be satisfied by the receiving device to use the MVC operation point, and a bitrate value that describes a bitrate of the MVC operation point, and that includes the data structure as part of the bitstream, and an output interface that outputs the bitstream comprising the data structure.

Abstract: In one aspect of this disclosure, rounding adjustments to bi-directional predictive data may be purposely eliminated to provide predictive data that lacks any rounding bias. In this case, rounded and unrounded predictive data may both be considered in a rate-distortion analysis to identify the best data for prediction of a given video block. In another aspect of this disclosure, techniques are described for selecting among default weighted prediction, implicit weighted prediction, and explicit weighted prediction. In this context, techniques are also described for adding offset to prediction data, e.g., using the format of explicit weighted prediction to allow for offsets to predictive data that is otherwise determined by implicit or default weighted prediction.

Abstract: In one aspect of this disclosure, techniques are described for selecting among default weighted prediction, implicit weighted prediction, and explicit weighted prediction. In this context, techniques are also described for adding offset to prediction data, e.g., using the format of explicit weighted prediction to allow for offsets to predictive data that is otherwise determined by implicit or default weighted prediction.