摘要:
An improved deblocking filter for a video encoder/decoder reduces the computation expense of evaluating deblocking conditions. The improved deblocking filter bases the decision to filter block edges on sampled statistics of edge presence and strength, and also uses information of the motion vector, coded block pattern and transform type.
摘要:
Techniques and tools for encoding and decoding video images (e.g., interlaced frames) are described. For example, a video encoder or decoder processes 4:1:1 format macroblocks comprising four 8×8 luminance blocks and four 4×8 chrominance blocks. In another aspect, fields in field-coded macroblocks are coded independently of one another (e.g., by sending encoded blocks in field order). Other aspects include DC/AC prediction techniques and motion vector prediction techniques for interlaced frames.
摘要:
Techniques and tools for encoding and decoding motion vector information for video images are described. For example, a video encoder yields an extended motion vector code by jointly coding, for a set of pixels, a switch code, motion vector information, and a terminal symbol indicating whether subsequent data is encoded for the set of pixels. In another aspect, an encoder/decoder selects motion vector predictors for macroblocks. In another aspect, a video encoder/decoder uses hybrid motion vector prediction. In another aspect, a video encoder/decoder signals a motion vector mode for a predicted image. In another aspect, a video decoder decodes a set of pixels by receiving an extended motion vector code, which reflects joint encoding of motion information together with intra/inter-coding information and a terminal symbol. The decoder determines whether subsequent data exists for the set of pixels based on e.g., the terminal symbol.
摘要:
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.
摘要:
Tools and techniques for applying scan patterns during encoding and decoding of progressive video are described. For example, a video decoder entropy decodes transform coefficients in a one-dimensional array and scans the transform coefficients into a block according to a scan pattern. The block is 8×4, and the scan pattern biases the vertical direction for at least the lowest frequency AC coefficients in the horizontal and vertical directions. Or, the block is 4×8, and the scan pattern biases the horizontal direction for at least the lowest frequency AC coefficients in the horizontal and vertical directions. A corresponding video encoder applies the scan patterns to scan transform coefficients from blocks to one-dimensional arrays.
摘要:
Techniques and tools for sub-block transform coding are described. For example, a video encoder adaptively switches between 8×8, 8×4, and 4×8 DCTs when encoding 8×8 prediction residual blocks; a corresponding video decoder switches between 8×8, 8×4, and 4×8 inverse DCTs during decoding. The video encoder may determine the transform sizes as well as switching levels (e.g., frame, macroblock, or block) in a closed loop evaluation of the different transform sizes and switching levels. The encoder and decoder may use different scan patterns for different transform sizes when scanning values from two-dimensional blocks into one-dimensional arrays, or vice versa. The encoder and decoder may use sub-block pattern codes to indicate the presence or absence of information for the sub-blocks of particular blocks.
摘要:
Techniques and tools for selecting search ranges and/or motion vector ranges during motion estimation are described. For example, a video encoder performs motion estimation constrained by a first search range, which results in multiple motion vectors. The encoder computes motion vector distribution information for the motion vectors. To compute the distribution information, the encoder can track the motion vectors in a histogram and count how many of the motion vectors fall within each of multiple intervals for the distribution information. The encoder then selects a second search range and performs motion estimation constrained by the second search range. Selecting the second search range can include selecting a motion vector range, which in some cases in effect determines the second search range.
摘要:
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).
摘要:
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.
摘要:
A request is received to play compressed video data in a reverse direction. A process identifies a most recent key frame received and decodes the most recent key frame. The process then identifies delta frames received after the most recent key frame and decodes these identified delta frames. The decoded delta frames are then played in the reverse direction. Additionally, compressed audio data can be decoded and played in the reverse direction along with the video data.