Methods and systems for compressing a video stream with minimal loss after subsampled decoding
AssigneeMicrosoft Corporation
InventorsShankar Moni, John A. Tardif
Life of this patent
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Abstract
Transcoding of a video stream to reduce the size of the video stream with little, if any, loss in video quality after subsampling. After accessing a video stream of video pictures (i.e., video frames or fields), the blocks of the video picture are each subject to matrix pre-multiplication and post-multiplication. Such matrix multiplication does degrade the video quality if subsampling was not to occur. However, the pre-multiplication and post-multiplication matrices are calculated based on the subsampling matrices that will be used to ultimately subsample the video stream such that after subsampling eventually occurs, the matrix multiplications result in minimal loss of video quality.
Claims23
In a video management system configured to receive a video stream containing one or more video pictures that are each divided into blocks, wherein the video management system is to provide a representation of the one or more video pictures to a subsample decoder for subsampling, a method of reducing the size of the one or more frames with minimal, if any, effect on the video quality generated from the one or more frames after subsampling, the method comprising the following:
- accessing a video picture that is to be provided to a video node having a subsample decoder;
- obtaining information specifying a subsampling ratio to be performed by the subsample decoder;
- and
- in response to the obtained information, for at least one block of the video picture, performing subsample transcoding of the at least one block, thereby reducing the size of the at least one block to generate at least one reduced size block in such a way that subsampled decoding the at least one reduced size block results in substantially the same reduced size image as subsampled decoding the at least one block prior to the subsample transcoding, wherein reducing the size of the block includes the following:
- representing the block as a matrix;
- pre-multiplying the block matrix by a pre-multiplication matrix, the pre-multiplication matrix generated from a first subsample matrix that represents the subsampled decoding in a first direction;
- and
- post-multiplying the block matrix by a post-multiplication matrix generated from a second subsample matrix that represents the subsampled decoding in a second direction that is substantially perpendicular to the first direction.
A computer-readable storage media having stored computer-executable instructions for implementing a method in a video management system configured to receive a video stream containing one or more video pictures that are each divided into blocks, wherein the video management system is to provide a representation of the one or more video pictures to a subsample decoder for subsampling, wherein the method is for reducing the size of the one or more frames with minimal, if any, effect on the video quality generated from the one or more frames after subsampling, the method comprising the following:
- accessing a video picture that is to be provided to a video node having a subsample decoder;
- obtaining information specifying a subsampling ratio to be performed by the subsample decoder;
- and
- in response to the obtained information, for at least one block of the video picture, performing subsample transcoding of the at least one block, thereby reducing the size of the at least one block to generate at least one reduced size block in such a way that subsampled decoding the at least one reduced size block results in substantially the same reduced size image as subsampled decoding the at least one block prior to the subsample transcoding, wherein reducing the size of the block includes the following:
- representing the block as a matrix:
- pre-multiplying the block matrix by a pre-multiplication matrix, the pre-multiplication matrix generated from a first subsample matrix that represents the subsampled decoding in a first direction;
- and
- post-multiplying the block matrix by a post-multiplication matrix generated from a second subsample matrix that represents the subsampled decoding in a second direction that is substantially perpendicular to the first direction.
Dependencies are inferred from the claim text.