US 9,544,597 B1Granted

Hybrid transform in video encoding and decoding

AssigneeGoogle Inc.

InventorsJingning Han, Debargha Mukherjee

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Abstract

Blocks of a frame of a video stream can be encoded using intra prediction followed by transforming the generated residual blocks. In some cases, coding efficiency can be improved by subdividing large blocks into smaller sub-blocks. Transform modes may be associated with at least one intra prediction mode so as to identify one or more transform modes for the block or its sub-blocks. A scan mode can be identified based on the transform mode. Desirably, each of a plurality of probability models is associated with a transform mode and a block size such that the appropriate model(s) may be selected for a block or its sub-blocks. Each probability model may be associated with only one transform mode and only one block size or may be associated with more than one transform mode and/or more than one block size and may be updated on-the-fly during encoding of a video stream.

Claims17

Dependent claims

A method for encoding a video stream having a plurality of frames, the method comprising:

identifying, by a processor, an intra prediction mode for a block of a frame, wherein the intra prediction mode is one of a plurality of intra prediction modes;
generating a residual block for the block using the intra prediction mode;
identifying a transform mode for the residual block based on the intra prediction mode identified for the block, the transform mode being one of a plurality of transform modes and each of the plurality of transform modes associated with at least one of the plurality of intra prediction modes;
wherein the plurality of transform modes comprises a 1D Asymmetrical Discrete Sine Transform (ADST) applied to each horizontal row followed by a 1D ADST applied to each vertical column, the 1D ADST applied to each horizontal row followed by a 1D Discrete Cosine Transform (DCT) applied to each vertical column, the 1D DCT applied to each horizontal row followed by the 1D ADST applied to each vertical column, and the 1D DCT applied to each horizontal row followed by the 1D DCT applied to each vertical column;
applying the transform mode to the residual block to generate a transform block comprising a plurality of transform coefficients;
identifying a scan mode for the transform block based on the transform mode identified for the residual block;
scanning the transform block to form a sequence of the plurality of transform coefficients using the scan mode identified for the residual block;
identifying a probability model of a plurality of probability models for generating an entropy code for the plurality of transform coefficients in the sequence, the probability model identified based on the transform mode identified for the residual block, and each of the plurality of probability models associated with at least one of the plurality of transform modes;
and encoding the sequence using the probability model identified using the residual block.

6 more elements

An apparatus for encoding a video stream having a plurality of frames, the apparatus comprising:

a memory;
and a processor configured to execute instructions stored in the memory to:
identify an intra prediction mode for a block of a frame, wherein the intra prediction mode is one of a plurality of intra prediction modes;
generate a residual block for the block using the intra prediction mode;
identify a transform mode for the residual block based on the intra prediction mode identified for the block, the transform mode being one of a plurality of transform modes and each of the plurality of transform modes associated with at least one of the plurality of intra prediction modes;
wherein the plurality of transform modes comprises a 1D Asymmetrical Discrete Sine Transform (ADST) applied to each horizontal row followed by a 1D ADST applied to each vertical column, the 1D ADST applied to each horizontal row followed by a 1D Discrete Cosine Transform (DCT) applied to each vertical column, the 1D DCT applied to each horizontal row followed by the 1D ADST applied to each vertical column, and the 1D DCT applied to each horizontal row followed by the 1D DCT applied to each vertical column;
apply the transform mode to the residual block to generate a transform block comprising a plurality of transform coefficients;
identify a scan mode for the transform block using the transform mode identified for the residual block;
scan the transform block to form a sequence of the plurality of transform coefficients using the scan mode identified for the residual block,
identify a probability model of a plurality of probability models for generating an entropy code for the plurality of transform coefficients in the sequence, the probability model identified based on the transform mode identified for the residual block, and each of the plurality of probability models associated with at least one of the plurality of transform modes;
and encode the sequence using the probability model identified using the residual block.

8 more elements

Dependencies are inferred from the claim text.

Facts

Application: 13/763,921Filed 11 Feb 2013
Granted: 10 Jan 2017
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

H04N 19/11
Selection of coding mode or of prediction mode: among a plurality of spatial predictive coding modes
H04N 19/122
Selection from among a plurality of transforms or standards, e.g. selection between discrete cosine transform [DCT] and sub-band transform or…:…
H04N 19/129
Characterised by the element, parameter or selection affected or controlled by the adaptive coding: scanning of coding units, e.g. zig-zag scan of…
H04N 19/157
Characterised by the element, parameter or criterion affecting or controlling the adaptive coding: assigned coding mode, i.e. the coding mode…