US 9,807,423 B1Granted

Hybrid transform scheme for video coding

AssigneeGoogle Inc.

InventorsJingning Han, Yaowu Xu, Cheng Chen

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Abstract

Blocks of a frame are encoded by selected according to a hybrid symmetrical discrete sine transform scheme. For a residual block resulting from inter prediction, the residual block is respectively transformed using a discrete cosine transform (DCT) and a symmetrical discrete sine transform (SDST). A first rate-distortion value for encoding the residual block using the DCT and a second rate-distortion value for encoding the residual block using the SDST are generated. For a residual block generated by intra prediction, the residual block is respectively transformed using at least one transform mode, each of which is not the SDST. Multiple inter prediction and intra prediction modes may be considered to encode the current block. The transform mode and the prediction mode resulting in a lowest rate-distortion value for encoding the current block are selected, and the current block is encoded into an encoded bitstream using the selected modes.

Claims18

Dependent claims

A method for encoding a video signal including frames, each frame including blocks and each block including pixels, the method comprising:

for each prediction mode of available prediction modes, and for a current block of a current frame:
generating a prediction block for encoding a current block using a prediction mode by a processor;
generating a residual block based on the prediction block and the current block;
when the prediction mode is an inter prediction mode:
transforming the residual block using a discrete cosine transform (DCT) as a transform mode;
generating a first rate-distortion value for encoding the residual block using the DCT;
transforming the residual block using a symmetrical discrete sine transform (SDST) as the transform mode;
and
generating a second rate-distortion value for encoding the residual block using the SDST;
when the prediction mode is an intra prediction mode:
transforming the residual block using other than the SDST as the transform mode by selecting the transform mode from a set consisting of the DCT, an asymmetric discrete sine transform (ADST), and a combination of the DCT and the ADST;
and
generating at least a third rate-distortion value for encoding the residual block using other than the SDST;
selecting the transform mode and the prediction mode resulting in a lowest rate-distortion value for encoding the current block;
and
encoding the current block into an encoded bitstream using the transform mode and the prediction mode as selected.

13 more elements

An apparatus for encoding a video signal including frames, each frame including blocks and each block including pixels, the apparatus comprising:

a memory;
and
a processor configured to execute instructions stored in the memory to:
for each prediction mode of available prediction modes, and for a current block of a current frame:
generate a prediction block for encoding a current block using a prediction mode;
generate a residual block based on the prediction block and the current block;
when the prediction mode is an inter prediction mode:
transform the residual block using a discrete cosine transform (DCT) as a transform mode;
generate a first rate-distortion value for encoding the residual block using the DCT;
transform the residual block using a symmetrical discrete sine transform (SDST) as the transform mode;
and
generate a second rate-distortion value for encoding the residual block using the SDST;
when the prediction mode is an intra prediction mode:
transform the residual block using other than the SDST as the transform mode by selecting the transform mode from a set consisting of the DCT, an asymmetric discrete sine transform (ADST), and a combination of the DCT and the ADST;
and
generate at least a third rate-distortion value for encoding the residual block using other than the SDST;
select the transform mode and the prediction mode resulting in a lowest rate-distortion value for encoding the current block;
and
encode the current block into an encoded bitstream using the transform mode and the prediction mode as selected.

16 more elements

Dependencies are inferred from the claim text.

Facts

Application: 14/950,024Filed 24 Nov 2015
Granted: 31 Oct 2017
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

H04N 19/625
Using transform coding: using discrete cosine transform [DCT]
H04N 19/103
Characterised by the element, parameter or selection affected or controlled by the adaptive coding: selection of coding mode or of prediction mode
H04N 19/12
Characterised by the element, parameter or selection affected or controlled by the adaptive coding: selection from among a plurality of transforms…
H04N 19/147
Data rate or code amount at the encoder output: according to rate distortion criteria