Harmonization of cross-component prediction and adaptive color transform in video coding

Patent metadata

Field	Value
Publication number	US-2016105657-A1
Application number	US-201514871235-A
Country	US
Kind code	A1
Filing date	Sep 30, 2015
Priority date	Oct 10, 2014
Publication date	Apr 14, 2016
Grant date	—

Abstract

A video coder transforms, based on a difference between a bit depth of an initial luma sample and a bit depth of initial chroma samples, a set of initial samples to a set of modified samples. The set of initial samples may include the initial luma sample and the initial chroma samples. The initial chroma samples may include an initial Cb sample and an initial Cr sample. The set of modified samples may include a modified luma sample and modified chroma samples. The modified chroma samples may include a modified Cb sample and a modified Cr sample. Additionally, the video coder adds the modified samples to corresponding samples of a predictive block to produce reconstructed samples.

First claim

What is claimed is:

1 . A method of decoding video data, the method comprising:
transforming, based on a difference between a bit depth of an initial luma sample and a bit depth of initial chroma samples, a set of initial samples to a set of modified samples, the set of initial samples including the initial luma sample and the initial chroma samples, the set of modified samples including a modified luma sample and modified chroma samples; and adding the modified samples to corresponding samples of a predictive block to produce reconstructed samples of the video data.

2 . The method of claim 1 , wherein:
the initial chroma samples include an initial Cb sample and an initial Cr sample, and the modified chroma samples include a modified Cb sample and a modified Cr sample.

3 . The method of claim 2 , wherein transforming the set of initial samples comprises:
determining a bit shift value as 3 plus a maximum of 0 and a value equal to the bit depth of the initial luma sample minus the bit depth of the initial chroma samples; determining a first parameter value as 1 left shifted by the bit shift value; determining a second parameter value as a cross-component prediction parameter for the initial Cb sample left shifted by a maximum of 0 and a value equal to the bit depth of the initial chroma samples minus the bit depth of the initial luma sample; determining a third parameter value as a cross-component prediction parameter for the initial Cr sample left shifted by a maximum of 0 and the value equal to the bit depth of the initial chroma samples minus the bit depth of the initial luma sample; determining a luma residual coefficient value as a sum of the first parameter value and the second parameter value, multiplied by the initial luma sample, plus the first parameter value multiplied by the initial Cb sample; determining a first chroma residual coefficient value as a difference between a first intermediate value and a second intermediate value,
the first intermediate value being equal to the first parameter value minus the second parameter value, multiplied by the initial luma sample, minus the first parameter value times the initial Cb sample,
the second intermediate value being equal to the third parameter value multiplied by the initial luma sample, plus the first parameter value multiplied by the initial Cr sample;
determining a second chroma residual coefficient value as a sum of the first intermediate value and the second intermediate value; determining the modified luma sample as the luma residual coefficient value right shifted by the bit shift value; determining the modified Cb sample as the first chroma coefficient value right shifted by the bit shift value; and determining the modified Cr sample as the second chroma coefficient value right shifted by the bit shift value.

4 . The method of claim 3 , further comprising:
obtaining, from a bitstream, syntax elements indicating the cross-component prediction parameter for the initial Cb sample and the cross-component prediction parameter for the initial Cr sample.

5 . The method of claim 3 , further comprising:
signaling, in a bitstream, syntax elements indicating the cross-component prediction parameter for the initial Cb sample and the cross-component prediction parameter for the initial Cr sample.

6 . A device for coding video data, the device comprising:
a data storage medium configured to store the video data; and one or more processors configured to: transform, based on a difference between a bit depth of an initial luma sample and a bit depth of initial chroma samples, a set of initial samples to a set of modified samples, the set of initial samples including the initial luma sample and the initial chroma samples, the set of modified samples including a modified luma sample and modified chroma samples; and add the modified samples to corresponding samples of a predictive block to produce reconstructed samples of the video data.

7 . The device of claim 6 , wherein:
the initial chroma samples include an initial Cb sample and an initial Cr sample, and the modified chroma samples include a modified Cb sample and a modified Cr sample.

8 . The device of claim 7 , wherein the one or more processors are configured such that, as part of transforming the set of initial samples, the one or more processors:
determine a bit shift value as 3 plus a maximum of 0 and a value equal to the bit depth of the initial luma sample minus the bit depth of the initial chroma samples; determine a first parameter value as 1 left shifted by the bit shift value; determine a second parameter value as a cross-component prediction parameter for the initial Cb sample left shifted by a maximum of 0 and a value equal to the bit depth of the initial chroma samples minus the bit depth of the initial luma sample; determine a third parameter value as a cross-component prediction parameter for the initial Cr sample left shifted by a maximum of 0 and the value equal to the bit depth of the initial chroma samples minus the bit depth of the initial luma sample; determine a luma residual coefficient value as a sum of the first parameter value and the second parameter value, multiplied by the initial luma sample, plus the first parameter value multiplied by the initial Cb sample; determine a first chroma residual coefficient value as a difference between a first intermediate value and a second intermediate value,
the first intermediate value being equal to the first parameter value minus the second parameter value, multiplied by the initial luma sample, minus the first parameter value times the initial Cb sample,
the second intermediate value being equal to the third parameter value multiplied by the initial luma sample, plus the first parameter value multiplied by the initial Cr sample;
determine a second chroma residual coefficient value as a sum of the first intermediate value and the second intermediate value; determine the modified luma sample as the luma residual coefficient value right shifted by the bit shift value; determine the modified Cb sample as the first chroma coefficient value right shifted by the bit shift value; and determine the modified Cr sample as the second chroma coefficient value right shifted by the bit shift value.

9 . The device of claim 8 , wherein the one or more processors are configured to:
obtain, from a bitstream, syntax elements indicating the cross-component prediction parameter for the initial Cb sample and the cross-component prediction parameter for the initial Cr sample.

10 . The device of claim 8 , wherein the one or more processors are configured to:
signal, in a bitstream, syntax elements indicating the cross-component prediction parameter for the initial Cb sample and the cross-component prediction parameter for the initial Cr sample.

11 . The device of claim 6 , wherein the device comprises at least one of:
an integrated circuit; a microprocessor; or a wireless handset.

12 . The device of claim 6 , further comprising a display configured to display decoded video data.

13 . The device of claim 6 , further comprising a camera configured to capture the video data.

14 . A device for coding video data, the device comprising:
means for transforming, based on a difference between a bit depth of an initial luma sample and a bit depth of initial chroma samples, a set of initial samples to a set of modified samples, the set of initial samples including the initial luma sample and the initial chroma samples, the set of modified samples including a modified luma sample and modified chroma samples; and

Assignees

• Qualcomm Inc

Inventors

• Zhang Li
• Chen Jianle
• Joshi Rajan Laxman
• Karczewicz Marta

Classifications

• H04N19/186 Primary

  the unit being a colour or a chrominance component · CPC title

• H04N19/176 Primary

  the region being a block, e.g. a macroblock · CPC title

• G06T9/20

  Contour coding, e.g. using detection of edges · CPC title

• H04N19/61

  in combination with predictive coding · CPC title

• H04N19/85

  using pre-processing or post-processing specially adapted for video compression · CPC title