Method for correcting SDR pictures in a SL-HDR1 system

Patent metadata

Field	Value
Publication number	US-12519960-B2
Application number	US-202318853259-A
Country	US
Kind code	B2
Filing date	Mar 21, 2023
Priority date	Apr 4, 2022
Publication date	Jan 6, 2026
Grant date	Jan 6, 2026

Abstract

A method for correcting a SDR video in a SL-HDR1 system comprising identifying samples of a SDR picture the chroma components values of which risking to be clipped during a SL-HDR1 process; and, correcting the identified samples to prevent from the clipping before a generation of a HDR picture from the SDR picture.

First claim

The invention claimed is:

1 . A method comprising:
obtaining chroma components from a current sample of an input standard-dynamic-range (SDR) picture using a color correction function; determining a clipping factor based on the obtained chroma components and on a first range; representing each obtained chroma component as a multiplication of a first sub-part depending on a luma component of the sample of the input SDR picture and a second sub-part depending on a corresponding chroma component of the sample of the input SDR picture and obtaining a first ratio of a correction factor to be applied to the first sub-part and a second ratio of the correction factor to be applied to the second sub-part, the correction factor being based on the clipping factor; obtaining a luma value of a sample of a corrected SDR picture corresponding to the sample of the input SDR picture using a division of the first sub-part by the correction factor to a power equal to the first ratio; and, for each chroma component, obtaining a chroma value for the sample of the corrected SDR picture corresponding to the sample of the input SDR picture by dividing the second sub-part of the chroma component by the correction factor to a power equal to the second ratio.

2 . The method of claim 1 wherein the first and second ratio depend on a characteristic of the current sample, the characteristic comprising at least one of a value representative of a brightness of the current sample and/or a value representative of a saturation of the current sample.

3 . A method wherein the method of claim 1 is applied to all samples of an input SDR picture and wherein the first and second ratio is fixed for all samples of the input SDR picture and depends on a characteristic of the input SDR picture, the characteristic comprising at least one of a value representative of a brightness of the input SDR picture and/or a value representative of a saturation of the input SDR picture.

4 . A method wherein the method of claim 1 is applied to all samples of an input SDR picture of a SDR video and wherein the first and the second ratio are fixed for all samples of all SDR pictures of the SDR video.

5 . The method of claim 1 wherein the first and the second ratio depends on a single value.

6 . A method wherein the method of claim 1 is performed in a process for generating SDR pictures or in a process for ingesting SDR pictures.

7 . A device comprising electronic circuitry configured for:
obtaining chroma components from a current sample of an input standard-dynamic-range (SDR) picture using a color correction function; determining a clipping factor based on the obtained chroma components and on a first range; representing each obtained chroma component as a multiplication of a first sub-part depending on a luma component of the sample of the input SDR picture and a second sub-part depending on a corresponding chroma component of the sample of the input SDR picture and obtaining a first ratio of a correction factor to be applied to the first sub-part and a second ratio of the correction factor to be applied to the second sub-part, the correction factor being based on the clipping factor; obtaining a luma value of a sample of a corrected SDR picture corresponding to the sample of the input SDR picture by using a division of the first sub-part by the correction factor to a power equal to the first ratio; and, for each chroma component, obtaining a chroma value for the sample of the corrected SDR picture corresponding to the sample of the input SDR picture by using a division of the second sub-part of the chroma component by the correction factor to a power equal to the second ratio.

8 . The device of claim 7 wherein the first and second ratio depend on a characteristic of the current sample, the characteristic comprising at least one of a value representative of a brightness of the current sample and/or a value representative of a saturation of the current sample.

9 . A device comprising electronic circuitry adapted to process each sample of an input standard-dynamic-range (SDR) picture by:
obtaining chroma components from a current sample of an input SDR picture using a color correction function; determining a clipping factor based on the obtained chroma components and on a first range; representing each obtained chroma component as a multiplication of a first sub-part depending on a luma component of the sample of the input SDR picture and a second sub-part depending on a corresponding chroma component of the sample of the input SDR picture and obtaining a first ratio of a correction factor to be applied to the first sub-part and a second ratio of the correction factor to be applied to the second sub-part, the correction factor being based on the clipping factor; obtaining a luma value of a sample of a corrected SDR picture corresponding to the sample of the input SDR picture by dividing the first sub-part by the correction factor to a power equal to the first ratio; and, for each chroma component, obtaining a chroma value for the sample of the corrected SDR picture corresponding to the sample of the input SDR picture by dividing the second sub-part of the chroma component by the correction factor to a power equal to the second ratio, wherein the first and second ratio are fixed for all samples of the input SDR picture and depends on a characteristic of the input SDR picture, the characteristic comprising a value representative of a brightness of the input SDR picture and/or a value representative of a saturation of the input SDR picture.

10 . A device comprising electronic circuitry adapted to process each sample of an input standard-dynamic-range (SDR) picture of a SDR video by:
obtaining chroma components from a current sample of an input SDR picture using a color correction function; determining a clipping factor based on the obtained chroma components and on a first range; representing each obtained chroma component as a multiplication of a first sub-part depending on a luma component of the sample of the input SDR picture and a second sub-part depending on a corresponding chroma component of the sample of the input SDR picture and obtaining a first ratio of a correction factor to be applied to the first sub-part and a second ratio of the correction factor to be applied to the second sub-part, the correction factor being based on the clipping factor; obtaining a luma value of a sample of a corrected SDR picture corresponding to the sample of the input SDR picture using a division of the first sub-part by the correction factor to a power equal to the first ratio; and, for each chroma component, obtaining a chroma value for the sample of the corrected SDR picture corresponding to the sample of the input SDR picture by using a division of the second sub-part of the chroma component by the correction factor to a power equal to the second ratio, wherein the first and the second ratio are fixed for all samples of all SDR pictures of the SDR video.

11 . The device of claim 7 wherein the first and the second ratio depends on a single value.

12 . The device of claim 7 wherein the device is for generating SDR pictures or for ingesting SDR pictures.

13 . Non-transitory information storage medium storing program code instructions for implementing the method according to claim 1 .

Assignees

• Interdigital Ce Patent Holdings Sas

Inventors

• Touze David
• Plissonneau Frederic
• Cauvin Laurent
• Poirier Guillaume

Classifications

• H04N1/60

  Colour correction or control {(H04N1/54 takes precedence)} · CPC title

• G06T2207/10024

  Color image · CPC title

• G06V10/60

  relating to illumination properties, e.g. using a reflectance or lighting model · CPC title

• G06T7/90

  Determination of colour characteristics · CPC title

• H04N19/85

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