Tone-curve optimization method and associated video encoder and video decoder

Patent metadata

Field	Value
Publication number	US-11336895-B2
Application number	US-201816640332-A
Country	US
Kind code	B2
Filing date	Sep 5, 2018
Priority date	Sep 6, 2017
Publication date	May 17, 2022
Grant date	May 17, 2022

Abstract

A method for generating metadata for use by a video decoder for displaying video content encoded by a video encoder includes: (1) accessing a target tone mapping curve; (2) accessing a decoder tone curve corresponding to a tone curve used by the video decoder for tone mapping the video content; (3) generating a plurality of parameters of a trim-pass function used by the video decoder to apply after applying the decoder tone curve to the video content, wherein the parameters of the trim-pass function are generated to approximate the target tone curve with the combination of the trim-pass function and the decoder tone curve, and (4) generating the metadata for use by the video decoder, including said plurality of parameters of the trim-pass function.

First claim

The invention claimed is:

1. An encoder method to generate trim-pass transformation parameters, the method comprising:
accessing a first tone-mapping curve;
accessing a second tone-mapping curve;
accessing a set of input image data and a set of corresponding input trim-pass data defining a first trim-pass function adapted for color grading the set of input image data after application of the first tone-mapping curve; and
determining parameters for a trim-pass transformation model for translating said input trim-pass data to trim-pass data for defining a second trim-pass function adapted for color grading the set of input image data after application of the second tone-mapping curve, said determining comprising minimizing a difference between:
a first set of image outputs generated by processing the set of input image data by applying the first tone-mapping curve and the first trim-pass function defined by the input trim-pass data, and
a second set of image outputs generated by transforming the input trim-pass data to output trim-pass data using the trim-pass transformation model and processing the set of input images by applying the second tone-mapping curve and the second trim pass function defined by the output trim-pass data,

wherein the difference minimization is constrained such that the first tone-mapping curve and the second trim-pass function have equal minimum and maximum values at an input channel.

2. The method of claim 1 , further comprising transmitting the parameters for the trim-pass transformation model to a decoder together with the input image data and the input trim-pass data.

3. The method of claim 1 , wherein the trim-pass transformation model is a linear model.

4. The method of claim 1 , wherein the input trim-pass data comprise slope (S), offset (O), and power (P) data.

5. The method of claim 1 , wherein said minimizing comprises: minimizing a sum of square differences between the first and second sets of image outputs.

6. A decoder method to process input video data, the method comprising:
accessing input video data and corresponding input trim-pass data defining a first trim-pass function adapted for color grading input video data after application of a first tone-mapping curve;
accessing trim-pass transformation parameters for a trim-pass transformation model to translate the input trim-pass data to trim-pass data defining a second trim-pass function adapted for color grading input video data after application of a second tone-mapping curve, wherein the trim-pass transformation model is a linear transformation model, wherein the trim-pass transformation parameters minimize a sum of squared differences between the first trim-pass function and the second trim-pass function, and wherein the difference minimization is constrained such that the first tone-mapping curve and the second trim-pass function have equal minimum and maximum values at an input channel;
translating the input trim-pass data to transformed trim-pass data by applying the trim-pass transformation model in accordance with the trim-pass transformation parameters to the input trim-pass data; and
generating output video data by applying the second trim-pass function defined by the transformed trim-pass data and the second tone mapping curve to the input video data.

7. The method of claim 6 , wherein input trim-pass data comprise HDR10+ metadata and the transformed trim-pass data curve comprise Dolby Vision metadata.

8. The method of claim 6 , wherein input trim-pass data comprise Dolby Vision metadata and the transformed trim-pass data comprise HDR10+ metadata.

Assignees

• Dolby Laboratories Licensing Corp

Inventors

• Choudhury Anustup Kumar Atanu
• Atkins Robin
• Beier Thaddeus
• Zandifar Ali
• Godin Ian

Classifications

• H04N9/69

  for modifying the colour signals by gamma correction (controlling camera response for colour signals H04N23/83) · CPC title

• H04N19/186

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

• H04N1/603

  controlled by characteristics of the picture signal generator or the picture reproducer · CPC title

• H04N19/136 Primary

  Incoming video signal characteristics or properties · CPC title

• H04N19/98

  Adaptive-dynamic-range coding [ADRC] · CPC title