Adaptive Chroma Quantization for HDR Video Coding

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Solution Overview

Problem

Existing video compression standards, such as HEVC, are inadequate for efficiently encoding high dynamic range (HDR) and wide color gamut (WCG) content, leading to chroma artifacts and inefficient bit usage due to the use of default chroma quantization tables optimized for standard dynamic range (SDR) signals.

Innovation Solution

Adaptive chroma quantization tables are developed for specific color formats like HDR Y′Cb′Cr′ PQ and HDR ICtCp PQ, allowing for dynamic selection based on the input color format, using multiple default QpC tables tailored for SDR Y′Cb′Cr′ gamma, HDR Y′Cb′Cr′ PQ, and HDR ICtCp PQ, and embedding the table ID in the bitstream for accurate decoding.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If default chroma quantization tables optimized for SDR signals are used, then compatibility with legacy standards is maintained, but chroma artifacts and inefficient bit usage occur for HDR content

Engineering Contradiction:

Improvecompatibility with legacy standardsVSAvoidchroma artifacts

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the chroma quantization process by creating separate quantization tables for different color formats (SDR YCbCr, HDR YCbCr PQ, HDR ICtCp PQ). Each table is optimized for its specific format, allowing the system to avoid chroma artifacts in HDR content while maintaining compatibility with legacy SDR standards through the dedicated SDR-optimized table.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the parameters of chroma quantization tables based on the color format being used. By adjusting quantization parameters specifically for HDR formats (PQ and ICtCp PQ), the system eliminates chroma artifacts that would otherwise appear when using SDR-optimized tables for HDR content.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If default chroma quantization tables optimized for SDR signals are used, then simplicity of implementation is maintained, but compression efficiency deteriorates for HDR content

Engineering Contradiction:

Improvesimplicity of implementationVSAvoidcompression efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent introduces dynamic selection of chroma quantization tables based on the color format of the input content. The system automatically switches between SDR and HDR optimized tables, and between different HDR format tables, based on metadata in the bitstream. This dynamic adaptation improves compression efficiency for HDR content while adding minimal complexity through format detection and table selection.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent creates a universal chroma quantization system that handles multiple color formats (SDR YCbCr, HDR YCbCr PQ, HDR ICtCp PQ) through a set of format-specific tables. This multi-functional approach allows a single encoding system to efficiently process diverse content types without requiring separate dedicated systems for each format.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Object-affected harmful factors

If multiple format-specific chroma quantization tables are implemented, then chroma artifact reduction is achieved, but system complexity increases

Engineering Contradiction:

Improvechroma artifactsVSAvoidsystem complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent performs preliminary identification of the color format (SDR, HDR PQ, HDR ICtCp PQ) and selects the appropriate chroma quantization table before the actual encoding process. This preliminary action allows the system to use the correct optimized table without requiring complex real-time adjustments during encoding, thereby reducing overall system complexity while still achieving chroma artifact reduction.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses color format metadata in the bitstream as an intermediary to bridge the content and the appropriate quantization table. This intermediary mechanism automatically directs the encoding process to use the correct table based on the content type, eliminating the need for complex analysis during encoding and simplifying the overall system architecture.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10477212B2Adaptive chroma quantization in video coding for multiple color imaging formats

Publication Date: 2019.11.12 DOLBY LABORATORIES LICENSING CORP

AI summary

Methods to improve the quality of coding high-dynamic range (HDR) signals are presented. Instead of using a single chroma quantization table for all color formats, a video encoder may adaptively use separate tables for each one, and transmit the table's ID to a decoder. Examples for chroma quantization tables for video content encoded in the YCbCr (PQ) and ICtCp (PQ) color formats under a variety of color gamut containers are provided.