Chroma Quantization Parameter Extension in HEVC

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Solution Overview

Problem

The current High Efficiency Video Coding (HEVC) standard limits chroma quantization parameter (QP) to a range of [0, 39], leading to difficulties in bit allocation and subjective quality control, especially at low bit-rates, and fails to properly handle video sources with different color formats.

Innovation Solution

Extending the chroma QP range to [0, 51] by replacing the existing mapping table and using equations to determine chroma QP values based on luma QP and offsets, allowing for more flexible bit allocation and handling of various color formats.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If chroma QP is limited to range [0, 39], then the HEVC standard maintains simplicity in implementation, but bit allocation flexibility and subjective quality control deteriorate, especially at low bit-rates

Engineering Contradiction:

Improveimplementation simplicityVSAvoidbit allocation flexibility

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent extends the chroma QP parameter range from [0, 39] to [0, 51], allowing encoders to allocate more bits to chroma components when needed. This parameter extension provides greater flexibility in bit allocation strategies while maintaining the same basic quantization mechanism, thus improving adaptability without significantly increasing implementation complexity.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If chroma QP is limited to range [0, 39], then the standard maintains consistency across different color formats, but the ability to handle video sources with different color formats deteriorates

Engineering Contradiction:

Improvestandard consistencyVSAvoidcolor format handling capability

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

By extending the chroma QP range to [0, 51], the patent enables better adaptation to different color formats (e.g., RGB, YCbCr) while maintaining the same standard framework. The extended range allows for format-specific optimizations without requiring separate standards, thus improving versatility while preserving standard consistency.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If chroma QP is extended to range [0, 51], then bit allocation flexibility and handling of different color formats are improved, but device complexity increases

Engineering Contradiction:

Improvebit allocation flexibilityVSAvoidencoder/decoder complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements chroma QP extension by modifying parameter ranges and updating lookup tables, rather than fundamentally changing the quantization architecture. This approach provides enhanced bit allocation flexibility while minimizing increases in device complexity, as the core encoding/decoding processes remain unchanged.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11445192B2Chroma quantization parameter extension

Publication Date: 2022.09.13 SONY GROUP CORP

AI summary

The quantization parameters (QP) for Chroma are extended up to and more preferably to the same range as Luma QP (e.g., 0 to 51). Previous, values of Chroma QP only extended up to 39. Techniques are provided for determining extended Chroma QP values (e.g., for Cr and Cb) based on the Luma QP and picture level chroma offsets. In one preferred embodiment, slice level offsets are added making the method particularly well-suited for slice level parallel processing. The extension of Chroma QP enhances functionality, flexibility and friendliness of the High Efficiency Video Coding (HEVC) standard for various applications.