Extended Color Range Mapping for HDR Video Coding Efficiency

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Solution Overview

Problem

Current methods for coding high-dynamic-range (HDR) video are inefficient due to limitations in dynamic range extension and color gamut, leading to suboptimal compression efficiency and quality, especially when transitioning between standard dynamic range (SDR) and HDR formats.

Innovation Solution

The implementation of an extended color range mapping function that mirrors the original mapping function beyond its defined range, allowing for improved prediction and compression efficiency by enabling the use of a wider color gamut in the encoding process, specifically by deriving an extended electro-optical transfer function (EOTF) and its inverse, which supports higher dynamic range signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If standard dynamic range mapping functions are used for HDR video coding, then compatibility with conventional displays is maintained, but coding efficiency and prediction accuracy deteriorate

Engineering Contradiction:

Improvedisplay compatibilityVSAvoidcoding efficiency

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent divides the HDR coding process into two segments: base layer encoded with standard dynamic range mapping for SDR display compatibility, and enhancement layer encoded with extended color range mapping for HDR display optimization. This segmentation allows each layer to be optimized for its specific purpose while maintaining overall system compatibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent extends the color space mapping from the standard sRGB gamut to a wider gamut by deriving extended electro-optical transfer functions (EOTF) that operate beyond the conventional 0-1 range. This dimensional extension in color space enables better prediction accuracy and coding efficiency for HDR content while maintaining backward compatibility through the base layer.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Productivity

If extended color range mapping is used for HDR video coding, then prediction accuracy and coding efficiency improve, but compatibility with standard displays deteriorates

Engineering Contradiction:

Improvecoding efficiencyVSAvoiddisplay compatibility

Core Design Contradiction:

ProductivityVSAdaptability or versatility

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The extended mapping function serves multiple functions: it provides accurate HDR prediction when available, while the base layer with standard mapping ensures compatibility with SDR displays. The system universally supports both SDR and HDR display types through this multi-functional approach.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Adaptability or versatility

If standard color gamut is used in layered encoding, then decoder compatibility is maintained, but residual error and quality deteriorate

Engineering Contradiction:

Improvedecoder compatibilityVSAvoidprediction accuracy

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic mapping function selection based on display capabilities. The encoder determines whether to use standard or extended mapping functions based on the target display type, allowing the system to adapt its prediction accuracy and color gamut usage dynamically while maintaining decoder compatibility through the base layer.

Inventive Principle:

Principle #15Dynamics

4Manufacturing precision

If HDR content is encoded directly without layered approach, then quality is maintained, but bandwidth consumption increases

Engineering Contradiction:

Improvecontent qualityVSAvoidbandwidth consumption

Core Design Contradiction:

Manufacturing precisionVSQuantity of substance

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies partial action by encoding only the essential base layer with standard mapping that provides sufficient quality for SDR displays, and optionally adding the enhancement layer with extended mapping for HDR displays. This avoids the excessive bandwidth consumption of encoding full HDR content at maximum quality for all display types.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentEP3213291B1Content mapping using extended color range

Publication Date: 2019.11.06 DOLBY LABORATORIES LICENSING CORP

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AI summary

In high-dynamic range (HDR) coding, content mapping translates an HDR signal to a signal of lower dynamic range. Coding and prediction in layered coding of HDR signals is improved if content mapping utilizes signal color ranges beyond those defined by a traditional electro-optical transfer function (EOTF) or its inverse (IEOTF or OETF). Extended EOTF and IEOTF functions are derived based on their mirror points. Examples of extended EOTFs are given for ITU BT. 1886 and SMPTE ST 2084.