HDR Image Encoding Mapping Function Reduces Bit Depth

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Solution Overview

Problem

Current HDR image encoding technologies face challenges in efficiently encoding high dynamic range images within existing frameworks, requiring either increased bits or complex dual-layer approaches, while also needing to be compatible with legacy LDR systems and hardware constraints.

Innovation Solution

A method of encoding HDR images using a single master EOTF function that reallocates luminances to luma codes, allowing for efficient encoding with 10 bits or less, and enabling both HDR and LDR image rendering by linking HDR and LDR images through a functional transformation, using a predetermined mapping function that includes a gamma transform and a peak luminance reference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If dual-layer approach is used to encode HDR images, then HDR rendering quality is improved, but device complexity increases

Engineering Contradiction:

ImproveHDR rendering qualityVSAvoidencoding complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges HDR and LDR encoding into a single unified encoding process. Instead of using separate dual-layer encoding structures, the invention combines both dynamic ranges into one encoding framework that produces a single image file capable of being rendered in both HDR and LDR modes, thereby reducing device complexity while maintaining HDR rendering quality

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The encoded image serves multiple functions simultaneously - it can be rendered as HDR content on HDR-capable displays and automatically adapted to LDR content on standard displays. This universal encoding approach eliminates the need for separate HDR-specific encoding pipelines, reducing overall system complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If more bits are used to encode HDR luminances, then HDR luminance precision is improved, but data quantity increases

Engineering Contradiction:

Improveluminance precisionVSAvoiddata amount

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent changes the encoding parameters by using floating-point representation with optimized bit allocation. Instead of uniformly increasing bit depth across all pixels, the system dynamically adjusts precision based on local luminance characteristics, maintaining high luminance precision where needed while reducing precision in less critical regions, thereby controlling overall data quantity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The encoding applies different precision levels to different regions of the image based on local luminance requirements. Areas with high luminance variation receive higher precision encoding, while uniform regions use lower precision, optimizing the balance between luminance precision and total data amount

Inventive Principle:

Principle #3Local quality

3Reliability

If HDR-specific encoding framework is created, then HDR encoding capability is improved, but adaptability to legacy systems decreases

Engineering Contradiction:

ImproveHDR encoding capabilityVSAvoidlegacy system compatibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent introduces an intermediary conversion process that transforms HDR-encoded images into LDR-compatible formats when needed. This intermediary step acts as a bridge between HDR and legacy LDR systems, allowing HDR content to be reliably encoded while maintaining adaptability to legacy display systems through automatic format conversion

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The encoding system dynamically adapts its output format based on the capabilities of the target display device. When transmitting to legacy systems, it automatically converts to LDR format, while HDR-capable systems receive the full HDR encoding, thus maintaining both HDR encoding capability and broad system adaptability

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10194162B2Methods and apparatuses for creating code mapping functions for encoding an HDR image, and methods and apparatuses for use of such encoded images

Publication Date: 2019.01.29 KONINKLIJKE PHILIPS NV

AI summary

To enable better encoding of the currently starting to appear high dynamic range images for use in full high dynamic range technical systems (containing an HDR display, and e.g. in an HDR grading application of a HDR movie), we invented a method of encoding a high dynamic range image, comprising the steps of: —inputting pixel colors of an input high dynamic range image, wherein the pixel colors have information of a luminance and a chromaticity; —applying an inverse of a mapping function to derive a luma code (v) of the luminance of a pixel color, which mapping function is predetermined as comprising a first partial function which is defined as (I), in which rho is a tuning constant, and v is the luma code corresponding to a luminance to be encoded, and a second partial mapping defined as L=LmPγ in which Lm is a peak luminance of a predefined reference display, and gamma is a constant which is preferably equal to 2.4, —outputting a matrix of pixels having a color encoding comprising the luma codes.