HDR Signal Tone Mapping Using Peak Luminance Metadata

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Solution Overview

Problem

Existing technologies fail to accurately convert HDR signals to SDR signals without altering the intended brightness, leading to differences in perceived image quality when viewed in HDR and SDR environments.

Innovation Solution

An image processing apparatus and method that acquires peak luminance information corresponding to different output dynamic ranges based on shooting settings and records this information as metadata, allowing for tone-mapping of HDR signals to SDR signals, ensuring consistent brightness across environments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If tone mapping is performed to convert HDR signal to SDR signal for viewing in SDR environment, then the HDR signal can be displayed in SDR environment, but the brightness changes and the intended image quality is altered

Engineering Contradiction:

Improvecompatibility with SDR environmentVSAvoidbrightness accuracy

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by embedding peak luminance information (maxCLL) in the HDR signal metadata during the shooting or encoding stage. This pre-prepared information enables the reproducing device to perform accurate tone mapping later, preserving the intended brightness characteristics without requiring real-time measurement or adjustment.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback by using the embedded peak luminance information to guide the tone mapping process. The reproducing device references the maxCLL value to determine the appropriate mapping curve, creating a closed-loop system where the original创作 intent feeds back into the reproduction process to ensure fidelity.

Inventive Principle:

Principle #23Feedback

2Ease of manufacture

If maximum luminance level (maxCLL) is used for tone mapping, then the tone mapping can be performed, but the mapped SDR signal may look brighter than the original HDR signal when the HDR signal was obtained by shooting in underexposure condition

Engineering Contradiction:

Improvesimplicity of tone mapping processVSAvoidbrightness fidelity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by using the peak luminance information to dynamically adjust the tone mapping curve parameters. Instead of using a fixed mapping approach, the system modifies the mapping parameters based on the specific peak luminance value of the HDR content, enabling accurate reproduction across different shooting conditions including underexposure scenarios.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If existing tone mapping methods are used without considering output dynamic range, then the tone mapping can be performed, but the output SDR signal does not represent the brightness intended by the producer

Engineering Contradiction:

Improveefficiency of tone mappingVSAvoidbrightness accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent introduces an intermediary element - the embedded peak luminance information (maxCLL) in the signal metadata - that mediates between the HDR source and the SDR display. This intermediary carries the necessary brightness information through the conversion process, enabling the tone mapping to accurately reflect the creator's intent without requiring complex communication between shooting and reproducing devices.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS11798143B2Image processing apparatus and control method thereof

Publication Date: 2023.10.24 CANON KK

AI summary

An image processing apparatus that records a high dynamic range (HDR) signal as a file. The apparatus acquires information indicating peak luminance corresponding to one output dynamic range, of a plurality of different output dynamic ranges, in accordance with shooting settings of the HDR signal. The apparatus then records a first value based on the acquired information to the file along with the HDR signal.