Backward-Compatible HDR Image Encoding via LDR Base Layer
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Solution Overview
Problem
Current methods for encoding and decoding high dynamic range (HDR) images lack backward compatibility with existing lower-dynamic-range (LDR) systems, leading to loss of information and suboptimal performance in reproducing both HDR and LDR images.
Innovation Solution
The method involves obtaining a lower dynamic range image corresponding to the HDR image, identifying groups of pixels with the same values, generating a prediction function based on HDR pixel values, computing a residual image, and encoding both the LDR and prediction functions to enable backward-compatible decoding of HDR images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high dynamic range data formats with larger numbers of bits per pixel are used, then the dynamic range and color fidelity are improved, but backward compatibility with prior lower dynamic range data formats is lost
Solution Approach 1:
The patent segments the HDR image data into multiple layers: an LDR base layer that maintains compatibility with existing systems, and an HDR enhancement layer that provides extended dynamic range. This segmentation allows different parts of the data structure to serve different purposes - the base layer ensures backward compatibility while the enhancement layer provides improved dynamic range for capable devices
Solution Approach 2:
The patent implements a nested structure where the LDR representation is embedded within the HDR data structure as a base layer, and the HDR-specific enhancement data is nested within or alongside it. This nested organization allows LDR systems to use only the base layer while HDR systems can access both layers for full functionality
2Adaptability or versatility
If 24 bits per pixel are used for image data, then the data format is compatible with existing systems, but the brightness range is insufficient for high dynamic range display
Solution Approach 1:
The patent applies partial action by providing more than 24 bits per pixel for HDR capability while maintaining 24-bit compatibility for LDR systems. The enhancement layer contains the additional bits needed for extended brightness range, but this extra data is only utilized by HDR-capable displays, allowing existing systems to function normally with the base layer
3Productivity
If lossy HDR video compression methods are used, then the compression ratio is improved, but information loss occurs and backward compatibility is not provided
Solution Approach 1:
The patent employs feedback mechanisms in the compression process where the encoder analyzes the relationship between LDR and HDR image data to optimize the enhancement layer. The compression algorithm uses feedback from the base layer reconstruction to minimize information loss while achieving efficient compression, ensuring that the residual HDR information is preserved with minimal degradation
Data Source
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AI summary
A method for encoding high dynamic range (HDR) images involves providing a lower dynamic range (LDR) image, generating a prediction function for estimating the values for pixels in the HDR image based on the values of corresponding pixels in the LDR image, and obtaining a residual frame based on differences between the pixel values of the HDR image and estimated pixel values. The LDR image, prediction function and residual frame can all be encoded in data from which either the LDR image of HDR image can be recreated.