Perceptually-Quantized Video Encoding for HDR Efficiency
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Solution Overview
Problem
Existing video encoding and decoding technologies face inefficiencies when handling high dynamic range (HDR) video signals, particularly in perceptually-quantized color spaces, as they are optimized for gamma-coded, standard dynamic range video signals, leading to increased complexity and reduced coding efficiency.
Innovation Solution
The implementation of encoding and decoding techniques in a perceptually-quantized opponent color space, such as IPT-PQ, which involves color transformations, perceptual quantization, and reshaping functions to optimize bit-depth requirements and simplify decoding processes, while preserving dynamic range ratios between luma and chroma channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If perceptual quantization is applied to reduce bit-depth requirements for HDR video, then storage and transmission efficiency improve, but coding efficiency deteriorates because existing codecs are optimized for gamma-coded video signals
Solution Approach 1:
The patent changes the fundamental parameter of luminance coding from gamma-coded to perceptually-quantized (PQ-coded). This parameter change enables the use of lower bit-depth (e.g., 10-bit or 12-bit) while maintaining HDR quality, directly addressing the bit-depth reduction goal. The PQ encoding transforms the luminance signal according to human perception characteristics, allowing efficient compression at reduced bit-depth despite existing codecs being optimized for gamma-coded signals.
2Adaptability or versatility
If HDR video is encoded with codecs supporting only lower bit-depth, then compatibility with existing video codecs is improved, but dynamic range representation capability deteriorates
Solution Approach 1:
The patent applies perceptual quantization transformation to convert HDR video into a format that can be efficiently represented with lower bit-depth. By changing the encoding parameter from linear or gamma-coded luminance to PQ-coded luminance, the system achieves better compression efficiency and codec compatibility while maintaining the full dynamic range representation capability through the perceptually-optimized transformation.
3Measurement precision
If color transformations are applied to convert video signals to perceptually-quantized opponent color space, then perceptual uniformity and hue linearity improve, but processing complexity increases
Solution Approach 1:
The patent performs the complex color transformations and perceptual quantization operations during the encoding phase rather than leaving them for the decoding phase. By applying the IPT-PQ color space transformation and PQ encoding in advance during encoding, the patent reduces the complexity of the decoder while maintaining the benefits of improved perceptual uniformity and hue linearity in the final output.
Data Source
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AI summary
Compared to traditional gamma-coded video, perceptually quantized video provides greater flexibility for the transmission and display management of high-dynamic range video, but it does not compresses as efficiently using existing standard codecs. Techniques are described to improve the coding efficiency of perceptually coded video by applying a color cross-talk transformation after the RGB/XYZ to LMS transformation. Such a transform increases luma and chroma correlation for color appearance models, but improves perceptual uniformity and overall coding efficiency for wide color gamut, HDR, signals.