Perceptual Quantizer EOTF for Video Encoding Luminance Accuracy
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Solution Overview
Problem
Current video and image encoding technologies, such as those using non-perceptually uniform color spaces like Rec. 709, fail to accurately represent luminance levels, leading to issues like loss of shadow detail, blocking, and banding, especially with the transition to high-definition displays that have different brightness and contrast characteristics.
Innovation Solution
Implementing a perceptually uniform electro-optical transfer function (EOTF), like the PQ EOTF according to SMPTE ST 2084 or ITU Rec. 2100, to optimize encoding settings and convert non-perceptually uniform code values into perceptually uniform ones, allowing for more precise encoding and reduced distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If non-perceptually uniform color spaces like Rec. 709 are used for encoding, then device compatibility and ease of manufacture are improved, but manufacturing precision and measurement precision deteriorate due to inaccurate luminance representation
Solution Approach 1:
The patent applies parameter changes by transforming the encoding approach from non-perceptually uniform color spaces to perceptually uniform color spaces using the PQ EOTF. This changes the fundamental parameters of how luminance is represented and encoded, allowing for accurate shadow detail preservation while maintaining compatibility through standardized transformation functions defined in SMPTE ST 2084 and ITU Rec. 2100.
2Device complexity
If non-perceptually uniform code values are used, then encoding complexity is reduced, but measurement precision and perceptual accuracy deteriorate
Solution Approach 1:
The patent introduces an intermediary transformation process using the PQ EOTF as a mediator between the encoded signal and the display output. This intermediary step allows the system to work with simplified code values during encoding while achieving perceptually accurate results through the standardized transfer function, effectively decoupling encoding complexity from measurement precision.
3Adaptability or versatility
If standard encoding methods are used, then compatibility with existing displays is improved, but adaptability to high-definition displays with different brightness characteristics deteriorates
Solution Approach 1:
The patent achieves universality by implementing encoding that works across multiple display types and luminance ranges. The PQ EOTF-based approach provides a unified encoding framework that adapts to both standard-definition and high-definition displays, as well as both SDR and HDR capabilities, through standardized transformation functions that maintain image quality consistency across different display characteristics.
Data Source
AI summary
Techniques for applying a perceptual quantizer (PQ) electro-optical transfer function to optimize dithering and adaptive quantization for non-perceptual quantizer (e.g., SDR) color spaces are described. According to some embodiments, a computer-implemented method includes receiving a request to encode a video comprising a frame having pixels with non-perceptual quantizer code values of luminance at a content delivery service, determining, by the content delivery service, perceptual quantizer code values for the frame based at least in part on the non-perceptual quantizer code values, determining, by the content delivery service, one or more encoding parameters based at least in part on the perceptual quantizer code values, encoding, by the content delivery service, the frame based at least in part on the one or more encoding parameters into an encoded frame, and transmitting the encoded frame from the content delivery service to a viewer device.