HDR Video Reshaping for Compression Efficiency
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Solution Overview
Problem
High Dynamic Range (HDR) video compression faces challenges in efficiently encoding and delivering HDR content due to its increased data requirements, particularly in low bitrate applications like video streaming, as existing compression standards are optimized for Standard Dynamic Range (SDR) video and do not fully match the Human Visual System (HVS) perceptual model.
Innovation Solution
The method involves reshaping HDR video frames from an IPT color space into a YCbCr-like color space for encoding, using a reshaping ratio that increases with pixel distance from a neutral level and spatial location, allowing for more efficient bit allocation based on perceptual importance, and then reversing this process after decoding to maintain the original IPT color space representation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If HDR video is encoded using existing compression standards optimized for SDR, then compatibility with existing encoding standards is maintained, but compression efficiency is insufficient and bandwidth requirements increase
Solution Approach 1:
The patent transforms HDR video from IPT color space to Y'CbCr color space, changing the parameter representation of video data. This parameter transformation enables existing SDR-optimized compression standards to effectively compress HDR content by mapping it into a more compressible color space format, thereby improving compression efficiency while maintaining compatibility with existing encoding standards
Solution Approach 2:
The patent introduces Y'CbCr color space as an intermediary representation between HDR source material (IPT color space) and the compression process. This intermediary transformation layer allows HDR content to be processed by legacy SDR compression standards, bridging the gap between new HDR content requirements and existing compression infrastructure
2Ease of operation
If uniform bit allocation is used for all pixels, then encoding simplicity is maintained, but perceptual quality deteriorates because important regions receive insufficient bits
Solution Approach 1:
The patent implements non-uniform bit allocation where different regions of the video frame receive different amounts of bits based on their perceptual importance. The transformation to Y'CbCr color space and subsequent compression allows for region-specific quality control, allocating more bits to visually important areas (such as regions with neutral luminance values) and fewer bits to less important areas, thereby improving overall perceptual quality while maintaining reasonable encoding complexity
3Manufacturing precision
If more bits are allocated to all pixels in HDR video, then video quality is improved, but bandwidth requirements increase
Solution Approach 1:
By changing the color space parameters from IPT to Y'CbCr, the patent creates a more efficient representation of HDR video data that requires fewer bits to achieve the same perceptual quality. This parameter transformation reduces the total bit requirement while maintaining video quality by exploiting the perceptual characteristics of human vision in the Y'CbCr color space
Data Source
AI summary
Systems and methods are disclosed for reshaping HDR video content to improve compression efficiency while using standard encoding/decoding techniques. Input HDR video frames, e.g., represented in an IPT color space, may be reshaped before the encoding/decoding process and the corresponding reconstructed HDR video frames may then be reverse reshaped. The disclosed reshaping methods may be combinations of scene-based or segment-based methods.