In-loop Reshaping Adaptive Direction for Video Coding
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Solution Overview
Problem
Current video encoding and decoding methods face inefficiencies in exploiting sample codeword values distribution, particularly in intra prediction mode, due to complex inverse mapping processes that increase computational complexity and reconstruction errors.
Innovation Solution
The method involves inserting parameters representing an in-loop reshaping filter into the bitstream for encoding and decoding, simplifying the inverse mapping process by using uniformly sampled look-up tables and signaling the nature of the reshaping LUT, either forward or inverse, to reduce computational complexity while maintaining coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If complex inverse mapping processes are used to exploit sample codeword values distribution, then coding efficiency is improved, but computational complexity increases
Solution Approach 1:
The patent changes the sampling method of the lookup table from non-uniform to uniform sampling. This parameter change simplifies the computational process while maintaining the ability to exploit sample codeword values distribution, thereby improving coding efficiency without increasing computational complexity
Solution Approach 2:
The patent uses a lookup table (copy) to represent the complex inverse mapping process. By pre-computing and storing the mapping relationships in a uniformly sampled lookup table, the complex calculations are replaced with simple table lookups, reducing computational complexity while preserving coding efficiency
2Productivity
If complex inverse mapping processes are used to exploit sample codeword values distribution, then coding efficiency is improved, but reconstruction errors increase
Solution Approach 1:
The patent changes the sampling distribution parameter from non-uniform to uniform, which simplifies the mapping process and reduces interpolation errors, thereby maintaining reconstruction accuracy while achieving coding efficiency
Solution Approach 2:
The patent applies forward reshaping in the encoder and inverse reshaping in the decoder in a coordinated manner. By inverting the reshaping operation at the decoder side with matching parameters, the original signal distribution is restored, minimizing reconstruction errors while maintaining coding gains
3Device complexity
If uniformly sampled look-up tables are used, then computational complexity is reduced, but mapping precision may be compromised
Solution Approach 1:
The patent carefully selects the number of lookup table entries and the range of mapping values as parameters. By optimizing these parameters, uniform sampling achieves sufficient mapping precision for practical applications while maintaining computational simplicity
Solution Approach 2:
The patent uses a finite number of uniformly sampled points in the lookup table, which is a partial approximation of the continuous mapping function. This partial action approach provides sufficient precision for video coding applications without requiring the full computational complexity of continuous mapping
Data Source
AI summary
A method and apparatus for performing a forward mapping function or its inverse is implemented through information conveyed in a bitstream to perform mapping. The information can be implemented in a uniform or non-uniform lookup table. A decoder can receive the information and derive the inverse function to be used. In one embodiment, a decoder receives information representative of an inverse mapping function and uses the information to implement an inverse mapping lookup table for intra coded picture portions and can derive a forward mapping lookup table to be used with an inverse mapping lookup table for inter coded picture portions.