Palette Mode Coding Syntax Signaling Optimization
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Solution Overview
Problem
Current HEVC palette coding methods are complex and inefficient in signaling and binarization of syntax elements, particularly in determining the number of palette indices and palette predictor runs, which affects video compression efficiency.
Innovation Solution
The proposed solution simplifies syntax signaling by using N-th order exponential Golomb codes for binarizing the number of palette indices and imposing constraints on palette predictor runs, allowing adaptive coding based on block size and context-based entropy coding for improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If current HEVC palette coding methods are used for signaling and binarization of syntax elements, then comprehensive palette index information can be signaled, but the complexity of signaling and binarization increases and encoding/decoding efficiency decreases
Solution Approach 1:
The syntax element signaling is divided into multiple parts: a first syntax element signals a first variable related to palette indices, and a second syntax element signals a second variable related to palette predictor runs. This segmentation allows different parts of the palette coding information to be signaled separately using appropriate binarization methods, reducing overall complexity while maintaining information completeness.
Solution Approach 2:
The patent applies N-th order exponential Golomb codes with different orders for different syntax elements. By changing the binarization parameter (the order N of the exponential Golomb code) according to the specific syntax element and block size, the patent optimizes the balance between information completeness and signaling complexity for each particular case.
2Manufacturing precision
If detailed palette coding syntax elements are signaled, then accurate video representation is achieved, but encoding and decoding efficiency decreases
Solution Approach 1:
The patent uses adaptive binarization by selecting different orders of exponential Golomb codes based on block size and syntax element type. This parameter change allows the encoding process to be more efficient for different block sizes while maintaining accurate video representation through appropriate level of detail in each syntax element.
Solution Approach 2:
The binarization method dynamically adapts to the specific coding context by selecting different N-th order exponential Golomb codes based on block size and syntax element characteristics. This dynamic adaptation improves encoding efficiency without sacrificing video representation accuracy, as each syntax element is binarized according to its specific requirements.
3Loss of information
If conventional binarization methods are used for palette indices, then all index values can be represented, but the bitstream length increases and compression performance decreases
Solution Approach 1:
The patent employs N-th order exponential Golomb codes where the order N is selected based on the expected value range and distribution of the syntax element. This parameter change in binarization order allows compact representation of small values while still being able to represent larger values when necessary, optimizing bitstream length without losing index value information.
Solution Approach 2:
The exponential Golomb coding uses partial action by representing only the necessary number of bits for each syntax element value based on its distribution characteristics. Instead of using a fixed binarization that must accommodate the maximum possible value, the adaptive approach uses just enough bits for each case, reducing overall bitstream size while maintaining complete information.
Data Source
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AI summary
A simplified syntax signalling for the number of palette indices is disclosed, where the syntax element corresponding to the total number of palette indices minus one is signalled and the palette indices are associated with the copy-index modes in the current block. In another embodiment, a syntax corresponding to the number of palette indices minus 1 is signalled, where the palette indices are associated with the copy-index modes in the current block. According to this embodiment, the syntax is constrained to a range from 0 to block size minus 1. In yet another embodiment, conformance constraint is imposed on the palette predictor run. For a current position of the palette predictor list, a syntax element corresponding to a current palette predictor run is parsed from the input bitstream and the syntax element is constrained to a range of values access valid entries in the palette predictor.