Dependent Quantization Sign Hiding for VVC Coefficient Segments
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Solution Overview
Problem
The Versatile Video Coding (VVC) standard incorporates dependent quantization to improve coding efficiency, but the sign bit hiding tool is turned off, limiting its performance.
Innovation Solution
A method and apparatus for dependent quantization with sign bit hiding, where transform coefficients are divided into segments, and the sign-hiding state of selected coefficients are encoded without signaling the signs, using a trellis structure, and parity information of the current segment, or both are encoded without signaling the signs associated with the coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If dependent quantization is used to improve coding efficiency, then coding performance is improved, but the sign bit hiding tool must be turned off, limiting its performance
Solution Approach 1:
The transform coefficients are divided into multiple segments, with each segment processed independently through the trellis structure. This segmentation allows the sign bit hiding mechanism to operate within each segment while maintaining overall dependent quantization, thus resolving the contradiction between coding efficiency and sign bit hiding capability.
Solution Approach 2:
The patent introduces a dynamic state machine with multiple states that adapts the quantization process based on the sign bit hiding requirements. The state transitions dynamically adjust the quantization behavior to accommodate both dependent quantization and sign bit hiding, enabling both tools to function simultaneously.
2Measurement precision
If sign bits are explicitly signaled for all coefficients, then decoding accuracy is improved, but bitstream length increases, reducing coding efficiency
Solution Approach 1:
The patent extracts and removes the explicit sign bit signaling for certain coefficients by using the trellis state information to implicitly represent sign information. This extraction reduces the bitstream length while maintaining decoding accuracy through the state-based sign recovery mechanism.
Solution Approach 2:
The trellis state acts as an intermediary that carries sign information implicitly. Instead of directly signaling sign bits, the state machine uses its internal state to encode and later recover sign information, thus reducing explicit signaling overhead while preserving decoding accuracy.
Data Source
AI summary
A method and apparatus for video coding using dependent quantization (DQ) with sign hiding. At the decoder side, for a current segment, a sign-hiding state of a selected coefficient, or parity information of the quantized transform coefficients associated with the current segment, or both are determined. The current segment comprises a sign-hiding coefficient. The signs associated with one or more sign-hiding quantization coefficients corresponding to one or more target coefficients in the current segment are determined based on the sign-hiding state, the parity information of the current segment, or both. The quantization coefficients with the signs recovered are dequantized using respective quantizers from the plurality of quantizers. A method and apparatus for a corresponding encoder are also disclosed.