Adaptive Loop Filter Clipping Signaling for Video Coding
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Solution Overview
Problem
Existing video coding technologies face challenges in achieving improved compression ratios with minimal sacrifice in picture quality, particularly in scenarios with limited network bandwidth and memory resources.
Innovation Solution
Implementing adaptive loop filtering (ALF) with a fixed length code for signaling clipping parameters, such as the clipping index, to simplify the process and enhance coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If variable length codes are used for signaling clipping parameters in adaptive loop filtering, then compression ratio is improved, but device complexity and processing overhead increase
Solution Approach 1:
The patent uses fixed length codes (e.g., 2-bit or 3-bit codes) for signaling clipping parameters instead of complex variable length codes. This approach sacrifices minimal compression efficiency to dramatically simplify the coding process, making the system more suitable for real-time applications with limited processing resources.
Solution Approach 2:
The patent changes the coding parameter from variable length to fixed length for clipping index signaling. This parameter change simplifies the encoder and decoder complexity while maintaining acceptable compression performance, particularly beneficial for real-time video processing where processing speed is critical.
2Reliability
If complex filtering algorithms are applied to improve picture quality, then picture quality is improved, but processing time and computational resources increase
Solution Approach 1:
The patent applies adaptive loop filtering selectively based on picture type and content characteristics rather than uniformly to all blocks. This partial application approach maintains picture quality where needed while reducing processing time and computational resources for blocks where filtering is less critical.
Solution Approach 2:
The patent uses different clipping values and filtering parameters for different regions and picture types (e.g., different clipping ranges for luma and chroma components, different parameters for different block types). This local adaptation maintains high picture quality where needed while reducing overall processing complexity.
3Measurement precision
If more detailed clipping parameters are signaled to improve filtering accuracy, then filtering precision is improved, but bitstream overhead increases
Solution Approach 1:
The patent uses compact fixed-length codes (2-bit or 3-bit) to signal clipping parameters instead of more detailed variable-length codes. This approach provides sufficient filtering accuracy for practical applications while dramatically reducing bitstream overhead and simplifying parameter signaling.
Data Source
AI summary
A method of coding, implemented by a decoding device, includes obtaining a bitstream, wherein at least one bit in the bitstream represents a syntax element for a current block, wherein the syntax element specifies the clipping index of the clipping value for an adaptive loop filter (ALF); parsing the bitstream to obtain a value of the syntax element for the current block, wherein the syntax element is coded using a fixed length code; applying adaptive loop filtering on the current block, based on the value of the syntax element for the current block. Herein fixed length code means that all possible values of the syntax element are signaled using the same number of bits.