Modified Quantizer for AV1 Video Bit Rate Granularity
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Solution Overview
Problem
The AV1 video coding format has limited quantization step size resolution, particularly evident in 10-bit and 12-bit internal bit depth, which affects the granularity of bit rates achievable by the codec.
Innovation Solution
The proposed solution extends the range of the quantization index by an offset value, allowing for the retrieval of a quantization step size from a lookup table based on the quantization index and offset, enabling more precise encoding and decoding of video data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the quantization index range is extended by an offset value, then the granularity of bit rates is improved, but the device complexity increases due to the need for extended lookup tables and modified parsing logic
Solution Approach 1:
The patent extends the quantization index range by adding an offset dimension to the existing index values. This allows the system to access additional quantization step sizes beyond the original range, effectively adding a new dimension to the quantization parameter space without fundamentally changing the core quantization mechanism.
Solution Approach 2:
The patent pre-extends the lookup table with additional quantization step sizes corresponding to the extended quantization index range. By preparing this extended mapping in advance, the system avoids complex real-time calculations during encoding/decoding, maintaining efficiency while supporting finer bit rate granularity.
2Productivity
If a lookup table is used to retrieve quantization step sizes based on extended quantization index, then the encoding and decoding efficiency is improved, but the memory requirements increase
Solution Approach 1:
The lookup table is pre-computed and stored with all quantization step sizes corresponding to the extended quantization index range. During encoding and decoding operations, the system simply performs a table lookup based on the quantization index, avoiding complex real-time mathematical calculations and significantly improving processing efficiency.
Solution Approach 2:
The patent uses a lookup table that stores pre-calculated quantization step sizes, effectively creating a reference copy of the quantization mapping relationship. This allows the system to retrieve quantization parameters efficiently without re-computing them, trading memory space for processing speed.
3Manufacturing precision
If the quantization step size resolution is increased in AV1, then the video compression precision is improved, but the compatibility with existing AV1 implementation is reduced
Solution Approach 1:
The patent extends the quantization index range by adding an offset value to the syntax element, allowing the encoder to signal finer quantization steps. The lookup table is pre-extended to map these extended indices to appropriate step sizes, enabling higher precision while maintaining the same syntax element structure used in AV1.
Solution Approach 2:
The patent modifies the quantization index parameter by adding an offset value, which shifts the range of representable quantization steps. This parameter change allows the system to access finer quantization granularity without changing the fundamental quantization mechanism or syntax element definition, thereby maintaining compatibility with AV1 while achieving improved precision.
Data Source
AI summary
A method, computer program, and computer system is encoding or decoding video data. Video data may include a syntax element indicating a quantization index, wherein a range of the quantization index is extended by an offset value. The syntax element may be parsed to determine the quantization index, a quantization step size may be obtained from a lookup table based on the quantization index and the offset value; and the video data may be encoded or decoded based on the quantization step size.