Arithmetic Coding for AMR-WB Pulse Indices
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Solution Overview
Problem
Current speech codecs, such as AMR-WB, face inefficiencies in encoding and decoding algebraic codebook indices, particularly in terms of bit rate usage, leading to suboptimal bandwidth utilization and increased distortion at varying bit rates.
Innovation Solution
The implementation of enumerative and arithmetic source coding methods to encode and decode algebraic codebook indices, specifically by representing pulse positions as indices and using binary arithmetic coding to reduce the number of bits required for encoding, thereby optimizing bit rate usage and reducing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of encoded pulse positions is increased to reduce distortion, then encoding precision is improved, but bit rate increases leading to worse bandwidth utilization
Solution Approach 1:
The patent applies arithmetic coding to transform the encoding parameters from fixed-length binary representation to variable-length codes based on probability distributions. By modeling the pulse position indices as random variables and using their probability mass functions to generate codewords, the system achieves more efficient bit representation that adapts to the actual distribution of pulse positions, thereby reducing bit rate while maintaining encoding precision.
2Ease of operation
If traditional binary encoding is used for algebraic codebook indices, then encoding simplicity is maintained, but bandwidth utilization deteriorates due to higher bit rates
Solution Approach 1:
The patent replaces the traditional mechanical binary encoding mechanism with an arithmetic coding system that uses mathematical probability models. Instead of simply assigning fixed-bit binary codes to pulse position indices, the system uses cumulative probability calculations and interval partitioning to generate optimized codewords, substituting a more complex mathematical approach for a simpler but less efficient mechanical encoding process.
Data Source
AI summary
Methods, and corresponding codec-containing devices are provided that have source coding schemes for encoding a component of an excitation. In some cases, the source coding scheme is an enumerative source coding scheme, while in other cases the source coding scheme is an arithmetic source coding scheme. In some cases, the source coding schemes are applied to encode a fixed codebook component of the excitation for a codec employing codebook excited linear prediction, for example an AMR-WB (Adaptive Multi-Rate-Wideband) speech codec.