Enhancement Layer Encoding for G.711 Quantization Error Reduction
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Solution Overview
Problem
The G.711 codec experiences quality degradation due to quantization errors, which are not effectively addressed by existing compression methods, especially in low-bit-rate communication networks.
Innovation Solution
An enhancement layer encoding and decoding method that dynamically allocates additional bits for mantissa information based on exponent information, reducing quantization errors by optimizing bit allocation in each sample frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If log PCM codec compresses speech signal to reduce bit rate, then transmission efficiency is improved, but quantization error increases causing quality degradation
Solution Approach 1:
The patent segments the speech signal processing into base layer (standard G.711 log PCM encoding) and enhancement layer (additional mantissa bits). This segmentation allows the base layer to maintain compatibility and basic compression while the enhancement layer selectively adds precision where needed, resolving the contradiction between compression efficiency and speech quality.
Solution Approach 2:
The patent applies local quality by adding enhancement bits selectively based on local signal characteristics (exponent values). Samples with larger exponent values (indicating higher quantization error potential) receive more enhancement bits, while samples with smaller exponents receive fewer or no enhancement bits. This localized approach improves speech quality where needed without uniformly increasing bit rate, thus resolving the contradiction between transmission efficiency and speech quality.
2Manufacturing precision
If additional bits are allocated to each sample to reduce quantization error, then speech quality is improved, but bit rate increases
Solution Approach 1:
The patent applies partial action by allocating enhancement bits to only some samples rather than all samples. Based on the exponent values, the system determines which samples benefit most from enhancement and allocates bits accordingly. This partial allocation improves speech quality for critical samples while keeping the overall bit rate increase minimal, thus resolving the contradiction between speech quality and bit rate.
Solution Approach 2:
The patent implements dynamic bit allocation where the number of enhancement bits per sample varies based on the exponent value of each sample. Samples with larger exponents (indicating coarser quantization in the base layer) receive more enhancement bits, while samples with smaller exponents receive fewer or no enhancement bits. This dynamic adaptation optimizes the trade-off between speech quality improvement and bit rate consumption.
Data Source
AI summary
Provided is a method and apparatus for encoding and decoding an enhancement layer to reduce quantization error in a G.711 codec. Exponent indices of additional mantissa information of each sample are calculated based upon exponent information of each sample in a frame. A process of allocating 1 bit to each sample with a current exponent index is repeated, the exponent index starting from the maximum value while decreasing by 1 at every repetition until the total number of bits allocated to the samples is equal to the total number of available bits in the frame. And the most significant bits, as many as the number of bits allocated to each sample, are extracted from the additional mantissa information of each sample in the frame.