CELP Codec Bit-Budget Allocation to Reduce ROM Table Complexity
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Solution Overview
Problem
Existing CELP codecs face inefficiencies in distributing bit-budgets due to large ROM tables and fluctuating bit-budget allocations among CELP core and supplementary modules, particularly at varying bit rates, leading to inefficient search and complexity in encoding sound signals.
Innovation Solution
A method and device for dynamically allocating bit-budgets among CELP core module parts using intermediate bit rates and symmetric distribution based on the total bit-budget, adjusting for fluctuations in supplementary module requirements, and optimizing bit allocation across sub-frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of bit rates supported by a codec increases, then the versatility of the codec improves, but the length of ROM tables proportionally increases and search efficiency deteriorates
Solution Approach 1:
The patent segments the bit-budget allocation into multiple components: a base bit-budget from ROM tables and additional bit-budgets allocated to specific coding parts (LP coefficients, codebook gains, etc.). This segmentation allows the system to support multiple bit rates without proportionally increasing ROM table size, as the tables only need to store base values rather than complete allocation schemes for each bit rate.
2Productivity
If the bit-budget allocated to supplementary codec modules fluctuates based on signal characteristics, then the encoding efficiency improves, but the bit-budget allocated to CELP core module becomes variable which increases complexity
Solution Approach 1:
The patent implements dynamic bit-budget allocation where the CELP core module bit-budget is determined by subtracting supplementary module bit-budgets from the total bit-budget. This dynamic adjustment allows encoding efficiency to improve based on signal characteristics while maintaining a systematic approach to complexity management through clear allocation rules.
Solution Approach 2:
The patent changes the parameter of bit-budget allocation from fixed to variable based on signal characteristics and network conditions. By allowing the CELP core module bit-budget to vary systematically through parameter changes rather than structural complexity, the system achieves adaptability without proportionally increasing device complexity.
3Manufacturing precision
If the bit-budget is carefully distributed among different coding parts at a given bit rate, then the quality at constant bit rate improves, but the search within ROM tables becomes less efficient
Solution Approach 1:
The patent segments the bit-budget distribution into predefined components stored in ROM tables (base bit-budget, LP coefficient budget, codebook gain budgets, etc.). This segmentation maintains manufacturing precision by ensuring careful distribution among coding parts while improving productivity by using structured table lookups rather than complex searches.
Data Source
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AI summary
A method and device for allocating a bit-budget to a plurality of first parts and to a second part of a CELP core module of (a) an encoder for encoding a sound signal or (b) a decoder for decoding the sound signal. In a frame of the sound signal comprising sub-frames, respective bit-budgets are allocated to the first CELP core module parts and a bit-budget remaining after allocating to the first CELP core module parts their respective bit-budgets is allocated to the second CELP core module part. According to an alternative, the second CELP core module part bit-budget is distributed between the sub-frames of the frame and a larger bit-budget is allocated to at least one of the sub-frames of the frame. The at least one sub-frame may be the first sub-frame of the frame, at least one sub-frame following the first sub-frame, or the sub-frame using a glottal-impulse-shape codebook.