Stereo Encoding Mode Switching for Low-Bit-Rate Audio
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Solution Overview
Problem
Existing low-bit-rate encoding techniques for speech/acoustic signals face challenges in achieving optimal coding performance due to insufficient performance in inter-channel time difference (ITD) and bit allocation in Mid-Side stereo coding schemes, leading to degraded coding quality.
Innovation Solution
An encoding apparatus and method that dynamically switches between Mid-Side and Left-Right stereo coding modes based on bit allocation and ITD analysis, using Code-Excited-Linear-Prediction (CELP) coding for improved encoding efficiency, particularly in low-bit-rate scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Mid-Side stereo coding is applied to reduce bit rate, then coding efficiency is improved, but coding performance deteriorates due to insufficient ITD handling and bit allocation
Solution Approach 1:
The patent implements dynamic switching between Mid-Side and Left-Right coding modes based on signal characteristics analysis. The system adapts the coding mode frame-by-frame or block-by-block, selecting the optimal mode for each segment to maintain coding performance while achieving low bit rate. This dynamic adaptation resolves the contradiction by making the coding system flexible rather than static.
Solution Approach 2:
The patent optimizes bit allocation parameters between mid-channel and side-channel dynamically based on signal characteristics. By adjusting the bit allocation ratio and ITD compensation parameters according to the actual signal content, the system achieves better coding performance at low bit rates without requiring increased overall bit rate.
2Productivity
If CELP coding is applied to mid-channel signal, then encoding efficiency is improved, but complexity of encoding process increases
Solution Approach 1:
The patent divides the stereo signal into mid-channel and side-channel components, applying different coding strategies to each. The CELP coding is applied only to the mid-channel signal where it provides significant benefits, while the side-channel uses simpler coding. This segmentation allows the system to gain encoding efficiency where needed without unnecessarily increasing overall complexity.
Solution Approach 2:
The patent applies high-quality CELP coding selectively to the mid-channel signal where it provides the most benefit, rather than applying complex coding uniformly across all channels. This localized application of advanced coding techniques optimizes the balance between encoding efficiency and complexity by concentrating computational resources where they yield the greatest performance improvement.
Data Source
AI summary
This encoding device comprises: a control unit that, if an inputted stereo signal is determined to be a signal suitable for encoding using a mid-side stereo system, determines whether to apply a first encoding mode or a second encoding mode on the basis of a numerical value calculated by using the number of bits estimated to be necessary for encoding a mid-channel and the number of bits estimated to be necessary for encoding a side channel; a first encoding unit that, if application of the first encoding mode is determined, applies code-excited-linear-prediction (CELP) encoding to a mid-channel signal; and a second encoding unit that, if application of the second encoding mode is determined, performs spectral encoding on a stereo signal.