Adaptive Audio Coding for Frame-by-Frame Spectral Switching
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Solution Overview
Problem
Existing sound signal coding methods are inefficient depending on the characteristics of the input sound signal, such as the steepness of the spectral envelope and the degree of spectral concentration, leading to either inefficient coding or artificial-sounding decoded signals.
Innovation Solution
A coding method that selects between different coding processing types frame by frame based on the energy of high-frequency components and the sparsity of high-frequency components, using either spectral envelope-based coding or variable-length coding on energy differentials, to adapt to the specific characteristics of the input sound signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If variable-length coding on average energy differential is used, then code amount is reduced for signals with gentle spectral envelope, but code amount becomes large for signals with steep spectral envelope
Solution Approach 1:
The patent changes the coding parameter (coding method type) based on the spectral characteristics of the input signal. When the spectral envelope has gentle ascents and descents, variable-length coding on average energy differential is used. When the spectral envelope has steep ascents and descents, spectral envelope-based coding is used instead. This dynamic parameter change allows the system to adapt to different signal characteristics and maintain efficient coding across various conditions.
2Productivity
If spectral envelope-based coding is used, then coding efficiency is improved for signals with steep spectral envelope, but coding efficiency decreases for signals with gentle spectral envelope
Solution Approach 1:
The patent implements a dynamic coding system that automatically selects the appropriate coding method based on the spectral characteristics of the input signal. The system evaluates the steepness of the spectral envelope and dynamically switches between spectral envelope-based coding and variable-length coding on average energy differential. This dynamic adaptation ensures high coding efficiency regardless of whether the spectral envelope has steep or gentle characteristics.
3Device complexity
If a single coding method is used for all frames, then device complexity is reduced, but coding efficiency varies significantly with signal characteristics
Solution Approach 1:
The patent introduces a conditional parameter change mechanism that selects between two coding methods based on spectral characteristics. By evaluating the steepness of spectral envelope ascents and descents, the system dynamically adjusts the coding parameter (method selection) to optimize efficiency for the current signal type, rather than using a fixed single method for all conditions.
4Adaptability or versatility
If coding method switches between frames, then adaptability to signal characteristics is improved, but risk of artificial sound increases
Solution Approach 1:
The patent employs a feedback mechanism where the coding method selection for each frame is based on the spectral characteristics of that frame. This closed-loop approach ensures that the selected coding method is appropriate for the current signal characteristics, thereby maintaining natural sound quality in the decoded output while adapting to different input conditions.
Data Source
AI summary
A coding technology that efficiently codes an input sound signal irrespective of the characteristics thereof and can obtain a decoded sound signal that sounds less artificial to a listener. A coding method codes an input sound signal frame by frame of a predetermined time segment by a selected coding processing from a plurality of types of coding processing in the frequency domain, the coding method makes it possible for a selection unit to select coding processing which is different from the coding processing of the preceding frame as coding processing of the present frame if at least one of the magnitude of the energy of high frequency components of the input sound signal of the preceding frame and the magnitude of the energy of high frequency components of the input sound signal of the present frame is smaller than or equal to a predetermined threshold value.