Pre-echo Attenuation in Digital Audio via Energy Trend Verification
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Solution Overview
Problem
Existing digital audio signal transform coding methods suffer from pre-echo noise, which is particularly disturbing due to the high energy levels before signal transitions, and current solutions either require auxiliary information transmission or fail to completely eliminate pre-echoes, especially at low bit rates.
Innovation Solution
A method that calculates a leading coefficient of energies for sub-blocks preceding a detected onset, comparing it to a threshold to inhibit pre-echo attenuation processing, thereby enhancing detection reliability and avoiding false detections without transmitting additional information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If pre-echo attenuation processing is applied to all low-energy sub-blocks preceding a sub-block with onset, then pre-echo noise is reduced, but false detections occur when energy trend verification is not performed
Solution Approach 1:
The patent calculates a leading coefficient of energies for sub-blocks preceding the onset sub-block before applying attenuation processing. This preliminary energy trend verification determines whether the sub-blocks truly represent pre-echo conditions or normal signal variations, preventing false detections while maintaining effective pre-echo reduction when conditions are met
Solution Approach 2:
The patent introduces a new parameter - the leading coefficient of energies - that characterizes the energy trend in pre-onset sub-blocks. By comparing this coefficient against threshold values, the system dynamically determines whether attenuation processing should be applied, transforming a static attenuation approach into an adaptive one that responds to actual signal characteristics
2Productivity
If transform coding uses long windows to improve coding gain, then compression efficiency increases, but pre-echo duration increases making it more audible
Solution Approach 1:
The patent applies attenuation processing selectively to specific sub-blocks that meet the energy trend criteria (leading coefficient below threshold) rather than uniformly across the entire signal. This localized approach targets pre-echo regions while preserving other signal portions, maintaining coding efficiency while reducing audible pre-echo in critical areas
Solution Approach 2:
The patent applies attenuation processing only to sub-blocks where the leading coefficient verification confirms pre-echo conditions, rather than applying it excessively to all pre-onset sub-blocks. This partial action approach reduces pre-echo where necessary while avoiding degradation of normal signal segments, balancing pre-echo reduction with signal quality preservation
3Device complexity
If pre-echo attenuation is applied without energy trend verification, then processing complexity is reduced, but false detections increase degrading signal quality
Solution Approach 1:
The patent replaces complex auxiliary information transmission mechanisms with a simpler energy trend verification approach using leading coefficient calculation. Instead of transmitting additional side information about pre-echo conditions from encoder to decoder, the system uses local energy analysis that can be performed with minimal computational overhead, substituting mechanical complexity with a more elegant mathematical verification
Data Source
AI summary
A method for discriminating and attenuating pre-echo in a digital audio signal and generated from transform coding. The method includes the following acts in which, for a current frame broken down into sub-blocks, the low-energy sub-blocks precede a sub-block in which a transition or attack is detected, and determine a pre-echo area in which a pre-echo attenuation process is carried out. In the event that an attack is detected from the sub-block of the current frame, the method includes: calculating an energy leading coefficient for at least two sub-blocks of the current frame preceding the sub-block in which an attack is detected; comparing the leading coefficient to a predefined threshold; and inhibiting the pre-echo attenuation process in the pre-echo area in the event that the calculated leading coefficient is lower than the predefined threshold. Also provided are a discrimination and attenuation device implementing the acts of the method described and a decoder including such a device.