Adaptive Compander Filtering for Low-Latency Audio Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing compander systems suffer from latency issues due to block-based processing, which affects the efficiency of noise reduction in audio transmission systems.
Innovation Solution
The implementation of adaptive pre-emphasis and de-emphasis filtering using linear prediction in a compressor and expander device, respectively, with feedback mechanisms, to dynamically adjust filtering without latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If block-based processing is used for pre-emphasis filtering, then noise reduction is achieved, but latency is introduced
Solution Approach 1:
The patent implements continuous adaptive filtering that processes audio samples in real-time without blocking. The filter coefficients are continuously updated based on the autocorrelation of the input signal, eliminating the need for block-based processing while maintaining noise reduction effectiveness.
Solution Approach 2:
The patent uses dynamic filter adaptation where the pre-emphasis filter coefficients are continuously adjusted based on the statistical properties of the input signal. This dynamic adaptation allows the system to respond to changing signal characteristics in real-time without introducing latency associated with fixed block processing.
2Loss of time
If adaptive filtering is implemented in real-time, then latency is reduced, but computational complexity increases
Solution Approach 1:
The patent changes the approach from complex block-based spectral processing to simpler time-domain autocorrelation-based filter adaptation. By using autocorrelation of the input signal to determine filter coefficients, the computational complexity is reduced while maintaining real-time processing capability.
Solution Approach 2:
The patent replaces complex block-based processing mechanisms with a continuous stream processing approach. Instead of accumulating blocks of data for spectral transformation, the system processes individual samples continuously with simplified filter coefficient updates based on autocorrelation.
3Illumination intensity
If pre-emphasis filtering is applied, then high frequencies are amplified, but noise at high frequencies is also amplified
Solution Approach 1:
The patent implements a feedback mechanism where the filtered output is combined with the original input signal. This feedback approach allows the system to amplify high frequencies while using the original signal to maintain the noise floor, effectively preventing noise amplification while achieving spectral shaping.
Solution Approach 2:
The patent combines the pre-emphasis filtered signal with the original unfiltered signal in a composite manner. By adding the filtered component (which shapes the spectrum) to the original signal (which contains the noise floor), the system achieves high frequency amplification without proportionally amplifying high frequency noise.
Data Source
AI summary
A compressor device for a compander system has a level detecting/control device and a pre-emphasis device for carrying out an adaptive pre-emphasis filtering. The invention is also directed to an expander device for a compander system with a level detecting/control device and a de-emphasis device for carrying out an adaptive de-emphasis filtering.