Audio Cross-Fading Using NLMS Filtering for Seamless Signal Switching
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Solution Overview
Problem
Conventional radio systems experience audio discrepancies and frequency attenuation during cross-fading due to non-linear characteristics and signal processing differences between analog and digital signals, leading to a compromised listening experience and increased computational complexity.
Innovation Solution
A cross-fading system that uses an adaptive filter with normalized least mean square (NLMS) algorithm to determine linear and non-linear data, synchronize audio signals based on a fine delay estimate, and perform time-domain cross-fading to eliminate audio discrepancies and reduce latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cross-fading is performed between analog and digital signals, then signal quality compensation is achieved, but audio discrepancies and frequency attenuation occur due to non-linear characteristics
Solution Approach 1:
The patent segments the second audio signal into linearly correlated data and non-linearly correlated data components. By separating these components, the system can selectively process only the linear portion during cross-fading, eliminating the harmful non-linear characteristics while preserving the beneficial signal quality compensation.
Solution Approach 2:
The patent extracts and removes the non-linearly correlated data from the second audio signal before cross-fading. This extraction process isolates the harmful non-linear components, allowing them to be excluded from the cross-fade operation while maintaining the useful linear signal components.
2Reliability
If conventional cross-fading is performed between analog and digital signals, then signal quality compensation is achieved, but computational complexity increases
Solution Approach 1:
The patent replaces complex frequency domain processing and sophisticated synchronization mechanisms with a simpler time-domain approach using normalized cross-correlation. This substitution maintains the essential cross-fading functionality while significantly reducing computational complexity and processing overhead.
Solution Approach 2:
The patent changes the processing domain from frequency domain to time domain, and simplifies the correlation method to normalized cross-correlation. This parameter change in the processing approach reduces computational complexity while preserving the core functionality of signal synchronization and cross-fading.
3Ease of operation
If conventional cross-fading is performed between analog and digital signals, then signal switching is achieved, but latency increases
Solution Approach 1:
The patent performs preliminary determination of linearly and non-linearly correlated data components before the actual cross-fading operation. This preliminary action allows the system to prepare the processed signal in advance, reducing the processing time required during the actual cross-fade and thereby minimizing latency.
Solution Approach 2:
The patent substitutes complex frequency domain processing and elaborate synchronization procedures with a streamlined time-domain normalized cross-correlation method. This substitution eliminates unnecessary processing steps, reducing the overall latency while maintaining effective signal switching capability.
Data Source
AI summary
A system for cross-fading audio signals receives temporal data associated with the audio signals. Initially, current playback data corresponds to one of the temporal data. The system determines linear and non-linear data of the other temporal data that are linearly and non-linearly correlated with the temporal data, respectively. Further, the system receives a cross-fade request when a parameter value of a signal quality associated with the audio signal of the temporal data exceeds a threshold value. In response, the system cross-fades the current playback data from the temporal data to the linear data of the other temporal data. Additionally, the system inserts the non-linear data to the current playback data to successfully transition from the current temporal data to the other temporal data.