Audio Signal Cross-Fading With NLMS Filtering for Analog-Digital Transitions
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Solution Overview
Problem
Conventional radio systems experience audio discrepancies and computational complexity during cross-fading between analog and digital signals due to non-linear characteristics, leading to frequency attenuation and compromised user experience.
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, synchronizes signals with a fine delay estimate, and transitions between signals using time-domain processing to minimize audio discrepancies and reduce latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cross-fading is used between analog and digital signals, then signal switching can be performed, but audio discrepancies and frequency attenuation occur due to non-linear characteristics
Solution Approach 1:
The patent introduces an intermediary signal processing system that includes an adaptive filter and a comb filter. The adaptive filter processes the secondary signal to compensate for non-linear characteristics, while the comb filter specifically targets and eliminates frequency attenuation. These intermediary components work together to bridge the audio quality gap between analog and digital signals during cross-fading transitions.
Solution Approach 2:
The patent implements feedback mechanisms through the adaptive filter that continuously adjusts its coefficients based on the correlation between primary and secondary signals. The normalized least mean square (NLMS) algorithm provides feedback-driven adaptation to minimize audio discrepancies in real-time during cross-fading operations.
2Productivity
If frequency domain processing is used for cross-fading, then signal processing can be performed, but computational complexity and latency increase
Solution Approach 1:
The patent substitutes frequency domain processing with time domain processing for the adaptive filter operations. By implementing the adaptive filter in the time domain using direct signal processing, the system eliminates the computational overhead and latency associated with frequency domain transforms while maintaining effective signal compensation during cross-fading transitions.
Data Source
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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 nonlinearly 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.