Hybrid Radio Audio Alignment via Correlation Detection
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Solution Overview
Problem
In the HD Radio™ system, aligning analog and digital audio signals in time and level is manually cumbersome and impractical, leading to potential harsh transitions during blending, especially due to differences in audio processing techniques and signal generation methods.
Innovation Solution
A method and apparatus that filter both analog and digital audio signals to calculate correlation coefficients for time alignment and signal power ratios for level alignment, allowing for automatic detection and correction of misalignments without requiring a test signal, using existing HD Radio™ receivers in split mode for measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual alignment calibration is performed using test equipment at the transmitter site, then time and level alignment between analog and digital audio signals can be achieved, but the process becomes cumbersome and impractical, especially when audio processing changes occur
Solution Approach 1:
The system performs self-alignment by automatically detecting and measuring time and level differences between analog and digital audio signals using correlation techniques. The alignment process does not require external test equipment or manual intervention - the system monitors its own signals and determines alignment parameters autonomously, eliminating the cumbersome manual calibration process while maintaining precise alignment measurement
Solution Approach 2:
The patent replaces the mechanical/manual alignment calibration process with an automated signal processing system. Instead of physically connecting test equipment and manually adjusting parameters, the system uses digital signal processing techniques (correlation coefficient calculation) to automatically detect and report alignment status, substituting mechanical operations with electronic/computational methods
2Adaptability or versatility
If analog and digital audio signals are generated with separate signal generation paths and different processing techniques, then flexibility in audio processing is improved, but alignment between the two signals becomes nontrivial and complex
Solution Approach 1:
The patent introduces an intermediary measurement system that receives both analog and digital audio signals and computes correlation coefficients to determine time and level alignment. This intermediary device acts as a mediator that translates the complex alignment problem into measurable parameters (correlation coefficients) that can be automatically analyzed, simplifying the overall alignment process while preserving the flexibility of separate signal generation paths
Solution Approach 2:
The system transforms the alignment problem from a complex multi-parameter adjustment task into a simplified measurement of specific parameters (time delay and level difference) represented by correlation coefficients. By changing the measurement approach to focus on these key parameters, the system maintains audio processing flexibility while reducing alignment complexity
3Ease of operation
If the blend function transitions between digital and analog audio, then smooth transition is achieved when signals are aligned, but harsh transitions occur when misalignment exists, affecting listening quality
Solution Approach 1:
The patent implements a feedback mechanism where the measurement device continuously monitors the alignment between analog and digital audio signals by calculating correlation coefficients. This alignment information is fed back to the broadcast station, which can then adjust its signal processing to maintain proper alignment during transitions, ensuring smooth blending and preventing harsh transitions that would degrade listening quality
Data Source
AI summary
This invention provides a method of detecting time alignment of an analog audio signal and a digital audio signal in a hybrid radio system. The method comprises the steps of filtering the analog audio signal to produce a filtered analog audio signal, filtering the digital audio signal to produce a filtered digital audio signal, and using the filtered analog audio signal and the filtered digital audio signal to calculate a plurality of correlation coefficients, wherein the correlation coefficients are representative of time alignment between the analog audio signal and the digital audio signal. An apparatus for performing the method is also provided.