Dynamic Delay Alignment for Radio Simulcast Audio Blending
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Solution Overview
Problem
Simulcast radio receivers face challenges in aligning analog and digital signals due to inherent delays, leading to audio artifacts during the blend operation from analog to digital sources, as static delay adjustments do not effectively prevent audible artifacts.
Innovation Solution
A dynamic time alignment method using a delay estimation unit that filters and decimates data streams to determine the delay between analog and digital signals, applying internal delays through sample rate converters or FIFO pointer adjustments to align them without generating audible artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a static delay adjustment is applied to align analog and digital signals, then the signals can be synchronized at the receiver, but audible audio artifacts are generated during the blend operation
Solution Approach 1:
The patent applies dynamics by transitioning from static delay adjustment to dynamic delay estimation. The receiver continuously estimates the delay between analog and digital signals and adjusts the delay accordingly, allowing the system to adapt to changing signal conditions and perform blend operations without generating audible artifacts.
Solution Approach 2:
The patent implements feedback through the delay estimation process. The receiver estimates the delay between analog and digital signals and uses this information to adjust the timing of the analog signal, creating a closed-loop system that continuously optimizes signal alignment and prevents audio artifacts during blend operations.
2Loss of time
If the analog signal is delayed to align with the digital signal, then time alignment is achieved, but the blend operation cannot be performed seamlessly
Solution Approach 1:
The patent applies preliminary action by estimating the delay between analog and digital signals before performing the blend operation. This advance knowledge of the delay allows the receiver to pre-adjust the analog signal timing, ensuring that when the blend operation occurs, both signals are properly aligned and no audible artifacts are generated.
3Measurement precision
If dynamic delay estimation is performed using filtered and decimated data streams, then accurate delay determination is achieved, but processing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the signal processing into distinct stages: filtering the data streams, decimating the filtered signals to reduce sampling rate, and then performing correlation on the decimated streams. This segmentation allows accurate delay determination while managing processing complexity by breaking down the overall task into manageable steps.
Solution Approach 2:
The patent applies partial action by filtering and decimating only the portions of the data streams needed for delay estimation, rather than processing the entire high-resolution signals. This partial processing achieves sufficient delay determination accuracy while significantly reducing the computational complexity compared to full-signal processing.
Data Source
AI summary
A method and apparatus is disclosed in which delay is applied to analog-sourced audio in a radio simulcast when the analog signal initially leads the digital signal. A radio receiver is configured to receive a simulcast radio program broadcast with an analog signal and a digital signal. The program content can be extracted from either the analog or digital signals, with the audio source eventually being blended to the digital signal. Audio is initially provided based on the analog signal. If the analog signal is initially leading the digital signal, delay is applied a data stream corresponding to the analog signal relative to a data stream corresponding to the digital signal. Delay applied to the data stream corresponding to the analog signal is increased at a rate that avoids audio artifacts of the output audio. The blend is performed when the data streams are aligned in time.