ASRC Audio Synchronization via Input Rate Adjustment
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Solution Overview
Problem
Wireless audio playback systems often experience synchronization issues due to differences in oscillator frequencies between master and slave devices, leading to perceptible discrepancies in playback speed across multiple channels.
Innovation Solution
The method involves generating a master channel stream and a slave channel stream using processors and memories in audio speaker devices, with an asynchronous sampling rate converter (ASRC) adjusting the input transfer rate to synchronize playback samples, and using a delay block to maintain constant output transfer rates and audio quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If wireless audio playback is used to allow flexible listening locations, then ease of operation is improved, but synchronization between multiple channels deteriorates due to oscillator frequency differences
Solution Approach 1:
The system continuously monitors the playback position of the master channel and sends feedback signals to slave devices. The master device transmits timing information including sample counters and trigger signals, allowing slave devices to adjust their playback position dynamically to maintain synchronization with the master channel despite oscillator frequency variations.
Solution Approach 2:
The system implements dynamic adjustment of playback timing by allowing slave devices to modify their playback speed and position in real-time based on received synchronization signals. The ASRC (Asynchronous Sample Rate Converter) dynamically adjusts the sampling rate to compensate for timing differences, enabling flexible synchronization adaptation.
2Reliability
If asynchronous sampling rate conversion is used to adjust input transfer rate, then playback synchronization is improved, but device complexity increases
Solution Approach 1:
The ASRC acts as an intermediary component between the received audio stream and the DAC. It mediates the timing and rate differences by converting samples asynchronously, inserting or removing samples as needed to match the master channel timing while maintaining audio quality through appropriate filtering.
Solution Approach 2:
The system changes the sampling rate parameter dynamically based on the timing difference between master and slave channels. The ASRC adjusts the input sampling rate to compensate for oscillator frequency variations, transforming the audio stream from one rate to another while maintaining synchronization.
3Reliability
If sample rate adjustment is performed to synchronize playback, then playback speed consistency is improved, but audio quality may deteriorate
Solution Approach 1:
The system applies different processing quality levels to different parts of the audio signal. Critical samples that affect synchronization are processed with high precision, while less critical samples use simpler processing. The filtering is applied locally at the boundaries of sample rate changes to minimize quality impact.
Solution Approach 2:
The system combines multiple processing techniques (ASRC, filtering, sample insertion/deletion) to create a composite solution that maintains audio quality while achieving synchronization. The combination of these methods compensates for the quality loss that would occur with any single method alone.
Data Source
AI summary
Implementations of a method of synchronizing audio playback may include, using a correction block and a second sample counter, comparing a number of playback samples in a slave channel stream with a number of master playback samples in a master channel stream received from a wireless telecommunication channel from a first audio speaker device. The method may include adjusting an input transfer rate of playback samples into an ASRC if the number of playback samples in the slave channel stream and the number of master playback samples is not the same, keeping an output transfer rate of playback samples of the slave channel stream out of the ASRC to a slave DAC at a constant value, and, through adjusting the input transfer rate into the ASRC, synchronizing the playback of audio data included in the slave channels stream with the playback of audio data included in the master channel stream.