I2S Word-Select Detector for Wireless Earbud Audio Sync
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Solution Overview
Problem
Truly wireless earbuds face challenges in synchronizing audio playback due to differences in distance and interference between earbuds and the audio source, leading to out-of-sync audio experiences, as there is no wired connection to synchronize digital-to-analog converters (DACs) and inter-IC sound (I2S) agents.
Innovation Solution
An audio codec system that includes an I2S agent, a DAC, and an I2S word-select (WS) detector, where the I2S WS detector ensures the I2S agent and DAC start processing data simultaneously by monitoring the WS signal and sending enable commands at predetermined times to minimize delays and maintain synchronized playback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If truly wireless earbuds receive audio signals wirelessly without wired connections, then wireless freedom and convenience are improved, but audio synchronization between earbuds deteriorates due to different distances and interference from the audio source
Solution Approach 1:
The system performs preliminary actions by buffering audio samples before playback and pre-calculating timing adjustments. The I2S agent receives and buffers digital audio samples in advance, and the system pre-determines the number of samples to skip or add based on measured playback timing, ensuring synchronized playback without real-time adjustments
Solution Approach 2:
The system implements feedback mechanisms by monitoring the actual playback timing of each earbud and using this information to adjust future playback timing. The processor measures the time between receiving audio samples and their playback, then uses this feedback to calculate appropriate sample skipping or insertion to maintain synchronization
2Device complexity
If the DAC and I2S agent are enabled independently without coordinated control, then device complexity is reduced, but playback synchronization deteriorates due to unknown delays in the audio codec
Solution Approach 1:
The system merges the control of the DAC and I2S agent by having the I2S agent buffer audio samples that are then transferred to the DAC's buffer. This coordinated buffering approach ensures that both components operate in sync, with the DAC processing samples at the same rate they are supplied by the I2S agent, eliminating timing mismatches
Solution Approach 2:
The audio codec buffer serves as an intermediary between the I2S agent and the DAC. This buffer mediates the data flow, allowing the I2S agent to supply samples at one timing rate while the DAC processes them at another rate, with the buffer absorbing timing differences and ensuring smooth, synchronized transfer
3Speed
If audio samples are processed immediately upon receipt, then processing speed is improved, but playback timing synchronization deteriorates due to variance in device under test delay
Solution Approach 1:
The system performs preliminary buffering of audio samples in the I2S agent before transferring them to the DAC. This preliminary action allows the system to maintain high processing speed while ensuring that samples are ready for immediate playback transfer, eliminating delays caused by on-the-fly processing decisions
Solution Approach 2:
The system dynamically changes processing parameters by adjusting the number of audio samples to skip or add based on measured playback timing. The processor calculates the appropriate parameter adjustment (number of samples) to apply, then implements this change to maintain consistent playback timing across different conditions
Data Source
AI summary
The technology provides for an audio codec with an inter-IC sound (I2S) word-select (WS) detector. The I2S WS detector is configured to enable an I2S agent and DAC within the audio codec such that they begin processing data simultaneously. The I2S WS detector may monitor a word-select signal received by the I2S signal for a rising edge and after detecting the rising edge on the WS signal, the I2S WS detector may send an enable command to the I2S agent and the DAC immediately before the a subsequent rising edge of the WS signal.