Server-Based Audio Clock Skew Compensation
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Solution Overview
Problem
Existing methods for synchronizing multi-channel speakers over a network face challenges in achieving precise timing due to clock skew, leading to psycho-acoustic distortions like the Haas effect, especially in wireless networked setups where real-time computational demands are high and precise synchronization is difficult to maintain.
Innovation Solution
A method where a server determines the relative clock rate of each speaker and adjusts audio streams by adding, deleting, or duplicating samples to compensate for clock skew, using protocols like NTP and RTCP, shifting the computational burden from client devices to a more powerful server.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If clock synchronization is performed using NTP and RTCP protocols over a wireless network, then network adaptability and ease of deployment are improved, but synchronization precision deteriorates due to clock skew and network jitter
Solution Approach 1:
The system performs preliminary clock skew compensation by adjusting the playback rate of audio samples before playback. The server determines the clock skew of each speaker and pre-adjusts the audio stream by adding, deleting, or duplicating samples to compensate for the skew, ensuring synchronized playback despite network variations
Solution Approach 2:
The system changes the playback rate parameter of audio samples to compensate for clock skew. By dynamically adjusting the playback rate based on measured clock skew values, the system maintains synchronization precision while operating over adaptive wireless networks
2Measurement precision
If audio streams are adjusted on client devices to compensate for clock skew, then synchronization precision is improved, but device complexity and computational burden increase
Solution Approach 1:
The system extracts the computational burden of clock skew compensation from client devices and relocates it to the server. The server determines clock skew values and performs audio stream adjustment, while clients only need to receive and playback the pre-adjusted streams, significantly reducing client complexity
Solution Approach 2:
The server acts as an intermediary that mediates between the audio source and client devices. It performs the complex clock skew compensation processing centrally and distributes the adjusted audio streams to clients, eliminating the need for complex local processing at each client device
3Measurement precision
If audio samples are added or deleted to compensate for clock skew, then synchronization precision is improved, but audio quality may deteriorate due to sample manipulation
Solution Approach 1:
The system applies partial compensation by adding or deleting only the minimum number of audio samples needed to compensate for clock skew. This selective approach maintains synchronization precision while minimizing impact on audio quality by avoiding excessive sample manipulation
Data Source
AI summary
A server is arranged to distribute at least one stream of audio data corresponding to an audio signal to two or more speakers across a network. Each speaker includes a respective clock for regenerating the audio signal from the audio data. For each speaker, the server determines a relative rate of the speaker clock to a real time rate; and for each stream of data provided to a speaker, the server determines from a respective relative rate, respective samples of the audio signal to be altered in accordance with said relative rate. The streams are altered accordingly and transmitted across the network.