Clock Synchronization

Acoustic Echo Cancellation (AEC) is a method of removing the echo from the audio signal captured by the microphone. This is done by using the audio that is played to the speakers as a reference audio signal. Most AEC algorithms require that both audio signals, i.e. the signal captured from the microphone and the signal sent to the speakers, MUST be clock synchronized otherwise the AEC algorithm is unable to lock-on the echo path and perform echo cancellation.

When will the Acoustic Echo Cancellation fail?

Most AEC algorithms will fail if the signal captured form the microphone and the signal sent to the speakers are not 100% clock-synchronized.   This can happen in many cases like:

• When the sound card that is being used is a low-end one that does not have a built-in clock mechanism to synchronize the input and output audio signals.
• When the VoIP application is configured to use different sounds card for input and for output. For example, a USB web-cam is used as the capture device while the laptop’s built-in speakers are being used for playback.

Conclusion

If your VoIP application needs to cancel echo in any of the above conditions, you should not use a standard echo cancellation. In such case you need to use a robust echo cancellation that is capable of working in volatile environments.  SoliCall’s unique echo cancellation is a robust algorithm that is capable of working in such complex conditions.