How to increase WebRTC AECM Filter length to cater longer echoes.

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khubaib ahmad

Aug 5, 2022, 12:53:50 PM (9 days ago) Aug 5
to discuss-webrtc

I have been working on echo cancellation on cross platform smartphones (iOS & Android) cluster in a room. Since the phones in the cluster don't have fix orientation with respect to common formation which is usually circular or linear array of phones. The phones are placed randomly in the room.
All phones play the audio in synchronization with accuracy up to 10ms. But the problem is there is echo (some kind of screeching sounds) which doesn't get cancelled. I have seen aec dump files and it seems that echoes are longer than typical window of delay which webrtc aecm caters  with default filter length of 128ms   i.e.

For Android:
low latency phones : 50ms -> [50 ms to 170 ms]
High latency phones: 150ms ->[150ms to 270ms]

For iOS:
Recording latency : 50ms
Playing latency : 50ms

I have rectified webrtc code to use HW AEC in combination with WebRTC AECM but the problem is the echoes are outside these windows. 

So how do I increase the filter length ?

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