[Speex-dev] AEC with different soundcards

[John Ridges]

The problem with different sound cards is that their clocks are not 
usually synchronized, and therefore the clock drift adds a non-linear 
factor to the audio path. The AEC can only cancel linear changes to the 
audio path, and so the AEC never converges.One solution is to measure 
the clock drift and resample either the input or output signal so that 
they *are* synchronized, and then the AEC can converge. It's not fun, 
but it works.

John Ridges