[Asterisk-Dev] Echo cancellation on GPU

[steve at daviesfam.org]

On Sun, 25 Sep 2005, Kevin P. Fleming wrote:

> 
> Modern GPUs are on the AGP port, or on a dedicated northbridge 
> connection. Latency concerns are valid though, for sure.


Forgive me whilst I display my ignorance, and enlighten me:

I've heard it said often on the list that echo cancellation must be done 
in the kernel - as close to the arrival of the bits as possible.

Now I understand that for echo can to work it needsa really consistent
delay - after all the whole point is to substract from the incoming signal
the computed estimated echo from "just the right length of time ago".

But what I don't understand is:  why not just timestamp the arriving audio 
as it arrives in the kernel, provide that timestamp back to userspace and 
use that remembered timestamp in the algorithm rather than the actual time 
now?

Steve