[Speex-dev] Server Side AEC

[Jean-Marc Valin]

> 1) Is it ok if the audio is encoded (using Nelly Moser ASAO) and sent
> to the client and decoded when it is recevied so the AEC is always
> performed on raw PCM16 8KHZ ?

No. The entire path from AEC to loudspeaker and from mic back to AEC
must be free of any non-linearity, codec, drift, ...

> 2) The audio is moved in 32ms (512 byte) chunks and the reading and
> writing to the AEC code will be done by separate threads at regular
> 32 ms intervals.

You're free to do the processing/blocking as you like.

> 3) Occasionaly audio is dropped if it has become delayed but a jitter
> buffer of 120ms is in use.

That'll cause problems.

> People at different distances from the server will have a slightly
> different round trip time. Do you think if using a large tail or
> something  we can get near perfect AEC? The same as you get with a
> hands free phone perhaps?

No. You may have good results if you compensate for the delay, though.

> Does it still sound like worth a try? Is Speex AEC as good as it gets
> or would it be worth contacting some vendors of such software?

>From what you write above, no AEC can work at all. Why not just move it
directly to the client instead?

	Jean-Marc

> Thanks again, Tabby
> 
> 
> Jean-Marc Valin <jean-marc.valin at usherbrooke.ca> wrote:  Tabitha
> Flash a écrit :
>> Hi, I am looking for AEC software which can be run on the server 
>> side. This means there will be a fairly constant 600ms or so gap 
>> between sending out an audio frame and getting it back with echo. 
>> Could Speex AEC be configured to handle these conditions?
> 
> Just use a ring buffer to put the delay back to normal.
> 
>> If so, how good can I expect it to be?
> 
> You'll need to try, but to have any chance of working, the following 
> conditions must be met: 1) No codec must be used in the echo path
> (maybe G.711 is OK) 2) There must not be any drift in the sampling
> clocks 3) There must not be any audio samples lost on the echo path
> 
> Jean-Marc
> 
> 
> 
> --------------------------------- Yahoo! Mail is the world's
> favourite email. Don't settle for less, sign up for your freeaccount
> today.