Hi
?
I used this "sample counting " method to?resample and put my audio
signals in synch.
It worked perfectly?in XP machines using a SoundMax?audio card, but it failed in
other XPs using Realtek cards.
As seen on
http://lists.xiph.org/pipermail/speex-dev/2008-September/006889.html?my
application?continously checked my AEC level to slighly modify resample
frequency, but convergence was impossible with?that audio?cards.
Then, I used ASIO (through port-audio library) in those machines, and?AEC worked
again. But this solution wasn?t practical (user?must install a special driver)
so?i can?t say if?this method will work or not on *every* machine.?
I think it will not work on Vista, no mather what card you use.
Just my 2c.
--- El mar, 7/7/09, John Ridges <jridges at masque.com> escribi?:
De: John Ridges <jridges at masque.com>
Asunto: Re: [Speex-dev] AEC with different soundcards
Para: "Alexander Chemeris" <Alexander.Chemeris at sipez.com>
CC: "speex-dev at xiph.org" <speex-dev at xiph.org>
Fecha: martes, 7 julio, 2009 9:36
Measuring clock drift is a thorny problem that depends greatly on your
hardware setup and OS. In my case (Windows machines) I simply measure
how many samples are played and captured in a given time period, and use
that ratio to calculate the clock drift. Unfortunately these
measurements are usually very noisy and require some high-powered
filtering to get stable results that converge in a reasonable time. I'm
afraid I'm not at liberty to get any more detailed than that. Sorry.
John Ridges
Alexander Chemeris wrote:> AFAIK, that's a common point for all AECs. But some of them
> solve the problem by resampling on of the end to keep it in sync
> with the other.
>
> On Tue, Jul 7, 2009 at 5:14 PM, ggb<ggb at tid.es> wrote:
>???
>> Thank you John.
>>
>> On 07/06/2009 11:03 PM, John Ridges wrote:
>>
>> ly 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.
>>
>> Is this a limitation common to all the AEC implementations/algorithms,
or
>> just the speex one?
>>
>> 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.
>>
>>
>> Could you detail me how to measure the clock drift?? Any pointer to doc
or
>> example?
>>
>> I apologize for my lack of knowledge in this topic,
>> G.
>>
>> _______________________________________________
>> Speex-dev mailing list
>> Speex-dev at xiph.org
>> http://lists.xiph.org/mailman/listinfo/speex-dev
>>
>>
>>? ???
>
>
>
>???
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