[wdmaudiodev] Re: AEC in Vista

  • From: Tim Roberts <timr@xxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Tue, 03 Oct 2006 13:37:15 -0700

Shuba Iyer wrote:

> The Voice capture DMO has two different working modes, "filter mode"
> and "source mode". In filter mode, the DMO works like a filter. It
> takes microphone (and speaker if AEC is enabled) input signals and
> produces clean output. Application is responsible for capturing
> microphone and/or speaker signal and sending them to the DMO. For
> per-stream echo cancellation you want to use filter mode.
>

So, am I, then, expected to add some kind of a "tee" to my application
in order to route the final output signal back to the DMO's speaker
input?  And this still doesn't address this quote from the DMO
documentation:

    If AEC is enabled, the DMO can capture speaker streams only after
    the audio mixer.  This means that all system sounds are canceled
    (per-system cancellation) as well as the far-end voice.

My application can't gain access to the speaker streams after the audio
mixer.  How is the DMO doing that?


> AEC and microphone array processing in Vista are application graph
> features. So it is up to the application to use the feature or not.
>

Well, that's certainly one position, but it is not unreasonable for a
user to want ALL of their microphone input (including Sound Recorder)
passed through AEC. That goal has now been made rather difficult to achieve.

-- 
Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.

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