[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

    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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