[wdmaudiodev] Re: SYSVAD WASAPI Eclusive playback mode does not work.
- From: Tim Roberts <timr@xxxxxxxxx>
- To: "wdmaudiodev@xxxxxxxxxxxxx" <wdmaudiodev@xxxxxxxxxxxxx>
- Date: Mon, 2 Jul 2018 10:16:05 -0700
Vincent Burel (VB-Audio) wrote:
While testing SYSVAD example…
When opening SYSVAD Speaker in WASAPI Exclusive mode
It uses OFFLOAD pin and changes the method to _WithNotification
Then the TimerNotifyRT function is called...
Q1: why it is using offload mode there (WASAPI input exclusive mode
does not use this)
I believe the audio engine always tries to use offload mode if it is
available, on the assumption that the hardware can do it more
efficiently. That doesn't particularly make sense in a virtual driver,
which is one reason I backed up to MSVAD for my recent project.
The problem is that this mode is not working correct.
When we playback a sound in SYSVAD speaker, the generated file is not
conform (noise is added ).
So, just to be sure, you're generating a 100Hz tone in your app and
feeding it to the SYSVAD speaker? How large are the buffers you're
generating? Are you sure your generation is keeping up?
Sounds is correct for 100 or 200 ms and then get disturbed by a noise
and then sounds correct again during hundreds ms and become noisy again.
Attached Picture show the noise incident on 100Hz sinus… we can see
the time drift and how the noise is added (small part of 16, 32, 48
samples, coming from other part of the DMA buffer)
Is this with an unmodified SYSVAD? The interruptions are coming every
512 samples, which is a suspiciously round number.
(How do I know? I measured the GIF. Peak-to-peak is 480 pixels, which
tells me one pixel == one sample.)
--
Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.
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