[wdmaudiodev] Re: dwChannelMask

  • From: wdm <wdm@xxxxxxxxxxxxx>
  • To: "'wdmaudiodev@xxxxxxxxxxxxx'" <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Mon, 10 Mar 2003 12:56:48 +0100

 
> there is a white paper in the files section of www.wdmaudiodev.de. it
> compares some testing results with what is described in the microsoft
> documentation. besides it covers some KMixer issues under win2k, which
> (hopefully) has been addressed under winxp meanwhile. unfortunately i
> haven't got the time to do any further investigations on this topic in
> the past. however, this paper should still be useful for your 
> purposes.

Thanks for the info. But it seems that kmixer and direct
access to the driver-interface differ in this respect.

Some drivers don't seem to like it, if only a subset of
the available channels is selected (in case of a 6-channel
card, selecting only 2 channels results in the error-code
0x80070491) - and it seems it does not matter if dwChannelMask
is set to 0x03 or 0x00. Those drivers only seem to work if
all channels are opened...

Same thing goes with a 2-channel-card and only selecting
a mono-channel.

If anyone has a hint on what may go wrong here, I'd be glad
to hear it...

The solution obviously is to always open all channels and
stream silence to the ones not in use - but I think this
is a waste of bandwidth/performance...

Tobias
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