[wdmaudiodev] WDM and DirectShow

  • From: Ulf Jaenicke-Roessler <ujr@xxxxxxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Thu, 05 Jun 2003 10:55:33 +0200


we use multichannel sound cards (Hoontech DSP24, Delta 4010) with WDM
drivers to play several wave/mp3 files at the same time in our application.

Unfortunately there is a DirectSound/Win2000 problem or bug, which
prevents us from using more than 8 sound channels in one machine. This
occurs, for instance, with two Delta 4010 in one PC. Hence we cannot
use devices that we get from the SystemEnumerator with CLSID

Our solution was to ask the SystemEnumerator for devices with CLSID
AM_KSCATEGORY_RENDER, which results in devices that are listed in
GraphEdits "WDM Streaming audio devices" section. The sound output works
quite well. However, the IBasicAudio interface which sets the volume
for "normal" DirectSound devices (CLSID_AudioRendererCategory) does
not do this anymore for AM_KSCATEGORY_RENDER devices.

Even for the onboard, single channel, sound device the volume cannot
be adjusted when the WDM output device is chosen like outlined above.

From what I read, I thought that ksproxy.ax transparently provides
an IBasicAudio interface and talks to the WDM devices itself. But it
seems it doesn't.

Now I wanted to query WDM properties directly. I requested the
IID_IKsPropertySet interface from the audio renderer successfully.
But as soon as I want to call QuerySupported/Get/Set with property
an error (not implemented or property id not supported, respectively).

Since that happens for all sound cards/WDM drivers I tried so far
I started thinking that there is some basic error in what I'm trying
to do...

I'm grateful for any advice or hint what I should do.
Thanks in advance


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