[wdmaudiodev] Re: AVStream for audio - change of direction?

  • From: Eugene Gavrilov <egavrilov@xxxxxxxxxxxxx>
  • To: Matt Gonzalez <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Fri, 30 Jun 2006 01:47:09 +0400

Hi Matt,

> It is possible to create audio subdevices dynamically with AVStream - in
> addition to KsCreateFilterFactor, you may also need to call 
> KsFilterFactorySetDeviceClassesState for things to work properly. You
> may also need to create the appropriate WDM interface.

Oops.  When  I tried to implement dynamic subdevices, I faced an issue
with  KsCreateFilterFactory:  it did not update the list of devices...
Will  try  to  use  KsFilterFactorySetDeviceClassesState now! One more
blank page in AVStream documentation...

> It is a fair amount of pain because there aren't any samples.  At the
> end of the day, you end up creating a filter that looks the same as it
> would with PortCls.  You also have to add support for things like 
> KSPROPERTY_AUDIO_POSITION yourself, instead of PortCls doing it for you.

By    the    way,    why    is    it    necessary    to    implement
KSPROPERTY_AUDIO_POSITION?  Our  FW  driver seems to work fine without
this call.  (In WinMM/DSound modes). Although this might be the reason
for 'ASIO Multimedia driver' to fail...

By the way, have you ever got a chance to try DESCRIPTOR_SYNCH_ON_TIME
and   RESOURCE_SYNCH_ON_TIME  flags?  We  require  them  for  correct
multidevice  synchronization,  but  this  seems to cause unpredictable
results and delays.

 Eugene Gavrilov
 Software Engineer,
 CEntrance, Inc.


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