[wdmaudiodev] Re: Distinguish between basic and extensible formats

  • From: "Daniel E. Germann" <deg@xxxxxxxx>
  • To: <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Wed, 13 Dec 2006 07:35:02 -0600

Hi, Eugene.

Actually, I think you want to support WAVE_FORMAT_EXTENSIBLE in your driver. It's a more recent format descriptor than WAVE_FORMAT_PCM that provides a way to specify bit depth and channel location. I believe it is required when using more than two channels of audio and/or audio samples with a depth of more than 16 bits.

You can find more information at:
http://www.microsoft.com/whdc/device/audio/multichaud.mspx
http://msdn.microsoft.com/library/en-us/Audio_d/hh/Audio_d/aud-design_35c3556b-05e1-4a90-97a3-e9945d400ee1.xml.asp

Hope that helps!

-Dan

----- Original Message -----
Date: Wed, 13 Dec 2006 11:55:49 +0600
From: Eugene Muzychenko <emuzychenko@xxxxxxxxx>
Subject: [wdmaudiodev] Distinguish between basic and extensible formats

Hello!

Does anybody know how to correctly distinguish between basic and
extensible audio formats in the driver? Working under Windows 2000 and
XP, my driver periodically get the KSDATAFORMAT descriptor with
KSDATAFORMAT_SPECIFIER_WAVEFORMATEX specifier from the sysaudio driver.
Checking the WaveFormatEx descriptor, the driver finds
WAVE_FORMAT_EXTENSIBLE in wFormatTag field and a zero in the cbSize
field.

Must the driver reject such format descriptor as invalid or simply
ignore the WAVE_FORMAT_EXTENSIBLE, assuming there is WAVE_FORMAT_PCM?

SubFormat parameter in the KSDATAFORMAT descriptor is
KSDATAFORMAT_SUBTYPE_PCM.

Regards,
Eugene

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