[wdmaudiodev] Windows 7, multi-channel, 16-bit, dither bug?

  • From: "David A. Hoatson" <dhoatson@xxxxxxxxxxxxxx>
  • To: <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Fri, 18 Dec 2009 09:54:36 -0800

It appears that Windows 7 WDM audio sub-system has a strange bug
(feature?!?).  When in 16-bit multi-channel mode (I'm using 5.1 for my
testing), and playing back a stereo file, there is some audio being played
back (at a very low level) on channels 3, 4, 5 & 6 when it should be
streaming zeroes.  It is about 94dB down from the original signal, which
leads me to think that somehow the audio sub-system is applying dither to
the channels that should be playing silence.  I haven't tried this on Vista
yet, so I don't know if it does the same thing.  Windows XP obviously
doesn't do this.  24-bit mode works as expected.

Any ideas?
Thank you,
David A. Hoatson
Lynx Studio Technology, Inc.


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