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

  • From: "David A. Hoatson" <dhoatson@xxxxxxxxxxxxxx>
  • To: <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Wed, 23 Dec 2009 08:33:39 -0800

Frank,

Should I submit a bug report on this one?

Thank you,
 
David A. Hoatson
Lynx Studio Technology, Inc.
www.lynxstudio.com
 

> -----Original Message-----
> From: wdmaudiodev-bounce@xxxxxxxxxxxxx 
> [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of David 
> A. Hoatson
> Sent: Sunday, December 20, 2009 3:53 PM
> To: wdmaudiodev@xxxxxxxxxxxxx
> Subject: [wdmaudiodev] Re: Windows 7, multi-channel, 16-bit, 
> dither bug?
> 
> Frank,
> 
> I am using our Lynx Demo app which I wrote.  It is using MME 
> (waveOutOpen) and the app doesn't touch the audio at all.  
> Playing a 44.1kHz file and the hardware is also set at 
> 44.1kHz so no SRC should be occuring in Windows.
> Our hardware level meters go to -114dB so I can clearly see 
> the extra bits getting messed with (shows -94dB, so I am 
> seeing 20dB of noise above the threshold of the meters).  
> Since I wrote the driver & app and it is our hardware the 
> only part we don't control is between MME and WDM in Windows, 
> which is of course why I made the post. :-)
> 
> We have not seen the same problem in Windows Vista, so it 
> must be something new in Windows 7.
> 
> Thank you,
>  
> David A. Hoatson
> Lynx Studio Technology, Inc.
> www.lynxstudio.com
>  
> 
> > -----Original Message-----
> > From: wdmaudiodev-bounce@xxxxxxxxxxxxx 
> > [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Frank Yerrace
> > Sent: Friday, December 18, 2009 2:54 PM
> > To: wdmaudiodev@xxxxxxxxxxxxx
> > Subject: [wdmaudiodev] Re: Windows 7, multi-channel, 16-bit, dither 
> > bug?
> > 
> > How are you playing the file? What application? Or if you wrote the 
> > application, what audio API family is the application calling?
> > 
> > Also, just curious, how did you notice this? What tools/process did 
> > you use?
> > 
> > Frank Yerrace
> > Microsoft
> >  
> > This posting is provided "AS IS" with no warranties, and confers no 
> > rights.
> > 
> > -----Original Message-----
> > From: wdmaudiodev-bounce@xxxxxxxxxxxxx 
> > [mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of David A. 
> > Hoatson
> > Sent: Friday, December 18, 2009 9:55 AM
> > To: wdmaudiodev@xxxxxxxxxxxxx
> > Subject: [wdmaudiodev] Windows 7, multi-channel, 16-bit, dither bug?
> > 
> > Hello,
> >  
> > 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.
> > www.lynxstudio.com
> > 
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