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In Reply to: Installed Vista on the weekend posted by Christine Tham on February 11, 2007 at 14:08:24:
Gang,Mercman-Steve emailed me this interesting Forum on the Creative site about Windows Audio Services.
This primarily because of a statement made by Thomas below that the Windows Services converted everything to 32 bit precision floating point and then back to what ever the output driver was looking for.
I have asked a number of times why this happens and if it has impact on bit perfect but have not got any response yet.
I guess I could connect my MacBook up with SPDIF I/O Toslink to my dScope and see what happens.
But it would be nice to know what the real story is and if Exclusive bypasses the Audio Services or what.
Too many questions....
Thanks
Gordon
J. Gordon Rankin
Follow Ups:
Hi Gordon,I was pretty busy but I eventually responded to your earlier question. Exclusive mode bypasses the stack and if you want to try you can download Ntrack 5 which has support for WASAPI.
I have not been able get this to work since ntrack complains about an incompatible buffer size. I will investigate and let you know how this works out.
Cheers
Thomas,Yea I know the feeling. I could use a week off just to regroup.
~~~~~
Ok basically any application written to WASAPI can bypass the stack and gain "Exclusive" mode if the user set's this option true?
I guess really the problem will be the ramp up time for applications to goto Vista.
And working device drivers...It's sort of hard to believe after 5 years in development but quite a few companies wait till after the product has shipped before seriously investing in driver development.
Cheers
... if you open a session in exclusive mode using WASAPI, then no conversion is performed (other than scenarios such as you sending 16-bit data, and the driver bitpadding for a 24-bit DAC, and of course assuming a well written driver that does not try and resample on it's own).Certainly for SPDIF mode, there should be no conversion.
The discussion is a bit academic at the moment since I do not know of any application that supports WASAPI exclusive mode. Even Sonar is still using DirectKS.
However, in shared mode, everything is mixed and resampled to a common resolution, which you can specify (defaults to 48/16, but can be changed for example to 44.1/24 which is what I set it to). I suspect the mixing is done in 32-bits.
However, I am not an authority on this. Suggest you pose a question directly to Microsoft (the best way to do this is by attending WinHEC).
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