Quote:
Originally Posted by
Warrax 
Yes, it does. But I'm not sure, if this is meaning, that Asio4all doesn't work under Windows XP, as it has other architecture, than Windows 7 or Vista.
This article expains it:
http://code.google.com/p/cmediadrivers/wiki/Bitperfect
On the software side, there are some more obstacles: in order to play multiple sounds simultaneously, a so called "kmixer" / "kernel audio mixer" (XP, 2000) respectively "audio service" (Vista) which is part of the sound subsystem of Windows mixes them together and adjusts the volume of the resulting stream. Contrary to popular belief, the kmixer of Windows 2000 and XP doesn't modify the sound and is thus bitperfect if these four conditions are met:
- The PCM/wave volume slider of the mixer (sndvol32.exe) must be set at its maximum. Some start-up applications modify the volume slider (e.g. hardware monitoring tools from Asus).
- The player must be compiled for the same architecture that the OS was compiled for - e.g. 32 bit player on a 32 bit OS, 64 bit player on a 64 bit OS. This is the case for the vast majority of installations because the 64 bit version of Windows XP isn't very commonly used.
- Applications other than the player mustn't play sounds, otherwise the two output streams will be potentially sample rate converted and mixed.
- Applications which are using the soundcard for recording have to use the same sample rate as concurrently running applications which are playing sounds - the soundcard has only one clock generator and hence this limitation arises.
I have also noticed, that when I am playing music over ASIO, and I'm using wave output (onboard audio), wave slider in windows control panel has no effect on sound. But when I play sound without ASIO, wave slider in windows control panel works normaly, and can adjust the sound.
So I think, when four above condictions are met, ASIO works under WindowsXP, and output signal is bitperfect.
I return a bit to this post, where we have been discussing about, if in Windows XP, kmixer can be bypassed and thus achieved bitperfect setup.
I've found this article
http://www.audialonline.com/html/articles/kmixer/
where is mentioned:
"To check whether you were successful in this or not, open the Mixer. Make sure that you choose USB Audio DAC and not some other device you may possibly have in the system; you can switch between Mixer Devices using the Options > Properties menu in the Mixer window. If all is done well, moving the slider Wave should have no effect on the playback volume."
I've remembered to my old post, where I've achieved same effect, that wave slider didn't do anything. Now I see, that was a proof, that kmixer has been really bypassed. So it is possible under Windows XP by ASIO.
Now, there's still a question, if bit-perfect output can be achieved even with kmixer not bypassed, with fullfill conditions, as suggested in upper quoted text. Any suggestions, how to test it?
