[e-t172]

Originally Posted by mogli

Interesting, how have you measured them? Did you account for phase changes?

Alot of people and companies suggested different mixing coefficients. Some switch phase for the surround channels or even apply adaptive loudness correction to some or all channels, e.g. have the surround channels louder in general but attenuate them when the front channels get loud.

I measured them by playing a test tone through each input channel in turn and measuring the level as it comes out the other hand. I'll admit I didn't try to determine whether it's doing any "clever" stuff like phase manipulation or non-linear processing. I was just trying to determine what the coefficients looked like in the simple, naive case so that I could compare them to other downmixers. I did not spend much time on it.

Originally Posted by mogli

So for now there's no reason to believe MS is doing anything wrong (here), they just use another method than the simplest one proposed by ITU.

Well, in my book not following the international standard qualifies as "doing it wrong", but I guess it's a matter of debate. Ideally it should default to ITU-R BS.775 and perhaps allow the user to select another approach in the settings.

Originally Posted by mogli

Regarding WASAPI vs DirectSound the former is definitely much harsher here and the latter softer. Not saying this has anything to do with quality. Actually DS sounds more pleasing to my ear. I guess MS is doing some polishing of the sound with DS (not that I'm aware of having any effects activated) but not with WASAPI.

Assuming nothing is broken on your system (e.g. your audio drivers are not doing dubious things behind your back), I cannot accept such claims. By default, aside from downmixing, the only thing the Windows audio engine does is mixing, sample format conversion, and sample rate conversion (if required). These cannot make the sound "harsher", "softer", or have any other audible effect unless they are done in a badly broken way, and they're not. This can easily be verified by e.g. using a virtual audio device (like Virtual Audio Cable) and then making loopback measurements: you'll find that there is no measurable difference whatsoever as the audio goes through the Windows audio engine and back again, aside from the obvious benign stuff that anyone would expect, like dithering noise.