A new page on Dmix

Dan Williams dcbw at redhat.com
Wed Jan 10 10:53:38 EST 2007


On Wed, 2007-01-10 at 10:27 -0500, Jean Piché wrote:
> 
> 
> Significantly more info than was previsouly availlable:
> 
> 
> http://alsa.opensrc.org/Dmix
> 
> 
> from the page:
> 
> 
> "For ALSA 1.0.9rc2 and higher you don't need to setup dmix. Dmix is
> enabled as default for soundcards which don't support hw mixing."
> 
> 
> A caveat from the same page:
> 
> 
> "Also, you should keep in mind, that software mixing is possible only,
> if all signals are at the same sample rate. So, if you want to play
> DVD's, which use 48kHz sample rate for audio, with this kind of plug,
> everything will be downsampled to 44.1kHz. Unfortunatelly it does'nt
> work wery well (there are some syncronization problems with some
> players). In this case you have two opportunities, either use a
> separate plug (and loose ability to playback mp3 and dvd on the same
> time) or tell your DVD player to sample audio down to 44.1khz, for
> example:

I remember reading that; and I didn't quite understand what they were
getting at.  Does that mean that dmix itself doesn't up/down sample?  Or
does it mean that dmix _does_ in fact up/down sample, but that
applications that aren't expecting to be up/down sampled might have
problems?

Can we just start shoving a variety of sounds at various sample rates
through from different programs and expect dmix to just do the right
thing, even if it does upsample everything to 44k.

Dan





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