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Re: Proposal: Rationalizing Fedora Audio

Date: Mon, 18 Oct 2004 13:59:02 +0200 From: Ralf Ertzinger <fedora-devel camperquake de> :

Even using the ALSA interface, Fedora defaults to sending/receiving
applications audio direct to the hardware device, hogging the interface.
By default audio output could go to ALSA or better yet a Dmix plug,
where the source and destination could be selected and mixed together.

Maybe I did not understand ALSA fully, but: IMHO you will need dmix only when your sound hardware is not capable of hardware mixing (like mine is, for example). If it was, you would not need (or want, for that matter) to use dmix. PS: inspired by this posting I tried to set up dmix again for my system (had tried it during FC2 testing, and was not impressed, crackling occured), but all seems well now. xine, mplayer, openttd (SDL layer) and bmp all happily sing along. The only thing not working are programs that want to use /dev/dspX directly, but those are few and far between for my uses.

This discussion is good to see as audio in Linux has been confusing me for some time now. I hope to learn a lot here :]

Your last point raises the question: *Should* legacy applications that are using OSS directly and don't know about ALSA be able to multiplex sound inputs/outputs together on a system that has ALSA? On my machine (using the onboard sound on an ASUS A7N8X Deluxe mobo) they don't and it makes things very awkward at times (i.e. I cannot talk using a VOIP app and play music or game at the same time). I don't know whether ALSA should be transparently mixing things no matter what interface the app uses or if this is impossible due to some limitations inherent in the OSS protocols ... if someone has any insight here, I would love to hear it.

I am very baffled at the moment since on my machine:
- two instances of aplay will multiplex things together as you would suspect ... indicating that either software or hardware mixing is possible on my audio card.
- playing something with XMMS (even with the ALSA output plugin selected) will block aplay from playing anything until XMMS is stopped (pausing XMMS still blocks aplay)
- Rhythmbox gets very confused at times when there is an OSS application running
- forget about trying to run two OSS apps at the same time ... if the second one runs at all, it will be silent.

If these are situations that are supposed to work, then I will be busy filling out bugzilla reports for a while. I was under the impression that these would go away over time as all the apps are migrated to be ALSA friendly. If OSS apps could be fooled into working properly today, then I hope that this could be set up by default soon.


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