Re: smart and automatic use of dmix and dsnoop - feature suggestion.

[Takashi Iwai <tiwai@suse.de>]

At Fri, 14 Nov 2003 14:01:09 +0100,
Peter Kirk wrote:
> 
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> Am Freitag, 14. November 2003 13:21 schrieb Paul Davis:
> > >So, these are two numbers - and basicly all is fine as long as you dont
> > > wan= t=20
> > >to excede them, but if you do, you need to use dmix or dsnoop. Why not
> > > use= =20
> > >dmix and dsnoop automaticly when necessary ? Wouldnt it be possible to
> > > have=
> >
> > because it would be catastrophic, or, well, at least very bad, for
> > applications that want to "sit close to the metal".
> >
> > this is a user-space configuration issue, not something that alsa-lib
> > should do by default. if the user (or the distributor) defines "dmix"
> > to be the default device type, then every conformant ALSA application
> > will do the right thing. apps like JACK that want to "site close to
> > the metal" will still use "hw:N" unless you tell it otherwise, but
> > consumer apps will use "default" (that's what i mean by conformant)
> > and get dmix behaviour.
> Hmm,
> 
> are you telling me that normal applications will already automaticly use
> dmix ? Its a pitty my soundcard (SB Live!) can play so many streams in
> hardware at once, so I dont realy know if alsa is doing dmixing *on*the*fly*.
> But I did *think* that if you had a cheepo laptop, you couldnt open 5 xmms
> and 5 xines and start playing back with all of them - I could be wrong of
> course. The thing Im quite certain of, is that there is no dmix jumping in if
> you try to run 2 playback oss apps through the oss emulation layer of alsa -
> this will give you trouble if your soundcard cant play two streams in
> hardware.
> Then there still would be the point with dsnoop - I _know_ it doesnt work on
> my soundcard to open two instances of TeamSpeak (voice communication -> full
> duplex) - and be able to talk and hear on both...this is because the capture
> device is taken.
> Is there anything being thought about of something like the automagic
> dsnooping I was talking about ? It realy would be nice to be able to use
> multiple applications of teamspeak on *normal* soundcards like mine...

you can override the "default" pcm to use dmix/dsnoop plugin by
defining it with '!' prefix in ~/.asoundrc.
this won't conflict with special apps like JACK, because they usually
open the hw layer directly.

as a future plan, we'll define dmix as default for el-cheapo
soundcards, but e.g. not for sb live, which supports such a function
on hardware.
so far, we leave it as user's own configuration, simply because dmix
had been under development and not quite stable.

well, there is still a problem that the ALSA's configuration is not
stream-wise.  a single definition is used for both playback and
capture directions.  this should be improved in the future.


Takashi


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