HW mix

HW mix

[Dino]

hi all,
   i want to mix some pcm streams using hardware (where possible). One process
with some thread witch want to play with one device (hw:0,0). Actually i simply
open the device as it can (32 at max for me) with snd_pcm_open() and hw:0,0 as
the device. It's seems to work but i don't know if it's the rigth way.

tnx,
   Dino


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Re: HW mix

[Clemens Ladisch]

Dino wrote:
>    i want to mix some pcm streams using hardware (where possible). One process
> with some thread witch want to play with one device (hw:0,0). Actually i simply
> open the device as it can (32 at max for me) with snd_pcm_open() and hw:0,0 as
> the device. It's seems to work but i don't know if it's the rigth way.

"hw:0,0" will fail if another program has already opened it.
Use "hw:0" which instructs ALSA to open the first available subdevice.


HTH
Clemens



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Re: HW mix

[Jaroslav Kysela]

On Mon, 18 Apr 2005, Clemens Ladisch wrote:

> Dino wrote:
> >    i want to mix some pcm streams using hardware (where possible). One process
> > with some thread witch want to play with one device (hw:0,0). Actually i simply
> > open the device as it can (32 at max for me) with snd_pcm_open() and hw:0,0 as
> > the device. It's seems to work but i don't know if it's the rigth way.
> 
> "hw:0,0" will fail if another program has already opened it.
> Use "hw:0" which instructs ALSA to open the first available subdevice.

Nope, hw:0,0 is correct (CARD,DEVICE). You meant probably hw:0,0,0 
(CARD,DEVICE,SUBDEVICE).

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SUSE Labs


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Re: HW mix

[Glenn Maynard]

On Mon, Apr 18, 2005 at 12:06:54PM +0200, Jaroslav Kysela wrote:
> On Mon, 18 Apr 2005, Clemens Ladisch wrote:
> 
> > Dino wrote:
> > >    i want to mix some pcm streams using hardware (where possible). One process
> > > with some thread witch want to play with one device (hw:0,0). Actually i simply
> > > open the device as it can (32 at max for me) with snd_pcm_open() and hw:0,0 as
> > > the device. It's seems to work but i don't know if it's the rigth way.
> > 
> > "hw:0,0" will fail if another program has already opened it.
> > Use "hw:0" which instructs ALSA to open the first available subdevice.
> 
> Nope, hw:0,0 is correct (CARD,DEVICE). You meant probably hw:0,0,0 
> (CARD,DEVICE,SUBDEVICE).

Is there anything wrong with using "hw:0" instead of "hw:0,0", or are they
equivalent?  It's what I've always used, without issue.

-- 
Glenn Maynard


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Re: HW mix

[Takashi Iwai]

At Tue, 19 Apr 2005 02:06:47 -0400,
Glenn Maynard wrote:
> 
> On Mon, Apr 18, 2005 at 12:06:54PM +0200, Jaroslav Kysela wrote:
> > On Mon, 18 Apr 2005, Clemens Ladisch wrote:
> > 
> > > Dino wrote:
> > > >    i want to mix some pcm streams using hardware (where possible). One process
> > > > with some thread witch want to play with one device (hw:0,0). Actually i simply
> > > > open the device as it can (32 at max for me) with snd_pcm_open() and hw:0,0 as
> > > > the device. It's seems to work but i don't know if it's the rigth way.
> > > 
> > > "hw:0,0" will fail if another program has already opened it.
> > > Use "hw:0" which instructs ALSA to open the first available subdevice.
> > 
> > Nope, hw:0,0 is correct (CARD,DEVICE). You meant probably hw:0,0,0 
> > (CARD,DEVICE,SUBDEVICE).
> 
> Is there anything wrong with using "hw:0" instead of "hw:0,0", or are they
> equivalent?  It's what I've always used, without issue.

"hw:0" is equal with "hw:0,0", but not with "hw:0,0,0".  The default
subdevice argument is -1, i.e. "hw:0,0,-1".  The -1 means the
auto-allocation as described above.  When you pass 0 explicitly there,
only the substream 0 is opened, and failed if it's already occupied.


Takashi


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