Re: HW mix

[Takashi Iwai <tiwai@suse.de>]

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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