[alsa-devel] RFC: support for 12 & 24Khz

[Vinod Koul]

On Thu, Jul 25, 2013 at 06:31:33PM +0200, Takashi Iwai wrote:
> At Thu, 25 Jul 2013 21:15:01 +0530,
> Vinod Koul wrote:
> > 
> > On Thu, Jul 25, 2013 at 08:50:40AM +0200, Clemens Ladisch wrote:
> > > Vinod Koul wrote:
> > > > For compressed audio we also need to support the PCM rates of 12 and 24KHz.
> > > >
> > > > Looking at pcm.h these are not defined
> > > 
> > > You don't need such symbols to use a rate.  These symbols are intended
> > > for often-used rates.  As long as only one or two drivers use a rate,
> > > they can just set KNOT and install a constraint.
> > okay so how exactly is the rate passed to driver and converted and sent to
> > drivers?
> 
> Define the own hw_constraint.  Usually it's implemented via
> snd_pcm_hw_constraint_list().
Thanks
> 
> > > > But am worried about wider impact of adding these rates.
> > > >
> > > > Can you let me know if more is required to be done or below is fine
> > > 
> > > Grep for 176400 in sound/core/, include/, and in alsa-lib.
> > SNDRV_PCM_RATE_176400?
> 
> Heh, this was an already added one.  Rather take a look at
> SNDRV_PCM_RATE_KNOT.
Okay so the orignal problem is that we use SNDRV_PCM_RATE_XXX to send the sample
rate to decoder. Some decoders very commonly use 12 and 24Khz, so I would like
them to be added.

I think 12 and 24 are fairly common rates and should be added. Do you agree?

~Vinod
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