[alsa-devel] [RFC PATCH 2/3] ALSA:core: Add rate 24kHz

[Takashi Iwai]

On Thu, 05 Sep 2019 16:00:51 +0200,
Pierre-Louis Bossart wrote:
> 
> 
> >>>> Adds SNDRV_PCM_RATE_24000 at the bottom to keep backward compability
> >>>> with alsa library.
> >>>>
> >>>> Signed-off-by: Pawel Harlozinski <pawel.harlozinski at linux.intel.com>
> >>>
> >>> No.  Such a fancy rate has to be handled inside the driver locally
> >>> instead of adding to the common rate.
> >>
> >> It's not that crazy, this is supported in the HDaudio spec:
> >>
> >> Sample Base Rate Divisor (DIV):
> >> 000 = Divide by 1 (48 kHz, 44.1 kHz)
> >> 001 = Divide by 2 (24 kHz, 22.05 kHz)
> >>
> >> I am not sure why 22.05 made the cut and not 24 kHz, they are both
> >> derived from common clocks with the same divider... Same for 11.025
> >> and 12...
> >
> > I'm not against supporting it.  It'd be fine if it were the changes
> > that are applied only to HD-audio driver side.  What I'm against is to
> > change the ALSA PCM core.  It's not necessarily done there at all.
> 
> Humm, out of curiosity what is the issue here? Would this addition
> break anything? I don't personally care too much but I've never quite
> understood why the ALSA core only defined a subset of 'common' rates.

It's simply a policy that we don't add a thing just because one driver
wants for some reason possibly no one would actually use.

In general such a core stuff is changed only when it has to be and
inevitably necessary, and/or it'd be benefit for all the rest and
majority users.


thanks,

Takashi