[alsa-devel] Why there is no SNDRV_PCM_RATE_24000 in pcm.h

Clemens Ladisch cladisch at fastmail.net
Fri Aug 10 09:39:57 CEST 2007

Wei Kai wrote:
> I checked the include/sound/pcm.h in kernel and find this problem, it
> seemed strange, so many codecs support the 24000 sample rate, why
> there is no such definition.

When the header file was created many years ago, 24000 Hz wasn't a
common sample rate.

To support a sample rate that is not in that list of predefined rates,
your driver should set the RATE_KNOT bit and call the
snd_pcm_hw_constraint_list() function; see the section "Constraints" in
the "Writing an ALSA Driver" document.


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