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

Wei Kai kai.wei.cn at gmail.com
Fri Aug 10 10:54:44 CEST 2007

Thank you, Clemens.

2007/8/10, Clemens Ladisch <cladisch at fastmail.net>:
> 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.
> Clemens

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