[alsa-devel] Increasing maximum sampling frequency?

[Lee Revell]

On Wed, May 27, 2009 at 9:47 PM, Cameron Stone
<camerons.lists at cse.unsw.edu.au> wrote:
> I've got a USB microphone application that I want to sample at 256000 8
> bit samples per second so I can listen to bats. I know that my device
> can get close to that rate, but alsa seems to restrict sampling rates to
> 192kHz.
>
> Is it possible to push the maximum sampling frequency higher? If so,
> where should I start looking?
>

For starters, try adding a 256K sample rate to include/sound/pcm.h:

 118 #define SNDRV_PCM_RATE_176400           (1<<11)         /* 176400Hz */
 119 #define SNDRV_PCM_RATE_192000           (1<<12)         /* 192000Hz */
 120

and sound/core/pcm_native.c:

1762
1763 static unsigned int rates[] = { 5512, 8000, 11025, 16000, 22050,
32000, 44100,
1764                                  48000, 64000, 88200, 96000,
176400, 192000 };
1765

Line numbers may vary, mine are from 2.6.27 kernel source.

Lee