[alsa-devel] snd_dummy on Centos - Redhat

[Giovanni Maruzzelli]

On Thu, Sep 3, 2009 at 3:12 PM, Giovanni
Maruzzelli<gmaruzz.lists at gmail.com> wrote:
> On Thu, Sep 3, 2009 at 3:05 PM, Clemens Ladisch<clemens at ladisch.de> wrote:
>> It would be easier to try to change the constraints of the sound card
>> that snd-dummy tries to emulate; set USE_PERIODS_MIN to four or so,
>> and increase period_bytes_min to some value that is at least as large
>> as the numer of bytes per timer tick (with 2 channels and 16 bits at
>> 48 kHz, there are 192000 bytes per second).
>>

I put a printk that prints the contents of runtime struct at the last
line of the snd_card_dummy_pcm_prepare() function, so to know how
Skype client uses the soundcard.

The result are:
Sep  3 16:11:04 localhost kernel: 253, cicopet1 rate=16000 channels=2,
period_size=2048, periods=2, buffer_size=4096,
timer_resolution=128000000
Sep  3 16:17:42 localhost kernel: 253, cicopet1 rate=16000 channels=2,
period_size=2048, periods=2, buffer_size=4096,
timer_resolution=128000000
Sep  3 16:17:42 localhost kernel: 253, cicopet1 rate=16000 channels=2,
period_size=2048, periods=2, buffer_size=4096,
timer_resolution=128000000
Sep  3 16:17:42 localhost kernel: 253, cicopet1 rate=16000 channels=1,
period_size=2048, periods=2, buffer_size=4096,
timer_resolution=128000000
Sep  3 16:17:42 localhost kernel: 253, cicopet1 rate=16000 channels=1,
period_size=2048, periods=2, buffer_size=4096,
timer_resolution=128000000

So, it seems that it opens 2 channels for playback and one channel for
capture, at 16k

What's the best values for constraints you counseil?

-giovanni