On Tue, Mar 11, 2014 at 11:21 PM, Gianfranco Ceccolini <gianfranco@portalmod.com.br> wrote:

And where does the 16 (from ALSA: use 16 periods for capture) affects?

As Jeremy noted ... JACK asks to use "N periods, or the nearest number of periods it can". You apparently have a device that can only do 16 periods, so when JACK asks for 2, it gets 16.

if I call jack using -p128 / -n2 and the opening message states that ALSA uses 16 periods for capture the sound card will buffer a total of 256 samples and ALSA will wake the client each 16 frames?

no, not at all. the total buffer size is always ACTUAL periods * period size. So as Jeremy said, it will buffer 2048 samples. During each traversal of that buffer, ALSA will wake the client 16 times, every 128 frames.

If I used -p256 / -n2 instead ALSA would wake the client each 32 frames?

I have no idea why you think that. As I tried to explain, the period size (256) is the interval between when ALSA wakes the client.