The correct way is to use snd_pcm_get_params() to get buffer_size and
period_size
*snd_pcm_set_params() has limitation
The most common sound card (e.g. HDA ) has the following constraints on period bytes and buffer bytes
snd_pcm_hw_constraint_step(runtime, 0, SNDRV_PCM_HW_PARAM_BUFFER_BYTES, 128); snd_pcm_hw_constraint_step(runtime, 0, SNDRV_PCM_HW_PARAM_PERIOD_BYTES, 128);
I am probably not good enough to understand these changes =( Pretty hard core stuff =)
you cannot get exactly 0.5 second period time when rate is multiple of 3 ( e.g. 48000 Hz )
Does this mean, that I shouldn't give snd_pcm_writei() the number of all the frames in the buffer, but only
sample_rate * latency = frames
?
So if I e.g. have: sample_rate = 44100 latency = 0.5 [s] all_frames = 100000
The number of frames that I should give to snd_pcm_writei() would be
sample_rate * latency = frames 44100*0.5 = 22050
and the number of iterations the for-loop should be?:
(int) 100000/22050 = 4; with frames=22050
and one extra, but only with
100000 mod 22050 = 11800
frames?