Hi, think the problem in pcm.c is, that period_time is hardcoded to 100000 (us). Thus snd_pcm_hw_params_set_period_time_near() returns a high value for period time. If I change period_time to buffer_time>>2, a much smaller value for buffer_time is returned and sine signal is fine. Regards Achim > Hi all, > > I'm completely new to sound and ALSA development and I have to develop an > application which is capturing periodically a small amount of audio data > (e.g. 64 frames), doing some processing and doing playback of the result. > > I started with ALSA example "pcm.c" to see if ALSA can meet these > requirements. During investigation i found out, that up to a choosen buffer > size of 140ms, generated sine sound is fine. Below 140ms, sound is > stuttering, independent of call method I'm using. > > For buffer size of 140ms I found out, that target buffer size is 6174 > frames (at 44.1kHz sample rate), period size is 3087 frames and loop inside > write_and_poll function is calculated every 70 ms and 3087 frames are > written. Think this is doublebuffering then, right? > > But if I now choose a buffersize of 139 ms or lower, target buffer size and > period size are always the same. So no double buffering anymore and sound > is stuttering. > > So, currently I'm far away from goal. I'd like to have a buffer size of > e.g. 128 frames (2ms). Thus, period size should be 64 frames and loop > should be calculated every 1ms. (If necessary I would use Linux-RT) > > If I choose a buffersize of 2ms, sound is far away from being sine :-) > > - Can I use ALSA for a application described in first sentence above? > > - What do I have to change in pcm.c to be able to create a sine signal > using a buffersize of e.g. 128 frames and a period size of 64 frames? > > Any hints are appreciated > Thanks in advance > Achim > _______________________________________________ > Alsa-devel mailing list > Alsa-devel@xxxxxxxxxxxxxxxx > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
