Clemens Ladisch wrote: > Eric Peters wrote: >>I'm a bit confused by the alsa documentation. I want to fill up a buffer >>of a alsa device with snd_pcm_writei and then if the buffer is full, I >>want to be able to start the playback manually. By looking to the >>documentation, I found the method snd_pcm_sw_params_set_start_threshold. >>In some other messages on this list there was the hint to set this >>threshhold larger than the max_buffer_size and then the device shouldn't >>start automatically. So I've done. But unfortunately the playback starts >>again automatically. > > What are the contents of /proc/asound/card?/pcm0p/sub0/sw_params during > playback? tstamp_mode: NONE period_step: 1 sleep_min: 0 avail_min: 1 xfer_align: 4096 start_threshold: 2703204728 stop_threshold: 16384 silence_threshold: 0 silence_size: 0 boundary: 1073741824 Can you explain me these values and what they're for? I think, I know the sense of start and stop threshold. But the other values... > >>/* calculating the number of frames of a buffer and a period */ >>buffer_frames = buffer_time * sample_rate; >>period_frames = period_time * sample_rate; > > Is this correct? Aren't the xxx_time variables in microseconds? I don't know. ;-) How is a frame defined? > >>snd_pcm_sw_params_set_start_threshold(..., 2*buffer_frames) > > This is OK, but it is common to use just the boundary value instead of > some explicitly calculated value. The boundary value in the output above? How can I determine this value in my application? > >>- I think, if I don't call snd_pcm_start there should be no output if >>the start threshold is larger than the max_buffer_size. Is this correct? > > ... if the start threshold is larger than the current buffer size, in > frames. Yes. > >>- Is it possible that the starting behaviour depends on the hardware I'm >>using? > > No, the software parameters are hardware independent. > > > Regards, > Clemens Thanks Clemens for your fast answer. Best regards, Eric ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-devel
