alejandro wrote: > Hello, > > Is there any document describing the ALSA components and functions? > Particularly the link between audio I/O and timers, in order to frame > accurate sync multiple audio cards and video. > > Thank you, > Alejandro, This is achieved using the snd_pcm_delay() function call. It gives you a measure of the number of samples between the current write pointer and the codec output. I.e. If you call snd_pcm_writei() now, it will be snd_pcm_delay() sample frames duration until the sample reach the speakers. So, from that you can accurately predict the exact time that a particular sample will reach the speakers, and therefore keep video in sync with it. This method is used in xine (http://xinehq.de) See the audio_out.c loop. One then combines this with a resampler (as xine does), to adjust for clock speed differences between sound cards and the system timer, so this prevents sync drift. James _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/alsa-devel
