On Fri 11 Jan 2008 10:01, Joachim Foerster pondered: > > My only question is - if you allow a mmaped intermediate buffer, how > > does the driver notice when ALSA writes into this buffer? > > It's the ack() callback. ALSA writes/reads something into/from the > intermediate buffer and calls the driver's ack() callback - if there is > any. In the ack() callback the driver should call one of the > snd_pcm_indirect_*_transfer() functions. There, the difference between > current and last seen appl_ptr gives the "new position" of the PCM Layer > in your intermediate buffer (where it will write/read next time). OK - thanks. >From just thinking about it - won't this will cause problems for things that need to understand where the audio device is in the PCM stream (like AEC, and lip-sync)? Since now everything from userspace is in reference to the position in the intermediate buffer - rather than what is actually coming out the DACs? _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
