Stefan Schoenleitner wrote: > Clemens Ladisch wrote: > > How do you synchronize the clocks of both devices? > > I don't. [...] > I guess if clock drift gets too high, I will get xruns as well ? Yes. > > Why would mmap be more ideal? > > I though that it would be possible to use mmapping to "connect" sound > devices together in a way that read/write operations in between are no > longer necessary. Indeed. > But as mmapping just seems to work for files, I no longer think it is > possible. Some optimization is possible even when only one device supports mmap: When you want to copy from the hardware device to the plugin, you could call the plugin's snd_pcm_writei with an address in the sound card's buffer as the source. > > To avoid overruns in the capture device, use a bigger buffer, which will > > _not_ increase latency. > > Can you explain to me why a bigger capture buffer will not introduce > latency ? > IMHO if there is a large capture buffer, then the sound-card will need > to capture until the buffer is filled. > Once this is the case, the application can start to read from the > capture device. The application can read from the capture buffer at any time. When using a blocking snd_pcm_read* call, it gets woken up at the end of each period, if avail_min is not larger than the period size. > It seems that at least one of my devices only supports a small avail_min > setting. avail_min can be as large as the buffer size. Regards, Clemens _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
