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