Re: [Jack-Devel] ALSA PCM multi plugin and xruns

On Sun, Dec 09, 2012 at 05:03:57PM -0800, Devin Anderson wrote:
> On Sun, Dec 9, 2012 at 6:46 AM, John Rigg wrote:
> > What code did you add to display the extra messages?
> I added:
> 
> 	if ((ret != LONG_MAX) && (ret != avail)) {
> 		fprintf(stderr, "snd_pcm_multi_avail_update: sync issue: %d %d\n",
> ret, avail);
> 	}
> 
> ... to the function `snd_pcm_multi_avail_update` in
> src/pcm/pcm_multi.c of the alsa-lib package.  I added the code just
> below:
> 
> 	if (avail < 0) {
> 		return avail;
> 	}
> 
> It should print data to the console when there is a difference between
> the number of frames available from one card and the number of frames
> available from another card.

I added the above code to pcm_multi.c (in alsa-lib-1.0.26)
then ran jackd using the following command:

jackd -d alsa -C capture16 -P playback16 -r 44100

where capture16 and playback16 are the pcm_multi devices in my .asoundrc.
This was with two ice1712 cards, with default period size of 1024.

When jackd detected no xruns it produced this message repeatedly:
snd_pcm_multi_avail_update: sync issue: 1025 1024

When jackd detected xruns it produced this message:
snd_pcm_multi_avail_update: sync issue: 1024 0
There appeared to be two of these messages for every xrun
indication.

Does this make sense?

John

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