[alsa-devel] Can't detect "XRUNs"

[Raphaël Dingé]

>> So I've run with the Audio USB card with your patch, and the behaviour
>> is the same as with HDMI, meaning that echo 1 > xrun_injection outputs
>> a xrun in /sys/kernel/tracing/trace, but apart from that, I never have
>> an xrun.
>
> It means that there is no XRUN error, handled neither in PCM core nor
> USB-audio driver.

It seems I have a total misconception of what is an XRUN then.

What I understand from your reply is that the program I launch doesn't
create XRUNs anyway (but my interpretation might be mistaken).

I changed the code of my test to the following in the write loop :

    snd_pcm_wait(pcm, 1000 /* milliseconds */);
    snd_pcm_sframes_t avail = snd_pcm_avail_update(pcm);
    if (avail < 0)
    {
      std::cout << "snd_pcm_avail_update failed\n";
      snd_pcm_recover (pcm, avail, 1);
   }

    snd_pcm_sframes_t nb_written = snd_pcm_writei(pcm, &buffer[0],
frames_per_buffer);
    if (nb_written < 0) {
      std::cout << "snd_pcm_writei failed\n";
      snd_pcm_recover(pcm, nb_written, 1 /* silent */);
      xrun_count++;
    }

    usleep (100000);  // 100 msec

So basically I introduced a large sleep to force an audio drop (my
buffers are 3 x 64).

But this doesn't trigger an XRUN anyway.

What is unclear for me is if the code above shall trigger an XRUN or not?

Thanks,

Raphael