Comment 103 for bug 743323

I managed to reproduce the problem today (using Ubuntu 11.04 _without_ natty-updates). It seems the root cause may be a bug in ALSA after all. PulseAudio complained in syslog:

Jul 11 11:47:16 leon pulseaudio[1810]: alsa-util.c: snd_pcm_avail() a retourné une valeur qui est exceptionnellement large : 2922048 octets (15219 ms).
Jul 11 11:49:31 leon pulseaudio[1810]: alsa-util.c: Il s'agit très probablement d'un bogue dans le pilote ALSA « snd_hda_intel ». Veuillez rapporter ce problème aux développeurs d'ALSA.
Jul 11 11:49:31 leon pulseaudio[1810]: alsa-util.c: snd_pcm_dump():
Jul 11 11:49:31 leon pulseaudio[1810]: alsa-util.c: Hardware PCM card 0 'HDA Intel' device 0 subdevice 0
Jul 11 11:49:31 leon pulseaudio[1810]: alsa-util.c: Its setup is:
Jul 11 11:49:31 leon pulseaudio[1810]: alsa-util.c: stream : PLAYBACK
Jul 11 11:49:31 leon pulseaudio[1810]: alsa-util.c: access : MMAP_INTERLEAVED
Jul 11 11:49:31 leon pulseaudio[1810]: alsa-util.c: format : S16_LE
Jul 11 11:49:31 leon pulseaudio[1810]: alsa-util.c: subformat : STD
Jul 11 11:49:31 leon pulseaudio[1810]: alsa-util.c: channels : 2
Jul 11 11:49:31 leon pulseaudio[1810]: alsa-util.c: rate : 48000
Jul 11 11:49:31 leon pulseaudio[1810]: alsa-util.c: exact rate : 48000 (48000/1)
Jul 11 11:49:31 leon pulseaudio[1810]: alsa-util.c: msbits : 16
Jul 11 11:49:46 leon pulseaudio[1810]: alsa-util.c: buffer_size : 96000
Jul 11 11:49:47 leon pulseaudio[1810]: alsa-util.c: period_size : 48000
Jul 11 11:49:48 leon pulseaudio[1810]: alsa-util.c: period_time : 1000000
Jul 11 11:49:48 leon pulseaudio[1810]: alsa-util.c: tstamp_mode : ENABLE
Jul 11 11:49:48 leon pulseaudio[1810]: alsa-util.c: period_step : 1
Jul 11 11:49:48 leon pulseaudio[1810]: alsa-util.c: avail_min : 95617
Jul 11 11:49:48 leon pulseaudio[1810]: alsa-util.c: period_event : 0
Jul 11 11:49:48 leon pulseaudio[1810]: alsa-util.c: start_threshold : -1
Jul 11 11:49:48 leon pulseaudio[1810]: alsa-util.c: stop_threshold : 1572864000
Jul 11 11:49:48 leon pulseaudio[1810]: alsa-util.c: silence_threshold: 0
Jul 11 11:49:48 leon pulseaudio[1810]: alsa-util.c: silence_size : 0
Jul 11 11:49:48 leon pulseaudio[1810]: alsa-util.c: boundary : 1572864000
Jul 11 11:49:48 leon pulseaudio[1810]: alsa-util.c: appl_ptr : 394960
Jul 11 11:49:48 leon pulseaudio[1810]: alsa-util.c: hw_ptr : 1152000
Jul 11 11:50:10 leon pulseaudio[1810]: alsa-util.c: snd_pcm_delay() a retourné une valeur qui est exceptionnellement large : -42434976 octets (-221015 ms).
Jul 11 11:50:10 leon pulseaudio[1810]: alsa-util.c: Il s'agit très probablement d'un bogue dans le pilote ALSA « snd_hda_intel ». Veuillez rapporter ce problème aux développeurs d'ALSA.
Jul 11 11:50:10 leon pulseaudio[1810]: alsa-util.c: snd_pcm_dump():
Jul 11 11:50:10 leon pulseaudio[1810]: alsa-util.c: Hardware PCM card 0 'HDA Intel' device 0 subdevice 0
Jul 11 11:50:10 leon pulseaudio[1810]: alsa-util.c: Its setup is:
Jul 11 11:50:10 leon pulseaudio[1810]: alsa-util.c: stream : PLAYBACK
Jul 11 11:50:10 leon pulseaudio[1810]: alsa-util.c: access : MMAP_INTERLEAVED
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: format : S16_LE
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: subformat : STD
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: channels : 2
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: rate : 48000
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: exact rate : 48000 (48000/1)
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: msbits : 16
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: buffer_size : 96000
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: period_size : 48000
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: period_time : 1000000
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: tstamp_mode : ENABLE
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: period_step : 1
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: avail_min : 95617
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: period_event : 0
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: start_threshold : -1
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: stop_threshold : 1572864000
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: silence_threshold: 0
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: silence_size : 0
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: boundary : 1572864000
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: appl_ptr : 406192
Jul 11 11:50:11 leon pulseaudio[1810]: alsa-util.c: hw_ptr : 11088001
Jul 11 11:54:18 leon pulseaudio[1810]: module-alsa-card.c: Failed to find a working profile.
Jul 11 11:54:18 leon pulseaudio[1810]: module.c: Failed to load module "module-alsa-card" (argument: "device_id="29" name="platform-thinkpad_acpi" card_name="alsa_card.platform-thinkpad_acpi" tsched=yes ignore_dB=no card_properties="module-udev-detect.discovered=1""): initialization failed.

The snd_pcm_avail() and snd_pcm_delay() values were definitely bogus... So I'm starting to suspect that a "small" bug in VLC triggers the issue, but the real problem lies in ALSA?