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After a number of updates, including upgrading to flashplayer 11 and kernel 3.8.2 sound from flashplayer and skype has become choppy.

Setup

In my setup I have .ascoundrc set up to use pulseaudio (copied from somewhere, because I have no clue about the syntax of .asoundrc)

pcm.pulse {
    type pulse
}
ctl.pulse {
    type pulse
}
pcm.!default {
    type pulse
}
ctl.!default {
    type pulse
}

Pulseaudio is setup to use jack as source and sink. Jack uses a firewire mixing console as soundcard.

And in case it matters, I have an nvidia graphics card (GeForce 8800 GT) with the proprietary drivers from nvidia (NVIDIA-Linux-x86-310.40) .

Symptoms

Sound from vlc or celementine works flawlessly. I believe these talk to pulseaudio directly. Using mplayer I can choose between -ao alsa pulse and jack and all work okay.So I have no reason to believe there is anything wrong on the tail end of the chain, i.e. pulse->jack->firewire.

But also aplay works fine, which I believe, must go through the alsa layer to access pulse.

Skype and especially flashplayer produce choppy sound, as if the samplerate were not right and the system has to jump a number of samples back or forth every half second or so. Flash shows this behavior not just in Firefox, but also in Chrome.

Skype sometimes works okay, i.e. when I kill and restart it I can get it to work.

Analyses so far

I have compared the output of pactl list when playing from aplay, firefox or skype and could not see any clues. My sample-rate seems to be 44100 and Skype comes in with 44800 so pactl shows that a speex-float-3 resampling is happening. But I can aplay wave files with 44100 and 48000, so my original hunch, that resampling is causing the problems is probably not right.

I also compared the ldd output of aplay and skype and skype uses the same shared libraries as aplay, plus of course some more.

I have tried to use the alsa jack plugin, such that alsa talks directly to jack, bypassing pulse, but then flash playback stops producing sound after a few seconds.

CPU usage is high when playing flash

16494 23.6 478m     1 martin    1000 1 S  20   0   58 firefox
14797  4.7  95m  4097 root         0 1 S  20   0   11 xorg
15979  5.1 103m 15806 martin    1000 1 S  20   0    7 jackd
25561  8.5 172m     1 martin    1000 0 S   9 -11    5 pulseaudio
25534  4.1  82m 17830 martin    1000 0 S  20   0    2 skype

dmesg occasionally shows

pulseaudio[15996]: segfault at 0 ip b256416a sp bfe34d40 error 4 in module-jack-sink.so[b2562000+4000]

This is certainly "not good", but pulseaudio gets restarted okay when needed

There is nothing in /var/log/messages or .xsession-error or on stdout/stderr of firefox or chrome.

Any help would be much appreciated. I would also be happy about pointers, where to look next or what to google. The strange thing is, that not many seem to have this problem.

share|improve this question
    
Meanwhile I tested two more scenarios: (1) alsa->analogueSoundcard (no jack, no pulse) => works. (2) alsa->jack->firewireConsole (no pulse) => works for aplay and clementine. Flash in firefox starts playing okay, but stops after 20 seconds and firefox is frozen. –  Martin Drautzburg Apr 28 '13 at 19:01

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