You are not logged in.
This is intended as a future reference for myself and for others who might experience a simmilar issue. I have an hybrid graphics laptop with an integrated intel GPU (This is an arrandale core i5 450m CPU with ironlake GPU) and a discrete radeon HD 5650. For some time I have been suffering from laggy/choppy sound both within firefox and with mplayer/totem/vlc. It turned out that this behavior was the result of the coincidence of a few factors:
1- The discrete GPU has HDMI output and is thus detected (by udev?) as another sound card
2- I had activated the pulseaudio combine module (for simultaneous output to all soundcards)
3- I had the GPU powered off to save power as I mostly used the integrated GPU
4- I had only adjusted sound settings through gnome's sound settings.
In the logs the messages below appeared whenever I tried to play any video:
Mar 17 23:49:34 acerito pulseaudio[2827]: [pulseaudio] module-combine-sink.c: [alsa_output.pci-0000_00_1b.0.analog-stereo] sample rates too different, not adjusting (48000 vs. 182803).
Mar 17 23:49:44 acerito pulseaudio[2827]: [pulseaudio] module-combine-sink.c: [alsa_output.pci-0000_00_1b.0.analog-stereo] Total latency of output is very high (18774.55ms), most likely the audio timing in one of your drivers is broken.It turned out gnome's sound settings don't offer the possibility to turn off a given card, so the pulseaudio combine module attempts to send the audio to the sound card which was turned off (at least this is my guess). When, by chance, I opened pavucontrol, I discovered the option to turn off the sound card associated to the Ati GPU, which solved the problem.
Offline