Bug #751265 describes the symptom: when VLC uses Pulseaudio for audio output, the sound from it becomes garbled after playing for a while, with heavy digital artefacts and echoing. Comment #23 in that report suggests modifying /etc/pulse/default.pa so that load-module module-udev-detect is followed by tsched=0. I’ve done that, and with it VLC seems to work fine with Pulseaudio. Furthermore, in comment #30 @David Henningsson prompted us suffering from this and with the tsched=0 workaround working to file our own reports for each specific hardware. This is my report.

I believe apport adds data about the hardware automatically. I’ll add to that that for me this only occurs with the Radeon HDMI output; through the analog output (via headphones) the audio works fine. As Bug #864735 describes, Radeon audio is off by default in recent kernels, but I’ve re-enabled it by passing the radeon.audio=1 kernel commandline parameter.

If I switch to ALSA output for VLC (without tsched=0), VLC audio goes mute after a while. After some time of silence it sort of fast forwards itself to get up to sync with the video again. This keeps repeating, so it’s not really a workaround.