Running 3.0 Standard, and I have never had a problem of this kind until the disk check at startup detected an error in my root partition. It rebooted, having apparently fixed that much, but now, while my mp3 audio works in my music player, none of my videos will play sound -- all I get is crackling, and that's only when I turn it up quite loud. I feel like I fixed an error just like this in Windows a few years back, but I'm completely stumped at this point. It happens on .avi, .flv and .mpg, though to be honest, I'm not sure which codecs they were encoded with. I tried reinstalling ubuntu-restricted-codecs or whatever that package is . . . gah, this is blowing my mind.

Weird, that crackling in eb3 is usually a systemwide phenomenon and can be mostly worked around by adjusting various volume controls in the mixer. Never heard of it affecting just videos.

Exactly -- I've tried Alsa, Oss, matching the VLC settings to the systemwide settings . . . And VLC is telling me that it's translating an audio stream, giving me the bits in realtime -- I just can't hear it. Mplayer gives me the same problem. Also having the problem with youtube, so it's got to be something systemwide that is stopping my videos from playing audio :-\

WOOP -- fixed for now, at least.

http://ubuntuforums.org/showthread.php?t=614589

In the terminal, my PCM was at 0, although it was always at 100 in the GUI. Which, I don't mind telling you, is bizarre to me. His command to save the settings permanently doesn't work for me (terminal doesn't know what "alsact" is), but I closed out of the terminal and started up a video, and we're golden.

Hope this helps someone else, too.