Comment 1 for bug 436248

When playing back video, and pulse audio active, no audio and video playback is too fast.
And lots of output:

Could not open ALSA device "/dev/dsp": No such file or directory
ALSA lib pcm.c:2211:(snd_pcm_open_noupdate) Unknown PCM /dev/dsp

The padsp workaround improves video playback, but the audio sounds choppy.

The workaround that works well for me (and others) is to use pasuspender
to suspect pulse audio and allow direct audio hardware access.

Further discussion:
http://ubuntuforums.org/showthread.php?t=1334403