Regression bug
Introduced by http://git.libav.org/?p=libav.git;a=commitdiff;h=375ca0aca8
Modified by http://git.libav.org/?p=libav.git;a=commitdiff;h=12cbbbb4ab

Steps to reproduce:
  avplay 20130507_audio-distortion.smk

You can hear distortions at 00:20-00:30