Choppy playback of audio belonging to wmv files

[Daniel]

A simple pyffmpeg-based video player I've made, works well with almost
every SD file format, except for wmv.
There, the video gets played nicely, but the audio skips, as if the
frames that are retrieved are too short. I have tried several wmv
files, of which I encoded some myself to make sure they weren't
corrupt, but this problem occured with every single one of them. I'm
not a big fan of the wmv format at all and discourage its usage, but I
hope that it can eventually be played well by the player.
Does anybody know why wmv-audio would suffer from this problem and
maybe how to solve it?