mpegpsdemux: duration calculation on VBR file incorrect (and thus bad seeking)

Submitted by Omer Akram

Description

someone in launchpad is facing a problem with playing videos of variable bitrate. the length of the video is 46secs or so but sometimes totem shows it as if its a 11min video and such. attached a 15mb sample from the launchpad bug report.

https://bugs.launchpad.net/ubuntu/+source/totem/+bug/200846/+attachment/1088223/+files/VBR.zip

originally reported at: https://bugs.launchpad.net/ubuntu/+source/totem/+bug/200846