Before the FFmpeg commit: github.com/FFmpeg/FFmpeg/commit/1c0885334dda9ee8652e60c586fa2e3674056586 FFmpeg would use deprecated variables to calculate the video fps. We don't use these deprecated variables anymore, so ensure that the duration is correct in ffmpeg versions without this fix. Reviewed By: Sergey, Richard Antalik Differential Revision: http://developer.blender.org/D11417