These values should not matter at all in principle because they
do not correspond to the time of display of any frame but it seems
ffmpeg becomes confused by them if they are far off and its not
strictly correct to set them to guessed values.


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@14746 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b