I have camtasia (the same version 8.5.1) installed on 2 different machines. I produce the same movie (which is a combintation of different mp4 clips) and get the output mp4 that on one machine has size 831 MB, while when produced on the other machine has size 172 MB. The second value seems much more reasonable as the total size of input mp4 files is around 160 MB. What can be cause of this behavior? It is annoying as I later share those movies and of course it is better to have smaller size if they are of the same quality.