one more problem with uploading

Hi, i bought hosting from dreamhost today to upload my website because i know that it supports ffmpeg. My site works fine but when i am trying to upload a video it appears me this message:
Your video was successfully added!
Your video is currently being processed and will be available to view in a few minutes.
but the videos aren't uploaded. I Have selected to create thumnail with ffmpeg because when i had ffmpeg-php it appeared me this message:
Fatal error: Class 'ffmpeg_movie' not found in /xxx/local/home/xxx/mywebsite.net/include/classes/class.video_duration.php on line 54
Please help me to face this problem
Thanks!