that means your cron is not working properly - I believe. 2 things handle the processing of video and music files - the cron jobs and your ffmpeg. When I first read your message, my first thought was it was your cron job although you said your crons are working, but after looking at your post about your cron message, it is obvious that your crons are not working properly. The message you are getting is saying that it can not find the cron.php file which you have listed as being located at /public_html/dolph/periodic.
So, the first thing to check is _ do you have a dolph folder in your public_html folder? If not, then that would be the problem with your crons - the path is set incorrectly.
EDIT:
One thing you can do to test if it is your cron - go to your periodic folder and rename the .htaccess file to htaccess.txt. Then go to yoursite.com/periodic/cron.php. This will manually run the cron and it should process all the files you want to be processed.