I've tried a number of hosts offering ffmpeg support recently and the ones I've been able to install phpmotion with no problems are:
I have tried a number of other hosts who claim to offer ffmpeg hosting, but present problems with installation. There seems to be a problem with phpshield and php versions above 5.2.4 .
Having said that HostingMarketers offer php 5.2.6, yet it still presents no problems.
The hosts I have tried and failed to install phpmotion (even after contacting support) are:
To me it seems to be that if a hosts website offers ffmpeg and lists the social media scripts they support, then you will be OK.
If a host just says they offer ffmpeg, with no backup about what scripts they can host, then you are in trouble.