you wont. ffmpeg is incredibly hard to install properly. i know linux well but it still took about 2 weeks for me to configure all the features it has so its compatible with all file formats.
you will not find any hosts that support it because bandwidth would go through the roof if people started hosting video content (and cheap hosting companies rely on users utilizing very little bandwidth). if you want it done right you need a very powerful server with a lot of bandwidth.
also, you'd need high level shell access to run the necessary scripts that convert the videos.
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