This changes the way the advanced output section's FFmpeg output
settings work by allowing the user to select whether they want to output
to a file or output to a URL, and makes it so file names are
automatically generated like other recording outputs.
If they choose to output to a file, it'll only require an output
directory similarly to how other recording outputs work. They can
select a directory to output to rather than being required to type in a
full path and filename; the filename is automatically generated. The
extension is also automatically retrieved from libff depending on the
format selected.
Otherwise if they have Output to URL selected, it'll show a simple edit
box where they can type in the target URL.
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