[Ring] Ring and proprietary codecs

[Thomas Daede]

I recently noticed that GNU Ring currently depends on several
proprietary video codecs:

* H.264
* H.263
* MPEG-4 ASP

The usage of those codecs (as implemented by ffmpeg) requires payment of
royalties for use. It also prevents its inclusion in Linux distros such
as Fedora [1]. However, Ring also supports free video codecs, such as
VP8. I think it would make sense to:

* Make dependence on proprietary codecs optional
* Turn off proprietary codecs by default

In addition, as far as I can tell, Ring does not need compatibility with
legacy software. Especially because good alternatives are available, I
think it would make sense to not support proprietary codecs at all, and
instead rely on a baseline of VP8 and Opus (or VP9 and Opus).

Thomas

[1]
https://lists.fedoraproject.org/archives/list/address@hidden/message/7EUHLUVNBCUKBLE3W2AHKJ4Y33QNYYXD/