However as you note, most video footage is originally shot or edited and encoded using other lossy encoding formats, meaning a WebM copy uploaded to us is often one generation of lossy encoding farther down than it would have been had we accepted MP4 H.264/AAC files or other common formats directly. And if someone wants to reuse the footage they find on Commons, they might need to reencode again, depending on the support in their editing tools.

When encoding at a suitably high data rate and quality this is not a huge problem, but I've seen a lot of Ogg and WebM videos on Commons that were encoded at *really* low bitrates by mistake and there's no way to restore the quality without an earlier-generation file to work from.

I would recommend backing up your own files just for certainly, especially if you want to pass the files on to be re-edited.

Ideally, we would accept your camera's output (likely MP4 H.264/AAC) directly, and you would have no need to manually maintain separate archives of your source files. The formats involved are well-documented international standards, well-supported by open-source software, but made difficult for some usage scenarios by the patents on encoding and decoding; unlike the early-2000s-era undocumented video formats they are not "proprietary", but they are still "patent-encumbered".

I cannot speak to the legal issues of redistributing MP4 H.264/AAC files that were encoded elsewhere, or decoding on our servers to re-encode as a free format for playback, but would be very interested in supporting such uploads if we can. And it would be very easy to do technically; we need only change a configuration option to allow MP4 uploads, which would then be treated just like our existing Ogg and WebM source uploads.

However allowing upload and redistribution of MP4 sources was one of the scenarios rejected by the Commons community in 2014 in favor of "no MP4 support": https://commons.wikimedia.org/wiki/Commons:Requests_for_comment/MP4_Video 

I think it would be wise to reconsider some of these past decisions; four years later support for WebM *playback* is better than it was with native MS Edge support and a JavaScript/WebAssembly shim for Safari, but the difficulties for *contributors and reusers* of video files remain as big as they were.

-- brion