[BUG] "No video with supported format and MIME type found" when trying to view mp4s on Firefox

[LordChildConsumer]

Describe the bug
When opening a link to an mp4 with Firefox, sometimes instead of playing it will show the error "No video with supported format and MIME type found".

To Reproduce

1. Upload mp4 file.
2. Share link
3. Open link in Firefox

Expected behavior
Video playback.

Screenshots
Error Message

Desktop

• Browser Firefox
• Version 136.0.1

[FlintSH]

We talked in DMs, some more info to add:

1. Not reproducible on Chromium based browsers.
2. The instance is running Flare 1.2.0 with Cloudflare R2 storage.

[FlintSH]

Ideal fix in my mind right now would be to look into some library to handle video playback instead of expecting the browser to handle it well.

Additionally should probably revisit and refactor video serving in general. There are some other small quirks to iron out like playback on Discord on mobile sometimes only playing audio but no frames.

Will revisit this asap.

[FlintSH]

I spent a few hours on this tonight.

This seems to just be a Firefox issue, not necessarily caused by Flare. Will leave this issue open, as it is still an issue, but as of now I don't see a way around this.

My new findings:

1. Doesn't happen to all videos and mp4's, only the one mentioned here.

• The video plays on Chrome but not on Firefox.

2. Regardless of whether the video is served via s3 provider directly or through /api/[userUrlId]/[filename]/raw, the video fails to play embedded on Firefox.
3. Even with a more embedded solution like a custom video player library (above), the video fails to play on Firefox.

I think it's likely:

1. The video has some weird encoding that Firefox doesn't like.
2. Firefox doesn't support something on the file.