@js this isn't even a federation issue, we're both in the same instance

@espectalll Yep, something you do with your videos is weird, and Mastodon does not seem to perform any sanitation.

@js I just use ffmpeg to properly convert them, here's the command I used for this one as it'd be too heavy at 1080p:

ffmpeg -i MEOWIN\'\ IN\ THE\ 90\'s-ra6FtdXrH4Q.mp4 -s 1280x720 -c:a copy MEOWIN\'\ IN\ THE\ 90\'s\ \(lol\)-ra6FtdXrH4Q.mp4

@espectalll Aha! You are not creating hardware-friendly videos, so they *must* be decoded in software. When browsers (mobile and macOS) try to use the system framework, that tries to just pass it to the hardware - which can't decode it. Try using -profile:v main

@js ...wait really???

@espectalll H.264 has several profiles. I guess without specifying one, ffmpeg uses all features to encode it as efficiently as possible. But HW decoders don't support all profiles.

@espectalll Add -level 3.1 and it should work down to an iPhone 4.

@js OK, how about this?

@espectalll Still won't play. Even says it's 0:00 long. 😕

@js did I type this wrong?

ffmpeg -i MEOWIN\'\ IN\ THE\ 90\'s-ra6FtdXrH4Q.mp4 -profile:v main -level 3.1 -s 1280x720 -c:a copy MEOWIN\'\ IN\ THE\ 90\'s\ \(lol\)-ra6FtdXrH4Q.mp4

@espectalll Hm, nope, this looks fine 😕. I'm not an expert on this, though.

@espectalll I wonder: What's the audio though? Maybe it refuses to play at all if the audio is not the correct format?

@js regular plain MP3

@espectalll Aha! Doesn't MP4 need the audio to be AAC?

@js definitely not lol

@espectalll Ah, it's in the spec. But it's uncommon I guess - never seen that being done.

@js ...anyway, all I can find is the H.264 profiles/levels thing 🤔 https://trac.ffmpeg.org/wiki/Encode/H.264#Compatibility

@js I've tried everything I could so far and failed (being more specific, trying many presets, encoding audio to AAC) and it just doesn't work, sorry.

@js OK one sec, I have an iOS device at hand

@js Alright, can't play it either from here... wonder why 🤔