That file looks like it’s barely playable in general.
FFmpeg and MPV can’t play it at all:
<span style="color:#323232;">max-p@desktop ~ [123]> mpv https://lemmynsfw.com/pictrs/image/f482b4d7-957a-4ed7-a9ec-0493907a8cb3.mp4
</span><span style="color:#323232;"> (+) Video --vid=1 (*) (h264 576x1024 30.000fps)
</span><span style="color:#323232;"> (+) Audio --aid=1 (*) (aac 1ch 44100Hz)
</span><span style="color:#323232;">File tags:
</span><span style="color:#323232;"> Comment: vid:v12044gd0000cp23h1vog65ukmo9lhkg
</span><span style="color:#323232;">Cannot load libcuda.so.1
</span><span style="color:#323232;">[ffmpeg] Cannot seek backward in linear streams!
</span><span style="color:#323232;">[ffmpeg/demuxer] mov,mp4,m4a,3gp,3g2,mj2: stream 1, offset 0x30: partial file
</span><span style="color:#323232;">[lavf] error reading packet: Invalid data found when processing input.
</span><span style="color:#323232;">[ffmpeg] Cannot seek backward in linear streams!
</span><span style="color:#323232;">[ffmpeg/demuxer] mov,mp4,m4a,3gp,3g2,mj2: stream 1, offset 0x30: partial file
</span><span style="color:#323232;">[lavf] error reading packet: Invalid data found when processing input.
</span><span style="color:#323232;">[ffmpeg] Cannot seek backward in linear streams!
</span><span style="color:#323232;">[ffmpeg/demuxer] mov,mp4,m4a,3gp,3g2,mj2: stream 1, offset 0x30: partial file
</span><span style="color:#323232;">[lavf] error reading packet: Invalid data found when processing input.
</span><span style="color:#323232;">[ffmpeg] Cannot seek backward in linear streams!
</span><span style="color:#323232;">[ffmpeg/demuxer] mov,mp4,m4a,3gp,3g2,mj2: stream 1, offset 0x30: partial file
</span><span style="color:#323232;">[lavf] error reading packet: Invalid data found when processing input.
</span><span style="color:#323232;">[ffmpeg] Cannot seek backward in linear streams!
</span><span style="color:#323232;">[ffmpeg/demuxer] mov,mp4,m4a,3gp,3g2,mj2: stream 1, offset 0x30: partial file
</span><span style="color:#323232;">[lavf] error reading packet: Invalid data found when processing input.
</span><span style="color:#323232;">[ffmpeg] Cannot seek backward in linear streams!
</span><span style="color:#323232;">[ffmpeg/demuxer] mov,mp4,m4a,3gp,3g2,mj2: stream 1, offset 0x30: partial file
</span><span style="color:#323232;">[lavf] error reading packet: Invalid data found when processing input.
</span><span style="color:#323232;">[ffmpeg] Cannot seek backward in linear streams!
</span><span style="color:#323232;">[ffmpeg/demuxer] mov,mp4,m4a,3gp,3g2,mj2: stream 1, offset 0x30: partial file
</span><span style="color:#323232;">[lavf] error reading packet: Invalid data found when processing input.
</span>
VLC seems to be able to, but it complains that it’s not proper:
<span style="color:#323232;">max-p@desktop ~> vlc https://lemmynsfw.com/pictrs/image/f482b4d7-957a-4ed7-a9ec-0493907a8cb3.mp4
</span><span style="color:#323232;">VLC media player 3.0.20 Vetinari (revision 3.0.20-0-g6f0d0ab126b)
</span><span style="color:#323232;">[00005ca01d39d550] main libvlc: Lancement de vlc avec l’interface par défaut. Utiliser « cvlc » pour démarrer VLC sans interface.
</span><span style="color:#323232;">[00007ea2f413f5c0] mp4 stream error: no moov before mdat and the stream is not seekable
</span>
Some players are more generous in what they tolerate but the file is undoubtedly mildly corrupted.
Lemmy should not let people upload corrupted files in the first place.