[Bug Report] "AtomicParsley error: unsupported MPEG-4 file brand found 'iso5'"

[bypie5]

AtomicParsely incorrectly labels MP4 videos with ftypiso5 in their header. This is the error message the gets printed when the following command is run on a video with the header mentioned before:

> AtomicParsely iso5brand.mp4 -T
AtomicParsley error: unsupported MPEG-4 file brand found 'iso5'

This is what the header for a mp4 video that produces this error looks like:

Note the ftypiso5 in the first few bytes of the header.

This seems to be an issue with libmagic itself. For more information about this bug, see this bug report for libmagic: https://mailman.astron.com/pipermail/file/2020-November/000441.html

Relevant part quoted below:

Hi,
We use libmagic to detect file formats and we got a report[1] that some MP4 files aren't detected properly. The file in question has a "\0\0\0$ftypiso5" signature of which "ftyp" is correctly detected as "ISO Media" (which annoyingly gives a application/octet-steam MIME type instead of some video/* fallback).
The "iso5" part isn't detected by libmagic and looking into /magic/Magdir/animation and https://github.com/FFmpeg/FFmpeg/blob/290de647595051034d8f021f24bb4610b2f39943/libavformat/movenc.c#L4925-L4961 you seem to be lacking a lot of MP4(-ish?) signatures.
Best regards,
Haelwenn (lanodan) Monnier
1: https://git.pleroma.social/pleroma/pleroma/-/issues/2287

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