Possible issue reading cpil field from m4a tags.

[milesegan]

Reproducer

Repo for reproduction is here:

https://github.com/milesegan/lofty-aac-compilation-bug

Summary

There seems to be an error reading the cpil compilation flag field from m4a tags. In the sample file the value is 1 but the tag reads as 0.

Expected behavior

No response

Assets

No response

[milesegan]

It seems like maybe the issue is here?

lofty-rs/lofty/src/mp4/ilst/read.rs

Lines 123 to 126 in 79336cd

	let data = match content[..] {
	[0, ..] => AtomData::Bool(false),
	_ => AtomData::Bool(true),
	};

When I read the tag the content is [0, 0, 0, 1] which gets parsed as false. Maybe an endian issue?

[Serial-ATA]

Yep, that's exactly where the issue is :)

These flag atoms seem to be pretty inconsistently implemented. Quite a few projects write a 1 byte flag (which is what I thought was correct). It seems like other tools (including iTunes) write an i32, though. Guess I'll have to account for both encodings during parsing.

[milesegan]

It sounds tricky! Please let me know if I can help out.