AtomicParsley is a lightweight command line program for reading, parsing and setting metadata into MPEG-4 files supporting these styles of metadata:

* iTunes-style metadata into .mp4, .m4a, .m4p, .m4v, .m4b files
* 3gp-style assets (3GPP TS 26.444 version 6.4.0 Release 6 specification conforming) in 3GPP, 3GPP2, MobileMP4 & derivatives
* ISO copyright notices at movie & track level for MPEG-4 & derivative files
* uuid private user extension text & file embedding for MPEG-4 & derivative files

The MPEG-4 container is based on Apple's Quicktime .mov container (just more sane) & there are a number of similarites - as well as differences. Each MPEG-4 file lists a "major file brand" that broadly says which specification the file adheres to. For example, an iTunes audio file typically lists 'M4A ' as its major file brand, while a 3GPP2 .3g2 file has something like '3g2a'. It is based on this major file brand that AtomicParsley allows a style of metadata to be set. Since there is nothing in the 3GPP2 specification regarding iTunes-style metadata, its use is prevented on such files. Similarly, a 3gp 'location' asset is not available for an iTMS video file. The first paragraph here sums the situation up well.

With the exception of artwork, all iTunes-style tags support only 1 piece of metadata - you can't have for example 3 title tags. 3gp assets and copyright notices support multiple tags, but they must differ in the language setting for that tag. You can have for example 3 title tags, but 1 in english, 1 in spanish, 1 in undefined. All iTunes-style text metadata is always in UTF-8; 3gp assets & copyright notices can be in set in UTF-8 or UTF-16. All strings are converted internally to UTF-8, converting as necessary. On *nix platforms, input is in UTF-8; the native Windows port supports full UTF-16 input.