Write custom (user defined) MP4 field with jaudiotagger

Question

I'd like to write a custom/user defined field in a mp4 file with jaudiotagger

For FLAC files, I can do this with VorbisCommentTagField.

For MP3 files using ID3v24Tag I can do this with a ID3v24Frame as ID3v24Frames.FRAME_ID_USER_DEFINED_INFO

Is there any way to do this in mp4? Looks like there is a Mp4FreeBox, but I can't find a public API to use it.

Moreover, does jaudiotagger expose any public API to set custom tags (key/value) in an unified way? Could not find any, and I need to treat each format independently.

Thank you

Answer 1

For Mp4 you want to use a reverse dns type tag using this constructor but there is not a way to create this as aprt of a unified api. Jaudiotagger does not currently provide a public api for creating custom tags, this is issue https://bitbucket.org/ijabz/jaudiotagger/issues/8/no-facilty-to-create-user-defined-frames

 Mp4FieldKey(String issuer, String identifier, Mp4FieldType fieldType, Tagger tagger)
    {

        this.issuer = issuer;
        this.identifier = identifier;
        this.fieldName = Mp4TagReverseDnsField.IDENTIFIER + ":" + issuer + ":" + identifier;
        this.subclassType = Mp4TagFieldSubType.REVERSE_DNS;
        this.fieldType = fieldType;
        this.tagger = tagger;
    }