How to register common, but undocumented boxes?

[Crissov]

There are a lot of metadata boxes in current use for audio and video files that apparently have never been registered, or are at least missing not documented at the MP4RA site (and in this repository). Many of them originate in Apple iTunes (or Quicktime), but are supported by other software as well, based upon reverse-engineered documentation I suppose. Some of these start with the copyright symbol, e.g. ©ART or ©nam, to mark them as private-use obviously, but others are not, e.g. stik, hdvd, tves or purl.

The following points are not clear to me:

1. Should all of these be registered, or just ones not starting with $a9?
2. Would registering them be possible at all without a formal and publicly available specification?
3. If a public specification is needed, but the vendor is not willing to release one, would it be acceptable to create and publish one elsewhere?
4. If so, would this require backing from a formal standardization body or a company, or could it be done as a collaborative open-source effort?

[dwsinger]

wow, that is one huge page. There is a whole load there is

• is not a 4CC used in MP4 files (or .mov) but other tags
• is already documented (most of the brands, for example)
• or are in spaces that at least once we considered 'private' (e.g. sample-entry boxes)

Nonetheless, it's great to encourage owners of unregistered 4CCs to go ahead and register them

[Crissov]

I have been informed that Apple used to publish an iTunes Metadata Format Specification somewhere on developer.apple.com, but doesn’t anymore. I’d absolutely expect everything that was documented therein to be registered with MP4RA and I don’t understand why this PDF was de-published as it would have served as a reference for interoperable implementations.

[Crissov]

This is most of what I‘m talking about.

Defined tags recognized by iTunes

Element	Additional Description	Tag	Data Type
Album Name	©alb	UTF string
Artist	©ART	UTF string
User Comment	©cmt	UTF string
Cover Art	One or more cover art images	covr	JPEG/PNG/BMP data
Copyright	cprt❓	UTF string
Release Date	YYYY-MM-DD format string (may beincomplete, i.e. only year)	©day	UTF string
Encoded By	Person or company that encoded the recording	©enc	UTF string
Pre-defined Genre	Enumerated value from ID3 tag set, plus 1 (set identifier = 0)	gnre	enum
User Genre	User-specified string	©gen	UTF string
Song Name	©nam	UTF string
Track Sub-Title	©st3	UTF string
Encoding Tool	Software which encoded the recording	©too	UTF string
Composer	©wrt	UTF string
Album Artist	Artist for the whole album (if different than the individual tracks)	aART	UTF string
Disc Compilation	Is disc part of a compilation?	cpil	8-bit "boolean" integer
Disc Number	The data-type 0 is used, implicitly identifying the disk-number record used above	disk	Binary data
Grouping	Overall work (like TIT1 in ID3)	grup❓	UTF string
Content Rating	Does song have explicit content?	rtng	8-bit "boolean" integer
Beats Per Minute	tmpo	32-bit integer
Track Number	The data-type 0 is used, implicitly identifying the track-number record used above	trkn	Binary data

The following tags may also be used; not all software recognizes or interprets them:

Element	Additional Description	Tag	Data Type
Art Director	Person(s) responsible for non-photographic artwork used with content	©ard	UTF string
Arranger	Person(s) responsible for the particular adaptation of composition	©arg	UTF string
Lyricist/Author	Name Writer of the song lyrics	©aut	UTF string
Copyright Acknowledgement(s)	Ackowledgements of those granting permission to use copyrighted material	©cak	UTF string
Conductor	Name of the person who directed the orchestra	©con	UTF string
Song Description	Explanation of the song	©des	UTF string
Director	Name of director for Movie/Video	©dir	UTF string
Equalization preset name	Setting for Equalization of content	©equ	UTF string
Liner Notes	Explanatory notes about a record album, cassette, or compact disk included on the jacket or in the packaging.	©lnt	UTF string
Record Company	Company releasing the song	©mak	UTF string, URL
Original Artist	Name of artist originally attributed with content	©ope	UTF string
Phonogram Rights (P-Line)	Like a copyright, but using the circled P symbol, for audio rights	©phg	UTF string
Producer	Person(s) responsible for creating/supervising the song	©prd	UTF string
Performer	Name/URL of the individual primary members of the band/group	©prf	UTF string, URL
Publisher	Company publishing the song	©pub	UTF string
Sound Engineer	The name of the person doing sound engineering	©sne	UTF string
Soloist	Name of the musician who performs the solo	©sol	UTF string
Credits	Credits for those who provided source content	©src	UTF string
Thanks/Dedications	Notes of acknowledgement/recognition from Artist	©thx	UTF string
Online Extras	Links to content that can only be accessed when connected to the Internet	©url	URL
Executive Producer	Person(s) responsible for creating/supervising the song	©xpd	UTF string

[dwsinger]

Yes, these are all user-data types, I think

On 16Mar, 2021, at 12:33 , Christoph Päper @.***> wrote:

This is what I‘m talking about.

Defined tags recognized by iTunes

Element Additional Description Tag Data Type Album Name ©alb UTF string Artist ©ART UTF string User Comment ©cmt UTF string Cover Art One or more cover art images covr JPEG/PNG/BMP data Copyright cprt UTF string Release Date YYYY-MM-DD format string (may beincomplete, i.e. only year) ©day UTF string Encoded By Person or company that encoded the recording ©enc UTF string Pre-defined Genre Enumerated value from ID3 tag set, plus 1 (set identifier = 0) gnre enum User Genre User-specified string ©gen UTF string Song Name ©nam UTF string Track Sub-Title ©st3 UTF string Encoding Tool Software which encoded the recording ©too UTF string Composer ©wrt UTF string Album Artist Artist for the whole album (if different than the individual tracks) aART UTF string Disc Compilation Is disc part of a compilation? cpil 8-bit "boolean" integer Disc Number The data-type 0 is used, implicitly identifying the disk-number record used above disk Binary data Grouping Overall work (like TIT1 in ID3) grup UTF string Content Rating Does song have explicit content? rtng 8-bit "boolean" integer Beats Per Minute tmpo 32-bit integer Track Number The data-type 0 is used, implicitly identifying the track-number record used above trkn Binary data The following tags may also be used; not all software recognizes or interprets them:

Element Additional Description Tag Data Type Art Director Person(s) responsible for non-photographic artwork used with content ©ard UTF string Arranger Person(s) responsible for the particular adaptation of composition ©arg UTF string Lyricist/Author Name Writer of the song lyrics ©aut UTF string Copyright Acknowledgement(s) Ackowledgements of those granting permission to use copyrighted material ©cak UTF string Conductor Name of the person who directed the orchestra ©con UTF string Song Description Explanation of the son g ©des UTF string Director Name of director for Movie/Video ©dir UTF string Equalization preset name Setting for Equalization of content ©equ UTF string Liner Notes Explanatory notes about a record album, cassette, or compact disk included on the jacket or in the packaging. ©lnt UTF string Record Company Company releasing the song ©mak UTF string, URL Original Artist Name of artist originally attributed with content ©ope UTF string Phonogram Rights (P-Line) Like a copyright, but using the circled P symbol, for audio rights ©phg UTF string Producer Person(s) responsible for creating/supervising the song ©prd UTF string Performer Name/URL of the individual primary members of the band/group ©prf UTF string, URL Publisher Company publishing the song ©pub UTF string Sound Engineer The name of the person doing sound engineering ©sne UTF string Soloist Name of the musician who performs the solo ©sol UTF string Credits Credits for those who provided source content ©src UTF string Thanks/Dedications Notes of acknowledgement/recognition from Artist ©thx UTF string Online Extras Links to content that can only be accessed when connected to the Internet ©url URL Executive Producer Person(s) responsible for creating/supervising the song ©xpd UTF string — You are receiving this because you commented. Reply to this email directly, view it on GitHub, or unsubscribe.

Dave Singer Multimedia and Software Standards, Apple

@.***