How do I write tags into MP4/M4V files in c++?

[ASilverblade]

Since I can't seem to find a way to write raw tag data to MKV's without an external XML file...

I want to write a c++ program to manipulate the tag data in an MP4/M4V file without an external library (from scratch),
but I can't find information on the internet on how to access that data.

Can anyone on here help me find the tag data on the file?
Even just the starting location/character of where the tags are stored.

Thanks in advance.

[Baldrick]

I would check the mp4box site and source code,
http://gpac.wp.mines-telecom.fr/mp4box/mp4box-documentation/

[Selur]

If you want to write it from scratch (no clue why since the existing libraries are LGPL) for mkv, you need to read the Matroska specification: http://matroska.org/technical/index.html

[ASilverblade]

Thank you baldrick and Selur, I'll look into it now.

Also Selur, it's because I believe not enough people know what 'from scratch' really means, I figure if I have a project, I want to do it from scratch. so I know it's mine.

(I know that's still kind of cheating since I'm using a pre-made video format, but if I use a custom format then my media player wont even need to play more used formats, but I'm making a player, so the formats it plays must be diverse.)

[Selur]

If you want to write it from scratch do so, for mkv you are basically writing your own mkvpropedit which shouldn't be to hard after reading and understanding the specification.
-> best of luck with your endeavour
If you end up writing your own matroska/mp4 tagging libraries it would be nice it you would open source and share them with the community.

Cu Selur

[jman98]

In my experience, it's almost always young people who want to "reinvent the wheel" they do it for one of the following reasons.

1) They've been assigned a school project that requires them to do it as a learning exercise.
2) They simply want to learn more about the subject at hand by doing it this way.
3) They think that everybody before them is old and stupid and surely there must be a better way to do this that only they are smart enough to think of and do.

[Selur]

at least 3. is probably right for most open source projects since refactoring is seldom done and due to the growing nature of most projects code tends to get ugly.

[ASilverblade]

jman98 - It's for three reasons:

1. I'm a perfectionist, when I want to say I built something from scratch, I want to make sure I'm not lying.
2. To learn everything I possibly can about as much as I possibly can, therefore expanding my abilities and knowledge.
3. Because no easy program seems to exist for these functions, so I want to make it. (My specialty is automation).

Selur - Thank you, and I'm sure I will opensource it.

I like to work with my version of 'modular' coding, it takes more time to built a stable 'core' function but it means making updates and adding extra features is much easier, I do it in my larger projects and boy does it help. :3