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Tag Parser

C++ library for reading and writing MP4 (iTunes), ID3, Vorbis, Opus, FLAC and Matroska tags.

Supported formats

The tag library can read and write the following tag formats:

  • iTunes-style MP4/M4A tags (MP4-DASH is supported)
  • ID3v1 and ID3v2 tags
    • conversion between ID3v1 and different versions of ID3v2 is possible
  • Vorbis, Opus and FLAC comments in Ogg streams
    • cover art via "METADATA_BLOCK_PICTURE" is supported
  • Vorbis comments and "METADATA_BLOCK_PICTURE" in raw FLAC streams
  • Matroska/WebM tags and attachments

File layout options

Tag position

The library allows you to choose whether tags should be placed at the beginning or at the end of an MP4/Matroska file.

Padding

Padding allows adding additional tag information without rewriting the entire file or appending the tag. Usage of padding can be configured:

  • minimum/maximum padding: The file is rewritten if the padding would fall below/exceed the specifed limits.
  • preferred padding: If the file needs to be rewritten the preferred padding is used.

However, it is also possible to force rewriting the entire file.

Taking advantage of padding is currently not supported when dealing with Ogg streams (it is supported when dealing with raw FLAC streams).

Additional features

The library can also display technical information such as the ID, format, language, bitrate, duration, size, timestamps, sampling frequency, FPS and other information of the tracks.

It also allows to inspect and validate the element structure of MP4 and Matroska files.

Text encoding, Unicode support

The library does not do any conversions for you (eg. converting Latin1 to UTF-8). However the API provides a way to check which encoding is present (when reading) and which encoding(s) can be used (when writing).

Usage

For examples check out the command line interface of my Tag Editor (which is also on Git).

Bugs, stability

  • Matroska files composed of more than one segment aren't tested yet and might not work.
  • To add new features I've had to revise a lot of code since the last release. I always test the library with files produced by mkvmerge and ffmpeg and several other file but can't verify that it will work with all files. Hence I recommend you to create backups of your files.

Build instructions

The tagparser library depends on c++utilities and is built in the same way. It also depends on zlib.

TODO

  • Support more formats (EXIF, PDF metadata, Theora, ...).
  • Allow adding tags to specific streams when dealing with OGG.
  • Do tests with Matroska files which have multiple segments.