Parse and generate id3v2 binary tags. * * This module provides ways to manipulate id3v2 tags * not attached to a file. It is quite low-level and, * despite good care in tightening its API, it is possible * to generate invalid id3v2 tags using it. The user is thus * advised to read about the id3v2 standard before using this * module. * * Currently, only attaching text-based frames are supported. * Reading tag's frames can only be done currently through the * common tag_title, ... API. * * See examples/tagutil.ml for an example of the use of this module.