extending taglib (ID3v2 frames)

[Pierre Delagrave]

Hi
 I need to use taglib for reading/writing tags in mpeg music files. I wanted to use standard non-implemented frames in taglib like URL (WXXX).
I read the docs and the code to know the best way to do it. I concluded I had to subclass (the docs say it) frameFactory and create frame subclass for the needed frame type.
I use the subclassed frameFactory with setID3v2FrameFactory and it works well.

While coding the overrided createFrame I have this problem:
I can't access the header class to read the frame id in it. The header class is protected and only declare the base frameFactory as friend.
Am I trying to use taglib incorrectly? What would be the best way to achieve my goal here?

I downloaded _many_ apps to see how they were using taglib but did not found one that subclassed frameFactory.
I don't have much practical experience with C++ and I still wonder if I'm misunderstanding some concept of it. But after some time not getting my thing done I try to ask here.

Thanks in advance for any usefull replies

Pierre Delagrave