Is ID3v2::FrameFactory really utilized?

[Tsuda Kageyu]

Hi, I have a question for the TagLib users. I want to know is there 
someone who creates your own version of ID3v2::FrameFactory.

Currently, TagLib allows you to interpret the frames in a ID3v2 tag in 
your preferred way by subclassing ID3v2::FrameFactory class (but it only 
affects MPEG files). However, I found that it's difficult to implement 
my own FrameFactory because user defined classes can't access the nested 
class ID3v2::Frame::Header. So I have a doubt that it is really utilized.

If there is someone using it, we'd better make changes so that it can 
affect all the file formats which support ID3v2 tag. Otherwise, we can 
remove it.

Kageyu.