Jonno said:

If it's actually authoring you're after, MultiAVCHD is well worth a look... It can generated a menu structure with a certain degree of control (using an interface which is admittedly rather fiddly) and most importantly doesn't re-encode compliant streams.

Worth a shot, it's free!

Thanks. I actually gave MultiAVCHD a shot, and it's all right. I just don't really have time to be working on menus and, for some strange reason, it stopped working on my computer... For that reason, I use one of the two programs above.