Lame 3.96 does this as well? In this case I can probably find it myself, let me take a look… yes, I found it!
Btw, here is a description of the Xing header I just found and used for implementing:
Something interesting: the files I ripped using CDex show a different default TLEN than this field! (only a few milliseconds, but still)…
Well, code has already been implemented roughly, just need to give it a short test with a few more files.