I think that the problem is that most files out there do not encode the
song duration at all. My guess is that various tools do some kind of
calculation to try and figure out how long the track is based on frame
length and the number of frames.
You can hexl-mode some of the files in question and see how many of them
have TLEN at the start. I just checked two files at random in my
collection and found no song duration in the header.
If this is true, we'll have to add that type of approximation
calculation to emms-info-native.
I think you may be right. I just had a look at the source of tinytag and it does quite lengthy computations to arrive at the duration.
Who knew?
---Fran