media file Properties!Details

[a2]

In every .TS file I've downloaded from a variety of sites, that I've
subsequently examined from within the Win 7 Shell (Windows Explorer),
a clip Length is provided in hh:mm:ss in the Properties Details tab.
(Even by mousing over the file in the Explorer window.)

My question is sort of a chicken and egg one:
1. Is Windows Shell doing the labor of analyzing a given file type's
program tables at a low level and coming up with this time length
value?

2. Or is it that an encoder/recorder written specifically to be run
on the Windows OS happened to have coincidentally written this value
we see (a Properties!Details value only available to Windows machines)
on all the .TS files I've looked at? And that not all .TS files'
lengths in the known world can be reported in the Windows Shell as a
Detail?

Thanks for any explanation.