Seek Tables Missing from Radio Downloads

[Budgie]

I find that I am unable to use the progress bar on control point
(BubbleDS) to select a point in mid programme on some downloaded radio
files.  I have been advised that these .m4a files have no seek tables.

I have searched for a while but cannot find out where and by what
program these tables are built in the GiP download process.  Are they
part of the data from the source or created during the downloading
process?  If the latter, by which program?

I am trying to understand the process a bit more so if anybody can help
or point me to a good source of info so I can read up it would be much
appreciated.

Budgie