Adding Seek Tables to .m4a audio file

I am running openSUSE Linux 3.4.63-2.44-desktop x86_64 with KDE: 4.8.5 (4.8.5) “release 2”. I use get_iplayer to download classical music programmes from time to time which are saved as .m4a files. The process uses AtomicParsley (AP) to tag the files but while I was updating my system a while ago I made a mistake and AP was not run. I believe this is why the files now have no seek data.

Whatever the reason I have a number of files without seek tables and this makes it impossible to play the file from anywhere but the start.

I would like to add seek tables and am asking for some help in how to do this please. I believe it should be possible using ffmpeg or AtomicParsley but have no idea how. I also understand it may be possible to select the time interval between data points and since I do not need editing precision I would like to do this to keep the data set to a reasonable size.

Can anybody advise please?

Happy New Year to All.