what's the story on MPEG-1 video and audio layer 1,2 licensing?

[Tim Olsen <tolsen718@gmail.com>]

Hello.  I researching why MPEG-1 video and audio layers 1 and 2 do not
require any royalty payments.  I have been googling for the past hour
and haven't been able to come up with any concrete explanation
(although it may just be that my google skills are not up to snuff).

I am guessing that MPEG-1 video and audio layers 1 and 2 are patented.
 Is it just that the none of the MPEG companies have looked to collect
any royalties?  Or have the MPEG companies agreed not to collect
royalties on these MPEG-1 technologies?  Is this something that could
change in the future?

thanks for your help.

-Tim