For a more complete answer, go head and search the Tex thread for 'ffdshow'. Short answer is ffdshow is used by the game to render the MPEG-2 video files used in the game. If memory serves, the game can only recognize certain rendering programs, of which ffdshow is the default (thus why it is installed when Overseer is installed).

Using ffdshow has always been a pointpoint when running the DVD version of Overseer (how the defaulted way of running the game from GOG). The community has asked for the old CD-ROM version to also be available to use, but thus far it hasn't come to fruition.

I think the collective hope from the community (at least it is for me!) is the upcoming poisoned pawn project (remake/retelling of overseer) will fix these nagging technical issues.

Hope this helps, again if you want more info just search the forum.

I was interested in the poison pawn, until I found out that they've replaced the frame story with a new frame story, turning it into a sequel to Tesla Effect, instead of the game right before it.

I get that ffdshow is for the MPEG-2. I just want to know how what all is told to run through ffdshow across the system.
I remember a long time ago, I installed that one codec pack, CCCP, and it didn't work out, so I uninstalled it, and it was apparently set up to run ALL my codecs, so I had to reinstall the OS.

So is ffdshow set up for more than MPEG-2 from the default GOG installation?

Per @ChronoWolf (Matt Van Rhoon) and Chaotic Fusion's last PP update (https://www.twitch.tv/videos/206243281), PP will have a play through mode that is the 'vanilla' overseer game (but with the upgraded graphics and videos).

Yes, my understanding is ffdshow is setup for MPEG-2 from the default GOG installation.

Oh, well screw trying to get Overseer to work then.
If Poisoned Pawn will have an option for the original frame story, I'll just buy that when it's done.

I think that is what most folks are going do to rather than continue to troubleshoot 'original' overseer.

I always delete the gog ffdshow and install another updated version and only select mpeg2 in the installation.
after you play through poisoned pawn you get the option to play the old overseer