Hi,
Ah, that's cool
You'll be quite happy at the command line typing cryptic streams of stuff with zillions of options which looks like line noise, know what pipes are and know that if you think you should be able to do it, you probably can (even if it breaks your system very badly...)
I just had a quick look at FFmpeg; it lists 'rawvideo' as an input and output format. So I reckon FFmpeg should be able to take a file containing video in pretty much any format, decode/crop/scale, convert to greyscale and write it straight to a memory card. If, say, 512 or 1024 bytes per line makes the player hardware easier; no problem. (I've spent some time making FFmpeg jump through hoops...)
Oh, and thanks! Though you really shouldn't be in awe; Unix (well, the X Window System) has been capable of being configured for fixed-rate monitors for as long as it existed. I've had a few (they were cheap because they were a PITA to use with Windows.) All I did was realise a 405-line telly could be seen as a fixed-rate monitor...
Anyway... it looks like getting raw video data onto some sort of memory card in whatever arrangement the player hardware requires is achievable without much effort and possibly without writing a line of code...
I might have a play around with that...
Kat