Fantastic. I'm thinking of converting some of my Seinfled collection into Quicktime files to play on my Mystic CC from an external 2GB SCSI drive. Maybe I should be using this thing called Cinepack? I have a Mystic CC (33mhz, 12mb RAM but no FPU currently) but I haven't done the VGA mod so I'm running at 512x384 still - will see how that works. It does run in thousands of colors!
What program are you using to convert them? Cinepak is one of the several codecs used by QuickTime, and depending on what software you're using, and on what machine you're doing it, you should be able to choose to encode the video using Cinepak.
You can encode Cinepak on a modern Mac using QuickTime Pro. Make sure that "Show Legacy Encoders" is enabled in the system preferences for QuickTime. Obviously, encoding will be much faster (but still slow due to the nature of Cinepak) on a modern Mac.
You would want to encode Cinepak using Thousands (if that's not a choice choose Millions). The trick is choosing the correct size and FPS. 30 FPS might be too much, so 15 FPS is recommended, but also remember that the CC screen most likely operates at 67 Hz and frame rates that are not divisible into 67 will appear to have tearing. 33.5 FPS is probably more than your source files, so the next choice is 22.3333 FPS followed by 16.75 FPS which is probably your best choice to avoid tearing and a pesky infinite decimal.
Then you want to pick a size that allows you to display the most pixels, while not bogging down the computer, and not requiring too much scaling. You could choose 320x240 but this requires funky scaling to 512x384 and will therefore be slow and kind of ugly looking. Assuming your source files are something like 640x480 (so you have some room to scale down), you might try 256x384 or 512x192. The former will probably look better. Either one encodes 98,304 pixels, and only requires a scale on one axis, plus it's a nice 2x scale and not a harder in the middle scale. 320x240 only encodes 76,800 pixels so going with 256x384 will actually give you more detail on the screen.
So my recommendation would be encoding the video with Cinepak, 256x384, 16.75 FPS if you want to display on an unmodified CC screen, which operates I assume at 67 Hz.
For sound your best bet I believe is IMA 4:1, 22.050 kHz. If the Mac supports stereo then you can use stereo, otherwise choose Mono.