Encoding black & white movies

[Scanline]

I'm having a shot at encoding a black & white movie, which got me thinking about the gray scale mode of the JPEG format. Is there any way to get a DiVX codec to encode in gray scale mode, which theoretically would reduce the file size a lot?

[benderman]

Grayscale dosn't reduce the filesize too much. The most space is used for the contrast and not for the colors. The reduction should not be bigger than 20-30%.

[d-clone]

i would turn down the brightness a little and up the contrast just a tiny bit so that divx can crunch it a bit more.