I've got no solid or official information to contribute however I was thinking about the leap that the RedRay codec makes from any previously available compression. Of course as time goes on compression only gets better but the massive difference between RedRay and older compression seems like there must be another other clever idea being implemented by Graeme...
Could it be possible that RedRay works by the same principle as RedCode? Most codecs encode three colour channels (RGB or YUV) but RedCode only has to deal with a bayer pattern greyscale image because it keeps the information RAW. As we know this image is then debayered resulting in an image that resolves about 80% of the original RAW resolution.
Would it be possible to blow up an image (any 3 channel image for instance) by 125% and apply a digital bayer patterned filter to create a greyscale image for encoding which would then be decoded and debayered on playback to form the original image?
Would this process be beneficial in achieving extremely low data rates such as demonstrated with RedRay?