I've heard that Canon's DIGIC processors are just slightly customized versions of the DaVinci media processors, which have a all documentation openly available,

I've heard that Canon's DIGIC processors are just slightly customized versions of the DaVinci media processors, which have a all documentation openly available, while Nikon's EXPEED processors are based on a closed product line by Socionext with basically zero public documentation and heavy customization. Though there used to be a project which worked on a few of the older EXPEED-based cameras.