Hi,
I have to say that I'm almost completely ignorant in this field but I'm following with interest this discussion ( and that one on SD 770!)
I'd dare ask you: isn't the dsp IC you are looking for something similar to the Renesas HD 4930? (may be something newer)
I found it in my old PowerShot SD10 cam.
http://www.renesas.com/fmwk.jsp?cnt=camera_root.jsp&fp=/products/assp/for_visual_equipment/camera/#I can try to open my brother's SD770 and see what I find if you say ther's something similar to look for.
Thank you for your work guys and forgive me if I said a foolishness.