At the very least we would need the make/model/cable provide to know what possibilities may exist ;).
My gut feeling says that any cable co box firmware/DVI out port will not support the correct DVI output to make a conversion possible as you desire. Also, what cable provider lets you buy/bring in your own box(??) That is limited to Satellite providers, at least in the U.S. AFAIK. Keep in mind simply because a device is depicted with a particular port, that doesn't mean it is active. The USB ports present on the various Motorola DVRs is a good example of this.
Another place to ask would be a user support forum for your cable provider, as well as AVS Forum. Satelliteguys.us IME is also a strong site for general issues like this one.
I recently got a deal on 21" SVGA and was hoping to use it instead of my box-TV. Many Cable-boxes will support HDMA or other output but sadly not VGA/RGB. I also have an opportunity to buy a DVR/Cable Combo Box that has a VGA output on it but would that likely only be for DVR output or include regular programming?
If I wanted to avoid this great additional expense, does anyone know of:
1. Small cheap cable box that supports VGA/RGB output?
2. Know of any cheap adapters I can buy to convert output to VGA?
Also FYI, I found something close to what I think I am looking for at:
also check out:
Please post your comments and additional suggestions on this, or anything else you know of. Thanks.