[Coco] CoCo 3 to VGA

[James Dessart]

On 22-May-04, at 5:12 PM, Mark Marlette wrote:

> I'm not a video guy so can someone explain to me why there is only 
> four levels per signal? The CoCo is RGB-A, I don't understand how the 
> CoCo can only have four levels.

Only 4 levels for each of the red, green and blue signals, since the 
CoCo's video only supports that much. Two bits per component, for 6 
bits total, and 64 colours. So multiply that by the number of pixels 
per scanline, by the number of scanlines and you have the amount you'd 
have to store in memory to have a frame of CoCo video stored. Then you 
could replay it at twice the rate until you get a new CoCo frame in 
memory.

I'm not sure how many scanlines and such there are, but I'm guessing 
that for an NTSC CoCo that the video matches an NTSC frame, so 720x486. 
That's 349920 pixels, at 6 bits each, which comes to just over 256K, if 
the 6-bits are packed to make best use of the memory.

Now, assuming that you want to store two frames, the one you're 
getting, and the one you're sending, you'd need just over 512K memory. 
Combine that with simple A/D components and such, and you've got a 
product that I'm sure many here would go gaga over. :)

James