NTSC Artifacting
potatohead
Posts: 10,261
I have a soft spot for the Color Computer 3. On an NTSC display, it's capable of a lot of colors. Most of you know I'm a sucker for squeezing colors out of old hardware, or the prop...
The attached program renders a 256 color picture to the screen, using only NTSC artifacting. It's a 640 pixel, 4 color display, with all 4 colors being just monochrome. It is a simulation of a Color Computer 3. (video only) I'm not able to load pictures into the thing with only a cassette, though somebody is working on that for me.
To demonstrate quality, I went ahead and used the Propeller to do similar video.
When you run the attached spin files (set for HYBRID), the tint of the display varies. I've narrowed this down to being unable to put the pixel clock in phase with the color burst. A long time ago, on another thread where I did a 400 or so color display, Jasper M suggested a code fix that eliminated the tint shift. I think that was for that display only... or I didn't get it, one of the two.
What I think I need to do is trigger the start of the video loop at a specific point during the color burst cycle. This is a counter thing I don't know how to do, and would like to. Anyone game to provide a coupla hints?
Rename the attached binary to match the file specification in the start program DAT section, and configure video for your board to run. This is a simple prototype program, no auto config, etc...
The attached screen capture is from a correct run of the program.
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Propeller Wiki: Share the coolness!
8x8 color 80 Column NTSC Text Object
Safety Tip: Life is as good as YOU think it is!
Post Edited (potatohead) : 12/26/2009 5:40:20 PM GMT
The attached program renders a 256 color picture to the screen, using only NTSC artifacting. It's a 640 pixel, 4 color display, with all 4 colors being just monochrome. It is a simulation of a Color Computer 3. (video only) I'm not able to load pictures into the thing with only a cassette, though somebody is working on that for me.
To demonstrate quality, I went ahead and used the Propeller to do similar video.
When you run the attached spin files (set for HYBRID), the tint of the display varies. I've narrowed this down to being unable to put the pixel clock in phase with the color burst. A long time ago, on another thread where I did a 400 or so color display, Jasper M suggested a code fix that eliminated the tint shift. I think that was for that display only... or I didn't get it, one of the two.
What I think I need to do is trigger the start of the video loop at a specific point during the color burst cycle. This is a counter thing I don't know how to do, and would like to. Anyone game to provide a coupla hints?
Rename the attached binary to match the file specification in the start program DAT section, and configure video for your board to run. This is a simple prototype program, no auto config, etc...
The attached screen capture is from a correct run of the program.
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Propeller Wiki: Share the coolness!
8x8 color 80 Column NTSC Text Object
Safety Tip: Life is as good as YOU think it is!
Post Edited (potatohead) : 12/26/2009 5:40:20 PM GMT
720 x 540 - 475K
Comments
I know you've been playing with artifacting for a while now, this is a great example of what can be done.
Well done Doug and a Happy Christmas to you!!!
Regards,
Coley
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PropGFX - The home of the Hybrid Development System and PropGFX Lite
Really, that picture is Smile, as the pixels are not well aligned with the color signal.
I'm having a rough time with the counters! I don't really understand how to sync up with the color_burst. Thought I would be able to just read PSA, look for a 0, or the transition around zero, then carry on from there. I've just introduced some friends to this technique on the Color Computer 3 and thought I would simulate it on the Prop for a nice alternative to standard Propeller color.
And that led to doing battle with counters... heh!
Merry Xmas back to you and yours!!
(my 6502 chips came in today)
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Propeller Wiki: Share the coolness!
8x8 color 80 Column NTSC Text Object
Safety Tip: Life is as good as YOU think it is!