Re: [stella] RSYNC

Subject: Re: [stella] RSYNC
From: Glenn Saunders <cybpunks@xxxxxxxxxxxxx>
Date: Sun, 04 Jun 2000 01:23:45 -0700
At 07:44 PM 6/3/2000 -0500, you wrote:
On the scope, I see the video signal shows up like this: (adventure
startup screen)


                          XXX               XXX
0                         |                   |
       |     XXXXXXX-------                   ---------
       |     |                                        |

Is this a vectorscope/waveform pattern?

Could Glenn, (or someone else) give us a lesson in what the parts of this
signal are, and which parts the TV is actually responding to?

I don't know about video down to the individual scanline. I do know that video has various properties, like black level, hue, saturation.. When calibrating video you make sure the darkest (lowest) and brightest (highest) video line up with the prescribed settings. To compare this with audio, the middle part becomes the effective dynamic range of the image. The video level, contrast, and brightness adjust this range, compressing, expanding, and sliding it around.

Composite video has a luminance and chrominance attribute. Both of them are waves intertwined kinda like stereo audio. This was done in order to add color to B&W NTSC without breaking backwards compatibility. As this gets decoded, noise or crosstalk is introduced, which is what we see as dot crawl and fuzziness and such. The color itself is determined by the phase shift of the chrominance signal. I think the saturation is determined by the depth of the wave. The 2600 therefore, in order to generate color video, needs only to generate this basic color wave and then modify its phase and amplitude. Color is therefore 16 degrees of delay of the color signal.

Glenn Saunders - Producer - Cyberpunks Entertainment Personal homepage: Cyberpunks Entertainment:

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