Re: [stella] Atari non-interlaced frame rate = ca. 59.922751 Hz?

Subject: Re: [stella] Atari non-interlaced frame rate = ca. 59.922751 Hz?
From: "Eric Ball" <ericball@xxxxxxxxxxxx>
Date: Sun, 21 Aug 2005 08:26:24 -0400
Yes, the frame & line rates of an NTSC VCS are slightly out of spec.  Let's just check your math.

First start with the colorburst:
60*1000/1001*525/2*455/2 = 3579545+5/11 Hz

The NTSC VSC line rate is 76*3=228 cycles of colorburst or 15699.76 Hz, versus NTSC standard which is 455/2=227.5 cycles or 15734.27 Hz

And a ideal NTSC VSC game has 262 lines or a frame rate of 59.92 Hz, instead of the NTSC standard, which is 525/2 lines or 60*1000/1001 fps or 59.94 Hz field rate.

The difference between the VSC and spec isn't significant enough to cause problems with most TVs.

Your idea for a 3:1 interlaced screen is interesting, but I'm not sure whether it would work.  You'd first have to time the VSYNC to occur 1/3rd of the way through the line, and even then I'm not sure whether anything but a pure analog TV wouldn't try to compensate and fudge it back to a 2:1 interlace.

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