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. Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://stella.biglist.com
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