Date: Thu, 18 Nov 1999 17:16:58 +0000 (GMT) From: Terry Lambert <tlambert@primenet.com> To: crh@outpost.co.nz Cc: tlambert@primenet.com, chat@FreeBSD.ORG Subject: Re: Judge: "Gates Was Main Culprit" Message-ID: <199911181716.KAA14495@usr02.primenet.com> In-Reply-To: <19991118050528.7618214C0D@hub.freebsd.org> from "Craig Harding" at Nov 18, 99 06:05:12 pm
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> > Even ignoring this, the rotating record head is away from the > > tape media for longer than the vertical blanking interval, and > > that means that you get a 1.5 reduction in frame rate. This > > reduction in frame rate is even more noticible because of > > horizontal retrace in PAL vs. NTSC. > > > > The result is that the 525 lines of vertical resolution are reduced > > to 200 for VHS, 400 for SuperVHS > > Erm, actually I think you're getting a couple of things confused here > Terry. You're right, I mistyped "vertical" instead of "horizontal"; if you looked at my link references, they had the information right. > Firstly, I don't know what you're trying to say about frame rate, as > far as I'm aware PAL video runs at 50 fields (25 frames) per second > and NTSC runs at 60 fields (30 frames) per second [1]. Frame rate was referring to the number of horizontal time number of vertical display pixels (as opposed to tape pixels) per frame. When reading from a tape, you end up with fewer full frames of data a second. This is actually to be expected, or we would all be using televisions instead of computer monitors. 8-). > Some camera test charts actually have a resolution grid on them, with > horizontal and vertical lines drawn in an increasingly-finer > gradient. When you can no longer distinguish individual lines, you've > hit the resolution limit of the camera (or monitor, or whatever). Cameras are another matter entirely. Many CCD cameras did not equal television resolution for a long time, and included even vertical pixel "tweening" as a result. 8-(. > VHS, as Terry mentioned, has about 200-240 lines resolution. Super > VHS has theoretically close to 500, Actually, it's 480 for SuperVHS... but it requires a better source, or GenLock-like hardware with a standard source, or spindle-sync for tape-to-tape, to achieve. > where as the broadcast > format BetaSP is only 450. This leads some people to claim that Super > VHS is superior to BetaSP because they are ignoring SVHS's terrible > colour resolution. 8-). You PAL guys just won't let that one go, will you? > Modern broadcast video cameras have a horizontal resolution of about > 850 lines. And VHS is still limited to 200... Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-chat" in the body of the message
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