Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!bbn!rochester!ritcv!cci632!ccicpg!leo!harald
From: harald@leo.UUCP ( Harald Milne)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Fixing flicker, & future frame rate issues
Message-ID: <2996@leo.UUCP>
Date: 23 Apr 88 11:17:30 GMT
References: <11157@ut-sally.UUCP> <8528@agate.BERKELEY.EDU> <11182@ut-sally.UUCP> <9101@agate.BERKELEY.EDU>
Organization: CCI CPD (Advanced Development), Irvine CA
Lines: 72
Summary: Really Amiga Video

In article <9101@agate.BERKELEY.EDU>, doug@eris (Doug Merritt) writes:
> In article <2988@leo.UUCP> harald@leo.UUCP ( Harald Milne) writes:
> >In article <869@gethen.UUCP>, farren@gethen.UUCP (Michael J. Farren) writes:
> >> This is not what happens at all.  Non-interlaced mode does NOT have
> >> "lines without information", and alternate half-frames are NOT absent.
> >	If you don't believe me, record Amiga video in Interlace and
> >Non-Interlace.  Interlace will look fine, where Non-Interlace will look like
> >sh*t. There is information absent.
> 
> I'm not sure I understand this; it seems strange. My understanding is
> that both the Amiga's interlaced *and* the non-interlaced video are
> fully NTSC compatible, meaning that the video signal always sends first
> a field of odd lines (starting at line 1), then a field of odd lines
> (starting at line 2).

	No, NTSC requires interlace and odd and even fields. Non-interlaced,
while recordable on a VCR, is not the true NTSC standard. It HAS to be
interlaced.

	This is getting hard to explain. The non-interlaced display in your 
terminology, starts at line 0, on every field. Forever.

	Call this the even fields. The odd fields are never present. That's 
the difference between interlaced and non-interlaced.

	Take a 640x400 interlaced display versus a 640X200 non-interlaced
display. While both displays take the same space on the monitor, the
difference between the two is alternate lines (or where there should
be lines) are missing in the non-interlaced display.

	That's why you get 50 lines of text instead of 25, you have more
lines to play with in an interlaced display.

	It's also the difference in information that I am talking about.

> If you look at any given field, you will see
> that half the lines are missing...they won't be there until the next
> field.

	Only true for an interlaced display. A non-interlaced display wil
never get the lines that are missing. It's always the same lines. 
(or the lack of them)

> The only difference between interlaced and non-interlaced Amiga
> video is that in the latter case, the odd fields are a duplicate
> of the even fields, while in the former (interlaced) case, they
> are new information.

	Yes, correct!

> Am I incorrect? If this is right, then the comment about recording
> Amiga video doesn't make sense...the recording on an NTSC video
> recorder should look exactly identical to the original Amiga display
> (assuming a normal, non-fF display).

	Again, correct. In the sense of what you record, you play back.
But again, non-interlace is not a true NTSC format, half the information
is missing.

> Or are you talking about something that *fF* does in non-interlaced
> mode, that has some different effect than an Amiga that doesn't
> have fF at all???

	No, not at all. This discussion has nothing to do with FF.
I'm just talking about Amiga video.

	Wow, what a difficult concept to describe! Can anybody help me?
I guess pictures would help.

-- 
Work: Computer Consoles Inc. (CCI), Advanced Development Group (ADG)
      Irvine, CA (RISCy business!) 
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