Re: [stella] Interlacing 101

Subject: Re: [stella] Interlacing 101
From: Chris Wilkson <ecwilkso@xxxxxxx>
Date: Wed, 21 Aug 2002 02:01:14 -0400 (EDT)
On Tue, 20 Aug 2002, Clay Halliwell wrote:

> ----- Original Message -----
> From: "Andrew Davie" <adavie@xxxxxxxxxxx>
> To: <stella@xxxxxxxxxxx>
> Sent: Tuesday, August 20, 2002 9:11 AM
> Subject: Re: [stella] Interlacing Success!
> > I still contend that on non-interlaced games, a '2600 'scanline' is
> actually
> > 2 TV-lines tall.
> Sigh... This is exactly like me arguing that I'm actually 12 feet tall, but
> that the top 6 feet are invisible.

Not quite.  But a close analogy, nonetheless.  I think you're both saying
the same thing.

[bunch of long message deleted]

I see what Andrew means, and he's right.  The effective screen real estate
that is taken by each line of a 2600 display is 2 TV scanlines.  There is
a blank TV scanline between each line that the 2600 draws.  It draws the
same line number in the same place for both fields, although the drawn image
may be different.

> I never disputed this. But all the muddled terminology surrounding this
> achievement is driving me nuts.

Yes, I agree.  The terminology is confusing when it's correct.  It's much
worse when it's used loosely.  And when multiple people are using it in
slightly different ways.  I've been guilty at times, though I try to at
least point out the differences between a frame and a field every now and
then.  :)

> BTW, has anybody considered hooking a scope to an old Astrocade to see how
> it generates its interlaced display?

I didn't know that the Astrocade used an interlaced display until someone
here metioned it recently.  But as soon as I get back to Boston, I'll be
raiding my storage locker and relocating all my stuff to Missouri, and
actually setting it up.  (Yay!)  I'll put this on the list of short projects.


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