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Oswald
Registered: Apr 2002
Posts: 5086 |
VIC and the odd/even fields
okay this is getting confusing for me now. in another thread on lemon64 groepaz says that the vic does always display the same field, but it doesnt matter if its odd or even, and it lights up both the odd/even lines.
some1 can tell me:
- does vic use odd or even or dontcare lines?
- what does the term field mean from the tv electronics viewpoint?
- how does the vic only light up the odd (forex.) lines on the tv screen, and a little bit from the other ones?
- are there really 2 modes in the tv electronics for odd / even fields
- why does computer graphics flicker a hell more lot while "normal" tv screens looks as steady as my ass?
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White Flame
Registered: Sep 2002
Posts: 136 |
The vertical color blending on PAL is actually due to hardware on the display deliberately performing the blend, not due to the signal itself, right?
And this might help or hinder the discussion: http://www.white-flame.com/interlace.gif
and the whole "half horizontal color resolution" thing is more about bandwidth than digital resolution. The signal can only change so sharply due to frequency limitation. So you can _start_ a color change anywhere on the analog line, but it's limited to how fast it can change. The luminance signal can change much more rapidly, thus has a finer resolution. |
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chatGPZ
Registered: Dec 2001
Posts: 11360 |
Quote:The vertical color blending on PAL is actually due to hardware on the display deliberately performing the blend, not due to the signal itself, right?
yep
Quote:And this might help or hinder the discussion: http://www.white-flame.com/interlace.gif
makes sense to me :) |
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Oswald
Registered: Apr 2002
Posts: 5086 |
whiteflames illustration makes sense even for me, but is again source of confusion.
according to jackesser this happens:
_e
ov
de
dn
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now is there an "empty" scanline between consecutive odd / even scanlines or not ?!
or: is one scanline "doubled" in height according to the above ascii art, and the vertical resolution only "doubles" by having an "half" scanline shift between odd/even frames?! |
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JackAsser
Registered: Jun 2002
Posts: 2014 |
Quote: whiteflames illustration makes sense even for me, but is again source of confusion.
according to jackesser this happens:
_e
ov
de
dn
10
12
32
34
54
56
76
78
now is there an "empty" scanline between consecutive odd / even scanlines or not ?!
or: is one scanline "doubled" in height according to the above ascii art, and the vertical resolution only "doubles" by having an "half" scanline shift between odd/even frames?!
"is one scanline "doubled" in height according to the above ascii art, and the vertical resolution only "doubles" by having an "half" scanline shift between odd/even frames?!"
BINGO! |
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Oswald
Registered: Apr 2002
Posts: 5086 |
jack, wont work if I take into consideration that the "half scanline shift" happens due to having "half screen wide" scanlines. :P o_O |
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MagerValp
Registered: Dec 2001
Posts: 1074 |
Quote: keep me out of that kthxbye :)
*sigh*
Here's another experiment for you:
Connect a C64 to a 1084 mounted on a table that has an adjustable height. Adjust the 1084 so that every VIC scanline is exactly 1 mm high. Now simultaneously display a 0.5 pixel upscroller, and move the table down at a constant speed of 25 mm per second. In what was does this display differ from that of an interlaced Amiga display (assuming a 1084 with infinite height, etc)?
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chatGPZ
Registered: Dec 2001
Posts: 11360 |
Quote:
Connect a C64 to a 1084 mounted on a table that has an adjustable height. Adjust the 1084 so that every VIC scanline is exactly 1 mm high. Now simultaneously display a 0.5 pixel upscroller, and move the table down at a constant speed of 25 mm per second. In what was does this display differ from that of an interlaced Amiga display (assuming a 1084 with infinite height, etc)?
next time when i am very very bored i am going to try this. or maybe make a wildcompo entry from it while at it :o) |
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AmiDog
Registered: Mar 2003
Posts: 97 |
I found this site quite interesting when I was trying to understand PAL color encoding a while back:
http://www.techmind.org/vd/paldec.html
(I had some plans to try to get my hands on a high quality sampler which would allow me to sample and decode non-standard video signals, like from the C128 in Risen from Oblivion. Turns out they are very expensive and I'm not good enough at electronics to be able to build my own video digitizer...) |
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JackAsser
Registered: Jun 2002
Posts: 2014 |
Quote: jack, wont work if I take into consideration that the "half scanline shift" happens due to having "half screen wide" scanlines. :P o_O
@oswald: How do you mean it doesn't work?, elaborate plz. Exactly what part did u misunderstand? |
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Oswald
Registered: Apr 2002
Posts: 5086 |
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^^^means the TV can shift scanlines "half" scanline down, but as someone said the TV knows nothing about interlace in itself so how can you tell it to shift one half scanline? |
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