A1200, interlaced screen, the screen "vibrate"

[CDE_MusiX]

Hello AMIGA fans, i've finally installed the HDD on the Amiga, and now i want to set the screen to the "interlaced high res. mode" (640x512x6). The operation succeeds, but the screen "vibrates", is "tremolante" when is in interlaced mode. Why happens? I have an AMIGA with a basic strutture (68020 processor, 3.0 ROM, 39.106 Kickstart, no Fast-RAM)

[motorollin]

What screen are you connecting it to? You will get this behaviour if the screen doesn't support interlaced screenmodes.

--
moto

[CDE_MusiX]

Is a Commodore 1074S (but i've to look better at home...)
It visualizes good the image of the interlaced mode, but it vibrate.

[motorollin]

Do non-interlaced screenmodes do the same thing?

--
moto

[CDE_MusiX]

no, cause for this problem, i'm using 640x256x6 non-interlaced res. mode

[Piru]

@CDE_MusiX

This is perfectly normal. It's interlace after all.

See http://en.wikipedia.org/wiki/Interlace

[srg86]

hmm As far as I can see, with interlaced mode, as it takes 2 passes to fill the screen, it effectivley halves your refresh rate. Hence the flickering.

Graphics on a normal TV  boardcasts also has this horizontal shimmering as it is interlaced.

I love interlaced modes because of the picture quality, and even the DBLPAL/NTSC aren't quite as good. Trouble is that I hate the flickering :-(

[bigdan]

@CDE_MusiX : you could also try the MagicTV  command available in aminet/util/wb to reduce the vibrates in interlaced modes... It's just a hack ;-P

[mihcael]

Lowering your brightness a tad will decrease the flickering (used to do this!)

changeing screen colors will aslo help, black and white are bad for this!

Use a program to change screen graphics so the windows have double thickness lines in them instead of single! (cant remember what program!)
 

[amigakit]

Another option is a flicker fixer which will eliminate the interlace flicker and also allow you to connect to a standard SVGA monitor.

[spirantho]

Some TFT monitors will display an interlaced composite signal too, without flicker. I know mine does. You can just use your A1200's composite out then - but of course you can't display DBLPAL/DBLNTSC modes without using the RGB->VGA connector as you can't do 31KHz over composite.

[mihcael]

Amigakit wrote:
Another option is a flicker fixer which will eliminate the interlace flicker and also allow you to connect to a standard SVGA monitor.

Allow or require?

I was always one for doing things for the least cost possible!

[SamuraiCrow]

Getting rid of the interlace will require you to use a monitor with a higher sync and scan rate than what a 1084s monitor can do.  The 1084s uses television scan rates.