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Old 19 July 2008, 01:36   #1
AAG
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Location: West Yorkshire, UK
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Winaue, fullscreen and ArcadeVGA (again?)

Hi

Can anyone please help with this - as the more I read the more confused I get!

From what I can tell, the following PAL resolutions are quoted for the
Amiga (non AGA) :-

PAL, non-interlaced (50 Hz, 15.60 khz)
320x256 (Low)
640x256 (High)
1280x256 (Super - from A500 plus onwards)

Pal interlaced (50hz, 15.60 kHz)
320x512 (Low)
640x512 (High)
1280x512 (Super - from A500 plus onwards)

(Sources, http://www.amigahistory.co.uk/resolute.html , http://amiga.resource.cx/mod/a2000.html)

However - the Amiga video ouput was flexible, and also allowed for several overscanned resolutions. The Amiga video output was also defined with TV output in mind.

Quote:
There are two horizontal graphics resolutions, "lowres" with 140 ns pixels and "hires" with 70 ns pixels. This makes the display 320 or 640 pixels wide without using overscan
Also the following link contains some amiga video specifics -http://lipas.uwasa.fi/~f76998/video/modes/


Questions - all for non aga games at the moment

Q1 - This seems to be quoted quite a bit
Quote:
*80%* of all Amiga games use a maximum resolution of *320x256*
*15%* use resolutions that vary between a minimum of *320x256* and a maximum of *362x283*
And *5%* use a special mode which gives a theoretical resolution of *320x512*
That list dosen't include the 640x256.

Did games actually use this resolution, or was this just via workbench? (I've seen a post where Tony said that games don't switch between 320 and 640 (can't find it at the moment - but that would indicate that they do exist?)

Q2 - Winuae video option
Depending pn the answer to 1, then the following combinations ae possible :-

Code:
GameRes   WinUaeRes  Outcome
Low         Low           Match - everything ok
Low         Hi             Mis-match! Does winuae just double the pixel horizontally?
Hi          Low          Mis-match? What happens here?
Hi          Hi             Match - everything ok
Also - what about the "super" resolutions?

Q3 - Max resolution for overscanned game
Anyone know what the max overscan area actually is?
I started ProjectX in windowed mode, and took a grab. The active screen size was 376x267 - which differs from the 15% quotes above.

Q4 - Winue and switching to an interlaced mode
Do some games switch into interlaced mode (for still images) ? How does winue cope with that?
If you in "double" line mode - does it switch to "Normal" (and thenback again) as needed?
What if your in "normal" and the game tries to use an interlaced mode - does winuae re-sample the image for the output?

Reason for asking, is that I've got an ArcadeVGA card from ultimarc, connected to an Atari ST SC1435 (which is a cut-down Philips CM8322MKII).

The AVGA is great, but is lacking 50hz resolutions. (Powerstrip doesn't work with these cards, nor do the standard ATI catalyst drivers due to the custom bios in grahpics card.)

I've been in touch with Andy from ultimarc to ask about the possibility of adding some 50hz modes - which he didn't give an outright "no" to.

What I've got back from him is that 320 X 256 @ 60hz is already in AVGA, so he doesn't want to add the same res @ 50hz.

However, if we can actually say that the amiga did output 640x256 - and that the 640 wasn't just the 320 mode with doubled pixels, then there might be the possibility of getting that resolution added?

If we could also find the max size for overscan, then maybe that could be added as well?

Or maybe to put it another way, what 50hz resolutions would be best to be requested to be added to avga? (Using "normal" line mode.)


Thanks in advance
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Old 19 July 2008, 12:24   #2
Toni Wilen
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Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 42
Posts: 19,924
Quote:
That list dosen't include the 640x256.

Did games actually use this resolution, or was this just via workbench? (I've seen a post where Tony said that games don't switch between 320 and 640 (can't find it at the moment - but that would indicate that they do exist?)
Some do use it and you can have hires and lores simultaneously.

Quote:
Code:
GameRes   WinUaeRes  Outcome
Low         Low           Match - everything ok
Low         Hi             Mis-match! Does winuae just double the pixel horizontally?
Hi          Low          Mis-match? What happens here?
Hi          Hi             Match - everything ok
WinUAE resolution setting sets "output" resolution. If amiga resolution < uae resolution = double pixels. if amiga resolution > uae resolution = drop every other pixel (or take average if filtered hires selected)

Quote:
Also - what about the "super" resolutions?
superhires = 1280. Very rarely used by games (some AGA games do use it) ECS superhires is useless for games (4 colors from palette of 64 colors..)

Quote:
Q3 - Max resolution for overscanned game
Anyone know what the max overscan area actually is?
I started ProjectX in windowed mode, and took a grab. The active screen size was 376x267 - which differs from the 15% quotes above.
Hardware max is about ~380 (2x in hires)

Quote:
Q4 - Winue and switching to an interlaced mode
Do some games switch into interlaced mode (for still images) ? How does winue cope with that?
If you in "double" line mode - does it switch to "Normal" (and thenback again) as needed?
What if your in "normal" and the game tries to use an interlaced mode - does winuae re-sample the image for the output?
There is never any resampling.

Interlace and double mode = "deinterlaced" screen (shows both even and odd fields simultaneously)
Interlace and normal mode = flickers, show odd field, show even field etc..

Quote:
What I've got back from him is that 320 X 256 @ 60hz is already in AVGA, so he doesn't want to add the same res @ 50hz.
Why not? You can have multiple rates, at least Windows allows it

Quote:
However, if we can actually say that the amiga did output 640x256 - and that the 640 wasn't just the 320 mode with doubled pixels, then there might be the possibility of getting that resolution added?
Yes, it is real 640 pixel wide mode.

Quote:
If we could also find the max size for overscan, then maybe that could be added as well?

Or maybe to put it another way, what 50hz resolutions would be best to be requested to be added to avga? (Using "normal" line mode.)
Do you want "authentic, black borders in non-overscan programs" TV-style display or "I want to see everything, even possible graphics garbage that no TV can show" -style display?

Last edited by Toni Wilen; 19 July 2008 at 13:26. Reason: frame -> field
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Old 19 July 2008, 17:38   #3
AAG
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Join Date: Jun 2007
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Posts: 30
Thanks for explaining how winuae works!

Quote:
Do you want "authentic, black borders in non-overscan programs" TV-style display or "I want to see everything, even possible graphics garbage that no TV can show" -style display?
I'd go for "authentic" - what resolutions would you suggest? (Although, out of interest, what about "including garbage" as well?)

If I'm understanding this stuff, then, the authentic view for the non-overscaned games always had black borders. So for that authentic look, do "we" need a resolution that matches the "tv" max resolution, which will be larger than the amiga video screen output, and hence our authentic borders are preserved??? Overscan games would then "just work" as the overscan would be constrained to the theoretical max tv resolution, which we're already in - maybe?

From the above PAL link abve,
Quote:
640 pixels at 70 ns pixel clock equals to 44.8 µs. In other words, the Amiga draws 640 pixels on the scanline using 44.8 µs of the available "active" area (time). The total length (time) of the "active" area is 52 µs, but since the Amiga only uses the middle 44.8 µs part of this (leaving 3.6 µs borders on each side), the picture is visible even if the tv set overscans and cuts the very edges of the active image area off
So if 640 pixels are drawn in 44.8 µs, then in the full 52µs 742 pixels are possible. (Which is slighly smaller than your ~760 (~380 x2 in hires))

50Hz refresh @ 15Khz = 300 vertical lines, although allowing for "active portion of the verical" 288 seems to be the maximum.

So would a good authentic resolution be 742 x 288 @ 50hz?

Thanks
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Old 19 July 2008, 19:53   #4
Toni Wilen
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Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 42
Posts: 19,924
Quote:
Originally Posted by AAG View Post
Thanks for explaining how winuae works!



I'd go for "authentic" - what resolutions would you suggest? (Although, out of interest, what about "including garbage" as well?)
I'd prefer user configurable resolution selection

Quote:
If I'm understanding this stuff, then, the authentic view for the non-overscaned games always had black borders. So for that authentic look,
Yes (except if you had 1081 or similar TV monitor and adjusted width and/or height)

Quote:
do "we" need a resolution that matches the "tv" max resolution, which will be larger than the amiga video screen output, and hence our authentic borders are preserved??? Overscan games would then "just work" as the overscan would be constrained to the theoretical max tv resolution, which we're already in - maybe?
"tv" resolution would be "authentic" but it seems to be TV specific.. Some TVs had less and some have more overscan.. (which is why I have never said any exact resolutions)

Quote:
From the above PAL link abve,


So if 640 pixels are drawn in 44.8 µs, then in the full 52µs 742 pixels are possible. (Which is slighly smaller than your ~760 (~380 x2 in hires))

50Hz refresh @ 15Khz = 300 vertical lines, although allowing for "active portion of the verical" 288 seems to be the maximum.

So would a good authentic resolution be 742 x 288 @ 50hz?
742 x 288 is not visible area (probably area that gets scanned by electron beam in tube TVs but part of it is hidden) I'd say something like (about) 360 (720) x 270 is usually visible. (I don't have 4:3 tube TVs for test anymore)
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