Difference between DS and DR video modes

[view666]

Hello

I have a question concerning the video modes. I am using Zsnes in 640x480 on a 4:3 22 inch Iiyama monitor. What I still don't understand - despite reading the documentation - is the difference between the "DS" and "DR" video modes. DR produces black bars on the right and left side. DS is full screen but the picture looks somehow "wrong". I always assumed that the Snes delivered a 4:3 output and therefore, since my monitor is also 4:3, there shouldn't be any problems and no need for scaling in order to achieve a fullscreen display.


What is the difference between these two modes and which one should I select in order to achive maximum display accuracy - and the correct aspect ratio ?

Thanks

[blackmyst]

S modes are the way it should be. Yes, the image must be stretched because a real SNES (analogue) stretches its output to 4:3 on a TV as well. That's why R modes, while having a correct pixel-to-pixel ratio, have a wrong aspect ratio.

I'm not sure if this is completely explained in the docs.

[sweener2001]

except resolutions like 640 x 480 are already 4:3, aren't they? so why should you have to stretch a 4:3 resolution into 4:3?

[franpa]

because 640x480 is a resoloution while 4:3 is a ratio.

640x480 is a 4:3 ratio however it needs to be stretched due to the nature of a standard 4:3 tv and the original snes.

[sweener2001]

The ratio 640 x 480 has a RATIO of 4:3. surprise, surprise, a 4:3 resolution for 4:3 monitors.

And, yes, you did say this already. however, if a television is 4:3, and my resolution is 4:3, i fail to see why stretching is necessary.

[franpa]

there are 224 lines on a tv i think and if not mistaken when playing at 640x480 the 224 lines gets stretched to 640 lines otherwise you would have a thick black border... 640x480 is not the snes's native resoloution so stretching is done... just because both resoloutions are 4:3 doesnt mean that no stretching has to be done.

[creaothceann]

The TV scans 224 or 239 lines per field (2 fields = 1 frame), and the SNES changes the "beam color" 256 times per scanline. The ratio of these dots is 4:3 since that's the ratio of the CRT (the cathode ray tube in the TV).

In ZSNES, 256x224 DR and higher modes draw each dot as a square group of pixels, which is too narrow.

You'd need a 256x224 graphics mode (the DOS port supports that IIRC) or higher to get the same effect without stretching artefacts.

[blackmyst]

The ratio 640 x 480 has a RATIO of 4:3. surprise, surprise, a 4:3 resolution for 4:3 monitors.

And, yes, you did say this already. however, if a television is 4:3, and my resolution is 4:3, i fail to see why stretching is necessary.

I don't see what's not to understand about it. With R modes you get a little square box in the middle, which is obviously not what real SNES games look like on your TV, and in S modes you stretch that to the proper 4:3.

Yes, that means that on a TV with a real SNES, each pixel is wider than it is high. Game developers take this into accout and have their sprites drawn accordingly.

[sweener2001]

after you finally explained it, i'm okay.

everyone else is just saying "tv property" and crap like that.

[Clements]

ZSNES does not simulate overscan. It merely stretches the raw output image to the correct 4:3 ratio like a real TV does (via analog stretch).

Standard TVs that have overscan typically crop a ~5% border all around the image.

http://scanline.ca/overscan/

As the border around the image is normally the same size, the 4:3 ratio of a DS mode is still the most correct - it's just that you may be seeing up to 5% extra than your TV. Some modern 4:3 TVs do not display any (or very little) overscan at all - and these will exactly match the output of ZSNES.

DR modes ignore overscan and TV analog stretch, giving an inaccurate representation of the output image you would typically see on a TV.