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Help with Output setting

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First post, by Captain Huggles

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I'm using DOSBox 0.70 on a Core 2 Duo E6600 with an ATI X1300 and 1gb RAM.

Apologies if this is a newbie question, but I've read through the Guides forum, the FAQ on the Dosbox site, the readme, the small info in the .conf file AND searched extensively on both VOGONS and Google, and I still for the life of me cannot find any information about the various output methods and which one is the best/fastest. There is zero documentation on the output setting, and nobody really seems to talk about it except for the odd passing comment, so I figured I might as well just ask myself as apparently it's a very important setting:

What does each one do?
Is surface bad?
Do they use DirectX?
Which is best for an ATI card?
What is openglnb and what does it stand for?
Fullscreen/window differences?
etc etc.


Reply 1 of 8, by DosFreak

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Well the output methods are really not that important.

OGL/D3D really aren't that usefull unless you want to use pixel shaders. (D3D not supported in Official DosBox).

Surface-Default setting because it's most compatible across all platforms. Nothing bad about it except that it doesn't support scaling.

overlay=Uses scaling.
ddraw=Uses DirectDraw. Supports scaling. If using 2000/XP/2003 probably faster than surface. (I've never seen a difference, mabye if someone wrote some synthetic benchmark they could see a difference)

Surface/Overlay use GDI I think. DDraw uses Directx (DirectDraw)

Opengl=Uses OpenGL. Also uses bilinear filtering which blurs the screen.
openglnb=Uses OpenGL. Does not use bilinear filtering so pixels are pixelated.

/EDIT Fixed

You have an ATI card so it's generally not recommended to use OPENGL.

You will see people say that there is a difference between fullscreen/window as far as speed but I've never seen a difference. There are tons of video cards/driver combinations out there so it's always a possibility.

I use an ATI card in Windows and I stick with Surface/Overlay. Always works fine for me. D3d isn't officially supported. OGL is terrible with ATI because ATI are shitty driver writers. I also use Vista and since GDI/ddraw isn't accelerated in Vista as it is in 2000/XP/2003 there really isn't a reason to use ddraw.

Last edited by DosFreak on 2007-03-07, 11:20. Edited 2 times in total.

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Reply 2 of 8, by gulikoza

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surface uses ddraw or gdi internally (depends on SDL_VIDEODRIVER).

And a small fix to DosFreaks explanation 😉

openglnb=Uses OpenGL. Does not use bilinear filtering so pixels are pixelated

D3D is also very fast and eventually might work better in Vista because it's accelerated (atm it sometimes crashes though)


Reply 5 of 8, by MiniMax

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Not sure how helpful this is, but these 3 articles give some info about SDL and output surfaces:

http://www.linuxdevcenter.com/pub/a/linux/200 … 5/sdl_anim.html
http://www.linuxdevcenter.com/pub/a/linux/200 … 7/sdl_anim.html
http://www.linuxdevcenter.com/pub/a/linux/200 … 3/sdl_anim.html

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Reply 6 of 8, by Captain Huggles

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Thanks a lot Dosfreak and MiniMax 😁. I'll use surface from now on because I don't use any scalers, which I think is why people were suggesting overlay because they had a scaler set.

Would OpenGL act kind of like an OGL patch for a game though?. I mean, if I ran System Shock 1 in Dosbox under OpenGL, would it smooth the wall textures?. I can't test it right now because that Core 2 computer in my post is actually the one I use at Uni 😜 (hence why it has the X1300). My comp at home is a useless P3 450 and an ATI Rage 🙁

Reply 7 of 8, by ProDigit

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MDK had a performance testing program, and my Xeon has a low single core CPU speed (but many cores), which affects performance negatively in DOSbox.
This it's easy to see for me which setting performs better.
Surface shows the image in original aspect ratio, with a performance rating of about 147.
Overlay stretches the image with a rating of 149.
Ddraw is the slowest at 145-146.
OpenGL is the fastest at 150. And when combined with fulldouble, reaches even higher, at 153. Probably the best setting for 3D games like MDK and Terminal Velocity.
OpenglNB is around 148.

I'm using a 1,8 GHz Celeron 10core, and an NVidia GT 1030.

It's interesting to see that some display modes prefer fulldouble, while others don't.
With OpenGl it prefers fulldouble.
Only thing is OpenGl stretches the image to screen.

Reply 8 of 8, by Yesterplay80

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ProDigit wrote:

Only thing is OpenGl stretches the image to screen.

No, it doesn't.

"aspect = false" does it. Set it to "true" and experience the marvel of black borders at the sides of the centered image!

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