why not Dosbox with overlay and composition

I was thinking about ...strange no one do it , can someone make this small upgrade to Dosbox 0.74 for AmigaOs4 ?

@tlosm

Probably the same reason that mplayer does not have composition support yet.

@LiveForIt

No know how to do?

@tsolm

There bunch of:

-- its not "small upgrade" and its not little easy task for few minutes
-- no skilled devs (those who skilled, are busy with everything already)
-- no one can say that adding of compositing/overlay to dosbox will in any way speed it up, as its all mostly cpu based loading and only faster cpu or jit will help: but that need developer's time and tests => all the usual answers :)

@kas1e

+ 1

Two software I never saw before. Someone may want to use them:
www.gnu.org/software/libjit/
http://www.gnu.org/software/lightning/manual/lightning.html

@kas1e

Yes, I was thinking exactly the same thing. I really doubt compositing or overlay would speed up the whole thing.

I'll ask Corto about this specific topic.

Compositing is hardware-accelerated while other is CPU render only.

In a Hollywood-Script i wrote for a test i got these resultes:

http://amigaworld.net/modules/newbb/v ... opic_id=36878&forum=32&19

The Demo is always hardware-accelerated, without it you can divide all screenrates by 10.

@tlosm
Overlays would make scaling faster, but if you don't use that it won't do much for you.

@kas1e

I dont know i see very big speed improving with composition and Overlay in Basilisk II graphic rendering .. Live4it Basilisk II is a true example :)

@bszili

In dosbox i see big difference in rendering speed if i swap 16 to 256 colors the performances degrase and become 1/8
Probably with compositing will become more faster because the use of the gpu for rendering and not the only cpu.
About overlay i know but scaled a winodw 320x240 to 640x480 will be for sure more faster of a 640x480 emulated ;)

@fingus

composition is faster on New HD cards on Old radeon serie is very slow.

@tlosm

Quote:

But there is one problem, and it hard to explain but I try anyway.

An emulator is divided into tasks or processes, some of memory in not sheared like real video memory, real video memory is what composition needs.

The CPU emulation runs in one task / process, the video emulation runs in another.
So for this to work there are two steps.

First copy system memory to video memory.
And then composite on to the screen (actually you can't render into a window, you most render over it).

Copy to video memory, then display, it should be similar in speed as rendering into video memory whit the CPU.

There is how ever two benefits to it, system memory is faster for the CPU to access then then Video memory (so CPU emulation speeds up a tiny bit), and you can scale the display output using hardware.

Full screen mode is faster than composition, if you do not need to convert the graphics, because you get a combination, the screen mode display graphics in the right resolution, and you get direct access. If you do not need to use picasso96 lock/unlock bitmap.

@LiveForIt

Thanks for explain it :)

Hi all
I haven't thought about that when I ported DosBox. And I have to say I have never played with compositing and overlay

But you can be sure the CPU pressure is due to the x86 CPU emulation. The display is really hard to improve (like other parts in DosBox) because of the spaghetti code (effects or resizing on pixels done in macros calling macros ...).

So I don't know what I can really do. But if Basilik sources are available I would be pleased to have a look at these parts.

For higher performance, JIT could be an idea (but difficult because there is no doc and no easy debug mechanism). And few other ideas could be checked too.

@corto
Thanks corto for the job you did :)
I have on Xe 933 a really good emulation , i can run fast windows 95 and inside of it can play Avi (old indeo) video clips and run game in multitasking dos mode with win 95 at 640x480x4(16colors) (look like a real peeceee 486 66mhz)
the only problems is when i make win95 run in 256 and hi color mode the speed drop down really much and make the emulation unusable.


The best dosbox config after my test on Xe 933is for have audio-video sync and fast:

core:normal
cpu: pentium_slow
vga:svga_noflb
cycles:6500

Look like the gfx rendering with more of 16 colors is the big gap of dosbox.

>About overlay i know but scaled a winodw 320x240 to 640x480 will be for sure more faster of a 640x480 emulated ;)

So try Aminet/CloneWindow : It is maded to clone a window/screen to an other resizable window with Compositing
Perhaps it will works with dosbox... (but it dont works with basilisk)

Alain Thellier

@thellier

Quote:

Hi Alain I looked at CloneWindow code when I write the composition modes in Basilisk II, but it's not the same code, its simplified.

@corto

Yes the code is OS4Depot.net if you like to look.
It should be the latest (if it was not rejected.)

if you do not find the code in video code, then send me a PM.

@LiveForIt

i see this on dosbox readme :P

* Ideas for the future / to do

- Improve access to the x86 registers
- Activate OpenGL
- Check CDROM access

will be great have this improvments and better/faster video rendering ;) ;) ;)(

@tlosm

Well in that case composition is bad choice, it's not 3D it's just a way to draw bitmaps using the GPU.

I think the future for all emulators are JIT, this the only way go get more out if etch CPU cycle.

OpenGL does not make sense if you can't emulate Windows95/98 at a good speed.

@LiveForIt

Quote:

Bad choice for what? Compositing is perfect for rescaling low-resolution screens to large windows without wasting extra CPU cycles.

Quote:
AFAIK, DOSBox doesn't provide OpenGL to the emulated environment, but can use OpenGL to scale and display the emulated screen. I'd say that compositing is a better option, as it's simpler and has lower overhead (no need to set up an OpenGL state). For example, MiniGL doesn't support non-power-of-two-textures, so using it for scaling a 320x240 screen would result in huge wastage (a 512x256 texture for a 320x240 screen).

Hans