Interlacing question from a new PCSX2 user

[cammelspit]

So, I have spent a half an hour searching the forum and my questions were not satisfactorily answered so I apologize if this has been covered before.

I have used PCSX2 on and off for some time now but never really had a PC powerful enough to rock it in the way I would consider playable, full speed or bust. I have recently been forced through hardware failure to build a brand new PC. i56600K, R9380, 16GB RAM, all the good stuff. I have on the other hand been using Dolphin for years as it needs less horsepower to get good playable framerates in the popular titles. Sorry, Dolphin is just my only frame of reference here I realize they are completely different.

So, When I am playing on PCSX2 the interlacing options, all of them, IMHO look pretty bad. Why is it that an emulator of the PS2 looks so bad with regards to interlacing? Also, why is it that there is even a need for interlaced output at all? I know I am going to get the whole PS2 is old it had interlaced graphics, I get this. I was repairing PS2s from the day they were released professionally along with everything else from Atari2600 and up so I am VERY versed in the hardware aspects of what interlaced, progressive and all that jazz actually is. Thing is, all of the other systems of the time all displayed in the (480i) standard as well as far back as the genesis and SNES had games that would use the 480i (high res) modes and when they are emulated they don't require any kind of false interlacing to display properly.

When my GPU renders the frame, why is it that it has to be interlaced in its output? Can't the GPU just display the 3D elements at least in a progrssive scan? I know I am sorry for doing it again, Dolphin displays games that on console never displayed in 480P they will still not need a saw tooth or interpolated deinterlacing to display properly and you couldn't tell it ever wasn't progressive. Now, i also realize that internally the GPU of the GameCube also output Progressive 480P and it was the video encoder that made it 480i but surely the PS2 can at least be similar to the older systems like the NES that didn't actually make the picture until the PPU, being tied to the TVs refresh rates and such, made the image directly. Because if it is in the interests of accuracy then I can respect that, kinda like what MAME does but in that case there shouldn't be any special filters because that too is not accurate.

A side note, setting my PC to output 1080i and not 1080P through the crimson additional settings actually works better than any of the modes PCSX2 has. My crappy 299$ 50inch with a brand I have never heard of surprised me in how well it can handle deinterlacing on its own, with an 8ms response time to boot. Annoying but if there is no way to remedy this in a better way then I will just have to switch to 1080i when I play PS2 games on my PC from now on.

TL;DR PCSX2 looks bad to me personally and I guess it all boils down to two things here.
1: CAN PCSX2 display in progressive and not have this faux interlacing necessary and can I make it not look so blurry or jittery as both are most unacceptable to my eyes?
2: Why is PCSX2 doing this? Is it a specific limitation of the way the PS2 handles the rendering and such or is it simply the specific approach that the PCSX2 devs have chosen to take?
What I would LOVE is to have someone actually versed in what the hell I am talking about giving a precise answer, don't worry I can understand it and am SUPER curious to boot.
Thank you in advance for humoring my silly inquiry here

[gregory]

OoO, so if I sum up the wall of text

* GameCube is progressive => PS2 is progressive
* In case previous hypothesis is wrong, NES is kind of progressive => PS2 is kind of progressive

=> Conclusion you don't understand why PCSX2 uses interlacing whereas the PS2 is progressive

Is it correct?

[ssakash]

AN PCSX2 display in progressive and not have this faux interlacing necessary and can I make it not look so blurry or jittery as both are most unacceptable to my eyes?

Currently, PCSX2 can only display in progressive for games which have native support for progressive modes. It's still possible to make games which don't have native support for progressive mode to run in progressive but that might probably cause some internal issues with the PLL/VCK Frequency. I'm not sure... I can't say much without investigating into it.

Why is PCSX2 doing this? Is it a specific limitation of the way the PS2 handles the rendering and such or is it simply the specific approach that the PCSX2 devs have chosen to take?

we're doing it this way since the PS2 also did it this way, AKA Accuracy

There's a specific SMODE2 register called INT,

* when the register is enabled - Interlaced mode
* when the register is disabled - Progressive mode

[billyash]

May be what he means is why pcsx2 using additional interlacing mode example: weave tff, weave bff, bob tff, etc?. While genesis and snes is interlanced but doesn't need those additional interlacing.

[cammelspit]

@billyash In a nutshell yes! Sorry, I can be a little word vomity ay times and have been known to ramble much more than I probably should so I apologize for not being as concise as I should have been.

@gregory Yes, you nailed it. I never meant to directly compare Dolphin/GameCube with PCSX2/PS2 but it can really cramp my style.

@ssakash THANKS! That explicitly answered my main question. So games with native progressive will work, I did test it so I knew at least that but in the interests of accuracy, I can't really complain. Is there any thought that the dev team might be looking into a user selectable way of disabling this register? Kinda reminds me of the GameCubes external frame buffer and how annoying it was to get just right with Dolphin. The problem was any and all resolution enhancements became 1x IR if it was accurate. Took until last year for the majority of games that required it to get to the point where it would work with the virtual buffer.

Thank you all for responding. I appreciate humoring a newb here. I am keeping a close eye on this emulator and I will just have to get creative to make my eye not go buggy. I mean the real PS2 looked like a muddy blurry mess anyways so it is still a massive improvement however you slice it.

[gregory]

The issue isn't the register per se (except if you rewrite the game). Rendering will be done in 2 separates buffers. Then the output merger will be configured to read both separates buffers and to interlace them. The interlace option merges the 2 buffers (I guess there are severals version for quality purpose) into a single buffers. If you disable this step, you might miss some lines. For example FMV there are send to the GS with all lines. First rendering step will be to split odd line in 1 buffer and even line in another buffer. Then later images will be merged back with interlacing.

[cammelspit]

So you are saying the PS2 has two framebuffers that are merged by the video encoder? Since the PS2 has not one single standard chip in the thing, I guess that is just the way it was designed? To me, it seems kinda crazy for a company like Sony to rigidly design a console with interlacing 100% intrinsic to its operation. I mean, I realize CRT TVs were the thing back then but progressive scan and even HD TVs were happening and they knew it would be a thing long before the PS2 had lived its full lifespan.

Correct me if I am wrong but what you imply is that if both buffers would be combined the odds or the evens would be one frame behind? Some of the crappier old DVD players had that problem too when trying to play something in progressive scan that itself wasn't explicitly encoded that way.

Seems to me the better way to do it would be like the GameCube or PS1 does it. Render the proper lines every frame internally in the GPU and allow the video encoder to do the rest of the work. I guess with PC GPUs like the GameCube or with SUPER low resolution like the PS1 it made less difference. Maybe a way for the PS2 to only need to render half the lines each pass for performance reasons? I know we all liked the PS2 in our own ways but it was kinda anemic in terms or horsepower. Even the Dreamcast had some advantages in some cases.

[gregory]

You can read 2 framebuffer at once to generate the image screen but it isn't mandatory.

What game designers do != What the PS2 can do.

For example, you can also use the 2 read buffer to blend an image with some texts. Or a background with frontground object.

The GS can do lots of operation that modern GPU aren't capable. But it is was designed in 199x, it is only a fixed function unit no shader. Not even a stencil buffer. What is the issue to be 1 frame late, TV aren't latency free anyway.