GT4 1080i on PSX despite D-Terminal port limitations?

Another PSX DESR-xxxx related question...

I gave GT4 (NTSC-J) a try because I was curious to see if the 1080i output can work, although the PSX D-Terminal port (D端子) standards D1 & D2 only support 480i and 480p output respectively (component to TV).

Well, it works and the TV's information screen suggests an input signal of 1080i at 60Hz. I've learned from an informative thread found here that GT4 does not offer "proper 1080i" but rather upscaling. There was an article linked but the url is dead...

I'm curious, apart from the suggested "software upscaling" implemented in GT4, how does this work? The PSX (still talking about that DVR system btw) hardware video output spec does not support 1080i yet the TV suggests it's an actual 1080i signal...?

 

The PS2 part probably does support everything the original PS2 part did, even if the DVR section doesnt.

 

The EE kernel and GS does have an actual 1080I mode, although the GS has insufficient VRAM to make it viable. So software that use it (which isn't actually an official mode within the standard SONY PS2SDK BTW) will be using a smaller frame buffer that probably gets magnified with the GS (i.e. done with hardware).

I don't know much about the D-terminal output though. It isn't impossible for it to actually support a newer standard, but SONY just stated what it will be usually supporting.

 

That makes sense. I'm just surprised since I am using the D-terminal to output all functions (PS2, DVR) to component.

What does "GS" stand for?
As for the D-terminal, I only read in the PSX manual and, well, various Japanese online sources that the standard used in the PSX (i.e. D1 & D2) does not support 1080i (which requires D3). Well, no big deal after all but I'm interested to learn how it works since I never used D-terminal plugs before.

 

Graphics Synthesizer, Its the GPU.

 

It's probably one of those things where "We totally don't support it, but it might work. Maybe."

 

It seems like the D-terminal connector itself is just the interface, which is standardized. Those D1/D2/D3/D4 standards determine what's supported by the device, which SONY could have very well just stated what the PlayStation 2/PSX will likely use (officially, it only supported NTSC, PAL and DTV 480P).
The Wikipedia page on the D-terminal mentioned that the PSP was downgraded to the D1 standard with a software update, so it probably shows that SONY will only state what the user can select.

BTW, the GS itself can be reprogrammed for a lot of video modes, so it doesn't actually support a set of predefined video modes (the modes are determined by the EE kernel). The SCPH-50000 series introduced the 576P video mode in its EE kernel.
I've also gotten it to output 1080P before.

 

For most purposes, you can treat a D－端子 signal as being identical to YPrPb component video - there are some extra lines used to indicate if this signal is interlaced or progressive scan and the number of lines, but any even moderately recent display works out the format from the signal anyway, and simply ignores those lines. There is also another line used for aspect ratio control, and that normally will be obeyed even on modern displays. If you are using a 3 x RCA to D-tanshi cable in input mode and you get a scrambled picture, it probably means that you have an old display that requires the control lines to be set up correctly to work.

The "Dx" designations are simply a method used to make it easy to understand what display modes a certain display can handle - basically D1 is SDTV, D2 is EDTV, D3 is 1080i, D4 is 720p and D5 is 1080p - by convention, if a display supports a certain mode then it must also support all lower numbered modes - so the only determination that a user has to make is to see that the D number of the source device is no greater than the D number of display or other sink device.

 

@all: thanks for the additional insight!

Following the PSX user manual where solely D1 & D2 standards are specified, I obviously assumed that 480i and 480p respectively where the only two supported output resolutions of the PSX (irrespective of what the PS2 and PS2 slim support).
Now it seems the information provided in the Japanese PSX user manual is merely a reference point and those "Dx standards" do no eliminate the possibility of getting a higher output resolution from games such as GT4's unproper 1080i, as long as the TV/screen can handle it. Good to know.

 

GT4 has a "hacked" 1080i mode, it's nowhere near native 1080i. If i'm not mistaken it envolves a 540p image mode. It also seems to reduce the color space.





Honestly, just use the 480p mode.

 

@Johnny: Cool, thanks for the videos! I guess 480p is the way to go... although I have to admit, I only bought that game to check if the 1080i "feature" would work on the PSX

 

The video player SMS also outputs 1080i, I don't know what you mean by "hacked" or near native 1080i, you definitely can output real 1080i on a PS2.

The colour space is likely reduced because the textures are lower quality, because most of the vram is being used for the framebuffer. Hires games on the PS1 suffered from similar compromises.

I don't think the PS2 has hardware scaling like the xbox 360, where 1080p games could actually be rendered at a lower resolution. At least if the PS2 does have it then GSM/HDTV player don't make use of it.

 

It does support 1080I. Just that the internal resolution is lower because the PlayStation 2 has only 4MB of VRAM, which means that it just has less controllable pixels than what a true 1080I video source would have.
It probably also reduced the colour dept to make it fit.
1920 x 1080 x 4 (32-bit) will be about 8MB, while 1920x540x4 will be slightly above 4MB.
So the only answer to make it fit, would be to either reduce the resolution further or to reduce the colour space (from 32-bit to 16-bit).

Also, 1080I is an interlaced video signal, so it will look slightly worse than DTV 480P.

It has hardware scaling (MAGH, MAGV), although the magnification values must be integers.

 

It's "hacked" because it's not native 1080i. Quotes from a avsforum:

http://www.avsforum.com/forum/143-general-gaming-help/485800-gran-turdismo-4-1080i-5-1-a-3.html

"This 1080i feature in GT4 can be quite misleading to a lot of people. Because the most people believe 1080i = 1920x1080i @ 60Hz/30fps. Hence, this can lead people to believe that PlayStation2 is rendering GT4 at 1920x1080 pixels @ 30fps or 1920x560 pixels @ 60fps.

TV standards (analogue ones in particular) are speced in terms of horizontal and vertical timings and pixel clocks (normally capped by B/W)
It is pretty simple to set the display hardware for a TV standard such as 720p or 1080i (1080 lines consisting of 1920 samples/pixels) but only generate 640 or 960 pixels... the same thing occured with older consoles (eg. 320 pixels for PlayStation1 and Genesis, 256 pixels for SNES )

As people have said before, if you are generating a 640x480 (480p) framebuffer, it isn't much of a step to generate a 640x540 frame buffer to display with 3x horizontal mag as 1080i. And with the help of RAMDAC, final images drawn on your display can get slightly post-processed look.

As many displays dont actually have horizontal resolutions anywhere near 1920 anyway it's a nice added feature for GT4. (Well, since 1080i standard is interlaced, it's never possible to achieve the full 1920 samples/pixels of horizontal resolution in theory anyway).

The bottom line is, PlayStation2 is not rendering it at 1080i resolution. No where near close to it."

and

"True" 1080i is debatable. You'd be surprised to find out the most of 1080i video sources don't resolve anywhere near 1920 samples/pixels of horizontal information. The most of them are capped around 1440. But this is still a major step forward from what we're used to such as 480i/p DVD. And it is getting better. But resolving the full 1920 samples/pixels of horizontal information is never possible with 1080i standard.

Anyway,
I believe what is being displayed in 1080i mode in GT4 is 640x540 (640x1080i) image rendered every 60th of a second. This is about 13% fillrate increase compared to 640x480. (Horizontal may go as high as 720, but I highly doubt it).

As for the horizontal scaling, that's not an issue at all. The info is transmitted to the display in analog (Y/Pb/Pr component video out) scanlines (number of samples per scanline), so basically with help of (using)the RAMDACs on both sides (PS2, and display), images get interpolated on the fly, resulting in images with less aliasing noises. Because like I said, TV standards are specced in terms of horizontal and vertical timings and pixel clocks, this is not at all difficult.

It's far from what we call "HD resolutions" meaning 1280 samples/pixels, and/or 1920 samples/pixels of horizontal informations.


Also it's important to remember that this "1080i mode" only works during races, it switches back to 480p for all menus. So with current tvs, the image get out of sync constantly during mode switches

 

RAMDACs on both sides? I think this person doesn't understand TV's at all.

He doubts it goes as high as 720? Sounds like a guess to me.

 

Seems like Johnny didn't understood that the GS chip is actually a full scale frame buffer controller (instead of a GPU) and it's main feature is video scaling. Which is exactly what it is doing with that "1080i" mode GT4 has.

That GS Cube SONY had in 1999/2000 actually had a GS chip with 32MB of embedded video memory. I suppose that was enough for 1080P, which any GS chip can do. (but on the regular GS with 16 colors maybe?)

 

I never said it can't be done. I don't even have the knowledge in the PS2 hardware to even try to deny something like that. All i said was that the 1080i mode in GT4 is not a real 1080 mode.

I do remember this being discussed over 10 years ago on lots of forums, before and after it's release. Most discussions / pictures are probably long gone, but by just by googling "GT4 Fake 1080i" you can come across some recent ones like this:

http://psx-scene.com/forums/f291/gs-mode-selector-development-feedback-61808-print/index206.html

I think we have to inspect Gran Turismo NTSC in order to figure out how it enables 1080i videomode.... If Gran Turismo NTSC can do it, probably every game can also do it---1080i.... What do you think?

I've already done this, in the early stages of GSM development.
Unhappilly, the Polyphony Digital's blockbuster GT4, made by Poliphony Digital team with ALL official documentation and technical support from Sony has a real resolution of 640x512 magnified (zoomed) by MAGH and MAGV to 1920x1024:
640 pixels zoomed by a MAGH value of 3 = 1920 pixels in horizontal
512 pixels zoomed by a MAGV value of 2 = 1024 pixels in vertical

For GT4, Doctorxyz explained the situation. GT4 has 3 modes in game. 480p, 480i, 1080i. As 1080i is a fake mode (640 512) in fact, 480p gives a cleaner display. Try it yourselves to see. You need the NTSC US version, as pal doesn't have these modes.

From the PCSX2 forums
http://forums.pcsx2.net/Thread-Gran-Turismo-4-NTSC-1080i-issue?page=3

The PS2's GS was capable of outputting any resolution up to a max of 1920x1080. Obviously no game used this, bandwidth constraints and raw power simply not being there, etc. -- but yeah.

As for GT4 and Tourist Trophy's "1080i" modes, it wasn't even true 1080i at that.

A 'true' 1080i frame is 1920x1080. A 1080i *field* (since it's interlaced) would be 1920x540. The PS2 couldn't even realistically process that type of frame (it couldn't even do a full 1280x720 frame), however gimped it is, so those games utilized a form of trickery to achieve this resolution. What Polyphony opted to do instead was render each frame as 640x540 by tripling the horizontal rendering resolution. They achieve this by 'squishing' the 640 frame and then stretching it out via simple post-processing/upscaling instead. This causes those pixels to show up three times instead of only once, which is why a lot of people reported 480p offering 'better image quality' than 1080i did. So in a sense, you're getting 1920 pixels horizontally, just not 'true native' pixels, causing the image to look a little distorted and compressed.

This is why PCSX2's internal scaling is superior to the in-game 1080i option. It's generally best in most cases to not bother with the in-game progressive/alternate render output modes, however in some games you can notice a slight improvement with them enabled.

 

Funny enough I was agreeing to you on my post. I just mention you didn't understand that it was a scaler. https://en.wikipedia.org/wiki/Video_scaler
A video scaler apply a algorithm (by software or hardware, like the GS chip) to reproduce a image in a different resolution than the original. That reinforces your argument.

 

I'm quite sure that it can, as 1280x720 will fit in the 4MB (1280 x 720 x 32-bit = ~3.6MB), especially with 16-bit colour. It's just 1920x1080 with true RGBA per-pixel colour that is out of its reach.

 

I understood your post, i was just pointing out that i have limited knowledge on the subject, from reading discussions about this when the game launched.

Which is why i was posting quotes from other people. I was just trying to find more confirmation about it and the last two quotes prove that what you wrote is totally right.