question about systems that support PAL60 systems

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psycopathicteen
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question about systems that support PAL60 systems

Post by psycopathicteen » Wed Feb 24, 2021 3:59 pm

I was browsing on Youtube thinking wondering how a game like Super Mario Bros on the NES would look like on the Nintendo Wii Virtual Console if running through composite, simply because I find composite artifacts interesting.

I found this video on youtube:
https://www.youtube.com/watch?v=mTvbU6qTF1I

The video description says it's running through composite cable. I said in the comments that I was surprised by the lack of rainbowing artifacts on the dithering patterns. I found out the guy is running the game on a PAL system, which made me want to look up about the PAL60 format. According to wikipedia PAL60 uses the same frame rate and vertical resolution as NTSC, but with the PAL color encoding.

The only thing I don't know is, because the PAL color decoding relies on there being 283.75 color cycles per scanline, if they're using the PAL h-blank timing, or if they're using NTSC h-blank timing, despite the color carrier being out-of-sync with horizontal frequency?
Last edited by psycopathicteen on Wed Feb 24, 2021 7:23 pm, edited 1 time in total.

lidnariq
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Re: question about systems that support PAL60 systems

Post by lidnariq » Wed Feb 24, 2021 4:26 pm

Depends! PAL60 isn't a formal standard, so hsync rate isn't well-defined.

FCEUGX defines its modes here: https://github.com/dborth/fceugx/blob/m ... o.cpp#L119
which is part of libogc
and those correspond to these tables of 8 different exact scanline timings: https://github.com/devkitPro/libogc/blo ... eo.c#L1514

Ultimately the Wii and Gamecube have access to 27MHz and 54MHz pixel clocks, so scanline length could be almost anything.

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Dwedit
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Re: question about systems that support PAL60 systems

Post by Dwedit » Wed Feb 24, 2021 6:27 pm

Probably lack of rainbows because it's not generating a picture the way a NES does (no square waves between two specific voltage levels)
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lidnariq
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Re: question about systems that support PAL60 systems

Post by lidnariq » Wed Feb 24, 2021 7:04 pm

It's not the square wave modulator that's the problem - the difference between a square wave and a proper sine doesn't matter until you hit the 3x harmonic - but instead
1- the real PPU doesn't bandlimit the chroma signal; a new color can be every pixel, for a chroma and luma bandwidth of 2.7MHz. NTSC doesn't have anywhere near that much chroma bandwidth, but maybe PAL's delay line demodulator gives more. In contrast, the Wii Video Interface might have some chroma filtering in it. (I don't know if it does.)
and
2- FCEUGX is almost certainly not using the nonstandard 227 ⅓ chroma cycle scanlines, but instead proper 227 ½ or 283 ¾ chroma cycles per scanline.

Oziphantom
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Re: question about systems that support PAL60 systems

Post by Oziphantom » Fri Feb 26, 2021 2:34 am

PAL 60 nominally is, NTSC scan lines for PAL frames.

The example of this is the DREAN VIC-II chip.

Code: Select all

       clocks per line
              lines
NTSC   65     263
PAL    63     312
DREAN  65     312
So you run a full frame but at the NTSC pixel clock. There is also NTSC 4.43 which is kinda PAL60 in the Japanese wanted to keep alignment with the US but also wanted to not suffer the crappy video of the US.

or if you are doing 480p then you just get raw colour data and it runs NTSC frame timings and size.
In order to get EDTV out of the WII and GC, I pretty sure you have to be component or better. I don't think you can do PAL-60 on Composite out. Unless you have a PAL-M encoder.

Once you are in 480p and have RGB or YPbPr then you have VGA timings.

but either way. NTSC sucks, and you get rainbows and colour clash with it. Old computers actually exploit this to get colour. For example the Apple II is colour but only on NTSC as it uses the NTSC phase shift to fake colour data. A few other old computers do this and Tandy 1000s do Composite CGA which gets away from the CGA colour set into slightly better.
PAL doesn't have these limitations and blends across lines by make new colours not weird red shift dot wobble messes.

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Re: question about systems that support PAL60 systems

Post by lidnariq » Fri Feb 26, 2021 2:58 am

Oziphantom wrote:
Fri Feb 26, 2021 2:34 am
The example of this is the DREAN VIC-II chip.
The Drean C64 is the complement of PAL60, being intended for the bizarre 50Hz video standard that was used in Argentina. NTSC chroma frequency, and chroma bandwidth, but PAL scanline length, count, and PAL chroma demodulation. See the UA6528P famiclone PPU.
(edit: misremembered PAL-N scanline duration because this famiclone PPU is rather nonstandard)

In contrast, PAL60 is PAL chroma frequency, chroma bandwidth, demodulation, and NTSC scanline count. I still don't know whether PAL60 is more often NTSC or PAL scanline length.
I don't think you can do PAL-60 on Composite out. Unless you have a PAL-M encoder.
The GC/Wii video interface has a set of bits for "what color modulation to use"; it's unrelated to any other constraints. See http://hitmen.c02.at/files/yagcd/yagcd/ ... tml#sec5.3, register 0xCC002002. I don't think PAL60 was used by the Virtual Console on the Wii - maybe someone can correct me - but FCEUGX is the homebrew version and it can do whatever it wants.
A few other old computers do this and Tandy 1000s do Composite CGA which gets away from the CGA colour set into slightly better.
Not just the Tandy 1000, but basically every CGA card. Trixter has written far more about that than one might think possible :)

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tokumaru
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Re: question about systems that support PAL60 systems

Post by tokumaru » Fri Feb 26, 2021 4:28 am

BTW, what's the difference between PAL 60 and PAL-M?

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Re: question about systems that support PAL60 systems

Post by Oziphantom » Fri Feb 26, 2021 5:07 am

tokumaru wrote:
Fri Feb 26, 2021 4:28 am
BTW, what's the difference between PAL 60 and PAL-M?
From what Lidnariq is saying.
PAL-60 480 lines
PAL-M 576 lines

ie. PAL-M has all the benefits of PAL at 60fps, PAL-60 gives you NTSC with better colour at 60fps.

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tokumaru
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Re: question about systems that support PAL60 systems

Post by tokumaru » Fri Feb 26, 2021 5:22 am

PAL-M is definitely 480 lines. I'm having a hard time distinguishing PAL-M from PAL 60.

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Re: question about systems that support PAL60 systems

Post by tepples » Fri Feb 26, 2021 5:36 am

PAL-M is 480 of 525 lines and 60 Hz, as anyone familiar with the history of analogue video in Brazil would be aware.

The difference between PAL60 and PAL-M is that PAL-M is a standard using a chroma subcarrier frequency close to NTSC's 3.58 MHz, whereas PAL60 is a nonstandard format using the same 4.43 MHz chroma as ordinary (50 Hz) PAL.

Standard formats
NTSC: 60 Hz, 262.5 lines per field, 3.58 MHz chroma, no inversion of V (red difference)
SECAM: 50 Hz, 312.5 lines per field, frequency-modulated chroma with U and V on alternate lines
PAL: 50 Hz, 312.5 lines per field, 4.43 MHz chroma, V inverted on odd lines, used in most of Europe, Australia, and NZ
PAL-N: 50 Hz, 312.5 lines per field, 3.58 MHz chroma, V inverted on odd lines, used in Argentina
PAL-M: 60 Hz, 262.5 lines per field, 3.58 MHz chroma, V inverted on odd lines, used in Brazil

Nonstandard formats
NTSC 4.43: 60 Hz, 262.5 lines per field, 4.43 MHz chroma, no inversion of V
NTSC50: 50 Hz, 312.5 lines per field, 4.43 MHz chroma, no inversion of V
PAL60: 60 Hz, 262.5 lines per field, 4.43 MHz chroma, V inverted on odd lines

Nonstandard progressive formats
NTSC 240p: 60 Hz, 262 or 263 lines per field, 3.58 MHz chroma, no inversion of V
PAL 288p: 50 Hz, 312 or 313 lines per field, 4.43 MHz chroma, V inverted on odd lines
PAL 240p: 50 Hz, 262 or 263 lines per field, 4.43 MHz chroma, V inverted on odd lines
PAL-N 288p: 50 Hz, 312 or 313 lines per field, 3.58 MHz chroma, V inverted on odd lines
PAL-M 240p: 50 Hz, 262 or 263 lines per field, 3.58 MHz chroma, V inverted on odd lines
NTSC 4.43 240p: 60 Hz, 262 or 263 lines per field, 4.43 MHz chroma, no inversion of V
NTSC 4.43 288p: 50 Hz, 312 or 313 lines per field, 4.43 MHz chroma, no inversion of V

Because of gray widespread importing into PAL markets, PAL TVs were more likely to support foreign and/or nonstandard formats than NTSC TVs were.

Though TVs were not required by law to support progressive formats because they were nonstandard, their timing was within the tolerance of analog SDTVs of the time (1970s). The popularity of home computers that generate 240p or 288p led to the sale of composite monitors designed for use with these sources. Progressive sources in SECAM regions tended to use SCART RGB.

Oziphantom
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Re: question about systems that support PAL60 systems

Post by Oziphantom » Fri Feb 26, 2021 6:34 am

yeah I keep getting PAL-M and PAL-N mixed up :roll:

Isn't NTSC 4.43 a standard though? NTSC-J.

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Re: question about systems that support PAL60 systems

Post by tepples » Fri Feb 26, 2021 8:46 am

At baseband (not RF), NTSC-J is so close to NTSC that very little bothers to correct for the relatively small differences in black level, primaries, and white temperature.

lidnariq
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Re: question about systems that support PAL60 systems

Post by lidnariq » Fri Feb 26, 2021 11:49 am

NTSC4.43 isn't a standard, and I'm not entirely clear when it's used. As far as I know, NTSC-J uses the same chroma frequency as NTSC-M.

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TmEE
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Re: question about systems that support PAL60 systems

Post by TmEE » Sat Feb 27, 2021 2:01 am

"NTSC4.43" is a thing that some VHS machines produce that where sold here (in europe) when they were playing back NTSC tapes, though it actually isn't NTSC on the machines I have seen but PAL60 instead.

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Re: question about systems that support PAL60 systems

Post by lidnariq » Sat Feb 27, 2021 1:47 pm

Oh, I see, those VCRs directly re-modulate the QAM from 0.6MHz off the cassette to 4.4MHz always, and if it was an NTSC recording originally it doesn't change that. I suppose it wasn't too hard to take that separate chroma signal and convert it to PAL encoding instead... hence the later PAL60 VCRs

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