Author Topic: Questions concerning SNES and video modes.  (Read 11230 times)

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Offline Catastrophic

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Questions concerning SNES and video modes.
« on: February 22, 2015, 12:15 AM »
Hello good folks. I recently got myself a Super Nintendo as I have wanted to get one for quite some time. As such, I also wish to get a flashcart for it and SD2SNES seems to be the best choice.

Just one problem. The PAL Super Nintendos are locked at 50hz as the video mode is hardware controlled as opposed to it being software controlled like with the N64, which made playing NTSC games on a PAL console no problem at all. Thankfully, I own a soldering iron and I have soldered on to a PCB once before(OneChip into a PSOne) so I'm quite certain that adding a 60hz switch into the unit won't be too hard. However, there are a few things that I do not quite understand.

Firstly, some PAL games received speed adjustments to accommodate for the lower refresh rate. I noticed that in games like Super Mario All-Stars for example the game ran just as fast as its NTSC counterpart although the lower framerate was definitely noticable. If I were to switch the console to run at 60hz instead of 50hz then would the game run faster than it should due to the adjustments?

Secondly, I have some problems with the LCD I use for my retro games where 240p content won't display correctly. Composite and S-Video would have insane discolorization. RGB has fine colors but the right side of the image is clipped out for some reason. I fear that this will also be the case for the SNES with 60hz switched on. I've heard that various TVs can be quite picky about signals. I recently ordered some LM1881M and plan on building a sync stripper to further improve video quality but I was wondering if anyone knows if using pure sync instead of sync on composite can fix video issues like these?

Sorry for long post.

Offline JonteP

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Re: Questions concerning SNES and video modes.
« Reply #1 on: February 22, 2015, 02:50 AM »
Don't know about All Stars specifically but if the game is PAL optimized you can expect issues (e.g. graphical glitches) if you enforce 60hz. And yes, if the optimization entails game speed it will likely run too fast. If you intend to use SD2SNES and install a 60hz switch this won't be a problem though. Just use NTSC roms in 60hz mode.

Bad image quality is to be expected with composite video. I don't think PAL SNES outputs csync, but you're better off using luma (pin7) for sync than composite video. The latter tends to be very noisy on LCD tvs. Remember that the rgb cables are different between pal and ntsc. What tv are you using? One solution could be using an upscaler if the tv doesn't handle rgb well.

Is that clipping off happening with the image in 4:3 aspect ratio?

Offline Catastrophic

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Re: Questions concerning SNES and video modes.
« Reply #2 on: February 22, 2015, 03:14 AM »
Don't know about All Stars specifically but if the game is PAL optimized you can expect issues (e.g. graphical glitches) if you enforce 60hz. And yes, if the optimization entails game speed it will likely run too fast. If you intend to use SD2SNES and install a 60hz switch this won't be a problem though. Just use NTSC roms in 60hz mode.

Bad image quality is to be expected with composite video. I don't think PAL SNES outputs csync, but you're better off using luma (pin7) for sync than composite video. The latter tends to be very noisy on LCD tvs. Remember that the rgb cables are different between pal and ntsc. What tv are you using? One solution could be using an upscaler if the tv doesn't handle rgb well.

Is that clipping off happening with the image in 4:3 aspect ratio?

I'm using an official SNES RGB cable. The clipping issue also occurs in 4:3 mode.

As for the sync. That's what I'm building a sync stripper for, to separate the sync information from composite video so I do not need to modify the consoles unnecessarily. I plan on getting a better TV sometime in the future, a good CRT for retro gaming such as a Triniton. The LCD I have now is what I have at the moment.
« Last Edit: February 22, 2015, 03:49 AM by Catastrophic »

Offline GreatFunky

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Re: Questions concerning SNES and video modes.
« Reply #3 on: February 22, 2015, 10:46 AM »
I think you'd better go to do the csync mod (pin 7 for sync) because i know that the sync stripper doesn't give a good result in comparison , especially on nintendo consoles.
« Last Edit: February 22, 2015, 10:49 AM by GreatFunky »

Offline Catastrophic

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Re: Questions concerning SNES and video modes.
« Reply #4 on: February 22, 2015, 02:22 PM »
I think you'd better go to do the csync mod (pin 7 for sync) because i know that the sync stripper doesn't give a good result in comparison , especially on nintendo consoles.

But I thought PAL SNES consoles did not have a csync pin?

Offline AmmoJammo

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Re: Questions concerning SNES and video modes.
« Reply #5 on: February 22, 2015, 02:25 PM »
I think you'd better go to do the csync mod (pin 7 for sync) because i know that the sync stripper doesn't give a good result in comparison , especially on nintendo consoles.

But I thought PAL SNES consoles did not have a csync pin?

They don't.
The suggestion seems to be to use pin 7, which is the luma signal, for the sync signal.
« Last Edit: February 22, 2015, 02:28 PM by AmmoJammo »

Offline Catastrophic

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Re: Questions concerning SNES and video modes.
« Reply #6 on: February 22, 2015, 02:41 PM »
I think you'd better go to do the csync mod (pin 7 for sync) because i know that the sync stripper doesn't give a good result in comparison , especially on nintendo consoles.

But I thought PAL SNES consoles did not have a csync pin?

They don't.
The suggestion seems to be to use pin 7, which is the luma signal, for the sync signal.

I see. I'm not very familiar with the whole sync business but is there any notable difference between a pure sync wave from the console and a pure sync wave that's been extracted from composite video? I'm wondering because I do not know why using the luma signal instead would benefit.

Offline GreatFunky

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Re: Questions concerning SNES and video modes.
« Reply #7 on: February 22, 2015, 06:56 PM »
Yes for sure ! i did it on a 1chip in rgb and it remove the X pattern problem
like here :
http://nfggames.com/forum2/index.php?topic=5266.0

Offline Catastrophic

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Re: Questions concerning SNES and video modes.
« Reply #8 on: February 22, 2015, 07:36 PM »
Yes for sure ! i did it on a 1chip in rgb and it remove the X pattern problem
like here :
http://nfggames.com/forum2/index.php?topic=5266.0

So using luma as sync will remove the checkerboard issue? That's good to know. Still, I always assumed that the checkerboard thing was a result of the other data going through the wire and that using a sync stripper would remove this issue. Is that not so?

Offline GreatFunky

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Re: Questions concerning SNES and video modes.
« Reply #9 on: February 22, 2015, 08:11 PM »
Yes for sure ! i did it on a 1chip in rgb and it remove the X pattern problem
like here :
http://nfggames.com/forum2/index.php?topic=5266.0

So using luma as sync will remove the checkerboard issue? That's good to know. Still, I always assumed that the checkerboard thing was a result of the other data going through the wire and that using a sync stripper would remove this issue. Is that not so?
In theory, but in practice .....
more informations here :
https://www.assemblergames.com/forums/showthread.php?41857-PAL-SNES-1CHIP-does-c-sync-exist-on-the-S-RGB-chip
https://www.assemblergames.com/forums/showthread.php?38248-PAL-Gamecube-c-sync

Offline Catastrophic

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Re: Questions concerning SNES and video modes.
« Reply #10 on: February 22, 2015, 09:20 PM »
Yes for sure ! i did it on a 1chip in rgb and it remove the X pattern problem
like here :
http://nfggames.com/forum2/index.php?topic=5266.0

So using luma as sync will remove the checkerboard issue? That's good to know. Still, I always assumed that the checkerboard thing was a result of the other data going through the wire and that using a sync stripper would remove this issue. Is that not so?
In theory, but in practice .....
more informations here :
https://www.assemblergames.com/forums/showthread.php?41857-PAL-SNES-1CHIP-does-c-sync-exist-on-the-S-RGB-chip
https://www.assemblergames.com/forums/showthread.php?38248-PAL-Gamecube-c-sync

Thanks for many great links. From what I understand, using sync on luma instead of sync on composite results in image quality that's on par with csync when it comes to SNES and N64 consoles, and that using a sync stripper won't necessarily fix problems associated with sync on composite.

Luma is present on pin 7 on all SNES and N64 units, but a csync pin is apparently present on pin 3 as well on PAL N64 consoles and NTSC SNES consoles. With this in mind I was wondering if it would be a good idea to install a small switch into the AV connector that switches between routing sync on composite and sync on luma to pin 20 on the SCART connector. That way I'll be able to easily switch between composite video and luma with the flick of a switch. Here's a bad MS Paint drawing of what I'm talking about:



My reason for doing this is that I use the same cable for both my SNES and my RGB modded French N64, and being able to switch between sync on composite and sync on luma will ensure full compatibility with most TV sets. What do you think? Is this a good idea?

EDIT: I just realized that the official cable does not have the metal connector for pin 7. I guess I can't modify an official cable easily. Does anyone know of a good 3rd party cable that has all the necessary pins?

EDIT2: I tried opening up an official composite AV cable to see what it looks like from the inside and after fiddling with the wires a bit I found that you can actually pull out the connectors from the plastic socket and then put them back in. If I borrow one of the pins from this cable and implement it into the RGB one then the mod mentioned above may very well work!
« Last Edit: February 22, 2015, 11:14 PM by Catastrophic »

Offline GreatFunky

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Re: Questions concerning SNES and video modes.
« Reply #11 on: February 23, 2015, 12:45 AM »
i also have a RGB modded French N64 and i use the luma sync also on it , but on the n64 pin 7 isn't connected on the MB , so you just need to solder a wire from the S-RGB A chip pin 17 to the connector pin 7

then you should be able to use the same cable on both consoles (i'm using official cables and just moved the connector from pin 9 to 7) and it will fix also the checkerboard effect on the n64.

Edit : Same thing about chroma on the N64 : present but not routed , you can solder a wire from S-RGB A chip pin 12  to the connector pin 8 then you'll get the same AV plug as your snes
« Last Edit: February 23, 2015, 01:55 PM by GreatFunky »

Offline Catastrophic

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Re: Questions concerning SNES and video modes.
« Reply #12 on: February 23, 2015, 01:11 AM »
i also have a RGB modded French N64 and i use the luma sync also on it , but on the n64 pin 7 isn't connected on the MB , so you just need to solder a wire from the S-RGB A chip pin 17 to the connector pin 7

then you should be able to use the same cable on both consoles (i'm using official cables and just moved the connector from pin 9 to 7)

Oh yeah. The FRA models do not output S-Video and this is probably why. Don't know about the chroma pin though.

I just pried open the connector on my RGB cable and tried moving the connector on pin 9 to pin 7. Tried it out on my Super Nintendo and I noticed that the checkerboard effect was gone. Good progress! However, when I was pulling the connector out of the housing in order to align it better I accidentally broke the connector. Not so good progress.  :-[

It's not a big problem though as I can just borrow a pin from the other cable and solder it on to the wire. All I need now is a slide switch and the screw bit needed to open up SNES and N64 consoles. I will solder the luma signal to pin 7 on the AV connector once I get it. Thanks a million for the help!