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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Thu Feb 20, 2020 1:10 pm 



Joined: 08 Mar 2017
Posts: 1364
One marked difference between S-Video and RGB is that they use an entirely different processing path in most CRT.
The resulting image can be much more affected by the stuff that a Chroma decoder does to the image than the signal itself.
My Sony CRT for example applies velocity modulation to CVBS and S-Video, so those signals look actually lots sharper (but worse) than RGB.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Thu Feb 20, 2020 3:42 pm 


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Joined: 05 Mar 2018
Posts: 1231
Einzelherz wrote:
You might see a tiny, very small bit of up close crispness, but from playing distance it'll be practically identical. Remember, the only difference (technically?) between svideo and rgb is that the colors travel on separate lines. The sync is separate on both and that's where most of the sharpness lives.

Sync has nothing to do with it. The reason svideo is so much sharper than composite is that the chroma data is separate from the luma.

The relevant part about the upgrade from svideo to RGB is not sharpness, it's color fidelity. As you said, svideo is already 90% there with respect to sharpness, but the color quality between them is worlds apart.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Fri Feb 21, 2020 12:04 pm 


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Joined: 09 Apr 2014
Posts: 1208
The color quality *can* be worlds apart. My 2 chip snes looks pretty indistinguishable on my several CRTs swapping between those two inputs.

And luma is, for all intents and purposes, sync in this case.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Fri Feb 21, 2020 7:47 pm 


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Joined: 16 Jan 2014
Posts: 927
The sync information is contained in the luma signal, but actual picture definition information is also contained in that same signal, so its not exactly the same. You plug Luma only into the Svideo connector or the green on a YPrPb component connector and you will get a very crisp, black & white picture on your display. You plug a composite sync signal only into an RGBS connector and you will get nothing but a black screen. We know this already, sure, but they are quite different, because of this.

As far as sharpness related to sync, I dont think thats the case. The only difference between sync-on-composite and pure composite sync is the latter's lack of vertical or diagonal jailbars that are only barely noticeable on solid colors. The actual edges of pixels are the same sharpness regardless . You either have sync or you dont, theres not a whole lot of in between. The real sharpness comes from the luma and chroma signals and the lack of crosstalk between the two and the sync signal when connected to the display. Luma signal itself is directly derived from a specific ratio of chroma signals.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Fri Feb 21, 2020 8:43 pm 



Joined: 19 Jul 2017
Posts: 1756
Josh128 wrote:
You plug a composite sync signal only into an RGBS connector and you will get nothing but a black screen.

By "RGBS connector", do you mean SCART (Or JP-21)?

Josh128 wrote:
The only difference between sync-on-composite and pure composite sync is the latter's lack of vertical or diagonal jailbars that are only barely noticeable on solid colors.

I believe that interference only happens if you use cheap, unshielded or poorly-shielded cables; there should be no visual interference when using a cable that properly shields the composite video/sync line.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Fri Feb 21, 2020 9:06 pm 


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Joined: 16 Jan 2014
Posts: 927
nmalinoski wrote:
Josh128 wrote:
You plug a composite sync signal only into an RGBS connector and you will get nothing but a black screen.

By "RGBS connector", do you mean SCART (Or JP-21)?

The physical connector doesnt matter. Im talking about RGBS (or RGBs) via SCART, RCA, or BNC.

Josh128 wrote:
The only difference between sync-on-composite and pure composite sync is the latter's lack of vertical or diagonal jailbars that are only barely noticeable on solid colors.

I believe that interference only happens if you use cheap, unshielded or poorly-shielded cables; there should be no visual interference when using a cable that properly shields the composite video/sync line.


It has nothing to do with cables, its because you are muxing two or more video signals onto a single wire, thereby reducing the analog bandwidth available to each signal. Composite video is one wire for all video signals, S-video is two wires for all video signals, component video is three wires, and RGBs is 4 wires. You have much greater bandwidth in 3 wires than one, and dont have to use filters to separate out specific signals.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Feb 22, 2020 12:11 am 



Joined: 19 Jul 2017
Posts: 1756
Josh128 wrote:
It has nothing to do with cables, its because you are muxing two or more video signals onto a single wire, thereby reducing the analog bandwidth available to each signal. Composite video is one wire for all video signals, S-video is two wires for all video signals, component video is three wires, and RGBs is 4 wires. You have much greater bandwidth in 3 wires than one, and dont have to use filters to separate out specific signals.

I won't argue the image degradation resulting from YC, CVBS, or RF. If that was your point, I clearly missed it; the way your post was written made it seem to me to be regarding the interference to RGB signals typically caused by using composite video as sync without properly shielding the sync line.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Feb 22, 2020 3:20 am 


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Joined: 01 Sep 2015
Posts: 340
Location: New York
geiger9 wrote:
Currently using s-video on a JVC i'Art CRT. I had planned on using a SCART to YPbPr transcoder with the CRT.


This is the way to go, especially if you are hooking up more than one console. I love my auto scart switcher > transcoder > crt setup, and would recommend it to anybody.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Feb 22, 2020 6:10 pm 


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Joined: 16 Jan 2014
Posts: 927
tjstogy wrote:
geiger9 wrote:
Currently using s-video on a JVC i'Art CRT. I had planned on using a SCART to YPbPr transcoder with the CRT.


This is the way to go, especially if you are hooking up more than one console. I love my auto scart switcher > transcoder > crt setup, and would recommend it to anybody.


Agree 100%. Using Keene SC > CSY 2100 clone > CRT and its near perfect now that I got the Keene fixed.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Wed Feb 26, 2020 11:28 pm 


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Joined: 06 Jul 2013
Posts: 3
On my PAL 1CHIP-01 using borti's 4.1a bypass I am looking for suitable vias to connect to.

Between the S-CPUN and the S-RBG A there are 160 Ohm resistors (R6, R7, R8) on the mainboard,
will these effect the input to the bypass board signal significantly using these via's?
Are these three resistors already considered in the pcb design?
https://photos.app.goo.gl/EBEANh3HcPoYJkYN7
https://www.assembler-games.com/threads ... ost-768707
"are a passive current sink to convert the DAC current to a voltage level"

With regards to R13, R14, R15 being 39Ω "for a PAL cable" should I have
75Ω resistors to ground on the RGB lines ( as wave reflection dampers ? ) ?
https://photos.app.goo.gl/kmoKXtr1dHAsmo8f9


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Tue Jun 30, 2020 5:11 pm 



Joined: 01 Feb 2020
Posts: 5
Just picked up my first SFC from ebay.

Pristine condition :)

High serial but wasn't noted as a 1chip in the auction.

S25002509
1chip-01


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