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Calling all SNES video output experts! HDTV problem ;(
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TheShadowRunner



Joined: 09 Mar 2007
Posts: 83

PostPosted: Fri Jul 11, 2008 5:10 am    Post subject: Calling all SNES video output experts! HDTV problem ;( Reply with quote

Hey All,
I got this weird issue with Super Famicom connected to HDTV via RGB 60hz (scart plug).
The bottom half of the picture looks OK, but the top-half looks interlaced.
It seems as if the SFC is incapable of outputing a correct 480i signal o_O
Tested on 2 SFCs, 2 different RGB scart cables and TV is OK with other 480i signals in RGB via scart like PS1/PS2 or DVD player.
On SDTV it looks absolutely perfect with above equipment thanks to SDTV scanlines but i'm sure the flaw is there too, just hidden.
I'm kinda lost so any help would be greatly appreciated Wink
Pictures + more details on this thread:
http://nfggames.com/forum2/index.php?topic=3263.0

If you don't want to register there, no problem, please just let me know what you think here Wink
Later,

TSR
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Silver



Joined: 21 Dec 2006
Posts: 34

PostPosted: Fri Jul 11, 2008 11:17 am    Post subject: Reply with quote

In answer to one of the questions in the other thread, the snes can output interlaced and progressive:
(wiki quote)

Images may be output at 256 or 512 pixels horizontal resolution and 224, 239, 448, or 478 pixels vertically. Vertical resolutions of 224 or 239 are usually output in progressive scan, while 448 and 478 resolutions are interlaced.

e.g.

Progressive: 256x224, 512x224, 256x239, 512x239
Interlaced: 512x448, 512x478
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TheShadowRunner



Joined: 09 Mar 2007
Posts: 83

PostPosted: Fri Jul 11, 2008 5:25 pm    Post subject: Reply with quote

Silver, thanks for your answer. Do you have exemples for games that are output in progressive, i'd like to try those to see if the flaw is still there.

After much searching, it seems the problem is inherent to the Super Famicom and nothing else.
While scanlines hide the flaw on SDTV; it shows up on HDTV which is much more precise.

If anyone has experience with hooking up Snes to HDTV via RGB signal, i would very much like your feedback.

Problem is that most people using snes on hdtv use composite or svhs and because the signal isn't as pure as RGB, the image flaw isn't visible.

Later,

TSR
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TheShadowRunner



Joined: 09 Mar 2007
Posts: 83

PostPosted: Sun Nov 23, 2008 1:26 pm    Post subject: Reply with quote

Tomy should upgrade phpbb code Confused
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kyuusaku



Joined: 26 Jul 2003
Posts: 941
Location: .ma.us

PostPosted: Sun Nov 23, 2008 7:26 pm    Post subject: Reply with quote

It's not that the flaws are visible on a HDTV, it's that your HDTV isn't a passive device like traditional CRTs so it gets confused at non-standard video.
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TheShadowRunner



Joined: 09 Mar 2007
Posts: 83

PostPosted: Sun Nov 23, 2008 7:52 pm    Post subject: Reply with quote

edit: well yes and no.
The hdtv is certainly deinterlacing, scaling and modifying the signal but the sfc signal isn't perfect to begin with.
http://nfggames.com/forum2/index.php?topic=3263.0
Later,

TSR
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kyuusaku



Joined: 26 Jul 2003
Posts: 941
Location: .ma.us

PostPosted: Sun Nov 23, 2008 8:49 pm    Post subject: Reply with quote

There is no such thing as perfect 240p, it was never intended in the first place. Video games exploit the nature of how interlaced TV toggles fields, and if your HDTV can't deal with it because the engineers were lazy/ignorant, that's not exactly Nintendo's fault. A lot of other consoles output the same video, so this problem shouldn't be SNES exclusive.
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TheShadowRunner



Joined: 09 Mar 2007
Posts: 83

PostPosted: Sun Nov 23, 2008 8:59 pm    Post subject: Reply with quote

well you obviously didn't check the thread i linked.
Ps1 240p works just fine on the same tv.
Later,

TSR
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kyuusaku



Joined: 26 Jul 2003
Posts: 941
Location: .ma.us

PostPosted: Mon Nov 24, 2008 4:42 am    Post subject: Reply with quote

I didn't need to, you obviously didn't notice that I posted multiple times in it (as did Silver) and I'm now just repeating what was said there.

The only difference between 240ps are the pixel rate, and the sync signal clocked out at the pixel rate, which changes with resolution and hardware optimization. One thing they all have in common though is that the sync is meant for relatively tolerant CRTs, and if a HDTV can't do a simple analysis of the signal, again it's the TV's fault. It's really not difficult to correctly detect any video.
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TheShadowRunner



Joined: 09 Mar 2007
Posts: 83

PostPosted: Mon Nov 24, 2008 9:37 am    Post subject: Reply with quote

.. i don't understand why you're repeating that here then.
All was said there already, clear enough for anyone to understand.
Later,

TSR
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kyuusaku



Joined: 26 Jul 2003
Posts: 941
Location: .ma.us

PostPosted: Mon Nov 24, 2008 8:08 pm    Post subject: Reply with quote

I'm repeating it here to assert that it ISN'T the TV's clarity/signal connection/SNES' fault as you stated. If you read the thread, you'd see others agree that the solution is to find another display.
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TheShadowRunner



Joined: 09 Mar 2007
Posts: 83

PostPosted: Mon Nov 24, 2008 9:09 pm    Post subject: Reply with quote

Trust me i did read the thread in its entirety. Cool
It's a combination of both my (and many) HDTV not liking the SFC signal, BECAUSE the SFC signal isn't perfect to begin with.
What sums it up the best is this :
"The timing of the pulses which tell the TV when to start a new line, new field, etc are a bit off. Nintendo (as well as all the others) allowed this because it reduces complexity and they knew they could get away with it - it worked with all TVs of the period."

Quote:
I'm repeating it here to assert that it ISN'T the TV's clarity/signal connection/SNES' fault as you stated


TV clarity? Signal connection? what?
And yes it is partly a SNES fault.
If it weren't, how on earth could you explain why the supposedly similar PS1 240p signal is flawless on the same TV?
Later,

TSR
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kyuusaku



Joined: 26 Jul 2003
Posts: 941
Location: .ma.us

PostPosted: Tue Nov 25, 2008 10:05 pm    Post subject: Reply with quote

TheShadowRunner wrote:
"The timing of the pulses which tell the TV when to start a new line, new field, etc are a bit off. Nintendo (as well as all the others) allowed this because it reduces complexity and they knew they could get away with it - it worked with all TVs of the period."

This is not the issue, all TVs including yours have to be tolerant of timing, what your TV (and his) isn't tolerant of is the signal itself. Obviously yours is detecting Hsync and Vsync fine, and it's locking to it or else lines would be offset like the poster in the other thread.

Quote:
TV clarity? Signal connection? what?

Look a few posts up...
TheShadowRunner wrote:
Problem is that most people using snes on hdtv use composite or svhs and because the signal isn't as pure as RGB, the image flaw isn't visible.

TheShadowRunner wrote:
On SDTV it looks absolutely perfect with above equipment thanks to SDTV scanlines but i'm sure the flaw is there too, just hidden.


TheShadowRunner wrote:
If it weren't, how on earth could you explain why the supposedly similar PS1 240p signal is flawless on the same TV?
I've already explained that, 240p from one console isn't the same as 240p from another, most importantly 240p can be 262 or 263 lines (or even fewer/more lines for arcade games) as long as the horizontal and vertical frequency is within tolerance. This isn't the issue as a lot of consoles are further from "spec" (which doesn't exist) than the SNES. Your TV's algorithm is to blame, most likely in detection.
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TheShadowRunner



Joined: 09 Mar 2007
Posts: 83

PostPosted: Wed Nov 26, 2008 2:33 pm    Post subject: Reply with quote

Quote:
Look a few posts up...
TheShadowRunner wrote:
Problem is that most people using snes on hdtv use composite or svhs and because the signal isn't as pure as RGB, the image flaw isn't visible.

TheShadowRunner wrote:
On SDTV it looks absolutely perfect with above equipment thanks to SDTV scanlines but i'm sure the flaw is there too, just hidden.


Well that's just what i see with my own eyes. Embarassed
On the same Sony HDTV, the flaw shows up in RGB (SFC connected via Scart), but doesn't show up with SVHS (SFC connected via Svideo).
What I came up with to explain this was that the signal wasn't as pure with SVideo therefore the flaw was hidden. If not that, possibly the HDTV is more tolerant to the SFC signal via SVHS than it is via RGB then? I can't think of anything else.

Quote:
I've already explained that, 240p from one console isn't the same as 240p from another, most importantly 240p can be 262 or 263 lines (or even fewer/more lines for arcade games) as long as the horizontal and vertical frequency is within tolerance. This isn't the issue as a lot of consoles are further from "spec" (which doesn't exist) than the SNES. Your TV's algorithm is to blame, most likely in detection.


OK thanks for these extra precisions. I've settled for SVideo and it works fine for me so I'm pretty much done looking into why my tv doesn't like the SFC via RGB anyway, but it's nice to know more details about this (specifically that 240p can be 262 or 263 lines.. i would never have thought it could change from device to device).
See you,

TSR
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kyuusaku



Joined: 26 Jul 2003
Posts: 941
Location: .ma.us

PostPosted: Wed Nov 26, 2008 9:51 pm    Post subject: Reply with quote

If it works fine through the S-Video port on the same TV, then there must be a bug in the SCART code. Apart from the video clarity, the sync and timing is exactly the same between the two connections. Perhaps VGA and SCART share the same algorithm, and since it doesn't detect the video as 480i, it assumes a custom VGA mode (normally you'd have to manually adjust).
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