Jittery picture w/ NES & SNES through A/V receiver

[Drixxel]

I recently picked up a second-hand Denon A/V receiver that upconverts composite & s-video signals to something resembling 480i from its component output and have encountered a bit of weirdness when running an NES or a SNES through it. The receiver is hooked up to a Samsung 720p plasma and handles every other console I've ran through without error except for the NES & SNES which, for whatever reason, experience a strangely shaky/jittery picture. The effect is the same with the SNES whether it's a composite or s-video connection, I've only tested the NES with composite. The actual video processing I find quite pleasing to the eye but the instability of the picture is completely distracting. The Denon manual makes only one mention of this video abnormality, which I'll paraphrase:

When using the video conversion function and the composite or s-video terminals are used to connect the receiver with a VTR, depending on the combination of the TV and VTR the picture may flicker in the horizontal direction, be distorted, be out of sync or not display at all when playing video tapes. If this happens, connect a video stabilizer with a time base corrector function between the receiver and the VTR, or, if your VTR has a time base converter function, turn it on.

The video is fine when connecting the consoles straight to the TV via composite. This particular television doesn't have any s-video inputs, making the receiver's video upconversion of an s-video signal quite appealing. Anyone have any ideas for how to resolve this, or might someone have a good suggestion for either a wacky time base correcting device or a video converter box like this (http://cgi.ebay.ca/ws/eBayISAPI.dll?...=STRK:MEWAX:IT)? Any and all suggestions appreciated.

[Zing]

The receiver may not support a "240p" input. The NES and SNES do not output 480i, but instead use a signal which resembles 240p. There have been many televisions over time which have struggled with up-converting this format. It's possible your receiver does not handle it well.

Any system earlier than the PS2 would be likely to have this problem.

[Drixxel]

That sounds reasonable, but I've hooked up a Genesis 1 & 2, an N64 and a PSX, all with either composite or s-video, and the picture is perfectly fine. While I don't doubt that there may be other older consoles that the receiver dislikes the video signal of, it's just the NES & SNES that are affected from all that I've tested.

[cynicalhat]

The television will always upscale the input to its native resolution. The receiver is trying to upscale as well. This is most likely the conflict. Try and set it so the receiver just passes through the signal without adjusting it and let your display do all the upscaling.

[Drixxel]

Right, and I've found that that works. The receiver's video upconversion can be bypassed by using the signal from its composite output versus its component and we're left with the same image quality as if the NES/SNES were running directly into the TV (no jitters). However, the TV in question does a lousy job of upscaling and the resulting picture is pretty ugly compared to what the receiver produces. Interestingly, there is a perceptible, although slight, difference in the image clarity when connecting the SNES to the receiver via s-video and then from the receiver to the TV via composite. As opposed to straight composite connections all around (no s-video inputs on the TV), the video is cleaned up a tad.

What I'm really hoping for is some kind of a solution that will stabilize the picture when running the NES or SNES through the receiver to enjoy the seemingly-superior video processing. Getting a non-jittery picture is definitely possible by bypassing its video upconversion.

[cynicalhat]

Have you tried putting the display into "game mode" or the equivalent?

[Mr. Smashy]

I think I've had a similar issue before while running an NES on a projector from the late '90s. Basically, it looked as though it was displaying the first 240 lines of the 480i signal where the second set of 240 lines of resolution should be. I'd just power the NES off and on until the signal was properly synchronised.