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Old July 13th, 2003, 11:28 AM   #1
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Pulsing image on HD Monitor

I recently made a new "investment" in a 34" widescreen Sony WEGA HDTV. Now other than making my DV footage look like so much aliased doo doo, I have noticed a peculiar problem.

When viewing footage from my g4 dual 1gig running FCP3, ported thru either my sony editing deck or my gl2, I get this strange pulsing of the image...it's semi-regular in nature...two pulses followed by a pause, and it seems to affect mid to 3/4 tones of the image by shifting them (in a ghosted fashion) several pixels to the right. I noticed it first on some footage where there wasn't any camera or subject movement, then I paused the footage and it continued in the still frame as well.

I have narrowed this down to the computer itself, as changing cables, decks and other connections had no effect. Footage viewed directly from the camera (including the same pulsing footage recorded onto tape) shows no problem whatsoever...the image is completely stable, as is anything viewed on DVD. The pulsing is relatively slow, not like interlacing jitter, and it happens on all viewing modes of the tv.

I don't know if I saw this on my old zenith 25 inch...which I no longer have to check...but it seems odd that the only source that causes this is the G4.

Any Ideas?
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Old July 13th, 2003, 12:10 PM   #2
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The pulsing is only visible when the video is played back from the G4? It could be some type of ground loop or RF effecting the video card.
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Old July 13th, 2003, 01:02 PM   #3
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Yep. just the g4...nothing else.

I'm not much of an electrical genius...what would rectify this, if it is indeed the problem...I tried putting one of those magnet doo-dads...(shield?) on the firewire cable, and it didn't stop the problem. I also tried running the cables (FW and S-video) in a path away from the rest of the cabling..no dice. The computer is plugged into a typical powerstrip/surgeprotector...nothing fancy, but not a cheapo one either.

I'm going to try hooking up to my laptop, and see if it does it as well, and I'll also check it with my field monitor.....

thanks for your help.

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Old July 13th, 2003, 03:48 PM   #4
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Post back what the laptop does when powered from battery. Also try the G4 just plugged into the wall, bypass the surge protector.
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Old July 14th, 2003, 08:47 PM   #5
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Ok...

1. I tried running from the laptop onto the HD set...and no pulsing (I only have iMovie on this machine...and I was only able to playback by exporting to tape...so I couldn't stop the footage to really look...but I didn't see any of the fluttering evident in the g4 FCP situation).

2. I tried plugging the computer and TV into several outlets in the house, trying to separate them and combine them onto different circuits. Nothing helped. Pulsing...Pulsing...pulsing. Also changed power cords on the computer.

3. I viewed the footage through my JVC field monitor...no pulsing evident

this is really wierd.

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Old July 15th, 2003, 08:03 AM   #6
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Through what equipment are you routing this? Sounds a bit like
"macrovision" protection....
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Old July 15th, 2003, 11:02 AM   #7
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Its just my g4 running FCP3 through either my sony walkman (gr300u?) editing deck, or a gl2 into the Sony 34" HD.

It's not something I'm proud of, but I usually go unprotected.

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Old July 15th, 2003, 02:54 PM   #8
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Was the field monitor battery or AC powered. Almost always, these pulsing issues are power supply or AC ground related. I've checked out a lot of surge protectors and they can do weird things to the current. I'm not sure I can help much further.
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Old July 15th, 2003, 03:38 PM   #9
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Is yr GL2 or GR300 also battery powered
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Old July 15th, 2003, 03:46 PM   #10
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The JVC monitor was AC powered. The gl2 was running on battery, the sony deck is hooked up to AC, but uses a dc transformer.

any chance this is just a defective video card on the g4?..although it seems unlikely, as the image recorded to tape is fine.

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Old July 15th, 2003, 04:01 PM   #11
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Some monitors have straps for gounding issues like cabinet grounding, mains to signal ground interconnection...Does the JVC have selectable gounding?
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Old July 15th, 2003, 04:26 PM   #12
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Not that I know of...remember though, the problem is with the Sony WEGA widescreen ...it should be acceptably grounded through the wall socket ( and I've tried it hooked to several outlets)... I'm still convinced this has more to do with the g4...as the camera and deck by themselves cause no problem, nor does my dvd player (AC) or the laptop...only footage viewed from the g4 has a problem.

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Old July 15th, 2003, 09:28 PM   #13
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Do you have a three prong to two prong adapter? They bypass the ground and you can tell if you have a ground loop causing the problem. Ground loops can generate dangerous charges so be careful.

If the pulsing is still present, after the above, I would suspect the power supply in the G4 or excess RF interfering with the video card. Since the video card is AGP it can't be moved to check RF problems.
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Old July 16th, 2003, 10:45 AM   #14
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Thanks for the help jeff & andre...My outlets are all 3 prong as are my power cords..I'm going to do one more test...hooking up my older g4...and if this causes no problem..then its time to go talk to my apple guy...just wanted to see if there were any options I hadn't thought of...

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Old July 16th, 2003, 02:18 PM   #15
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Barry, one of the possibilities is that you are getting feedback through the ground. This is called a ground loop. One way to check for a ground loop is to use a 3 prong to 2 prong connector (sometimes referred to as a cheater). It is not a permanent solution as ground loops can be very dangerous. But it can point you in the right direction for finding the proper solution.
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