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High video level causing jitter

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Tom Brooks
High video level causing jitter
on Dec 9, 2006 at 3:11:53 pm

After editing a sequence for what seemed like quite a while with no problems, some of my clips began to jump and jitter vertically. Turned out it was the scenes that had a light fixture in the scene that was overexposed and hitting about 110 IRE on the analog waveform monitor. Color correcting the highlights down a notch fixed the problem. Of course, this is the whole reason for preventing out-of-spec video, but in the non-broadcast world, I occasionally let small areas go. This was a large fluorescent fixture, so it was more than a minor specular highlight. Nonetheless, I was taken aback at the LHe's sensitivity to this and my impression that it got worse over time. Is this normal for the LHe?

PS-Turning on the "Limit to legal levels" switch also cleared up the problem. If the rest of my footage was within legal spec, would this be a recommended fix?

Final Cut Studio, FCP 5.1.2, After Effects 6.5 Pro, Quicktime 7.1.3, G5 Quad 2.5, Kona-LHe V3, 4.5GB RAM, Nvidia GeForce 7800-GT, G-RAID 2x1TB FW800.


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walter biscardi
Re: High video level causing jitter
on Dec 9, 2006 at 3:34:06 pm

110 normally doesn't cause a jitter, but the flourescent light sure would. It has an inherrent flicker when viewed on a video monitor and anything above 100 would enhance that flicker. Depending on the monitor you're using to actually view the output of your LHe, that would also determine how badly your image would be affected.

Walter Biscardi, Jr.
http://www.biscardicreative.com
HD Editorial & Animation for Food Network's "Good Eats"
HD Editorial for "Assignment Earth"

"I reject your reality and substitute my own!" - Adam Savage, Mythbusters


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Tom Brooks
Re: High video level causing jitter
on Dec 9, 2006 at 9:48:47 pm

I don't mean a mere flicker of an element within the frame, but rather vertical instability of the whole frame. It jumps up and down about 10 lines worth.

Final Cut Studio, FCP 5.1.2, After Effects 6.5 Pro, Quicktime 7.1.3, G5 Quad 2.5, Kona-LHe V3, 4.5GB RAM, Nvidia GeForce 7800-GT, G-RAID 2x1TB FW800.


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walter biscardi
Re: High video level causing jitter
on Dec 9, 2006 at 9:52:53 pm

[Tom Brooks] "I don't mean a mere flicker of an element within the frame, but rather vertical instability of the whole frame. It jumps up and down about 10 lines worth."

I've never seen anything like that here.

Walter Biscardi, Jr.
http://www.biscardicreative.com
HD Editorial & Animation for Food Network's "Good Eats"
HD Editorial for "Assignment Earth"

"I reject your reality and substitute my own!" - Adam Savage, Mythbusters


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Bob Zelin
Re: High video level causing jitter
on Dec 9, 2006 at 9:53:18 pm

Are you seeing this flicker only in FCP. Many VTR's can't handle hi video levels, and many TV monitors have clamping issues with illegal levels. If this signal looks ok directly out of the VTR into your TV, but only jitters when digitized into FCP, and then flickers - I would be very surprised. Digital capture cards simply clip the video.

Bob Zelin


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Tom Brooks
Re: High video level causing jitter
on Dec 9, 2006 at 11:11:53 pm

[Bob Zelin] "Are you seeing this flicker only in FCP."

I captured straight FW into FCP, so I didn't really analyze the video prior to that, but would have to answer, yes, it's only coming out of FCP. It doesn't jump in the Canvas either, only on the output from the Kona.

I tried a couple monitors (Sony PVM type) with identical results, so I can rule out a flaky monitor.

And, color correcting the highlights down OR using the Kona's "limit to legal video levels" switch fixed the jumping. I think the hot spot from the light is actally spiking chroma down into the vertical sync area. I've just never seen this coming out of an NLE system before--they usually clip things to the point where this can't happen. The levels might be illegal, but not to the point of causing sync problems.




Final Cut Studio, FCP 5.1.2, After Effects 6.5 Pro, Quicktime 7.1.3, G5 Quad 2.5, Kona-LHe V3, 4.5GB RAM, Nvidia GeForce 7800-GT, G-RAID 2x1TB FW800.


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JeremyG
Re: High video level causing jitter
on Dec 11, 2006 at 4:00:04 pm

I am having a problem in hot areas of video as well. I am working in 10 bit uncompressed. This only happens to me on clips that have been scaled and instead of a jitter I get a plaid pattern throughout all the hot highlights. SOmeone else noticed this exact problem on the FCP forum as well and has contacted AJA. THe pattern does not show up in any quicktime movie, only on external displays. The only way I can get rid of it is to render in 8 bit or correct all the highlights way down and then the pattern goes away. What codec are you working in?

Jeremy


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John Christie
Re: High video level causing jitter
on Dec 11, 2006 at 5:24:06 pm

I've seen this as well with some consumer level DV imported into a DV 50 timeline using a Kona LHe. As it was an offline edit and there were only a few shots in the timeline from that source, a quick broadcast safe filter took care of the problem.

However, for final mastering it's important to look at the offending clips on a scope and use colour correction filters to bring the levels down, don't just rely on the broadcast safe filter.

Cheers

John Christie


Keyframes Editing



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JeremyG
Re: High video level causing jitter
on Dec 11, 2006 at 5:30:46 pm

In my case, this happens with whites that are well within broadcast safe. I have to turn them near grey before the pattern goes away.


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Tom Brooks
Re: High video level causing jitter
on Dec 11, 2006 at 9:01:13 pm

My shot in question is plain old mini-DV shot on an HVX-200. Very much a run & gun type of shot. On the waveform outside of FCP, the light sources is hitting right at 110 IRE and it is just starting to clip at that point. If I color correct the highlights down, the problem gets better. If I go the other way and make it worse, what I see on the scope as the white clips, is sort of a phantom baseline below the 0 IRE line. When this happens the video starts really jumping. I guess the initial learning here is that the LHe is not very forgiving of clipped levels above 100 IRE. If you throw that kind of garbage into it, it throws something else back out at you. Thanks for your thoughts.


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JeremyG
Re: High video level causing jitter
on Dec 11, 2006 at 9:05:43 pm

Hmm, I'd put your call or email into AJA tech support.

For the record, my base levels are NOT above 100 ire and they are still busted.


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Ramona Howard
Re: High video level causing jitter
on Dec 11, 2006 at 10:53:20 pm

In 6 years we have never seen this issue using the AJA boards. We do encounter hot levels and do not limit the incoming video (the image is exactly what comes in). I would think this is a FCP/AJA issue, giving them a call should yield results.

Good luck,
Ramona



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Tom Brooks
Re: High video level causing jitter
on Dec 12, 2006 at 1:51:20 am

Will do.


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JeremyG
Re: High video level causing jitter
on Dec 12, 2006 at 2:41:39 am

Hey Ramona, if you can, can you capture a 10 bit clip, scale it, and tell me what you see in the highlights on a monitor?

Here's the link to a previous problem:

http://forums.creativecow.net/cgi-bin/new_read_post.cgi?forumid=8&postid=91...


My original link:

http://forums.creativecow.net/cgi-bin/new_read_post.cgi?forumid=98&postid=8...

AJA was able to replicate it, but I have not heard back. I meant to call them today but I ran out of time. This problem is biting me all day again today.

Never had this problem until FCP 5.1.2

Jeremy




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Kevin Wild
Re: High video level causing jitter
on Dec 12, 2006 at 3:22:04 am

I have been having this EXACT problem. I was dealing with some very nicely shot run and gun footage from digital beta source tapes. On my plasma (component out of the AJA LHe), it was doing occasional jitters that resembled a sync problem. Thanks to reading this post last night, I threw on the broadcast safe filter and the problem immediately disappeared.

That said, it reminds me of another problem I was having last week. I was getting a ton of shaky, jitty footage from some HVX200, DV clips. I attributed it to it being shot anamorphic and the flag being screwed up, because I would change the number in the distort menu to -33.3 and make it unrendered and it would stop. If I would render it, the jitter came back.

So, both of these problems are very similar. It's possible that there is something going on in 5.2.1 and AJA's latest that is being goofy on the component output. I've never had problems with my setup before, so I hope they figure something out.

Thanks.

Kevin


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R.Howard
Re: High video level causing jitter
on Dec 12, 2006 at 3:33:52 am

Sure, what do you wish it to be scaled with.(we don't use FCP). I do remember reading your thread. I don't think I have any 720 content on our systems, pretty much all 1080 (both 8 & 10bit) and it's all been captured over SDI, not FW and no DVCproHD.

We and our customer have manipulated images coming thru the AJA boards pretty much every way you can think of with nothing like this. Which is why I'm pretty sure it's the combination and not just the AJA hardware.

Anyway let me know what exactly you need and I will send you a few frames.

Cheers,
Ramona

Ramona Howard
SpectSoft, LLC
593 Hi-Tech Parkway Suite B
Oakdale, CA 95361
Phone: 209.847.7812 extension 104
Fax: 209.847.7859
http://www.spectsoft.com

RaveHD - Changing the way you think about HD


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JeremyG
Re: High video level causing jitter
on Dec 12, 2006 at 3:40:36 am

Well shoot, Ramona, I appreciate your enthusiasm but I didn't realize you were FCP free. I'm sure it's a silly FCP thing, or more likely an Apple 10bit codec dealy but that is just my hunch.

Thanks for the offer, though.

Jeremy


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R.Howard
Re: High video level causing jitter
on Dec 12, 2006 at 3:51:20 am

Actually if you send me your email I will send you a few frames which may help narrow a few things down.

We wrote our own driver for the AJA boards and again do nothing to the image. I do have some 720 stuff that we captured in as both 8bit and 10bit.

Let me know,
Ramona@spectsoft.com

Ramona Howard
SpectSoft, LLC
593 Hi-Tech Parkway Suite B
Oakdale, CA 95361
Phone: 209.847.7812 extension 104
Fax: 209.847.7859
http://www.spectsoft.com

RaveHD - Changing the way you think about HD


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JeremyG
Re: High video level causing jitter
on Dec 12, 2006 at 4:24:50 am

Done and done.

Thanks!


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Tom Brooks
Re: High video level causing jitter-AJA response
on Dec 25, 2006 at 5:44:14 pm

I got a call back from AJA. The engineer said that the Kona will pass video through it untouched, no matter what the level. If you feed it wildly overexposed video, it will pass it through just the same--not clipped at all or modified in any way. So, it could be that it's inside FCP that the over-level video is getting messed up. I'm not sure how I could put this to the test. I could however test the Kona card. I'll just run some component analog through it and compare input to output. Should be the same, no matter what the input looks like. I'll let you know when I get time.

Final Cut Studio, FCP 5.1.2, After Effects 6.5 Pro, Quicktime 7.1.3, G5 Quad 2.5, Kona-LHe V3, 4.5GB RAM, Nvidia GeForce 7800-GT, G-RAID 2x1TB FW800.


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Kevin Wild
Re: High video level causing jitter-AJA response
on Dec 26, 2006 at 6:17:40 am

Sure, but there is no problem on my computer monitor...it's only on the output to my Plasma, so it could be FCP.

Is it just coincidence that they took away the broadcast safe setting for Kona and this is happening? Could it have had a bug or something? Not sure, but putting the b'cast safe filter on from FCP fixes the jitter.

Thanks for following up.

Kevin


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Tom Brooks
Re: High video level causing jitter-AJA OK-more notes
on Jan 6, 2007 at 7:10:27 pm

Kevin,
Not sure you're still following this thread, but I did test the Kona yesterday and it's picture perfect. As AJA predicted, anything I ran through it came out clean on the other end.

Lots of my video with high levels in it has the jitter problem. The jitter appears on one or two frames at a time. It happens on clipped blue sky shots and anything with a lot of white in it. One frame will have the jitter and the next will be steady. Using the color corrector, taking the highlight levels down one tick from 255 to 254 gets rid of the jitter. I don't get what's going on here at all. I even bought a new firewire cable but that made no difference. I'll post this on FCP and see what I get.
-Tom

Final Cut Studio, FCP 5.1.2, After Effects 6.5 Pro, Quicktime 7.1.3, G5 Quad 2.5, Kona-LHe V3, 4.5GB RAM, Nvidia GeForce 7800-GT, G-RAID 2x1TB FW800.


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