Flicker On The Bottom Of The Screen During FCP Dissolve at DVinfo.net

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Old July 9th, 2008, 09:33 AM   #1
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Flicker On The Bottom Of The Screen During FCP Dissolve

i've been experiencing this issue for years, and i've never been able to figure it out. sometimes during a dissolve, there is a 1-6 pixel flicker on the bottom of the screen. it has occurred with DV or HDV footage, and with various version of FCP over the years. it seems to happen more frequently when there are filters on the clips. it's not noticeable with full-frame NTSC, because the television usually crops it off. but with anamorphic video, it's very annoying. i've searched around, but could not find any mention of this on the net...but i'm sure someone else out there has noticed it. any ideas?
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Old July 14th, 2008, 10:43 AM   #2
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I have no idea, but someone did show me a problem they had where their exported quicktime flashed whenever a lower third bar faded in. They hit apple J for the movie properties (in quicktime), and I think what the did was click the video track and in visual settings there's a drop down menu that says transparency. Selecting one of those fixed it. (this is all from memory though).
At one time I did an edit where at the end of every dissolve I got a flash frame from the previous clip. That was really weird but it did not appear in the final export, so I didn't care.
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Old July 14th, 2008, 12:35 PM   #3
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Quote:
At one time I did an edit where at the end of every dissolve I got a flash frame from the previous clip. That was really weird but it did not appear in the final export, so I didn't care.
I get this all the time...I almost always use an opacity key frame for fade outs now, but it's interesting to hear the same problem occurring for others.
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Old July 24th, 2008, 10:00 AM   #4
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this is still driving me NUTS! if anyone has any suggestions, please let me know...
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Old July 24th, 2008, 10:35 AM   #5
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Edit: I thought it may be video tearing, which is common in your canvas, especially if it is set to "fit to window" and not 100%. but after reading the post a 3rd time, I don't think I understand what your describing. You are literally seeing a 1 pixel imperfection?
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Old July 24th, 2008, 04:53 PM   #6
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it manifests itself a few different ways...it is either a white flashing line that runs along the bottom of the canvas, flashing "on" and "off" every frame (i zoomed in on a screen grab and noticed the "flashing white line" varies from 1-5 pixels in height).

it sometimes also appears much taller, but more opaque...so the bottom 20-30 pixels on the screen flashes during the fade, but it's not a solid white line of interference...it's more like every frame get, the bottom of the screen gets quickly darker and lighter.

it's tough to describe. i don't even understand it when i read it back. i'll upload a video later tonight. tough to describe, easy to see.
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Old July 24th, 2008, 05:17 PM   #7
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see the bottom of the video during the crossfade? this isn't a problem with 4:3 video, because the television usually crops it off...but with 16:9 material, it can be seen. it doesn't happen with every fade. i can't figure out why it does happen...i can't link it to a certain effect or type of shot, it just pops up every once in a while:

http://www.thebrotherkite.com/stuff/issue.mov
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Old July 28th, 2008, 04:27 PM   #8
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i used "apple-zero" to changed the field dominance of the sequence from "lower" to "none", and the problem went away. why is that? is it a good idea to change the field dominance to "none"?
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Old July 28th, 2008, 04:41 PM   #9
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well, it seems there is significant aliasing noise introduced when i set the field dominance to "none." so it seems like the flickering is related to interlacing somehow. man...
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Old July 28th, 2008, 05:48 PM   #10
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setting the field dominance to "none" also creates a "stroby" image in general. so even though it fixes the flicker on the bottom of the screen during the transition, it creates new problems...if anyone knows why this is happening, please let me know.
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Old July 28th, 2008, 06:05 PM   #11
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John, just to make sure, there is no imperfection in either the outgoing or incoming clip, right?

What version of FCP?
What codec is the source footage?
What codec are you editing with?
Have you tried deleting the render files and re-rendering?
Does the effect happen if you just do a dissolve with the two clips in a new sequence?

Curious to know what is causing this...
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Old July 28th, 2008, 06:26 PM   #12
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hi david,

Powermac G5 (OSX 10.4.11)
FCP 5.0.4
Footage is anamorphic DV, captured with FCP's DV NTSC Anamorphic preset
Sequence is FCP's DV NTSC Anamorphic preset

yes, i've re-rendered. i've also tried pasting the clips into a new sequence with different settings (DV50, Uncompressed 8-bit), and it doesn't help. it only happens during a dissolve between two clips with effects. it is not specific to certain effects...and i've tried all the different dissolve types, and a bunch of different effects...it's completely random.
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Old July 28th, 2008, 07:20 PM   #13
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so it's related to Frame Blending...

when i unchecked "Frame Blending" in the "Speed" menu, it fixed it. of course, the slow motion is not quite as smooth, but i'll take that over the flickering image.

does anyone know of a better slow motion plugin for FCP? something that will allow me to use Frame Blending for smooth slow mo without the flicker crap?
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Old July 29th, 2008, 05:46 PM   #14
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I've seen this too, but with all progressive material. its like the last couple of lines are blended into the underlying video. all 720P24 material in a prores TL, both PPC and intel and since at least FCP5.1, currently on 6.0.4
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Old July 29th, 2008, 09:28 PM   #15
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steve, does yours go away when you turn off Frame Blending?
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