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vertical line artifact on SD 8 bit footage
This is a very particular, odd behavior I am seeing in FCP 5.1.4. I ran into into it while onlining a project for a client to 525 29.97 8bit uncompressed, but I can recreate the problem using good old fashion black slug.
Here’s the situation:
Place any Final Cut generator (text, Title 3D, Joe’s etc) on a layer above an 8-bit Uncompressed clip with black footage and you will see 4 gray, vertical lines,very close to each other, along the right-most edge of the screen. They can be seen in the FCP Canvas as well as an external video monitor if you’ve got a Kona or BM card and the monitor is set to underscan. (Make your FCP canvas larger to be sure you can see it).
Now, I can only see these lines when the footage contains black, as my client’s clips did. You can recreate this by making some slug in an 8bit timeline and exporting a Quicktime. Then bring this 8bit slug Quicktime back in to FCP and do as above. It doesn’t matter what kind of timeline I use, 8bit, 10bit, or DV; if the video clip under the generator is 8bit it will produce these line. Doing the same with DV or 10 bit Quicktimes of the same black slug does not create the lines. The only way to get rid of it if using an 8bit clip is to render that timeline in RGB rather than 8bit or 10bit High Precision.
Has anyone seen this or can confirm it occurs if they follow the above instructions? Again, it is only visible over black footage, any other colors do not produce it. Have confirmed on both our systems.
System: Quad G5, FCP 5.1.4, Kona 3, QT 7.1.6
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4 Replies
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Yes. I see the lines on the right side of the screen. I used a slug and exported it, then re-imported it back into the timeline. However, I do have mixed results:
When the 8bit Text generator is placed over the original slug, there are no artifact lines.
When the 8bit Text generator is placed over the 8bit re-imported slug there are artifact lines.
I have the same result with Title 3D, but
-not Matte Color Solid and
-not BCC4 Mixed Colors (turn brightness down all the way).The lines are about 8 IRE (flat) on an external scope and not far from that on FCP’s internal scope.
I had similar results in a 10bit timeline as well. Sometimes in both it looked fine until it was rendered.
FCP 5.1.2
QT 7.1.3
AJA Kona LH -
Sort of glad to hear corroboration, but concerned about the cause and what should be done. I haven’t found 10 bit to cause it at all regardless of rendering. I may be misreading your post, but I still see it when I create a Quicktime of solid black matte and reimport. It seems to only exist on black.
I can’t believe no one has brought this up before.
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I almost never work in 8-bit. Maybe once this year. I’ve had several documented artifacts in 10bit, most noticeably in white over white and Broadcast safe filter.
I don’t think I would’ve noticed had you not pointed it out. Sometimes I don’t see it until I’ve rendered.
In my 8bit timeline, I don’t see the lines on my re-imported black slug until I put a generated black on top of it in track V2, and then only some of the generators show it.
In my 10bit timeline, I don’t see the lines on my re-imported clip until I render the clip (with no generators above it). -
Hello,
I am experiencing this issue now because I am working on an older project and getting ready to burn it to DVD for screening.
I specifically noticed this on a few dark frames of my source footage and the newly generated title sequence I created (which makes sense based on what your saying about generated blacks).
Would you have any further info on this issue? Also, do you know if it would be possible to re-render at a higher bit-rate and then export to get rid of the lines?
I am dealing with a DV 720×480 project at 29.97. Thanks in advanced for any help!
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