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Why are there occasional black flashes in my exported video?

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Noam Osband
Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 4:02:41 pm

I exported a video from FCP 7. There are no gaps in the timeline. But in the exported video, occasionally there is a quick black frame between cuts, as if there was a frame or two open. Again, I've checked the timeline and that is definitely not the case. Any thoughts?


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Noam Osband
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 4:05:53 pm

I should say I wonder if it's related to the fact some of the footage was shot in 24 fps but when I look at the info of the clip in the browser, it says it is 29 fps. I dont know why/how that happened. I never changed it and I dont think Log and Transfer changes it. So frustrating.


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Shane Ross
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:11:30 pm

What was this shot with? Some cameras shoot a 24p that's still 29.97, but with the 24p "look." So it may appear to be 24fps, but really run at 29.97.

And since you mention LOG and TRANSFER that all the footage was converted to ProRes.

Is your sequence settings 29.97? Does it match the footage exactly? Meaning when you added a clip, did you need to render?

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Noam Osband
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:13:17 pm

Yeah, I dont get it. I shot in 24p. For sure. But the video does look 24fps even if the file is 30fps. When I exported as 30fps, the problem disappeared. Hmmm.....


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Shane Ross
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:15:20 pm

Then you shot a 24p format that runs at 30fps. And when you export from FCP, you should always export a self contained QT file, and do whatever compressing in Compressor. You might even be able to do a REVERSE TELECINE and get it to 24fps and look fine.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Noam Osband
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:17:46 pm

I'm not sure that means, a 24fps that runs at 30fps. Can you link me to an article or something with more info to explain it?

thanks as always!


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Shane Ross
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:21:41 pm

The short explaination is that it's like when we take film, shot at 24pfs, and transfer it to video tape, that runs at 29.97. PULLDOWN is added...frames are spread out amongst the fields of the interlaced 29.97 so that 6 extra frames (from 24 to 30) are added, and smoothly. And many early video cameras, and some current ones, still do this...have the 24fps LOOK, but really run at 29.97.

http://en.wikipedia.org/wiki/Telecine#2:3_pulldown

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Dave LaRonde
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:29:24 pm

[Noam Osband] "I'm not sure that means, a 24fps that runs at 30fps. "

Open the FCP project in question. Highlight one of the 24P clips. look at the frame rate. What does it say?

If it's 29.97, the clip contains 3:2 pulldown.
It it's 23.98 or 23.976, it means you cut in the wrong frame rate.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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David Roth Weiss
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:36:23 pm

Noam, you never answered Shane's question. What cam was used to shoot the material in questionl?

David Roth Weiss
Director/Editor/Colorist
David Weiss Productions


David is a Creative COW contributing editor and a forum host of the Apple Final Cut Pro forum.


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Noam Osband
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:37:04 pm

It was a Canon XA-10


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Shane Ross
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:42:08 pm

You must have shot in PF24 mode, and not native 24.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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David Roth Weiss
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:46:45 pm

Your canera shoots two versions of 24 fps video - the PF24 generates 60i files encoded in order to be able to apply a pulldown removal; 24p generated true progressive output at 23.978 framerate without pulldown.

Sounds as if you shot at PF24.

David Roth Weiss
Director/Editor/Colorist
David Weiss Productions


David is a Creative COW contributing editor and a forum host of the Apple Final Cut Pro forum.


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Noam Osband
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:50:03 pm

Oy. I thought shooting in PF24 was the right move for a film in 24fps. Was I wrong about that? I realize phrasing the question that way is a bit naive.


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Shane Ross
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:51:34 pm

If you want 24fps, then you need to use the Native 24p setting.

PF24 shoots 24p at 29.97

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Noam Osband
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 5:53:04 pm

I can't believe I completely mixed that up. I thought I had it right. Is there a way to import PF24 so it'll play like 24fps?


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Shane Ross
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 7:00:06 pm

[Noam Osband] "Is there a way to import PF24 so it'll play like 24fps?"

Not on import...because it's not flagged as 24p ADVANCED...advanced meaning that it's ripe for pulldown removal. You might be able to reverse telecine (Compressor does this) after it's imported. But that would mean completely recutting your sequence. You can try to reverse telecine your full res output, but that's not ideal, and might not look right.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Dave LaRonde
Re: Why are there occasional black flashes in my exported video?
on Feb 13, 2015 at 11:51:32 pm
Last Edited By Dave LaRonde on Feb 13, 2015 at 11:59:48 pm

I'll go a step further than Shane and say you MUST recut after removing the pulldown.

Here's why: when pulldown is added to 29.97 video, it's added in a specific CADENCE of whole frames and split frames. In this cadence, there are two whole frames in a row: they look just fine. The split frames show evidence of interlacing.

I have five whole American dollars that say someplace in your current edit, you set in & out points on the 29.97 clips that are off-cadence. If you try to remove pulldown from your current edit, things will indeed look goofy.

I know, I know, you're thinking "ugh -- that's a lot of work" as you read this. It won't hurt to TRY to remove the pulldown from the current edit, just be prepared for a little disappointment. Maybe a lot of disappointment, and that's when you have to re-cut.

But there is a silver lining to this cloud. You've learned two things.
First, you've learned to double-check the workings of your camera so you KNOW it's properly set.
Second, you probably also learned that it's good practice to run tests on a new piece of gear or a new piece of software BEFORE you jump into the deep end of the pool.

When my daughter was three years old, she grabbed the business end of a sparkler just after the sparks stopped. Yipes! Hot! Pain! She never, EVER made that mistake again.

You're in the same boat with my kid Gretchen.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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