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How do interlaced frames work? [ANSWER]

Posted: Fri, 30th Dec 2005, 2:26am

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GeneralGrievous

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Can someone explain to me how interlaced frames work in EL.When I shot the footage with a mini dv camera and on one part of the scene it looks like there is an extra pair of blades.

Thanks
Posted: Fri, 30th Dec 2005, 8:29am

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Hendo

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GeneralGrievous wrote:

Can someone explain to me how interlaced frames work in EL.When I shot the footage with a mini dv camera and on one part of the scene it looks like there is an extra pair of blades.
When you create an interlaced project, ELab will treat each interlaced field as its own frame in the timeline. When you render your project, ELab will combine the fields back together again into an interlaced video.

For example, a 4 second PAL DV clip is 100 interlaced frames (4 x 25). In ELab, you will see 200 frames in the timeline (as long as you created an interlaced project). But when you render your project, the output will be 100 interlaced frames.

As for the "extra pair of blades" in your footage, I'm guessing that this appears when the blades are in fast motion. Maybe you could post a screenshot? (You can upload an image to http://imageshack.us for free.)
Posted: Fri, 30th Dec 2005, 8:58am

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GeneralGrievous

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Ok that makes sense, thanks.

How would I be able to tell in EL if my project is interlaced? I don't remember what I chose origonally.
So then do I just ignore every other frame? Is the 1st frame the real frame?

Maybe it was dark and my camera was having trouble keeping up. They were moving fast.

I could upload a 22.5 meg avi. of it.

Thanks
Posted: Fri, 30th Dec 2005, 9:07am

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Hendo

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Rating: +1

GeneralGrievous wrote:

How would I be able to tell in EL if my project is interlaced? I don't remember what I chose origonally.
There's no window that you can bring up to tell you. But it's probably interlaced. ELab detects what kind of footage it is when you create a project. So if you're using a DV clip and you just accepted the default values in the Project Settings window, then the project will be interlaced.

One method you can try is: Import a new stock media object, right-click it and choose 'Media Properties', then look at the 'Scan Method'. It defaults to what the project is using.

Another way of telling is to compare the number of frames in the timeline to your source movie. If the ELab project is interlaced then the timeline will contain twice the number of frames as the source movie.

GeneralGrievous wrote:

So then do I just ignore every other frame? Is the 1st frame the real frame?
No, you need to work on all the frames in the timeline. Sorry if I was unclear on that. If you skip a frame then it will affect the output render when ELab tries to combine the 2 fields together.

Try rendering a short test (like 50 frames) so that you can see what it looks like. Use the In and Out points to select the area that you want to render.

GeneralGrievous wrote:

I could upload a 22.5 meg avi. of it.
Since you're on Windows, you may find VirtualDub quite useful. Among many other things, it will let you copy a frame of an AVI video which you can then save as an image and upload onto the web. Much easier for people to download than 22 MB. smile
Posted: Sun, 1st Jan 2006, 12:13pm

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GeneralGrievous

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It looks like every other frame is a fraction of a second behind the one in front of it.

I'm confused sad
Posted: Sun, 1st Jan 2006, 1:49pm

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SGB

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I think you tried making it a "progresive" project, instead of an "interlaced" one.
Posted: Sun, 1st Jan 2006, 4:22pm

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GeneralGrievous

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It's interlaced. It's like the interlaced frames EL put in are a fraction of a second behind the real frames.
Posted: Sun, 1st Jan 2006, 4:37pm

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SGB

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that has happened to me before. try changing the type of interlacing, like if you have interlace odd, make it interlace even and vice versa.

this has happened to me before. all i can say is try making a new project and re-importing the footage making sure to use a different kind of interlacing.
Posted: Mon, 2nd Jan 2006, 10:32am

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Simon K Jones

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Yes, if frames are jumping back and forth in time it's because you're using the wrong type of interlaced project. Simply switch it from Odd to Even (or vice versa) in the project settings.
Posted: Tue, 3rd Jan 2006, 9:48am

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GeneralGrievous

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I switched it to odd interlaced instead of even and it looks fine.
Thanks
Posted: Thu, 26th Jan 2006, 10:29pm

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FXhomer919

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well, turns out i imported my media wrong. (even instead of odd Interlacing)

but i am half way through a project.

any way to replace my underlying media with a new one - properly interlaced - while keeping all the effects layers i have created so far?

or...is there any way to change the interlacing properties of my project half way through?

please say yes, someone.

please.
Posted: Fri, 27th Jan 2006, 2:23pm

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Oeyvind

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Maybe you could save your half-finished effect as a preset and load it in the right project...? Just a thought wink

Oeyvind
Posted: Sat, 28th Jan 2006, 11:24pm

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alpha54

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So far, whenever I export interlaced footage from EffectsLab the result is very blocky; you get a "tooth" effect around fast-moving objects. Therefore, whenever I worked with interlaced footage now I have to import it as deinterlaced, add my effects, then export the effects as alpha layers and then superimpose them onto the interlaced footage in Premiere. Seems like this process is a lot more work than it should be unsure
Posted: Sat, 28th Jan 2006, 11:44pm

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Simon K Jones

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Interlaced footage will always look 'toothcombed' when viewed on a computer: that's exactly what interlaced footage is. You don't need to do all those deinterlacing/reinterlacing steps.

Are you sure your source video is interlaced? If it is, then it sounds like EffectsLab is exporting it ok - I don't see why it wouldn't work in Premiere. As long as you set your EffectsLab project up correctly it should be fine.
Posted: Sun, 29th Jan 2006, 8:18am

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alpha54

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Yes, my source footage is definitely interlaced (lower field first, standard DV video).

The thing is, when I export my interlaced footage from Premiere, it does not look tooth-combed, even on my computer screen. I was just thinking, if the EL timeline breaks the footage down into frames, then shouldn't each muzzle flash (for example) last two frames (two fields) on the EL timeline so that it lasts for one frame in the exported video? Or am I completely offtrack here?
Posted: Sun, 29th Jan 2006, 10:17am

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Oeyvind

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alpha54 wrote:

I was just thinking, if the EL timeline breaks the footage down into frames, then shouldn't each muzzle flash (for example) last two frames (two fields) on the EL timeline so that it lasts for one frame in the exported video? Or am I completely offtrack here?
No, as far as I know, thats right, thats why it's kind of easyer to work with progressive footage. But, hey, you'll get used to it! I have! biggrin

Oeyvind