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rendering speed

Posted: Sun, 1st May 2011, 5:58pm

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nerb2k10

Force: 1600 | Joined: 14th Oct 2010 | Posts: 6

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I've a file (edited in vegas) that's just below 3 minutes of green screen footage. It's rendered at 25fps, so I would think -> 3 * 60 = 180 and 180*25 = 4500 frames.

However, when I key out the background and then render it in Composite lab, it renders 8500 frames and it takes 2 hours to render ...

It a long wait just to change my background. Is there anything I can do to speed this up?

Sample video: http://www.youtube.com/watch?v=b0Q_7Pmqljc

So it's a very simple weekly update, but I end up editing for 4 hours or so unsure
Posted: Sun, 1st May 2011, 7:44pm

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Axeman

Force: 17995 | Joined: 20th Jan 2002 | Posts: 6124

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SuperUser

Are you sure its rendering 8500 frames and not 8500 fields? If the footage is interlaced there are two fields per frame, which could give the impression of doubling the frame count.

As far as render times, it really depends on the hardware you have, the resolution of the footage, and the complexity of the composite. But rendering takes time, any way you slice it.
Posted: Sun, 1st May 2011, 8:09pm

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nerb2k10

Force: 1600 | Joined: 14th Oct 2010 | Posts: 6

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thanks for the quick reply and it's probably fields then

So if I don't put it on interlaced, it should speed up the rending time?
Posted: Sun, 1st May 2011, 9:00pm

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Axeman

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SuperUser

Theoretically yes, but its not nearly that simple.

If you convert the footage from Interlaced to Progressive, then there will only be half as many images to render. However, since each field contains half of the image data for the frame it is associated with, converting to progressive instantly deletes half of the data from your video file, which naturally results in a noticeable quality loss. There are programs available that can combine the fields into a single image, thereby retaining the quality, but they will cost extra money.

If quality is an issue at all, then your best option is to record the footage in progressive if it needs to be progressive. And, if it was originally recorded as Interlaced, then keep it interlaced throughout editing.
Posted: Mon, 2nd May 2011, 2:21am

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nerb2k10

Force: 1600 | Joined: 14th Oct 2010 | Posts: 6

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ok cool, thanks for the info!