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Greg Robbins
Pixel Aspect Ratio
on Feb 12, 2010 at 9:53:09 pm

First off I'm sorry for this repetive question I know I've seen similar posted, but none answered my specific question. I shoot on my friends HD camera in 1080 and capture it and bring it into after effects, the actual pixel sizes are 1440x1080. I realize this means it has a PAR of 1.33. But when I click on the "correct pixel aspect" button on the comp window to work with it and off again to render into a quicktime animation file and play in quicktime, the video is squashed because I take it quicktime does not recognize the correct PAR. So my question is what is the best way to correct this. What I've been doing is importing the 1440x1080 footage that is interperted as having a 1.33 PAR and placing it into a full 1920x1080 comp with a PAR of 1. That's been working for me. Am I loosing any quality in doing this and is there a better way? Thank you for any help.

Greg Robbins


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Dave LaRonde
Re: Pixel Aspect Ratio
on Feb 12, 2010 at 10:21:22 pm

The important question isn't if looks right in quicktime. What's really important is this: how will you be using this file NEXT? Answer that, and we can give you a really useful answer.

Putting the video into a 1920x1080 comp won't hurt the video quality... but it may confuse the next application you use. We can't say for sure until you tell us that.

Perhaps you haven't had any rendering problems yet, but HDV is notorious for giving AE fits. So if you DO encounter rendering problems, keep the following in mind:


Dave's Stock Answer #1:

If the footage you imported into AE is any kind of the following -- footage in an HDV acquisition codec, MPEG1, MPEG2, AVCHD, mp4, m2t, H.261 or H.264 -- you need to convert it to a different codec.

These kinds of footage use temporal, or interframe compression. They have keyframes at regular intervals, containing complete frame information. However, the frames in between do NOT have complete information. Interframe codecs toss out duplicated information.

In order to maintain peak rendering efficiency, AE needs complete information for each and every frame. But because these kinds of footage contain only partial information, AE freaks out, resulting in a wide variety of problems.


Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Greg Robbins
Re: Pixel Aspect Ratio
on Feb 12, 2010 at 10:40:54 pm

The video is just for fun for me and my friends. Its a shot of a army tank I modeled and then matchmoved the original footage in pf track and composited the tank and footage together. So the footage is only going to be used for showing it to friends via playing it in quicktime (ie why I needed it to look correct in quicktime) and uploading it to vimeo, youtube. The footage was shot on a HD panasonic I forgot the name (hvx100 I think sounds familiar)but it records to a P2 card.
Thanks for responding dave I appericate all the advice you give everyone. This is a very helpful forum


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Dave LaRonde
Re: Pixel Aspect Ratio
on Feb 12, 2010 at 11:37:33 pm

If that's what you're doing, 1920x1080 is fine. Depending on your platform, I'd use Adobe Media Encoder or Apple's Compressor to convert that big ol' HD picture into web-friendly stuff.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Greg Robbins
Re: Pixel Aspect Ratio
on Feb 13, 2010 at 1:47:32 am

Yea that's what I usually do compress with adobe media encoder. Thanks for the help. I just wasn't sure if using different PAR's would loose quality. Thatnk you for lending your knowledge once again Dave!


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Joey Foreman
Re: Pixel Aspect Ratio
on Feb 14, 2010 at 5:16:12 am

Having worked with footage of this nature for some time, from cameras like the HVX 200 that record a smaller number of actual pixels than are displayed (using a scaling algorithm), I think I can state with some confidence that you will indeed be losing a small amount of quality this way because you are stretching the footage horizontally from its actual pixel resolution to force it into its "correct" aspect ratio.

Better I've found to leave it native and squished in AE, using Pixel Aspect Correction on for reference, but toggling it off to check edges when pulling keys, etc.

This keeps your graphics and effects, as well as the footage itself, at their sharpest throughout the project. If you are finishing in an editing app, as is usually the case, then you can render at this native size and pixel aspect ratio, and the editing app will know how to properly interpret and display the clip. From there, you can output everything as you usually do.

If you're going straight to the web, you could drop your comp into that square pixel comp just before rendering, in case the compression app can't interpret the native-to-displayed resolution correctly. (I'm assuming you plan to compress for the web in another app, as compression is not one of AE's strong suits.)

I wouldn't mind hearing another opinion on this workflow, though. I do believe it's essential for pulling the highest quality keys with footage of this nature, but for non-keyed footage the difference in quality might be visually imperceptible.


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