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Pixel Aspect Ratio Correction….
I am sure this has been posted a thousand times on these forums, but I am not finding the specific post that involves my specific problem.
Mine problem is when I use After Effects with a composition setting of DVCPRO HD 1080 29.97.
MY aspect ratio is set to DVCPRO HD 1080 (1.5)
I have been editing the whole thing with the Pixel Aspect Ratio Correction turned on, but when I export it squishes the footage to what it looks like with the ratio correction turned off. I am a little confused as to what ration correction it needs to be set on to get rid of having to do the correction at all…. I don’t know when I will be able to check this post again, so if you have any answers could you email me?
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4 Replies
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[Burleson Matthew] “I have been editing the whole thing with the Pixel Aspect Ratio Correction turned on”
Pixel Aspect Ratio Correction is for preview purposes only. If you want to output 1920×1080 square pixels then you need to place your footage in a 1920×1080 square pixel composition (like the HDTV 1080 preset).
Pixel Aspect Ratio correction is there to emulate display devices that stretch the image, such as NTSC which has rectangular pixels.
The funny thing about some HD codecs is that they use rectangular pixels in order to reduce the data size requirements of the footage on tape (e.g. 1440×1080 footage as in HDV has 3/4 of the pixels that 1920×1080 footage does, if your footage is 1280×1080 then it has 2/3 of the pixels of a full frame of 1920×1080). So your capture device has rectangular pixels… but every HDTV in the world uses square pixels!
If you want a square pixel 1920×1080 output then you need to properly interpret your footage with the correct pixel aspect ratio from your captured footage and then place this footage in a composition that has the same settings as your display device.
However! If you’re printing your rendered footage to DVCPRO HD tape then you want your footage to conform to the DVCPRO HD standard (which it sounds like is 1280×1080 with a 1.5 pixel aspect ratio). In that case you should stick with the output settings/render you have.
Darby Edelen
Designer
Left Coast Digital
Santa Cruz, CA -
Everytime a read a post on this issue I get a bit more confused; I guess the DVCPRO HD section of my brain is a bit under-developed…
One user suggested interpreting the source footage PAR as “DVCPRO HD”, but set the composition PAR to “Square”. It seems to work, but is this a good idea?
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I have the same issue with a DVCPRO25 composition I am working on. The footage looks fine but the outputs the comp “squished”. I placed it in a DV timeline appears to match the settings from my clip. Does the same apply here, or am I missing something?
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Jeremey @ DI -
Here’s a shorter (and hopefully simpler) explanation:
1. Interpret your footage as whatever it is.
2. Create your Composition to reflect whatever the final output will be stored on.
So if your footage was shot in DVCPRO HD 1080 it has a 1.5 pixel aspect ratio. When you import the footage make sure that it is interpreted with that pixel aspect ratio.
If you are putting your final output back onto DVCPRO HD then you should create your composition with a 1.5 pixel aspect ratio. If you are putting your final output on HDCAM SR or hard drive for HDTV then your composition should have square pixels (because HDCAM SR uses square pixels… and so does HDTV… use the HDTV presets). However, HDCAM (not SR) uses a 1.33 pixel aspect ratio, so if you’re printing to HDCAM after output create your composition with a 1.33 pixel aspect ratio.
So the mantra is:
1. Interpret your footage as whatever it is.
2. Create your Composition to reflect whatever the final output will be stored on.
Darby Edelen
Designer
Left Coast Digital
Santa Cruz, CA
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