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Are these pixels normal?
I recently shot video for the first time (used to shoot film when I could afford it). I have a question regarding pixel aspect ratio. I would simply like to know if what I’m seeing is normal, or if something went wrong during the capture.
We shot DVCPRO50 16:9. The captured files (NTSC 720X480), when imported into AE, are read as having a 0.9 pixel aspect ratio. They appear squeezed.
The only way to make them look normal, that is, the ONLY way, is to interpret them as 1.2 PAR (while toggling the PAR correction, of course).
Is this normal? I was expecting them to look correct when interpreted with square pixels. Somebody educate me.
I ask because I’m trying to work out how to render some background plates in my 3D application. The only way to make these plates fit, at 720×480, is to render them with a 1.2 PAR. This is a problem for me. Poor detail. But that’s another thing.
Thanks – SGM
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8 Replies
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720×480 widescreen has a 1.2 PAR. That’s how they should be interpreted. AE might not do it automatically, so you might have to interpret manually sometimes.
They should not be interpreted as square pixels, since that’s not what they are.
Rarely should you ever interpret something as something that it’s not. The only time I’ve done that is with a clip that mixes interlaced and progressive sources – import twice and use a different interpretation.
Maybe you don’t have to do this in AE. Can your 3D app use non-square pixel background plates and work in non-square pixels?
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Yes (if I understand your question correctly) Maya can render my plates at any PAR I choose.
The problem for me is really as simple as it sounds: My live-action footage has 720×480 res and 1.2 pixels. My rendered background must therefore also have a 720×480 res and 1.2 pixels. This causes some loss of detail in the render. Square would be better.
But if I render out with square pixels, the plate no longer fit the live-action comp size. Too narrow, horizontally. No surprise there, I suppose.
Since you advise against using two different pixel aspect ratios when compositing, that means I should find another way to retain detail in the render.
Am I getting this right?
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Your background plate must look correct in the final render, of course.
Can you render the slightly lossy widescreen movies to use only when *working* in Maya, then render in Maya (no BG, render with alpha) to 720×480, 1.2 PAR, then composite that with the original (interpreted correctly at 1.2 PAR) BG plate in AE in a DV *widescreen* comp, rendering a DV widescreen movie at 720×480, 1.2 PAR?
This way, you work with the native aspect ratio until the very end of the process, at the display stage. Does that make sense?
By the way, what is your final deliverable and display format? DVD? Broadcast? Letterboxed?
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Taken care of.
My problem, from the get go, was that I was trying to avoid rendering my plates with a 1.2 pixel aspect ratio. I was secretly hoping my live-action 19:6 footage had been poorly captured, thus changing the standard I was working with.
Turns out, the ugly aliasing I was seeing on my 1.2 PAR renders are more about display than anything else. The aliasing doesn’t show up on TV. TV makes them square. Looks fine.
What with the 6 months I needed to grasp fields and interlacing, this PAR thing, I hope, has finally given me an understanding of video. How does one juggle all of this? Baffling. I guess film enjoyed a Kodak-centric monopoly that prevented various standards from popping up everywhere.
Off topic. Thanks for replying.
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Non-square pixels are used in Standard Def TV. It’s in the spec. They look odd on computers, but fine on TV, as you’ve found.
You should search the COW for Rick Gerard’s “Pixel Madness” or “Dr. Strangepixel” tutorial. Hopefully, it will answer more questions than it raises. There’s also a lot of stuff about this on the web.
By the way, it’s “16:9”, not “19:6”. But you knew that. 🙂
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[Steve Roberts] “You should search the COW for Rick Gerard’s “Pixel Madness” or “Dr. Strangepixel” tutorial.”
“Strangepixel” Terrific article. Thanks for that – SGM
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[SSGGMM] “Turns out, the ugly aliasing I was seeing on my 1.2 PAR renders are more about display than anything else. The aliasing doesn’t show up on TV. TV makes them square. Looks fine.”
If you’re coming from Film then you should understand the concept of an anamorphic lens. This is similar to pixel aspect ratio. The lens condenses the captured footage horizontally so that it will fit on the 4:3 film strip. As you look at the footage on the film strip it will look strange, but when it is projected back out of a projector the reverse effect is applied: the footage is stretched horizontally back to its ‘proper’ aspect ratio by the projector’s lens.
The TV doesn’t make the pixels square. The pixels on the TV are not square, they’re stretched (in the case of widescreen) out horizontally. This needs to be taken into consideration when working with footage that will be displayed on the TV, the footage must be ‘squashed’ so that it looks correct when it’s ‘stretched.’
Darby Edelen
DVD Menu Artist
Left Coast Digital
Aptos, CA -
Yes. Of course! I hope your anamorphic analogy is a good one because I think I’ll stick with it. And thanks for the clarity: TV pixel = not square.
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