Custom Pixel Aspect Ratios

[Pat Ortman]

Well, he may be opening up HDV footage that’s squeezed and noticing that when he goes to make a composition that there doesn’t seem to be any presets that fit the 1.3 ratio he wants. Of course, you can just drag your footage to the “make new comp” button and you’ll magically get a new comp with the right settings…

Pat

[Steve Roberts]

[Dave LaRonde] “A classic case study in the principle that you can’t shove ten pounds of a certain vile-smelling substance into a five-pound bag.”

Yeah, it’s called long-GOP MPEG-2. 🙂

The HDV format is 1440×1080, giving the ratio. So is the HDCAM format, actually, which surprised me. But HDCAM is 185 mb/s as opposed to HDV’s 50. Whee!

Steve

[Steve Stone]

Thanks for your response.

Here’s the deal:

This will be used for a large corporate clients’ sales meeting. The main screen is 65 feet wide by 18 feet tall. The aspect of the screen is 3.638:1

The output will be 1080i HD from HDCAM. (1920×1080). This signal is resized on the fly to stretch to that ratio. So, we would like the ability to be working in After Effects at this custom aspect so we can see what it looks like, otherwise, it is a stretched vertical image that is hard to work with.

Photoshop has enabled a user to input a custom pixel aspect since CS. If you want to see what we would like. Launch Photoshop and create a new 1920×1080 image and set the custom aspect to 3.638:1. Draw a circle and then turn Pixel Aspect off. See the result?

There are many situations where the “Drop Down List” isn’t enough.

Any ideas?

Thanks again,

Steve Stone

S t e v e S t o n e
A n i m a t o r

D X D ( P o s t / D e s i g n / F X )
https://www.d-x-d.com

[Andrew Yoole]

You create custom Pixel Aspect Ratios using the text file “Interpretation Rules” in the AE application folder. Make a backup of the file before you begin, in case you stuff it up.

Here’s an example of text you can paste into the rules to define an HDV preset:

# Andy’s HDV rule
# soft rule; assume 1440×1080 formats with all frame rates have HDV 1.33 pixel aspect ratio & upper field first
1440, 1080, *, *, * ~ 1920/1440, U, *, *

This tells after effects that when it sees a footage item that is 1440×1080 pixels, it should expand the footage by 1.33 (square pixel size divided by rectangular pixel size) and that the footage should be interpreted as Upper Field First. (All interlaced HDV formats are UFF).

[Steve Stone]

Hey Andy, Thanks alot! Is there also a way to make a comp have a custom Pixel aspect ratio? Thanks again

Steve Stoe

S t e v e S t o n e
A n i m a t o r

D X D ( P o s t / D e s i g n / F X )
https://www.d-x-d.com

[Andrew Yoole]

Once you define a rule as explained above, AE automatically recognises the setting as a new Pixel Aspect Ratio.

So in the case of the HDV rule above, you will now have a new item in the Pixel Aspect Ratio list (under Composition Settings) that reads 1.33, which is the HDV PAR. You can create a Composition Preset and save it to use regularly.

[Todd Morgan]

You may want to look at Dataton Watchout. If you create your AE comp to the size of the screen, then render two half sections (or maybe even three sections), you would want to have some overlap when projection happens, using two or three projectors. That way you don’t have to worry about pixel aspect problems and testing.

Todd

[Thomas Leong]

Agreed…or AVStumpfl’s Wings Platinum Module version but with a higher learning curve than Watchout.

In any case, doing the Foot Lambert maths regarding the brightness of the projected image, it makes more sense to split the whole image into manageable sections (Master PC -> multiple Slave Display PCs -> multiple Projectors) would give a far higher on-screen brightness than doing it with one projector. Stacked multiple projectors is another possiblity but these have an inherent problem in alignment especially for graphics which require a far more accurate alignment between the stack compared to moving video footage.

Intended Projected Image area = 65ft x 18ft = 1170 sq. ft.
If Projector’s ANSI lumens = 10,000, then this only gives a
10K/1170 = 8.55ft Lambert result. This is going back to the old slide projector show days (without the xenon arc lamps). The acceptable image these days is a minimum 16ft Lamberts (20ftx16ft image with a 5K Projector), preferably double that with a 10K projector. There are higher rated projectors on the market, but the rental costs would be much higher too.

To achieve a 65x18ft final projected image, using Watchout and native 1024×768 10K projectors, my calculations say that one would need 3 projectors overlapping at 15% (150 pixels). This would be the bare minimum overlap required and would demand a tweaking of the soft-edge blend within Watchout to get an even image where the blended areas are not so obvious.

My advice is to liase with the projection people for this project, and work eveything thing out before production, else you may be wasting your time and find you have to alter your production specs at a later stage, i.e. re-work.

Thomas Leong