Customizing pixel aspect ratios in AE CS4

Chris Meyer explains the new corrected pixel aspect ratios in After Effects CS4 and how you can deal with some of their ramifications in the New Pixel Aspect Ratios, a free video in the Lynda.com After Effects CS4 New Creative Techniques series.

But some people have problems with the new CS4 pixel aspect ratio (PAR) when working with other video systems and apps. If you can't live with the new PARs, there are undocumented and unsupported workarounds to:

1. add custom PARs
2. disable the automatic interpretation of PAR
3. add anti-aliasing to pixel aspect ratio corrected comps

First, via Joost van der Hoeven, you can add custom PAR to the popups (pictured above) in Interpret Footage and Compositions Settings using interpretation rules. Here's example text to add to the file "interpretation rules.txt" that adds custom CS3 NTSC and PAL 601-SD PARs to the list in CS4:

# adds custom pixel aspect ratio to the PAR popup for CS3 PAR
0, 0, 0, "0000", * = 648/720/"D1/DV NTSC (CS3)", *, *, *, *, *
0, 0, 0, "0000", * = 768/720/"D1/DV PAL (CS3)", *, *, *, *, *

You can find the "interpretation rules.txt" file here:

• On Mac OS: Applications/Adobe After Effects CS4
• On Windows: C:\Program Files\Adobe\Adobe After Effects CS4\Support Files

Next, Chris and Trish Meyer have already explained how to flip a switch in the Preferences to disable the automatic interpretation and allow you to continue to work with the old PARs in CS4. This will still leave you with a command to Upgrade Pixel Aspect Ratios (under the File menu when you follow their instructions). See Make It Go Away! Undoing the PAR and color management enhancements in After Effects CS4 at PVC.

Finally, in Non-Square Strategies: Suggested workflows when dealing with non-square pixels and anamorphic formats, Chris Meyer expands on the Lynda.com explanation, and shows you the secret text preference which enables high quality PAR correction in After Effects (with a performance hit). The Throttle script by Lloyd Alvarez works with the new multi-processing system in CS4, and also exposes the hidden preference that allows you to set the quality of the Toggle Pixel Aspect Correction button in the Comp View (After Effects needs to be restarted after changing the PAR quality).

Additional info and background on pixel aspect ratios can be had in these resources:

• Adobe AE Help page has the basic rundown with always refreshed resources in Pixel aspect ratio and frame aspect ratio.
• The new PAR scheme is also explained in Chris and Trish Meyer's free CS4 upgrade chapter for Creating Motion Graphics owners. See the summary at PVC, The Differences Between AE CS3 and CS4.
• Mike Afford, who did graphics at the BBC, has put together his own explanation for PAL users, with diagrams and as little mathematics as possible: PAL D1/DV Widescreen square pixel settings in After Effects (CS4 vs CS3).
• Chris Pirazzi, who with Chris Meyer interpreted the tech dirt for regular users even before Apple stopped developing eWorld, has all sorts of material on videosyncracies.