I don’t know how to set the pixel aspect ratio in the render queue but if you render a PAL anamorphic comp without any stretch after effects tags the file as anamorphic pal, if it’s a 4:3 comp it tags it too. As long as the final file is 720×576 you should be ok as you can always interpret it as widescreen later if the target application does not detect the pixel aspect ratio correctly.
I hope this helps, it seems like after effects tags the render based on the comp settings but it is a bit of a black box, I’m not sure where that information is stored and whether all applications can access it. I’ve only tested quicktime for this, not sure how other formats detect or store this information.
Just make sure you tell whoever you’re giving the file to whether it’s anamorphic or not.
Glenn Stewart
1K studios