Which may mean the issue is how Vimeo is handling the file.
I think h.264 might be the issue, because when I tried converting that 640 x 351 animation codec file on my own computer to h.264, I had jagged lines on here as well.
If you’re doing animation why not use HD 1280×720 and upload at that frame size and avoid scaling. The scaling on Vimeo of your source file might be part of the issue.
I animated the whole piece in only Pal Widescreen. :/ I’m running AE on a four year old MacBook with 3GB of Ram, it is struggling with anything in Pal resolution already, any attempt I made to produce something in HD failed gloriously.
How would that avoid resizing? Also never use odd frame sizes. Most codecs don’t like odd numbers. 640×360 is 16:9 but you’re better off doing 1280×720 so you can viewers can use Vimeo’s HD mode.
I meant resizing as in resolution resizing, not converting. =)
Am confused now, I started this using the Pal Widescreen preset in AE, which is 1050 by 576. When I resize this with Aspect Ratio controlled, then it doesn’t end up at 640×360, but at 640×351. :/ Just tried to fit it into 640×360, but it obviously gives me black lines at the top and bottom.