jaggies in cartoon

[AlanHK]

I've got some fairly low res (mostly 352x240) AVIs of cartoons.

I notice the outlines are often jaggy. Is there a way to smooth these?

I'm making these into MPEG2 with HCEnc. I'm keeping the original resolution, believing upsizing to 720x480 would just create more artifacts -- is that right?

[Chainmax]

Upsizing shouldn't create more artifacts, it would rather make existing ones bigger. As for how to clear those jaggies, it would be best if you could upload a small (~30s) sample somewhere so that we can better treat it.