AE is just about the WORST thing you can use to convert footage to mpeg2. There are two reasons: AE is incapable of multipass encoding, which makes the picture much, MUCH better. AE can't make the file you need, an mpeg 2 program stream. AE is fine to use for mpeg 2 encoding if you want to show a client how the project is going. It is totally unacceptable for final delivery.
You should use something other than AE to convert your footage. Soprenson Video 3, Apple's Compressor, and Adobe Media Encoder are popular compression applications, and they will all do a better job than AE. Furthermore, they can actually DO the job, and AE can't.
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA
if you have cs4, you should have adobe media encoder. it will create a .mpg mpeg2....
ame can also render a comp from a ae project file, select the ae project when importing, then select the comp... although i still render from ae and import that into the utility... maybe i'm too old -- or i just need time to do some test comparisons. i have noticed that ae rendering is usually faster (w/ mp enabled) than ame, for whatever that's worth.