Bad video quality when encoding in Premiere Pro CS3

[Rocky88]

I'm trying to edit and encode a couple of videos I captured using my TV tuner and upload them to youtube.
But no matter what settings I use the result is always complete disaster. I tried using XviD, DivX, H264 at highest quality settings, 320x240px and all the recommended settings I found on internet and the encoded video is always shaking, there's a lot of pixelation and lagging and some elements in video are leaving long visible traces. The same happens with all codecs. Note that the original video has very high quality and is already encoded with MPEG4.

[spysr]

I have the same problem. I saw a clip somewhere on youtube that said to put a softblur on your vids (very mild, like 1) and they will look better in youtube. Less pixelization. Counterintuitive. I havn't tried it yet, but have seen videos that have, and they look pretty good.

[edDV]

Note that the original video has very high quality and is already encoded with MPEG4.

That is your problem. How are you capturing?