I writing this in case it will save someone else the 7 hours I spent debugging the stupid issue.

I had pristine video shot in great lighting with a pair of Panasonic AG-DVX100 cameras.

But every time I rendered my project little problems would pop up in the video. Certain sections would be wavy. Camera flashes that took up a single frame on the original video now looked like venetian blinds on the rendered frame.

It didn't look horrible, but the problems were there.

I tried different codecs. I tried frameserving. Nothing solved the problem.

I brought the same clips into a new project and they looked great.

Finally it hit me. It was my own stupid fault.

Near the end of the video there is a still. I had imported the still and there was someone's head at the bottom of the frame. So I had clicked on track motion and resized the frame to eliminate the person's head. The source frame was much larger then video size, so I figured I was downsampling anyway.

Not only was that still resized, but I had just resized the entire main video track. Duh! That was my problem.

I cropped the still in Photoshop and reset the track size to normal.

All is well now.

Mark