Whenever I reduce the velocity of a video clip and render it...it jitters during playback. I have tried rendering it into different formats and it still gives the same result.
The process is interpolation. Anytime you slow down a clip (slow motion) Vegas needs to caculate the frames in-between and create them. Unless the frames are resampled there may be jitter. This is opposed to Hollywood that typically uses cameras that shoot the video at much higher frame rates, so when slowed down to normal it appears the movent has slowed down. If you have Vegas 4, it should on its own resample. If you have version 3, you need to set a switch (right click on the event).
Don't forget jitter can and frequently is a byproduct of previewing. The jitter shoudn't appear in the rendered file. In fact Vegas is one of the best for creating slow motion which if done correctly is very smooth and jerk free.
This question is asked a lot. The usual answers are:
1. Right click on the video event that has slow motion and make sure to set the Resample switch to "Force."
2. In the View menu, enable viewing of the Video Bus Track. Then, enable super-resampling. After doing this, move the superresampling line at the bottom of the bus track up to 1, 2, 3, etc. Setting it to 2 will double the rendering time, 3 will triple the rendering time, etc. However, in return, you will get more intermediate frames for your slow motion.
3. Play with the track motion blur (generally I think it is better if enabled).
Also, when rendering, you can click on the Custom icon and then change the rendering quality from Good to Best. This will also significantly increase rendering time because it uses a different rendering algorithm. Generally, from what I've read on these forums over the past year, this doesn't help much with slow motion, and is primarily for animation and for rendering zoom/pan of still photos.
Hope this helps. With the proper settings, slow motion is very good.