Re: What is Seconds Per Keyframe? by Matt Crowley on Oct 16, 2011 at 5:50:00 pm
"Seconds per keyframe" specifies the interval between reference frames in the video compressing/encoding process. All the other frames are encoded as the difference between the keyframe and the current frame, so generally the more keyframes, the more accurate the encoding... but the more space the video data takes up. Don't fiddle with these settings until you understand more about the encoding process.
What you are seeing in that frame-grab you linked to is "blending", which is how Vegas creates "in-between" frames when de-interlacing or converting frame-rates.
If you don't like this deinterlacing method, you can choose "interpolate" for deinterlacing in the project properties.
If this is the result of frame-rate conversion (eg using 25fps footage in a 30fps project) then you can try disabling resample in each video event's properties. You might get slightly jerky motion though.