in a 30 fps project? How does Vegas treat such files?Vegas handles video files that have slower frame rates than the project frame rate by adding additional fields and frames so that the slower frame rate video file ends up with the same number of frames per second as the project frame rate.

The "resample" setting determines how this is done. If it is set to either "smart" or "forced" then Vegas creates the new fields and frames by blending adjacent fields and frames. This can result in ghosted frames and fields and the general sense that the video is "softer" than the original. However, the playback should seem quite smooth. If it is instead set to none, then fields and frames are simply duplicated in order to achieve the project frame rate. This results in video that is as sharp as the original video, but the motion may seem "juddery" or lacking in smoothness.

Only software that uses motion estimation (like Twixtor) can produce video which is both sharp and smooth. However, since there is no free lunch, this type of software sometimes produces "morphing" artifacts that can be quite nasty, although when it doesn't do this, the results can be stunning.

By contrast, the two approaches offered by Vegas will produce very predictable results containing no surprise artifacts.