Disable Resampling?

Kimberly wrote on 5/1/2010, 4:19 AM
Hello All:

I'm using a Sony HDR-HC3 and shooting in HDV.

I've seen advice from the Gurus in this forum to "disable resampling" to help improve the quality of video output.

What does resampling do and why would it help the quality to disable it? I'm asking because I don't understand resampling. Is there a circumstance when resampling is a good thing? I know where to disable it, I just don't understand it.

Kim

Comments

Chienworks wrote on 5/1/2010, 6:14 AM
The "resampling" referred to is frame rate interpolation. If the video clip on the timeline doesn't match the frame rate of the project then Vegas will combine or interpolate new frames to make it match. For example, suppose you put a 24fps clip on the timeline but your project is 30fps. Frame 1 of the clip lines up with frame 1 of the timeline. However, frame 2 of the timeline starts before frame 1 of the clip is over, but frame 2 of the clip starts before frame 1 of the timeline ends. Vegas will mix a little of frames 1 & 2 of the clip together to produce timeline frame 2. This mixing continues until the next time that the frames align exactly, which will be clip frame 6 and timeline frame 5. This can cause ghosting, especially in fast motion, because Vegas is merely mixing two different images together to produce the output.

Why does it do this? Well, if it didn't, then Vegas will have to either drop some frames (if the source has a higher frame rate than the project) or duplicate some frames (if the project has a higher frame rate than the source). This can cause a sort of juddery motion where things may seem to skip forward or pause for very brief bits of time. Resampling smooths the motion out instead of having it be uneven.

Which is better? It's really up to the individual viewer. Personally i find the ghosting that resampling produces to be more annoying than uneven motion. In fact, i don't even see the uneven motion. Maybe my eyes don't respond fast enough to pick it up. On the other hand, the blurred images look really awful to me. So, i prefer no resampling.

Note that if your frame rates match, such as putting 29.97 video on a 29.97 timeline, then resampling is moot. It isn't needed, so it won't happen regardless of the setting you choose.
musicvid10 wrote on 5/1/2010, 8:15 AM
Excellent response, Kelly.

Here's a practical example: I had to add a closeup take of a dance sequence to a different performance. There was a 3% tempo difference between the performances. I squeezed the take to match the tempo. Disabled resample because I didn't like the blurred frames. Now the take was jumpy because of dropped frames. The soloist even looked like she had three legs at times. I applied a bit of sharpening, then added motion blur to smooth the differences between the discontiguous frames. The result, although not perfect, was quite acceptable for the demo reel I was producing.