Slow Motion, but maintain accurate timecode

John222 wrote on 5/15/2013, 2:30 PM

Here is a good question. I have a video clip of a machine performing a job. We need to analyze the motion of the machine with respect to timing. The operation is pretty quick so I need to stretch the clip to view in slow motion. I also want to add the timecode effect, but I want the timecode to be accurate, not stretched like the video clip. How can this be accomplished?

Comments

Steve Grisetti wrote on 5/15/2013, 3:10 PM

What do you mean by "accurate"?

You can certainly have the timecode indicate the frame rate of your timeline, even if you slow down the actual video.

But it won't be accurate, with regards to your original footage, because the original footage has been slowed down, UNLESS you time stretch it too.

John222 wrote on 5/15/2013, 8:23 PM

Yes, I want to stretch time.

Steve Grisetti wrote on 5/16/2013, 7:21 AM

I still don't understand.

Are you saying that you want the timecode to slow down at the same rate as you're slowing down the video clip? Please be specific.

Chienworks wrote on 5/16/2013, 8:35 AM

Seems to me the request was pretty obvious and specific.

Apply the timecode effect to the video clip in the Project Media window by right-mouse-button clicking on it and choose Media FX from the popup menu. This timecode effect will reflect the actual timecode from the source media, regardless of how much you speed it up, slow it down, slice or dice it, etc. on the timeline.

You may also wish to disable resampling so that Vegas doesn't generate new frames by blending adjacent frames together resulting in a blurry image.

c3hammer wrote on 5/16/2013, 10:32 AM

You can't stretch time, though many of us might want to :)

You have to scale the playback rate of your clip under media properties, then stretch the clip by that exact amount on the timeline.

An example with a 10 sec. 60p clip on a 30p timeline -

- Set the playback rate to 50% (0.500)
- Double the length in the timeline to exactly 20 seconds.
- Click on disable resample to prevent ghosting.

You now will have a perfectly scaled slow motion clip that is exactly twice the length of the original in the timeline. Render to a 30p file and what people see will be time accurate, just with a specific scale factor.

If your original is 30p you can frame double by setting the playback rate to 0.500 and stretching the clip to exactly twice the length. This will be inaccurate by one frame at the start or end as you don't have that piece of information stored in the original clip. This will also strobe a bit and look imperfect, but is nearly perfectly time accurate.

If you have 60p footage and go to a 24p timeline it is a 0.400 playback rate and a stretch of the clip by exactly 2.5 times the length to give perfectly accurate scale in your slow motion.

Bottom line is you need to use the playback rate and stretching in an equal ratio and then note the exact scale factor to get frame for frame slow motion. It's not stretching time, but is something you can know with certainty what is going on.

Cheers,
Pete

c3hammer wrote on 5/16/2013, 10:47 AM

Also if you want to show the original time code, there's probably a way to film a clock and slow it the exact amount as you slow the clip and overlay that so you can see it in slow motion with the clip as a pip.

Curious if anyone has ever done something like that?

Cheers,
Pete

John222 wrote on 5/16/2013, 11:46 AM

Thank you Chienworks. That worked perfect.

The person receiving the video needs to be able to analyze the mechanical motion of the machine components I filmed. The whole video is only 5 seconds long. By observing, in slow motion, the machines timing marks in motion with a reasonable accurate time code he can calculate acceleration and velocity to complete his design..