Vexed by Velocity Envelopes

dogwalker wrote on 6/22/2009, 1:57 PM
I've been periodically dabbling with velocity envelopes, but I just can't seem to control them very well. I pick my start and end frames, add the four points, then drag the middle section down (or up), and dang, the video seems to shift under me, such at that the envelope is no longer on those four points.

I have a video clip of some of us jumping on a trampoline several years ago, and I want to see how it would look if I speed up (what's a good number, 4x?) sections, followed by dramatic, sudden slowdowns (again, .25x?), but I can't seem to do this very well.

Do I need to split the event where I want to put the envelopes? I can see that, but to me, it kind of defeats one of the flexible advantages of envelopes.

I found this while googling, and I think it's incredible. This is the kind of thing I'd like to be able to emulate:

Comments

jetdv wrote on 6/22/2009, 2:41 PM
As you speed up or slow down video, the end point WILL move.
dogwalker wrote on 6/22/2009, 3:14 PM
So, is there some trick to making this more predictable, where we can select the frames on which to start and stop the velocity change? Do I need to split the event at those frames? That's my next plan, when I can set aside an hour or two for more experimenting.

I just seem to get stuck in a loop, because (a) after I set the points and change the velocity, then those frames are no longer aligned with the points - it would be nice if the points shifted with the time-shifting frames; so (b) I move the points again, which (c) causes the problem again.

The only way I see out of this is having lots of splits - one for every start/stop velocity changes, and then after editing the particular event, drag it left or right to get rid of loops (or to fill out the correct length if I've slowed it).
TeetimeNC wrote on 6/22/2009, 5:01 PM
dogwalker, here is what I am able to do - see if this works for you?

1. Insert a velocity envelope in your event.

2. Start at the left - it is necessary to always move from left to right.

3. Move the Vegas cursor to the first position in the clip where you want to set the speed.

4. Double left click on the velocity envelope at the cursor position to create a velocity envelope point at that position.

5. Click to select the point and drag it vertically up or down to set the speed at the selected position.

6. Repeat steps 3-5 moving left to right until all your speed changes are in place.

7. Move to the right of the right-most velocity point and split the clip at the desired ending point.

When I do this, all of my velocity points remain at the "point of action" where they were placed. Note that it is the point of action that is retained, not specific frame numbers because the frames HAVE to get renumberd as the total number of frames in your clip will vary with the overall length of your retimed clip (e.g., 29.97 fps).

Jerry
dogwalker wrote on 6/22/2009, 6:28 PM
Yes!! Thanks! I had posted this question on Digital Juice, and a fellow there had the same suggestion. I had a chance to try it, and you're right, that works great!

My mistake was in placing all four points and then moving the velocity. You have the key - set the left point, set the velocity, and then move to the right.

Thanks, Jerry - very cool stuff!
Tim L wrote on 6/22/2009, 6:53 PM
Another thing that might help is to embed markers within your clip for key points where you want to do something.

Open the clip in the *trimmer* and find the key points where you want to do something (like freeze, speed up, slow down, etc.) . At each point press the "M" key to add a marker in the trimmer. Inside the trimmer these will look like regular markers, but you will then notice that wherever you have the clip on the timeline you will see a little embedded marker in the clip. As you change the velocity nodes, you can easily see how it shifts the location of your key frames of interest.

Tim L
TeetimeNC wrote on 6/22/2009, 7:23 PM
Good idea Tim.

Jerry
dogwalker wrote on 6/22/2009, 9:29 PM
Oh my gosh, Tim, I just tried it - how cool!! I know very little about the trimmer, I certainly didn't know about the markers and how they're placed in the timeline event, too. It was nifty watching them move as I moved the velocity up and down. That is really excellent!

I finally used the trimmer recently, and I thought it was great (I was using it to selectively pull lots of little segments from a long video to create a musical montage). Now I've learned something new.

Thanks!
MarkWWWW wrote on 6/23/2009, 5:40 AM
And just to add one further useful item in the same vein:

You'll find that there may be times when you would like the markers you have embedded in the clip (while in the trimmer) to be available at the project level - so that you can snap other events to their location, etc. You can do this by running the "Promote Media Markers" script.

Mark
dogwalker wrote on 6/24/2009, 2:52 PM
Thanks, Mark - where do I locate that script? Is it available for Vegas Pro 8?

Thanks again!