Slo-mo problems

[Dan Bridges]

I've been working with a 21fps video sequence from a Pentax K20D DSLR. It contains two jumps by my kids into a motel swimming pool. I've set it up for PAL SD with 82 787x576 framed PNG image files. I want to do a 1/3x or 1/4x slo-mo of the sequence in Vegas Pro 8.

My first attempt was a 3x/4x replication of each image during insertion (Options | Preferences | Editing | New still image length = 0.120s/0.160s (3f/4f at 25fps) - untick "Automatically overlap multiple selected media when added". This works but I thought I might get better results through Supersampling because it would interpolate the transition from one 3x/4x set to the next one, so smoothing it out.

I must admit I can't see much difference in smoothness with a 4x supersample besides a 46% increase in WMV filesize.

Here is a link to the 4x frame replication to get x0.25 playback (without supersampling):

http://users.on.net/~dosdan/slo-mo/s...eplication.wmv


Here is a WMV of the 4x supersample of the 4x frame replication:

http://users.on.net/~dosdan/slo-mo/slo-m_ss4.wmv


Also I tried to set the Velocity to 0.25/0.33 but this does not seem to work.

Here is a link to a 60MB ZIP file containing the 82 images and a VEG file for the different methods mentioned. The Video master bus track is currently set to a supersample of 1.

http://users.on.net/~dosdan/slo-mo/png%20and%20veg.zip


In the Resampling Video section of p. 243 of the Vegas 8 manual is says:

To resample the project, choose Render As from the File menu. In the Render As dialog, click the Custom button to access custom rendering settings. Select the Resample the frame rate of all video check box.

I can't see that check box. Is that because Smart Resample is already selected fro the events?

Can someone explain why Velocity 0.25 is not working in the VEG? Which is the best way to slow this sequence down?

[Dale Guthormsen]

Dan,

I down loaded your file and have spent about an hour tinkering with it. I was curious if you have rendered the file to an avi codec and then did some playback / velocity changes?

I take it you are trying to make it 4 times slower than you already have it in the replicated clip?

With only 80 frames i wonder if you just do not have enough frames to slow it effectively without some image issues.

I got it to play for about 8 seconds but there is a bit of image flicker in two places.

what is your actual marker you want to reach?

[Dan Bridges]

Dale, thanks for trying it out. What I am trying to do is find the best way, with what I have, to do slo-mo. I could have made the clip longer, but the principle's the same.

Are you seeing flicker in a rendered version? If you're running NTSC, it might look better if you chage the properties of the project to that instead of PAL.

I added 82 shots to the timeline & in the process quadrupled them to 328 frames. Let's look a sequence of just 3 shots:

[1][2][3] - Original sequence

I'm using the [2] notation here to represent a movement (say a ball thrown] over 3 shots (after the quadrupling, now 12 frames). "[2]" means the ball is part-way between the [1] & [3] positions.


[1][1][1][1][2][2][2][2][3][3][3][3] - Quadrupled. At the same frame rate, now 1/4x of the original speed.


With 2x supersampling, if I understand it, it becomes something like:

[1][1][1][1.5][2][2][2][2.5][3][3][3][3] (assuming the ball stops at [3])


with 3x:
[1][1][1.3][1.7][2][2][2.3][2.7][3][3][3][3]


with 4x:
[1][1.25][1.5][1.75][2][2.25][2.5][2.75][3][3][3][3]


If my understanding is correct, then 4x supersampling should work best with quadrupled frames, whereas, in this example, 2x & 3x supersampling will be less smooth.

So the supersampling should smooth out the "4 in a row" nature of this sequence, making the 1/4x playback better.

What I'm trying to work out is, is the way I've done this exactly the same as taking the 82 shots, applying 0.25x Velocity to the track and then 4x supersampling? Did you manage to get the 0.25x Velocity working with the .VEG in the zipfile?

Dan.

[Dan Bridges]

Dale, I've done more tests and supersampling does not appear to work as well as I expected.
I rendered the first 5 shots (each quadrupled -20 frames in all) using 4x supersampling to DV so I could single-step through each frame. The supersampling barely shows any interpolation at all.

The rendered sequence (3 MB). Don't bother playing it - it's too short. Load it in Vegas and single-step through it noticing how & when supersampling alters each set of 4 identical frames.

http://users.on.net/~dosdan/slo-mo/s..._5%20shots.avi


Here is a replacement VEG file. The sequencing of some of the shots is corrected.

http://users.on.net/~dosdan/slo-mo/slo-mo.veg

[Dale Guthormsen]

Dan,

tomarrow I will set down with the latest stuf in your last post.

What you are actually doing is the manner which premiere pro and elements as well as other nles make slow motion and that is by adding duplicate frames.

One of the reasons I have Vegas is that it actually interpolates the inbetween frames, basicly builds an entire new frame between the other two. At least that is how i understand it.

In Vegas you can manipulate the play back rate too, this can give the slo mo look as well.

So, as I read it you are creating slow mo similar to many other nle.


What I think needs doing is to have more frames, set the frame rate you want, say playing 60 full frames in one second. If you needed it slower I might then render it and then put a velocity envelope on the new clip and change the velocity and then this should give you the interpolated frames and a slower slightly more complete image movement.


I work on this slow mos stuff all the time, wish I had a better method, like a video or still camera that cranks out 300 frames a second in full 1080P!!!

[Ryan Laytart]

This is the most basic of suggestions, so please don't frown on me!

What about a slight motion blur on the bus track? Perhaps not enough to see any blur, but more to create those extra frames you're looking for.

Just a thought.

[Dan Bridges]

Thanks Ryan for the suggestion. Motion blurring works better than supersampling. I tried 4 frame blurring. I tried all the blurring calculation methods offered in Vegas. However, in my opinion, none of them realistically interpolated a clip with a quadrupled set of images.

Dan