Boris FX Optical Flow - Speeding up video

Yep wrote on 1/9/2016, 1:55 AM

I'm trying to figure out a problem I'm having speeding up video with Boris Optical Flow.

If I apply Optical Flow to a clip in my timeline and set the speed to 200% the video turns to black half way through the clip. If I trim off the part of the clip that is now black the remaining clip will again go to black half way through.

Is there any way I can stop Optical flow making the video go black at the half way point? I've searched Youtube and the Boris site and Google, but can only find information about slowing down video with this filter.

Any help would be much appreciated.

TIA

Comments

JohnnyRoy wrote on 1/9/2016, 7:23 AM

The problem is cause by the way the Vegas Pro plug-in API works. The plug-ins only have access to the frames in the event. So at 200%, Optical Flow has consumed all of the frames and renders black. Regardless of how you resize the event, it will always run out of frames early when the Velocity is set to greater than 100.

Optical Flow is designed to synthesize new frames when you slow down video by estimating the motion between two frames of video and rendering an intermediate frame that interpolates the motion. There is no need to use it to speed up video where you actually want to drop frames not make new ones.

Bottom line: Don't use Optical Flow to speed up video in Vegas Pro. Just use the built-in velocity.

~jr

Yep wrote on 1/9/2016, 2:50 PM

Thanks for the very comprehensive explanation JohnnyRoy. I've wasted a lot of time trying to figure it out an it was bugging me. I was sure there was some little trick I was missing. I was working on a clip that I wanted to start slow and then speed up. With a little bit of clip butchery and the built in velocity envelope I was able to get the effect I wanted.

Thanks again.