Optical Flow Anomalies

[Jeremy Garchow]

Optical flow doesn’t work in every situation, unfortunately.

It’s wholly dependent on what’s in the scene.

I’d try a demo of Twixtor if you can.

Very generally, higher contrast images work better. I’m sure with snow, there’s probably not a lot of range there.

Do you have sample footage?

[Tony West]

I used it on a shot when a flash from a camera went off and when I stepped back through it, it looked like the person’s head was going to explode.

Crazy frame. I don’t still have it.

[Eric Santiago]

After testing with other apps such as After Effects, I can see the anomalies caused by the time warp.
I dont think these h.264 files at 29.97 can cut the the slow-mo Im looking for.
Now I really wished I had an Epic for this one 😉

[Kevin Patrick]

So, you done a lot of optical flow work, with other formats and have not seen issues.

Now, you are using a Drift Camera and FCP X and you see issues?

Is this the first time you’ve used FCP X? Or have you seen issues before?
Is this the first time you’ve used the Drift Camera?

What formats have you used before without issues?

Recently, I’ve worked with XDCAM EX and optical flow. Both natively and converted to Pro Res. I didn’t notice much, if any difference between the two formats. I was never able to get acceptable results. I always wound up with warping.

In my case I believe the issue was the source material, not the format. It was a sporting event. So there was a lot of fast motion. People going in one direction, the background moving by slower and people moving in the opposite direction. All this movement, in various directions seemed to overwhelm the optical flow algorithms.

I tired FCP X, Premier Pro and After Effects (which I believe are the same engine) and Twixtor in PP. Twixtor provides more controls and settings, so you can definitely improve over all the other implementations. They do have a trial plug-in you can download. I highly recommend reading their manual and watching their tutorials. If you’ve never used Twixtor.

One thing you should probably consider is conforming your video first. I shot 720 60P and conformed it to 24P, which slows it down to 40% without having the create new frames. Then work with Twixtor, or the other optical flow implementations.

[Eric Santiago]

Thanks Kevin for the tips.
Yes done numerous FCPX work using Optical Flow and sadly its the Drift and the conditions it was shot.
The last GoPro HD footage I worked with used a GoPro grip and a Chesty.
Using the helmet option is not best due to the excessive shake.
The Drift is basically a helmet cam since its glued to the side of the helmet.
Other successful formats are DV Cam using Canons and Sonys, then XDCAM and of course RED MX.
However, those were not in the same or even close to conditions as the Drift.
The anomalies actually look cool but too much is too much 🙂
We have Twixtor at work but on an Avid MC.
I guess if I had the time I would test that.
I ran out of time with this one, just wanted to see why my recent FCPX Optical project didn’t come close to most examples Ive seen out there.