Optical Flow Analysis Files Are Huge!

I had some 4K footage (about 25 gigs worth from my Panasonic LX100) that I retimed/sped up 10x and stupidly used 'optical flow' quality. (Since I was speeding up the footage maybe I don't need 'optical flow' ?)

After I was finished with the project, I realized that the hard drive was practically filled up. Even after using delete rendered files/proxy/optimized etc, that library remained large.

After peeking into the contents of of that FCPX library, I see that the Analysis files>Optical flow folder in that event was a whopping 681 gigs. I'm going to toss it, but how strange it didn't clear out after many attempts to delete rendered files.

Yes, they are huge. No, they are not render files, they are actually database files. Once a clip is analyzed, it doesn't need to be re-analyzed if changes are made. And no, optical flow doesn't help fast motion effects, only slow motion.

Actually Optical Flow can help fast motion. If you speed up a clip, you can get some jerky motion unless you speed it up exactly 200%, 300%, etc otherwise it can seem choppy. For example if you have a pan or a slider shot going left to right. Depending on the % of speed increase the frames displayed may not be in the right place, giving a stuttery movement. Using Optical Flow helps this. I've done it myself on many occasions and the difference is real.

Interesting to know, I've never seen it do anything. I'll have to test this some more.

Very cool. Thanks for the heads up. My biggest complaint is for archiving–with the Optical Flow folder being that large, it makes archiving expensive. (I use bare 3.5" hard drives with an eSata dock.)

No worries, it is save to delete them! FCPX can re-analyze the clips if necessary, so you don't have to keep the OF-files for archiving purposes!