Lars, does the app have to speed up the motion?
You mention speeding it up up to 12 times. But what if you want to keep the motion at 1x speed, but just smooth it out. Could it do that, or is the speeding up essential to the smoothing process?
I’m asking as if the app does not have to speed up the footage, this could end the need for steadycam use. Then one could keep the audio that goes with the video.
I’d check it myself, but I’m an Android man, so no access to the app as yet.

Started out doing photography at the age of 6 using an uncle's old 1940 kodak brownie box camera. At 15 years of age, I decided to buy my very own 1975 Praktica SLR camera. I now shoot with a Nikon D850. I do unpaid TFP and commercial paid work.