Butterflow is an easy to use command-line tool that lets you create fluid slow motion and motion interpolated videos.

It works by rendering intermediate frames between existing frames. For example, given two existing frames A and B, this program can generate frames C.1, C.2...C.n that are positioned between the two. This process, called motion interpolation, increases frame rates and can give the perception of smoother motion and more fluid animation, an effect most people know as the "soap opera effect". butterflow takes advantage of this increase in frame rates to make high speed and slow motion videos with minimal judder.

In this example, butterflow slowed down a 1s video down by 10x. An additional 208 frames were interpolated from 30 original source frames giving the video a smooth feel during playback. The same video was slowed down with ffmpeg, but because it dupes frames and can't interpolate new ones the video has a noticeable stutter.

Here is another example where the frame rate has been increased from 30fps to 60fps with butterflow. The video has been slowed down to make the interpolated frame (marked Src: N) between original source frames more apparent. Playing it back in full speed would produce a "soap opera effect".

See the In Action page for more demonstrations.

With homebrew:

brew install homebrew/science/butterflow

A package is available in the AUR under butterflow.

Refer to the Install From Source Guide on the wiki.

After installing the package, you still need to install at least one vendor-specific implementation of OpenCL that supports your hardware. No setup is necessary on OS X because support is provided by default. See Suggested OpenCL Packages for some options.

When finished, you can run butterflow -d to print a list of all detected devices.

For additional information on how to satisfy the OpenCL requirements, please read How to set up OpenCL in Linux. If you're on Arch Linux, have a look at their GPGPU wiki page.

Run butterflow -h for a full list of options and their default values.

See Example Usage for typical commands.