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 has slowed down a 1s video down by 10x. An additional 270 frames were interpolated from 30 original source frames giving the video a smooth feel during playback. The same video was slowed down with FFmpeg alone, but because it dupes frames and can't interpolate new ones the video has a noticeable stutter.

Here is another example of the same concept. Interpolated frames between source frames are marked Int: Y. Opening the Butterflow'd video and frame-stepping through it would make the interpolated frames more obvious.

See the In Action page for more demonstrations.

With Homebrew:

brew install homebrew/science/butterflow

A package is available in the AUR under butterflow.

This is the only way to install Butterflow on Ubuntu, Debian, and Windows.

Refer to the Install From Source Guide for instructions.

Butterflow requires no additional setup to use but it's too slow out of the box to do any serious work so you're expected to set up a functional OpenCL environment on your machine to take advantage of hardware accelerated methods that will make rendering significantly faster.

See Setting up OpenCL for details on how to do this.

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

See Example Usage for typical commands.