FFmpeg

FFmpeg is a set of libraries and command-line tools that converts between almost all video and audio formats, compresses, cuts, changes resolution and frame rate, extracts frames as images or audio from a video, and assembles a video from an image sequence. Engineers use it to batch-convert many files in a script, to make a video from simulation frames or a site time-lapse, and to shrink files for sending. It is the engine behind many programs such as HandBrake and Shutter Encoder. Limitations: there is no graphical interface, the syntax takes learning, and the project ships source code only, so Windows and macOS binaries come from third-party builders linked from the site.