FFmpeg - Open source multimedia suite for conversion, playback, profiling, and streaming.
HandBrake - HandBrake allows users to easily convert video files into a wide variety of different formats.
Adobe Media Encoder CC - Create optimized video for any screen size and resolution with Adobe Media Encoder. Available only in Adobe Creative Cloud.
321Soft Video Converter for Mac - 321Soft Mac Video Converter allows you to easily download, convert and edit video, HD video, 4K video, audio on Mac OS X.
gstreamer - GStreamer is a library for constructing graphs of media-handling components. The applications it supports range from simple Ogg/Vorbis playback, audio/video streaming to complex audio (mixing) and video (non-linear editing) processing.
Format Factory - Format Factory is software that allows the user to convert media into various file formats. The software is a product of PC Free Time, a Chinese software development company. Read more about Format Factory.