FFmpeg - Open source multimedia suite for conversion, playback, profiling, and streaming.
VLC Media Player - VLC is a free and open source cross-platform multimedia player and framework.
HandBrake - HandBrake allows users to easily convert video files into a wide variety of different formats.
AIMP - AIMP : Free Audio Player : Официальный сайт программы
Adobe Media Encoder CC - Create optimized video for any screen size and resolution with Adobe Media Encoder. Available only in Adobe Creative Cloud.
foobar2000 - An advanced freeware audio player for the Windows platform.