HandBrake - Open Source Video Transcoder

free and available for Windows, Mac, Linux

download: https://handbrake.fr/

input format: 3GP, AVI, Blu-ray video, DVD video, FLV, Matroska, MP4, MPEG-PS, Ogg, QuickTime, SVCD, TS, TOD, VCD, WMV

output format: mp4, mkv