MP4Box

MP4Box is a multiplexer from the open-source GPAC multimedia framework that allows you to import several video formats (DivX, XviD, H264, 3ivx, etc.), audio and subtitles into MP4 containers. The program works from the command line and is able to encode MPEG-4 XMT / W3C SVG scenes into the binary MPEG-4 BIFS and LASeR formats and decode them back, add / delete video and sound tracks, multiplex ISO files like MP4 and 3GP, encrypt streams, add metadata and prepare content for DASH and HLS streaming. With simple commands, MP4Box users can, for example, repackage DivX video into the MP4 format without re-encoding or add additional audio tracks to a video. The program also allows you to extract streams from MP4 files. GPAC is free software under the LGPL licence.

MP4Box efficiently multiplexes various video, audio, and subtitle formats into MP4 containers.