muxing

Muxing, short for multiplexing, is the process of combining multiple separate data streams into a single, synchronized stream or file. In multimedia, muxing is used to package video, audio, subtitles, and metadata so they can be stored or transmitted together while preserving the ability to independently access each stream during playback.

In digital video and audio, muxing typically occurs when encoded streams are placed into a container format. The container defines how the individual streams are stored, indexed, and timed, while the actual data remains encoded with its own codecs. Common containers include MP4, MKV, AVI, and MPEG-TS. The muxer interleaves data from the different streams according to a timeline, adds necessary headers and metadata, and writes the result to disk or a network stream.

The process involves mapping each input stream to a track in the container, aligning durations and timestamps, and handling optional streams such as subtitles or alternate audio tracks. The goal is to enable synchronized playback while keeping the streams separable for decoding.

Tools and formats: software such as FFmpeg and MP4Box perform muxing for various containers. Muxing is distinct from demuxing, the latter extracting the original streams from a muxed file.

Applications include film and television production, live broadcasting, streaming, and archival. Limitations can arise from container capabilities, timing precision, and the need to maintain synchronization across formats and devices.