What is remux?

Remuxing refers to the process of copying the video and audio streams from one container format (such as MKV or AVI) to another container format (such as MP4 or M4V) without re-encoding the streams. This means that the quality of the video and audio is preserved, and the file size is reduced without any loss in quality.

Remuxing is often used for video files that have already been encoded in a high-quality format and don't require any further video or audio processing. It's also a popular method for creating smaller file sizes for video files that don't need to be transcoded, such as when copying a Blu-ray or DVD to a digital format for playback on a media server or streaming device.

Remuxing can be done using various software tools, including ffmpeg, Handbrake, and MakeMKV. However, it's important to note that not all media players are compatible with all container formats, so it's recommended to check the compatibility of your media player before remuxing your video files.