What is transmuxing?
Transmuxing is the process of changing the container and delivery format for video and audio without encoding or transcoding the original content. The benefit of doing this is it's less time consuming and requires less processing power. So long as your video and audio codecs are compatible with the container you want to change to, you can use transmuxing to put the same content into different containers for delivery to different sources that may require that particular container in order to work correctly.
What's the difference between a video container and a video codec?
Containers/formats and codecs are easy to confuse, and what makes it more complicated is they're often used interchangeably. A container is what contains all the packages of video, audio and meta data that are created by the codec. You can read more detail about this in Every Video Format, Codec, and Container Explained. The video format (part of the container) is described by the file extension and it describes the rules for how the container, compressed content, and codecs will be stored and handled.
What are the most popular video containers/video formats?
Containers can often accomodate multiple types of video codecs, but it's important to determine which containers and codecs are compatible and which aren't. Some of the most popular video containers are:
Hands down the most popular video format is MP4, which is short for MPEG 4. This format supports video, audio and data like subtitles, captions and images. This format is sometimes confused with M4A, which is short for the audio-only format MPEG 4 Audio.
What are the most popular video codecs?
There are lots of video codecs out there, optimized for specific use cases for anything from editing and doing special effects to storing or streaming. Currently the most popular codecs out there are:
Currently, H.264 is the most widely used codec, but that will likely change. H.265 offers superior compression to H.264 with higher quality playback. You must pay to use it, so it's not as popular as it could be. VP9 and AV1 are free codecs with similar performance to H.265, but nothing has yet become the dominant replacement for H.264. We'll just have to wait and see what happens!