Glossary → Audio fundamentals
Audio fundamentals
Container format
A container format is the file wrapper that packages encoded audio (and video, captions, metadata) — MP4, MKV, WebM and WAV are containers holding streams produced by codecs.
'Will this file work' is usually a container question, and re-wrapping streams into a new container is instant because nothing is re-encoded. Transcription services accept many containers because they extract and decode the audio stream regardless.