M4V is a video format: it stores data in the M4V format. OPUS is a audio format that stores data in the OPUS format. This extracts the audio stream from the video container, discarding the video track. The audio track is decoded and re-encoded (or stream-copied if the codec matches) while the video frames are discarded. Converting between these two formats is common when the source application does not support OPUS natively or when the target platform only accepts OPUS. 1converter processes this conversion server-side using open-source tools. Files are transferred over HTTPS, converted on secure cloud servers, and automatically deleted after 24 hours.