The MPEG-4 Audio format stores AAC-encoded audio in an MPEG-4 container, the standard audio format produced by iTunes and Apple devices. Converting to OPUS produces a audio file that stores data in the OPUS format. This conversion changes the file's encoding, compression method, and supported feature set. Metadata such as creation date and embedded colour profiles is preserved where the target format supports it. This makes OPUS the practical choice when the destination system requires it or when the target format offers better compatibility or compression. 1converter runs this conversion on the server: your file is uploaded encrypted over HTTPS, converted using trusted open-source libraries, and the output is held for 24 hours before automatic deletion.