The QuickTime Movie format packages video and audio in Apple's QuickTime container, which can hold ProRes, H.264, or HEVC tracks. Converting to MP3 produces a audio file that applies psychoacoustic lossy compression to remove frequencies the human ear perceives least, producing small files at acceptable audio quality. 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. This makes MP3 the practical choice when the destination system requires it or when the original format is not supported by the target application. 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.