The AMR file format stores data in the AMR format. Converting to MKV produces a video file that stores video, audio, subtitles, and chapters in an open-standard container that supports virtually every codec. This wraps the audio track in a video container, which some platforms require for upload. Metadata such as creation date and embedded colour profiles is preserved where the target format supports it. This makes MKV 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.