Digital Speech Standard (DSS) is a proprietary compressed digital audio file format defined by the International Voice Association, a co-operative venture by Olympus, Philips and Grundig. DSS was originally developed in 1994 by Grundig with the University of Nuremberg. In 1997, the digital speech standard was released, which was based on the previous codec. It is commonly used on digital dictation recorders. Modern phycoacoustical codecs that perform nearly as well at only slightly higher bitrates have led to this speech coding standard being less used in modern voice recording equipment.

M4R – is a digital multimedia container format used to store audio in mono channel mode. This format is suitable for store ringtones and it is widely used by Apple iPhone for its ringtones. Needless to say that M4R and M4A formats shares many similar features.