http://www.rfc-editor.org/rfc/rfc3802.txt
RFC 3802: Toll Quality Voice - 32 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) MIME Sub-type Registration, G. Vaudreuil, G. Parsons2004-06-01T23:00:00-00:00This document describes the registration of the MIME sub-type audio/32KADPCM Adaptive Differential Pulse Code Modulation for toll quality audio. This audio encoding is defined by the ITU-T in Recommendation G.726. [STANDARDS-TRACK]