Toll Quality Voice - 32 kbit/s ADPCM MIME Sub-type Registration (RFC2422)
Original Publication Date: 1998-Sep-01
Included in the Prior Art Database: 2019-Feb-11
Internet Society Requests For Comment (RFCs)
G. Vaudreuil: AUTHOR [+1]
This document describes the registration of the MIME sub-type audio/32KADPCM for toll quality audio. [STANDARDS-TRACK]
Network Working Group G. Vaudreuil Request for Comments: 2422 Lucent Technologies Obsoletes: 1911 G. Parsons Category: Standards Track Northern Telecom September 1998
Toll Quality Voice - 32 kbit/s ADPCM MIME Sub-type Registration
Status of this Memo
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1998). All Rights Reserved.
This document describes the registration of the MIME sub-type audio/32KADPCM for toll quality audio. This audio encoding is defined by the ITU-T in Recommendation G.726.
This document describes the registration of the MIME sub-type audio/32KADPCM for toll quality audio. This audio encoding is defined by the ITU-T in Recommendation G.726. This document refines an earlier sub-type registration in RFC 1911.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [REQ].
2. ITU-T Definition
Recommendation G.726 [G726] defines the characteristics that are recommended for the conversion of a 64 kbit/s A-law or m-law pulse code modulation (PCM) channel at 8000 samples/second to and from a 40, 32, 24 or 16 kbit/s channel. The conversion is applied to the PCM
Vaudreuil & Parsons Standards Track [Page 1]
RFC 2422 32 kbit/s ADPCM September 1998
bit stream using an adaptive differential pulse code modulation (ADPCM) transcoding technique. This Recommendation obsoletes G.721 which only defined the 32 kbit/s characteristics.
Recommendation G.726 was prepared by Study Group 15 of the Telecommunications Standardization Sector of the International Telecommunication Union (ITU-T) and was approved under the ITU’s Resolution No. 2 procedure on the 14 of December 1990.
3. MIME Definition
CCITT Recommendation G.726 [G726] describes the algorithm recommended for conversion of a 64 kbit/s A-law or u-law PCM channel to and from a 32 kbit/s channel (this is the same algorithm as described in the deprecated G.721). The conversion is applied to the PCM stream using an Adaptive Differential Pulse Code Modulation (ADPCM) transcoding technique.
The MIME sub-type audio/32KADPCM is defined to hold binary audio data encoded in 32 kbit/s ADPCM exactly as defined by ITU-T Recommendation G.726. No header information shall be included as part of the audio data. The content transfer encoding is typically either binary or base64.
An additional consideration that this document defines for clarity is the choice of little endian ordering of the four bit code words. This default ordering is defined in ITU-T Recommendation X.420 [X420] for the equivalent X.400 body pa...