Toll Quality Voice - 32 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) MIME Sub-type Registration
RFC 3802
| Document | Type |
RFC - Draft Standard
(June 2004; No errata)
Obsoletes RFC 2422
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 3802 (Draft Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Ned Freed | ||
| Send notices to | <jwn2@qualcomm.com> | ||
Network Working Group G. Vaudreuil
Request for Comments: 3802 Lucent Technologies
Obsoletes: 2422 G. Parsons
Category: Standards Track Nortel Networks
June 2004
Toll Quality Voice - 32 kbit/s Adaptive Differential Pulse Code
Modulation (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 Notice
Copyright (C) The Internet Society (2004).
Abstract
This 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.
1. Introduction
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
obsoletes an earlier sub-type registration contained in RFC 1911.
This document also obsoletes RFC 2422.
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].
Vaudreuil, et al. Standards Track [Page 1]
RFC 3802 32 kbit/s ADPCM June 2004
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 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
3.1. audio/32KADPCM
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 part, but is also detailed below in the
IANA Registration.
3.2. VPIM Usage
The audio/32KADPCM sub-type is a primary component of the VPIM
specification [VPIM]. In this context, the Content-Description and
Content-Disposition headers are used to succinctly describe the
contents of the audio body. As well, only the little endian bit
ordering is valid. Refer to the VPIM Specification for proper usage.
Vaudreuil, et al. Standards Track [Page 2]
RFC 3802 32 kbit/s ADPCM June 2004
4. IANA Registration
To: ietf-types@iana.org
Subject: Registration of MIME media type audio/32KADPCM
MIME media type name: audio
MIME subtype name: 32KADPCM
Required parameters: none
Optional parameters: none
Encoding considerations:
Binary or Base-64 generally preferred
Security considerations:
There are no known security risks with the sending or playing
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