RTP Payload Format for the G.729.1 Audio Codec
RFC 4749
| Document | Type |
RFC - Proposed Standard
(October 2006; No errata)
Updated by RFC 5459
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Replaces | draft-sollaud-avt-rtp-g729-scal-wb-ext | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Reviews | |||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 4749 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Cullen Jennings | ||
| Send notices to | (None) | ||
Network Working Group A. Sollaud
Request for Comments: 4749 France Telecom
Category: Standards Track October 2006
RTP Payload Format for the G.729.1 Audio Codec
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 (2006).
Abstract
This document specifies a Real-time Transport Protocol (RTP) payload
format to be used for the International Telecommunication Union
(ITU-T) G.729.1 audio codec. A media type registration is included
for this payload format.
Table of Contents
1. Introduction ....................................................2
2. Background ......................................................2
3. Embedded Bit Rates Considerations ...............................3
4. RTP Header Usage ................................................3
5. Payload Format ..................................................4
5.1. Payload Structure ..........................................4
5.2. Payload Header: MBS Field ..................................4
5.3. Payload Header: FT Field ...................................6
5.4. Audio Data .................................................6
6. Payload Format Parameters .......................................7
6.1. Media Type Registration ....................................7
6.2. Mapping to SDP Parameters ..................................8
6.2.1. Offer-Answer Model Considerations ...................9
6.2.2. Declarative SDP Considerations .....................11
7. Congestion Control .............................................11
8. Security Considerations ........................................11
9. IANA Considerations ............................................12
10. References ....................................................12
10.1. Normative References .....................................12
10.2. Informative References ...................................12
Sollaud Standards Track [Page 1]
RFC 4749 RTP Payload Format for G.729.1 October 2006
1. Introduction
The International Telecommunication Union (ITU-T) recommendation
G.729.1 [1] is a scalable and wideband extension of the
recommendation G.729 [9] audio codec. This document specifies the
payload format for packetization of G.729.1 encoded audio signals
into the Real-time Transport Protocol (RTP).
The payload format itself is described in Section 5. A media type
registration and the details for the use of G.729.1 with SDP are
given in Section 6.
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 RFC 2119 [2].
2. Background
G.729.1 is an 8-32 kbps scalable wideband (50-7000 Hz) speech and
audio coding algorithm interoperable with G.729, G.729 Annex A, and
G.729 Annex B. It provides a standardized solution for packetized
voice applications that allows a smooth transition from narrowband to
wideband telephony.
The most important services addressed are IP telephony and
videoconferencing, either for enterprise corporate networks or for
mass market (like Public Switched Telephone Network (PSTN) emulation
over DSL or wireless access). Target devices can be IP phones or
other VoIP handsets, home gateways, media gateways, IP Private Branch
Exchange (IPBX), trunking equipment, voice messaging servers, etc.
For all those applications, the scalability feature allows tuning the
bit rate versus quality trade-off, possibly in a dynamic way during a
session, taking into account service requirements and network
transport constraints.
The G.729.1 coder produces an embedded bitstream structured in 12
layers corresponding to 12 available bit rates between 8 and 32 kbps.
The first layer, at 8 kbps, is called the core layer and is bitstream
compatible with the ITU-T G.729/G.729A coder. At 12 kbps, a second
layer improves the narrowband quality. Upper layers provide wideband
audio (50-7000 Hz) between 14 and 32 kbps, with a 2 kbps granularity
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