G.729.1 RTP Payload Format Update: Discontinuous Transmission (DTX) Support
RFC 5459
| Document | Type |
RFC - Proposed Standard
(January 2009; No errata)
Updates RFC 4749
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Replaces | draft-sollaud-avt-rfc4749-dtx-update | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 5459 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Cullen Jennings | ||
| Send notices to | (None) | ||
Network Working Group A. Sollaud
Request for Comments: 5459 France Telecom
Updates: 4749 January 2009
Category: Standards Track
G.729.1 RTP Payload Format Update:
Discontinuous Transmission (DTX) Support
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) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (http://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
Abstract
This document updates the Real-time Transport Protocol (RTP) payload
format to be used for the International Telecommunication Union
(ITU-T) Recommendation G.729.1 audio codec. It adds Discontinuous
Transmission (DTX) support to the RFC 4749 specification, in a
backward-compatible way. An updated media type registration is
included for this payload format.
Sollaud Standards Track [Page 1]
RFC 5459 G.729.1 DTX Support in RTP January 2009
Table of Contents
1. Introduction ....................................................2
2. Background ......................................................2
3. RTP Header Usage ................................................3
4. Payload Format ..................................................3
5. Payload Format Parameters .......................................4
5.1. Media Type Registration Update .............................4
5.2. Mapping to SDP Parameters ..................................5
5.2.1. DTX Offer-Answer Model Considerations ...............5
5.2.2. DTX Declarative SDP Considerations ..................6
6. Congestion Control ..............................................6
7. Security Considerations .........................................6
8. IANA Considerations .............................................6
9. References ......................................................6
9.1. Normative References .......................................6
9.2. Informative References .....................................7
1. Introduction
The International Telecommunication Union (ITU-T) Recommendation
G.729.1 [ITU-G.729.1] is a scalable and wideband extension of the
Recommendation G.729 [ITU-G.729] audio codec. [RFC4749] specifies
the payload format for packetization of G.729.1-encoded audio signals
into the Real-time Transport Protocol (RTP) [RFC3550].
Annex C of G.729.1 [ITU-G.729.1-C] adds Discontinuous Transmission
(DTX) support to G.729.1. This document updates the RTP payload
format to allow usage of this Annex.
Only changes or additions to [RFC4749] will be described in the
following sections.
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 [RFC2119].
2. Background
G.729.1 supports Discontinuous Transmission (DTX), a.k.a. "silence
suppression". It means that the coder includes a Voice Activity
Detection (VAD) algorithm to determine if an audio frame contains
silence or actual audio. During silence periods, the coder may
significantly decrease the transmitted bit rate by sending a small
frame called a Silence Insertion Descriptor (SID) and then stop
transmission. The receiver's decoder will generate comfort noise
(CNG) according to the parameters contained in the SID. This DTX/CNG
scheme is specified in [ITU-G.729.1-C].
Sollaud Standards Track [Page 2]
RFC 5459 G.729.1 DTX Support in RTP January 2009
The G.729.1 SID has an embedded structure. The core SID is the same
as the legacy G.729 SID [ITU-G.729-B]. The first enhancement layer
adds some parameters for narrowband comfort noise, while a second
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