Enhancements to RTP Payload Formats for EVRC Family Codecs
RFC 4788

 
Document Type RFC - Proposed Standard (January 2007; No errata)
Updated by RFC 5188
Updates RFC 3558
Last updated 2013-03-02
Replaces draft-xie-avt-compact-bundle-evrc
Stream IETF
Formats plain text pdf html
Stream WG state (None)
Consensus Unknown
Document shepherd No shepherd assigned
IESG IESG state RFC 4788 (Proposed Standard)
Telechat date
Responsible AD Cullen Jennings
Send notices to avt-chairs@ietf.org, Qiaobing.Xie@motorola.com, rkapoor@qualcomm.com, csp@csperkins.org
Network Working Group                                             Q. Xie
Request for Comments: 4788                                      Motorola
Updates: 3558                                                  R. Kapoor
Category: Standards Track                                       Qualcomm
                                                            January 2007

       Enhancements to RTP Payload Formats for EVRC Family Codecs

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 IETF Trust (2007).

Abstract

   This document updates the Enhanced Variable Rate Codec (EVRC) RTP
   payload formats defined in RFC 3558 with several enhancements and
   extensions.  In particular, it defines support for the header-free
   and interleaved/bundled packet formats for the EVRC-B codec, a new
   compact bundled format for the EVRC and EVRC-B codecs, as well as
   discontinuous transmission (DTX) support for EVRC and EVRC-B-encoded
   speech transported via RTP.  Voice over IP (VoIP) applications
   operating over low bandwidth dial-up and wireless networks require
   such enhancements for efficient use of the bandwidth.

Xie & Kapoor                Standards Track                     [Page 1]
RFC 4788              EVRC RTP Format Enhancements          January 2007

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Support of EVRC-B Codec  . . . . . . . . . . . . . . . . .  3
     1.2.  Compact (Header-free) Bundled Format . . . . . . . . . . .  3
     1.3.  Discontinuous Transmission (DTX) . . . . . . . . . . . . .  4
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  EVRC-B Codec . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Compact Bundled Format . . . . . . . . . . . . . . . . . . . .  5
     4.1.  Single-Rate Operation  . . . . . . . . . . . . . . . . . .  5
   5.  Storage Format for EVRC-B Codec  . . . . . . . . . . . . . . .  6
   6.  Media Type Definitions . . . . . . . . . . . . . . . . . . . .  6
     6.1.  Registration of Media Type EVRC1 . . . . . . . . . . . . .  6
     6.2.  Registration of Media Type EVRCB . . . . . . . . . . . . .  9
     6.3.  Registration of Media Type EVRCB0  . . . . . . . . . . . . 11
     6.4.  Registration of Media Type EVRCB1  . . . . . . . . . . . . 12
     6.5.  Updated Registration of Media Type EVRC  . . . . . . . . . 13
     6.6.  Updated Registration of Media Type EVRC0 . . . . . . . . . 15
     6.7.  Mapping MIME Parameters into SDP . . . . . . . . . . . . . 17
     6.8.  Usage in Offer/Answer  . . . . . . . . . . . . . . . . . . 18
   7.  Backward Compatibility with RFC 3558 . . . . . . . . . . . . . 19
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 19
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 19
   10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 20
     11.2. Informative References . . . . . . . . . . . . . . . . . . 20

Xie & Kapoor                Standards Track                     [Page 2]
RFC 4788              EVRC RTP Format Enhancements          January 2007

1.  Introduction

   This document defines support for the header-free and interleaved/
   bundled packet formats for the EVRC-B codec, a new compact bundled
   format for the EVRC and EVRC-B codecs, as well as discontinuous
   transmission (DTX) support for EVRC and EVRC-B-encoded speech
   transported via RTP.  Voice over IP (VoIP) applications operating
   over low bandwidth dial-up and wireless networks require such EVRC
   RTP payload capabilities for efficient use of the bandwidth.

1.1.  Support of EVRC-B Codec

   EVRC-B [3] is an extension to EVRC [2] developed in the Third
   Generation Partnership Project 2 (3GPP2).  EVRC-B [3] compresses each
   20 milliseconds of 8000Hz, 16-bit sampled speech input into output
   frames of one of the four different sizes: Rate 1 (171 bits), Rate
   1/2 (80 bits), Rate 1/4 (40 bits), or Rate 1/8 (16 bits).  In
   addition, there are two zero-bit codec frame types: null frames and
   erasure frames, similar to EVRC [2].  One significant enhancement in
   EVRC-B is the use of 1/4-rate frames that were not used in EVRC.
   This provides lower average data rates (ADRs) compared to EVRC, for a
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