RTP Payload Format for the Enhanced Variable Rate Wideband Codec (EVRC-WB) and the Media Subtype Updates for EVRC-B Codec
RFC 5188

Network Working Group                                        H. Desineni
Request for Comments: 5188                                      Qualcomm
Updates: 4788                                                     Q. Xie
Category: Standards Track                                       Motorola
                                                           February 2008

                        RTP Payload Format for
          the Enhanced Variable Rate Wideband Codec (EVRC-WB)
             and the Media Subtype Updates for EVRC-B 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.

Abstract

   This document specifies Real-time Transport Protocol (RTP) payload
   formats to be used for the Enhanced Variable Rate Wideband Codec
   (EVRC-WB) and updates the media type registrations for EVRC-B codec.
   Several media type registrations are included for EVRC-WB RTP payload
   formats.  In addition, a file format is specified for transport of
   EVRC-WB speech data in storage mode applications such as email.

Desineni & Xie              Standards Track                     [Page 1]
RFC 5188               EVRC-WB RTP Payload Format          February 2008

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Background . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  EVRC-WB Codec  . . . . . . . . . . . . . . . . . . . . . . . .  3
   5.  RTP Header Usage . . . . . . . . . . . . . . . . . . . . . . .  4
   6.  Payload Format . . . . . . . . . . . . . . . . . . . . . . . .  4
   7.  Congestion Control Considerations  . . . . . . . . . . . . . .  5
   8.  Storage Format for the EVRC-WB Codec . . . . . . . . . . . . .  5
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  5
     9.1.  Media Type Registrations . . . . . . . . . . . . . . . . .  5
       9.1.1.  Registration of Media Type audio/EVRCWB  . . . . . . .  6
       9.1.2.  Registration of Media Type audio/EVRCWB0 . . . . . . .  8
       9.1.3.  Registration of Media Type audio/EVRCWB1 . . . . . . .  9
       9.1.4.  Updated Registration of Media Type audio/EVRCB . . . . 11
       9.1.5.  Updated Registration of Media Type audio/EVRCB0  . . . 13
   10. SDP Mode Attributes for EVRC-WB and EVRC-B . . . . . . . . . . 15
   11. EVRC-B Interoperability with Legacy Implementations (RFC 4788) 15
   12. Mapping EVRC-WB Media Type Parameters into SDP . . . . . . . . 16
   13. Mapping EVRC-B Media Type Parameters into SDP  . . . . . . . . 16
   14. Offer-Answer Model Considerations for EVRC-WB  . . . . . . . . 16
   15. Offer-Answer Model Considerations for EVRC-B . . . . . . . . . 18
   16. Declarative SDP Considerations . . . . . . . . . . . . . . . . 18
   17. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
   18. Security Considerations  . . . . . . . . . . . . . . . . . . . 22
   19. Changes to RFC 4788  . . . . . . . . . . . . . . . . . . . . . 22
   20. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
     20.1. Normative References . . . . . . . . . . . . . . . . . . . 22
     20.2. Informative References . . . . . . . . . . . . . . . . . . 23

Desineni & Xie              Standards Track                     [Page 2]
RFC 5188               EVRC-WB RTP Payload Format          February 2008

1.  Introduction

   This document specifies the payload formats for packetization of
   EVRC-WB encoded speech signals into the Real-time Transport Protocol
   (RTP).  It defines support for the header-free, interleaved/bundled,
   and compact bundle packet formats for the EVRC-WB codec as well as
   discontinuous transmission (DTX) support for EVRC-WB encoded speech
   transported via RTP.  The EVRC-WB codec offers better speech quality
   than the EVRC and EVRC-B codecs.  EVRC-WB belongs to the EVRC family
   of codecs.  This document also updates the media type registrations
   for the EVRC-B codec.

2.  Conventions

   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 [1].

3.  Background

   EVRC-WB is a wideband extension of the EVRC-B [4] speech codec
   developed in the Third Generation Partnership Project 2 (3GPP2) with