RTP Payload Format for BroadVoice Speech Codecs
RFC 4298

 
Document Type RFC - Proposed Standard (December 2005; No errata)
Last updated 2013-03-02
Replaces draft-chen-rtp-bv
Stream IETF
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IESG IESG state RFC 4298 (Proposed Standard)
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Responsible AD Allison Mankin
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Network Working Group                                         J.-H. Chen
Request for Comments: 4298                                        W. Lee
Category: Standards Track                                     J. Thyssen
                                                    Broadcom Corporation
                                                           December 2005

            RTP Payload Format for BroadVoice Speech 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 Internet Society (2005).

Abstract

   This document describes the RTP payload format for the BroadVoice(R)
   narrowband and wideband speech codecs.  The narrowband codec, called
   BroadVoice16, or BV16, has been selected by CableLabs as a mandatory
   codec in PacketCable 1.5 and has a CableLabs specification.  The
   document also provides specifications for the use of BroadVoice with
   MIME and the Session Description Protocol (SDP).

Chen, et al.                Standards Track                     [Page 1]
RFC 4298           RTP Payload Format for BroadVoice       December 2005

Table of Contents

   1. Introduction ....................................................2
   2. Background ......................................................2
   3. RTP Payload Format for BroadVoice16 Narrowband Codec ............3
      3.1. BroadVoice16 Bit Stream Definition .........................4
      3.2. Multiple BroadVoice16 Frames in an RTP Packet ..............5
   4. RTP Payload Format for BroadVoice32 Wideband Codec ..............6
      4.1. BroadVoice32 Bit Stream Definition .........................6
      4.2. Multiple BroadVoice32 Frames in an RTP Packet ..............8
   5. IANA Considerations .............................................8
      5.1. MIME Registration of BroadVoice16 for RTP ..................9
      5.2. MIME Registration of BroadVoice32 for RTP ..................9
   6. Mapping to SDP Parameters ......................................10
      6.1. Offer-Answer Model Considerations .........................11
   7. Security Considerations ........................................11
   8. Congestion Control .............................................11
   9. Acknowledgements ...............................................11
   10. References ....................................................12
      10.1. Normative References .....................................12
      10.2. Informative References ...................................12

1.  Introduction

   This document specifies the payload format for sending BroadVoice
   encoded speech or audio signals using the Real-time Transport
   Protocol (RTP) [1].  The sender may send one or more BroadVoice codec
   data frames per packet, depending on the application scenario, based
   on network conditions, bandwidth availability, delay requirements,
   and packet-loss tolerance.

   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

   BroadVoice is a speech codec family developed for VoIP (Voice over
   Internet Protocol) applications, including Voice over Cable, Voice
   over DSL, and IP phone applications.  BroadVoice achieves high speech
   quality with a low coding delay and relatively low codec complexity.

   The BroadVoice codec family contains two codec versions.  The
   narrowband version of BroadVoice, called BroadVoice16 [3], or BV16
   for short, encodes 8 kHz-sampled narrowband speech at a bit rate of
   16 kilobits/second, or 16 kbit/s.  The wideband version of
   BroadVoice, called BroadVoice32, or BV32, encodes 16 kHz-sampled
   wideband speech at a bit rate of 32 kbit/s.  The BV16 and BV32 use

Chen, et al.                Standards Track                     [Page 2]
RFC 4298           RTP Payload Format for BroadVoice       December 2005

   very similar (but not identical) coding algorithms; they share most
   of their algorithm modules.

   To minimize the delay in real-time two-way communications, both the
   BV16 and BV32 encode speech with a very small frame size of 5 ms
   without using any look ahead.  By using a packet size as small as 5
   ms if necessary, this allows VoIP systems based on BroadVoice to have
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