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PROPOSED STANDARD

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).






















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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



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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
   a very low end-to-end system delay.

   BroadVoice also has relatively low codec complexity when compared
   with ITU-T standard speech codecs based on CELP (Coded Excited Linear
   Prediction), such as G.728, G.729, G.723.1, and G.722.2.  Full-duplex
   implementations of the BV16 and BV32 take around 12 and 17 MIPS,
   respectively, on general-purpose 16-bit fixed-point digital signal
   processors (DSPs).  The total memory footprints of the BV16 and BV32,
   including program size, data tables, and data RAM, are around 12
   kwords each, or 24 kbytes.

   The PacketCable(TM) project of Cable Television Laboratories, Inc.
   (CableLabs(R)) has chosen the BV16 codec for use in VoIP telephone
   services provided by cable operators.  More specifically, the BV16
   codec was selected as one of the mandatory audio codecs in the
   PacketCable(TM) 1.5 Audio/Video Codecs Specification [8] and has been
   implemented by multiple vendors.  The wideband version (BV32) has
   been developed by Broadcom but has not yet appeared in a public
   specification; since it is technically very similar to BV16, its
   payload format is also defined in this document.

3.  RTP Payload Format for BroadVoice16 Narrowband Codec

   The BroadVoice16 uses 5 ms frames and a sampling frequency of 8 kHz,
   so the RTP timestamp MUST be in units of 1/8000 of a second.  The RTP
   timestamp indicates the sampling instant of the oldest audio sample
   represented by the frame(s) present in the payload.  The RTP payload
   for the BroadVoice16 has the format shown in the figure below.  No
   additional header specific to this payload format is required.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      RTP Header [1]                           |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |                                                               |
   |             one or more frames of BroadVoice16                |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





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RFC 4298           RTP Payload Format for BroadVoice       December 2005


   If BroadVoice16 is used for applications with silence compression,
   the first BroadVoice16 packet after a silence period during which
   packets have not been transmitted contiguously SHOULD have the marker
   bit in the RTP data header set to one.  The marker bit in all other
   packets is zero.  Applications without silence suppression MUST set
   the marker bit to zero.

   The assignment of an RTP payload type for this new packet format is
   outside the scope of this document, and will not be specified here.
   It is expected that the RTP profile for a particular class of
   applications will assign a payload type for this encoding, or if that
   is not done, then a payload type in the dynamic range shall be
   chosen.

3.1.  BroadVoice16 Bit Stream Definition

   The BroadVoice16 encoder operates on speech frames of 5 ms
   corresponding to 40 samples at a sampling rate of 8000 samples per
   second.  For every 5 ms frame, the encoder encodes the 40 consecutive
   audio samples into 80 bits, or 10 octets.  Thus, the 80-bit bit
   stream produced by the BroadVoice16 for each 5 ms frame is octet-
   aligned, and no padding bits are required.  The bit allocation for
   the encoded parameters of the BroadVoice16 codec is listed in the
   following table.

      Encoded Parameter      Codeword     Number of bits per frame
      ------------------------------------------------------------
      Line Spectrum Pairs    L0,L1            7+7=14
      Pitch Lag              PL                    7
      Pitch Gain             PG                    5
      Log-Gain               LG                    4
      Excitation Vectors     V0,...,V9       5*10=50
      ------------------------------------------------------------
      Total:                                      80 bits

   The mapping of the encoded parameters in an 80-bit BroadVoice16 data
   frame is defined in the following figure.  This figure shows the bit
   packing in "network byte order", also known as big-endian order.  The
   bits of each 32-bit word are numbered 0 to 31, with the most
   significant bit on the left and numbered 0.  The octets (bytes) of
   each word are transmitted with the most significant octet first.  The
   bits of the data field for each encoded parameter are numbered in the
   same order, with the most significant bit on the left.








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RFC 4298           RTP Payload Format for BroadVoice       December 2005


    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     L0      |     L1      |      PL     |   PG    |  LG   | V0|
   |             |             |             |         |       |   |
   |0 1 2 3 4 5 6|0 1 2 3 4 5 6|0 1 2 3 4 5 6|0 1 2 3 4|0 1 2 3|0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | V0  |    V1   |    V2   |    V3   |    V4   |    V5   |   V6  |
   |     |         |         |         |         |         |       |
   |2 3 4|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4|0 1 2 3|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |V|    V7   |    V8   |   V9    |
   |6|         |         |         |
   |4|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 1: BroadVoice16 bit packing

3.2.  Multiple BroadVoice16 Frames in an RTP Packet

   More than one BroadVoice16 frame MAY be included in a single RTP
   packet by a sender.  Senders have the following additional
   restrictions:

      o  SHOULD NOT include more BroadVoice16 frames in a single RTP
         packet than will fit in the MTU of the RTP.

      o  MUST NOT split a BroadVoice16 frame between RTP packets.

      o  BroadVoice16 frames in an RTP packet MUST be consecutive.

   Since multiple BroadVoice16 frames in an RTP packet MUST be
   consecutive, and since BroadVoice16 has a fixed frame size of 5 ms,
   recovering the timestamps of all frames within a packet is easy.  The
   oldest frame within an RTP packet has the same timestamp as the RTP
   packet, as mentioned above.  To obtain the timestamp of the frame
   that is N frames later than the oldest frame in the packet, one
   simply adds 5*N ms worth of time units to the timestamp of the RTP
   packet.

   It is RECOMMENDED that the number of frames contained within an RTP
   packet be consistent with the application.  For example, in a
   telephony application where delay is important, the fewer frames per
   packet, the lower the delay; whereas, for a delay insensitive
   streaming or messaging application, many frames per packet would be
   acceptable.





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RFC 4298           RTP Payload Format for BroadVoice       December 2005


   Information describing the number of frames contained in an RTP
   packet is not transmitted as part of the RTP payload.  The only way
   to determine the number of BroadVoice16 frames is to count the total
   number of octets within the RTP payload, and divide the octet count
   by 10.

4.  RTP Payload Format for BroadVoice32 Wideband Codec

   The BroadVoice32 uses 5 ms frames and a sampling frequency of 16 kHz,
   so the RTP timestamp MUST be in units of 1/16000 of a second.  The
   RTP timestamp indicates the sampling instant of the oldest audio
   sample represented by the frame(s) present in the payload.  The RTP
   payload for the BroadVoice32 has the format shown in the figure
   below.  No additional header specific to this payload format is
   required.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      RTP Header [1]                           |
   +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
   |                                                               |
   |             one or more frames of BroadVoice32                |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   If BroadVoice32 is used for applications with silence compression,
   the first BroadVoice32 packet after a silence period during which
   packets have not been transmitted contiguously SHOULD have the marker
   bit in the RTP data header set to one.  The marker bit in all other
   packets is zero.  Applications without silence suppression MUST set
   the marker bit to zero.

   The assignment of an RTP payload type for this new packet format is
   outside the scope of this document, and will not be specified here.
   It is expected that the RTP profile for a particular class of
   applications will assign a payload type for this encoding, or if that
   is not done, then a payload type in the dynamic range shall be
   chosen.

4.1.  BroadVoice32 Bit Stream Definition

   The BroadVoice32 encoder operates on speech frames of 5 ms
   corresponding to 80 samples at a sampling rate of 16000 samples per
   second.  For every 5 ms frame, the encoder encodes the 80 consecutive
   audio samples into 160 bits, or 20 octets.  Thus, the 160-bit bit
   stream produced by the BroadVoice32 for each 5 ms frame is octet-
   aligned, and no padding bits are required.  The bit allocation for



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RFC 4298           RTP Payload Format for BroadVoice       December 2005


   the encoded parameters of the BroadVoice32 codec is listed in the
   following table.
                                                        Number of bits
      Encoded Parameter                  Codeword       per frame
      ---------------------------------------------------------------
      Line Spectrum Pairs                L0,L1,L2       7+5+5=17
      Pitch Lag                          PL                    8
      Pitch Gain                         PG                    5
      Log-Gains (1st & 2nd subframes)    LG0,LG1          5+5=10
      Excitation Vectors (1st subframe)  VA0,...,VA9     6*10=60
      Excitation Vectors (2nd subframe)  VB0,...,VB9     6*10=60
      ---------------------------------------------------------------
      Total:                                                 160 bits

   The mapping of the encoded parameters in a 160-bit BroadVoice32 data
   frame is defined in the following figure.  This figure shows the bit
   packing in "network byte order", also known as big-endian order.  The
   bits of each 32-bit word are numbered 0 to 31, with the most
   significant bit on the left and numbered 0.  The octets (bytes) of
   each word are transmitted with the most significant octet first.  The
   bits of the data field for each encoded parameter are numbered in the
   same order, with the most significant bit on the left.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     L0      |    L1   |    L2   |       PL      |    PG   |LG0|
   |             |         |         |               |         |   |
   |0 1 2 3 4 5 6|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4 5 6 7|0 1 2 3 4|0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | LG0 |   LG1   |    VA0    |    VA1    |    VA2    |    VA3    |
   |     |         |           |           |           |           |
   |2 3 4|0 1 2 3 4|0 1 2 3 4 5|0 1 2 3 4 5|0 1 2 3 4 5|0 1 2 3 4 5|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    VA4    |    VA5    |    VA6    |    VA7    |    VA8    |VA9|
   |           |           |           |           |           |   |
   |0 1 2 3 4 5|0 1 2 3 4 5|0 1 2 3 4 5|0 1 2 3 4 5|0 1 2 3 4 5|0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | VA9   |    VB0    |    VB1    |    VB2    |    VB3    |  VB4  |
   |       |           |           |           |           |       |
   |2 3 4 5|0 1 2 3 4 5|0 1 2 3 4 5|0 1 2 3 4 5|0 1 2 3 4 5|0 1 2 3|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |VB4|    VB5    |    VB6    |    VB7    |    VB8    |   VB9     |
   |   |           |           |           |           |           |
   |4 5|0 1 2 3 4 5|0 1 2 3 4 5|0 1 2 3 4 5|0 1 2 3 4 5|0 1 2 3 4 5|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 2: BroadVoice32 bit packing



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RFC 4298           RTP Payload Format for BroadVoice       December 2005


4.2.  Multiple BroadVoice32 Frames in an RTP Packet

   More than one BroadVoice32 frame MAY be included in a single RTP
   packet by a sender.  Senders have the following additional
   restrictions:

      o  SHOULD NOT include more BroadVoice32 frames in a single RTP
         packet than will fit in the MTU of the RTP.

      o  MUST NOT split a BroadVoice32 frame between RTP packets.

      o  BroadVoice32 frames in an RTP packet MUST be consecutive.

   Since multiple BroadVoice32 frames in an RTP packet MUST be
   consecutive, and since BroadVoice32 has a fixed frame size of 5 ms,
   recovering the timestamps of all frames within a packet is easy.  The
   oldest frame within an RTP packet has the same timestamp as the RTP
   packet, as mentioned above.  To obtain the timestamp of the frame
   that is N frames later than the oldest frame in the packet, one
   simply adds 5*N ms worth of time units to the timestamp of the RTP
   packet.

   It is RECOMMENDED that the number of frames contained within an RTP
   packet be consistent with the application.  For example, in a
   telephony application where delay is important, the fewer frames per
   packet, the lower the delay; whereas, for a delay insensitive
   streaming or messaging application, many frames per packet would be
   acceptable.

   Information describing the number of frames contained in an RTP
   packet is not transmitted as part of the RTP payload.  The only way
   to determine the number of BroadVoice32 frames is to count the total
   number of octets within the RTP payload, and divide the octet count
   by 20.

5.  IANA Considerations

   Two new MIME sub-types, as described in this section, have been
   registered.

   The MIME names for the BV16 and BV32 codecs have been allocated from
   the IETF tree since these two codecs are expected to be widely used
   for Voice-over-IP applications, especially in Voice over Cable
   applications.







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RFC 4298           RTP Payload Format for BroadVoice       December 2005


5.1.  MIME Registration of BroadVoice16 for RTP

   MIME media type name: audio

   MIME media subtype name: BV16

   Required parameter: none

   Optional parameters:
      ptime:    Defined as usual for RTP audio (see RFC 2327 [4]).

      maxptime: See RFC 3267 [7] for its definition.  The maxptime
         SHOULD be a multiple of the duration of a single codec data
         frame (5 ms).

   Encoding considerations:
      This type is defined for transferring BV16-encoded data via RTP
      using the payload format specified in Section 3 of RFC 4298.
      Audio data is binary data and must be encoded for non-binary
      transport; the Base64 encoding is suitable for Email.

   Security considerations:
      See Section 7 "Security Considerations" of RFC 4298.

   Public specification:
      The BroadVoice16 codec has been specified in [3].

   Intended usage:
      COMMON.  It is expected that many VoIP applications, especially
      Voice over Cable applications, will use this type.

   Person & email address to contact for further information:
      Juin-Hwey (Raymond) Chen
      rchen@broadcom.com

   Author/Change controller:
      Author: Juin-Hwey (Raymond) Chen, rchen@broadcom.com
      Change Controller: IETF Audio/Video Transport Working Group
         delegated from the IESG

5.2.  MIME Registration of BroadVoice32 for RTP

   MIME media type name: audio

   MIME media subtype name: BV32

   Required parameter: none




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RFC 4298           RTP Payload Format for BroadVoice       December 2005


   Optional parameters:
      ptime:    Defined as usual for RTP audio (see RFC 2327 [4]).

      maxptime: See RFC 3267 [7] for its definition.  The maxptime
         SHOULD be a multiple of the duration of a single codec data
         frame (5 ms).

   Encoding considerations:
      This type is defined for transferring BV32-encoded data via RTP
      using the payload format specified in Section 4 of RFC 4298.
      Audio data is binary data and must be encoded for non-binary
      transport; the Base64 encoding is suitable for Email.

   Security considerations:
      See Section 7 "Security Considerations" of RFC 4298.

   Intended usage:
      COMMON.  It is expected that many VoIP applications, especially
      Voice over Cable applications, will use this type.

   Person & email address to contact for further information:
      Juin-Hwey (Raymond) Chen
      rchen@broadcom.com

   Author/Change controller:
      Author: Juin-Hwey (Raymond) Chen, rchen@broadcom.com
      Change Controller: IETF Audio/Video Transport Working Group
         delegated from the IESG

6.  Mapping to SDP Parameters

   The information carried in the MIME media type specification has a
   specific mapping to fields in the Session Description Protocol (SDP)
   [4], which is commonly used to describe RTP sessions.  When SDP is
   used to specify sessions employing the BroadVoice16 or BroadVoice32
   codec, the mapping is as follows:

      -  The MIME type ("audio") goes in SDP "m=" as the media name.

      -  The MIME subtype (payload format name) goes in SDP "a=rtpmap"
         as the encoding name.  The RTP clock rate in "a=rtpmap" MUST be
         8000 for BV16 and 16000 for BV32.

      -  The parameters "ptime" and "maxptime" go in the SDP "a=ptime"
         and "a=maxptime" attributes, respectively.






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RFC 4298           RTP Payload Format for BroadVoice       December 2005


   An example of the media representation in SDP for describing BV16
   might be:

      m=audio 49120 RTP/AVP 97
      a=rtpmap:97 BV16/8000

   An example of the media representation in SDP for describing BV32
   might be:

      m=audio 49122 RTP/AVP 99
      a=rtpmap:99 BV32/16000

6.1.  Offer-Answer Model Considerations

   No special considerations are needed for using the SDP Offer/Answer
   model [5] with the BV16 and BV32 RTP payload formats.

7.  Security Considerations

   RTP packets using the payload format defined in this specification
   are subject to the security considerations discussed in the RTP
   specification [1] and any appropriate profile (for example, [6]).
   This implies that confidentiality of the media streams is achieved by
   encryption.

   A potential denial-of-service threat exists for data encoding using
   compression techniques that have non-uniform receiver-end
   computational load.  The attacker can inject pathological datagrams
   into the stream that are complex to decode and cause the receiver to
   become overloaded.  However, the encodings covered in this document
   do not exhibit any significant non-uniformity.

8.  Congestion Control

   The general congestion control considerations for transporting RTP
   data apply to BV16 and BV32 audio over RTP as well (see RTP [1]) and
   any applicable RTP profile like AVP [6].  BV16 and BV32 do not have
   any built-in mechanism for reducing the bandwidth.  Packing more
   frames in each RTP payload can reduce the number of packets sent, and
   hence the overhead from IP/UDP/RTP headers, at the expense of
   increased delay and reduced error robustness against packet losses.

9.  Acknowledgements

   The authors would like to thank Magnus Westerlund, Colin Perkins,
   Allison Mankin, and Jean-Francois Mule for their review of this
   document.




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RFC 4298           RTP Payload Format for BroadVoice       December 2005


10.  References

10.1.  Normative References

   [1] Schulzrinne, H.,  Casner, S., Frederick, R., and V. Jacobson,
       "RTP: A Transport Protocol for Real-Time Applications", STD 64,
       RFC 3550, July 2003.

   [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
       Levels", BCP 14, RFC 2119, March 1997.

   [3] Cable Television Laboratories, Inc., BroadVoice(TM)16 Speech
       Codec Specification, Revision 1.2, October 30, 2003.

   [4] Handley, M. and V. Jacobson, "SDP: Session Description Protocol",
       RFC 2327, April 1998.

   [5] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
       Session Description Protocol (SDP)", RFC 3264, June 2002.

   [6] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
       Conferences with Minimal Control", STD 65, RFC 3551, July 2003.

   [7] Sjoberg, J., Westerlund, M., Lakaniemi, A., and Q. Xie, "Real-
       Time Transport Protocol (RTP) Payload Format and File Storage
       Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate
       Wideband (AMR-WB) Audio Codecs", RFC 3267, June 2002.

10.2.  Informative References

   [8] Cable Television Laboratories, Inc., PacketCable(TM) 1.5
       Audio/Video Codecs Specification, PKT-SP-CODEC1.5-I01-050128,
       January 28, 2005.
       http://www.cablelabs.com/specifications/archives/

















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RFC 4298           RTP Payload Format for BroadVoice       December 2005


Authors' Addresses

   Juin-Hwey (Raymond) Chen
   Broadcom Corporation
   Room A3020
   16215 Alton Parkway
   Irvine, CA 92618
   USA

   Phone: +1 949 926 6288
   EMail: rchen@broadcom.com


   Winnie Lee
   Broadcom Corporation
   Room A2012E
   200-13711 International Place
   Richmond, British Columbia V6V 2Z8
   Canada

   Phone: +1 604 233 8605
   EMail: wlee@broadcom.com


   Jes Thyssen
   Broadcom Corporation
   Room A3018
   16215 Alton Parkway
   Irvine, CA 92618
   USA

   Phone: +1 949 926 5768
   EMail: jthyssen@broadcom.com


















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RFC 4298           RTP Payload Format for BroadVoice       December 2005


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Chen, et al.                Standards Track                    [Page 14]


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