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
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 |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Chen, et al. Standards Track [Page 3]
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.
Chen, et al. Standards Track [Page 4]
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.
Chen, et al. Standards Track [Page 5]
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
Chen, et al. Standards Track [Page 6]
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
[email protected]
Author/Change controller:
Author: Juin-Hwey (Raymond) Chen,
[email protected]
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
Chen, et al. Standards Track [Page 9]
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
[email protected]
Author/Change controller:
Author: Juin-Hwey (Raymond) Chen,
[email protected]
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.
Chen, et al. Standards Track [Page 10]
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.
Chen, et al. Standards Track [Page 11]
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/
Chen, et al. Standards Track [Page 12]
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:
[email protected]
Winnie Lee
Broadcom Corporation
Room A2012E
200-13711 International Place
Richmond, British Columbia V6V 2Z8
Canada
Phone: +1 604 233 8605
EMail:
[email protected]
Jes Thyssen
Broadcom Corporation
Room A3018
16215 Alton Parkway
Irvine, CA 92618
USA
Phone: +1 949 926 5768
EMail:
[email protected]
Chen, et al. Standards Track [Page 13]
RFC 4298 RTP Payload Format for BroadVoice December 2005
Full Copyright Statement
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Chen, et al. Standards Track [Page 14]
