draft-ietf-avt-rtp-bv-04.txt   rfc4298.txt 
Internet Draft Juin-Hwey Chen Network Working Group J.-H. Chen
draft-ietf-avt-rtp-bv-04.txt Winnie Lee Request for Comments: 4298 W. Lee
April 4, 2005 Jes Thyssen Category: Standards Track J. Thyssen
Expires: October 4, 2005 Broadcom Corporation Broadcom Corporation
December 2005
RTP Payload Format for BroadVoice Speech Codecs RTP Payload Format for BroadVoice Speech Codecs
Status of This Memo Status of This Memo
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Abstract Abstract
This document describes the RTP payload format for the This document describes the RTP payload format for the BroadVoice(R)
BroadVoice(TM) narrowband and wideband speech codecs developed by narrowband and wideband speech codecs. The narrowband codec, called
Broadcom Corporation. The document also provides specifications BroadVoice16, or BV16, has been selected by CableLabs as a mandatory
for the use of BroadVoice with MIME and SDP. 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).
Table of Contents Table of Contents
1. Introduction....................................................2 1. Introduction....................................................2
2. Background......................................................2 2. Background......................................................2
3. RTP Payload Format for BroadVoice16 Narrowband Codec............3 3. RTP Payload Format for BroadVoice16 Narrowband Codec............3
3.1 BroadVoice16 Bit Stream Definition..........................4 3.1. BroadVoice16 Bit Stream Definition .........................4
3.2 Multiple BroadVoice16 Frames in an RTP Packet...............5 3.2. Multiple BroadVoice16 Frames in an RTP Packet ..............5
4. RTP Payload Format for BroadVoice32 Wideband Codec..............6 4. RTP Payload Format for BroadVoice32 Wideband Codec..............6
4.1 BroadVoice32 Bit Stream Definition..........................6 4.1. BroadVoice32 Bit Stream Definition .........................6
4.2 Multiple BroadVoice32 Frames in an RTP Packet...............8 4.2. Multiple BroadVoice32 Frames in an RTP Packet ..............8
5. IANA Considerations.............................................8 5. IANA Considerations.............................................8
5.1 MIME Registration of BroadVoice16...........................9 5.1. MIME Registration of BroadVoice16 for RTP ..................9
5.2 MIME Registration of BroadVoice32...........................9 5.2. MIME Registration of BroadVoice32 for RTP ..................9
6. Mapping to SDP Parameters......................................10 6. Mapping to SDP Parameters......................................10
6.1 Offer-Answer Model Considerations..........................11 6.1. Offer-Answer Model Considerations .........................11
7. Security Considerations........................................11 7. Security Considerations........................................11
8. Congestion Control.............................................11 8. Congestion Control.............................................11
9. Acknowledgments................................................12 9. Acknowledgements ...............................................11
10. References.....................................................12 10. References ....................................................12
10.1 Normative References......................................12 10.1. Normative References .....................................12
10.2 Informative References....................................12 10.2. Informative References ...................................12
11. Authors' Addresses.............................................13
12. RFC-Editor Consideration.......................................13
1. Introduction 1. Introduction
This document specifies the payload format for sending BroadVoice This document specifies the payload format for sending BroadVoice
encoded speech or audio signals using the Real-time Transport encoded speech or audio signals using the Real-time Transport
Protocol (RTP) [1]. The sender may send one or more BroadVoice Protocol (RTP) [1]. The sender may send one or more BroadVoice codec
codec data frames per packet, depending on the application scenario, data frames per packet, depending on the application scenario, based
based on network conditions, bandwidth availability, delay on network conditions, bandwidth availability, delay requirements,
requirements, and packet-loss tolerance. and packet-loss tolerance.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
this document are to be interpreted as described in RFC 2119 [2]. document are to be interpreted as described in RFC 2119 [2].
2. Background 2. Background
BroadVoice is a speech codec family developed by Broadcom for VoIP BroadVoice is a speech codec family developed for VoIP (Voice over
(Voice over Internet Protocol) applications, including Voice over Internet Protocol) applications, including Voice over Cable, Voice
Cable, Voice over DSL, and IP phone applications. BroadVoice over DSL, and IP phone applications. BroadVoice achieves high speech
achieves high speech quality with a low coding delay and relatively quality with a low coding delay and relatively low codec complexity.
low codec complexity.
The BroadVoice codec family contains two codec versions. The The BroadVoice codec family contains two codec versions. The
narrowband version of BroadVoice, called BroadVoice16 [3], or BV16 narrowband version of BroadVoice, called BroadVoice16 [3], or BV16
for short, encodes 8 kHz-sampled narrowband speech at a bit rate of for short, encodes 8 kHz-sampled narrowband speech at a bit rate of
16 kilobits/second, or 16 kbit/s. The wideband version of 16 kilobits/second, or 16 kbit/s. The wideband version of
BroadVoice, called BroadVoice32, or BV32, encodes 16 kHz-sampled BroadVoice, called BroadVoice32, or BV32, encodes 16 kHz-sampled
wideband speech at a bit rate of 32 kbit/s. The BV16 and BV32 use wideband speech at a bit rate of 32 kbit/s. The BV16 and BV32 use
very similar (but not identical) coding algorithms; they share most very similar (but not identical) coding algorithms; they share most
of their algorithm modules. of their algorithm modules.
To minimize the delay in real-time two-way communications, both the 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 BV16 and BV32 encode speech with a very small frame size of 5 ms
without using any look ahead. This allows VoIP systems based on without using any look ahead. By using a packet size as small as 5
BroadVoice to have a very low end-to-end system delay, by using a ms if necessary, this allows VoIP systems based on BroadVoice to have
packet size as small as 5 ms if necessary. a very low end-to-end system delay.
BroadVoice also has relatively low codec complexity when compared BroadVoice also has relatively low codec complexity when compared
with ITU-T standard speech codecs based on CELP (Coded Excited with ITU-T standard speech codecs based on CELP (Coded Excited Linear
Linear Prediction), such as G.728, G.729, G.723.1, G.722.2, etc. Prediction), such as G.728, G.729, G.723.1, and G.722.2. Full-duplex
Full-duplex implementations of the BV16 and BV32 take around 12 and implementations of the BV16 and BV32 take around 12 and 17 MIPS,
17 MIPS, respectively, on general-purpose 16-bit fixed-point DSPs. respectively, on general-purpose 16-bit fixed-point digital signal
The total memory footprints of the BV16 and BV32, including program processors (DSPs). The total memory footprints of the BV16 and BV32,
size, data tables, and data RAM, are around 12 kwords each, or 24 including program size, data tables, and data RAM, are around 12
kbytes. kwords each, or 24 kbytes.
The PacketCable(TM) project of Cable Television Laboratories, Inc. The PacketCable(TM) project of Cable Television Laboratories, Inc.
(CableLabs(r)) has chosen the BV16 codec for use in VoIP telephone (CableLabs(R)) has chosen the BV16 codec for use in VoIP telephone
services provided by cable operators. More specifically, the BV16 services provided by cable operators. More specifically, the BV16
codec was selected as one of the mandatory audio codecs in codec was selected as one of the mandatory audio codecs in the
PacketCable (TM) 1.5 Audio/Video Codecs Specification [4]. 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 3. RTP Payload Format for BroadVoice16 Narrowband Codec
The BroadVoice16 uses 5 ms frames and a sampling frequency of 8 kHz, 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 so the RTP timestamp MUST be in units of 1/8000 of a second. The RTP
RTP timestamp indicates the sampling instant of the oldest audio timestamp indicates the sampling instant of the oldest audio sample
sample represented by the frame(s) present in the payload. The represented by the frame(s) present in the payload. The RTP payload
RTP payload for the BroadVoice16 has the format shown in the figure for the BroadVoice16 has the format shown in the figure below. No
below. No additional header specific to this payload format is additional header specific to this payload format is required.
required.
0 1 2 3 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 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] | | RTP Header [1] |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| | | |
| one or more frames of BroadVoice16 | | one or more frames of BroadVoice16 |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
If BroadVoice16 is used for applications with silence compression, If BroadVoice16 is used for applications with silence compression,
the first BroadVoice16 packet after a silence period during which the first BroadVoice16 packet after a silence period during which
packets have not been transmitted contiguously, SHOULD have the packets have not been transmitted contiguously SHOULD have the marker
marker bit in the RTP data header set to one. The marker bit bit in the RTP data header set to one. The marker bit in all other
in all other packets is zero. Applications without silence packets is zero. Applications without silence suppression MUST set
suppression MUST set the marker bit to zero. the marker bit to zero.
The assignment of an RTP payload type for this new packet format is 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. outside the scope of this document, and will not be specified here.
It is expected that the RTP profile for a particular class of It is expected that the RTP profile for a particular class of
applications will assign a payload type for this encoding, or if applications will assign a payload type for this encoding, or if that
that is not done then a payload type in the dynamic range shall be is not done, then a payload type in the dynamic range shall be
chosen. chosen.
3.1 BroadVoice16 Bit Stream Definition 3.1. BroadVoice16 Bit Stream Definition
The BroadVoice16 encoder operates on speech frames of 5 ms The BroadVoice16 encoder operates on speech frames of 5 ms
corresponding to 40 samples at a sampling rate of 8000 samples per corresponding to 40 samples at a sampling rate of 8000 samples per
second. For every 5 ms frame, the encoder encodes the 40 second. For every 5 ms frame, the encoder encodes the 40 consecutive
consecutive audio samples into 80 bits, or 10 octets. Thus, the audio samples into 80 bits, or 10 octets. Thus, the 80-bit bit
80-bit bit stream produced by the BroadVoice16 for each 5 ms frame stream produced by the BroadVoice16 for each 5 ms frame is octet-
is octet-aligned, and no padding bits are required. The bit aligned, and no padding bits are required. The bit allocation for
allocation for the encoded parameters of the BroadVoice16 codec the encoded parameters of the BroadVoice16 codec is listed in the
is listed in the following table. following table.
Encoded Parameter Codeword Number of bits per frame Encoded Parameter Codeword Number of bits per frame
------------------------------------------------------------ ------------------------------------------------------------
Line Spectrum Pairs L0,L1 7+7=14 Line Spectrum Pairs L0,L1 7+7=14
Pitch Lag PL 7 Pitch Lag PL 7
Pitch Gain PG 5 Pitch Gain PG 5
Log-Gain LG 4 Log-Gain LG 4
Excitation Vectors V0,...,V9 5*10=50 Excitation Vectors V0,...,V9 5*10=50
------------------------------------------------------------ ------------------------------------------------------------
Total: 80 bits Total: 80 bits
The mapping of the encoded parameters in an 80-bit BroadVoice16 data The mapping of the encoded parameters in an 80-bit BroadVoice16 data
frame is defined in the following figure. This figure shows the bit frame is defined in the following figure. This figure shows the bit
packing in "network byte order", also known as big-endian order. packing in "network byte order", also known as big-endian order. The
The bits of each 32-bit word are numbered 0 to 31, with the most 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 significant bit on the left and numbered 0. The octets (bytes) of
each word are transmitted most significant octet first. The bits of each word are transmitted with the most significant octet first. The
data field for each encoded parameter are numbered in the same bits of the data field for each encoded parameter are numbered in the
order, with the most significant bit on the left. same order, with the most significant bit on the left.
0 1 2 3 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 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| | 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| |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 | | 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| |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 | |V| V7 | V8 | V9 |
|6| | | | |6| | | |
|4|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4| |4|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4|
skipping to change at page 5, line 24 skipping to change at page 5, line 23
| | | | | | | | | | | | | | | |
|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| |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 | |V| V7 | V8 | V9 |
|6| | | | |6| | | |
|4|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4| |4|0 1 2 3 4|0 1 2 3 4|0 1 2 3 4|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: BroadVoice16 bit packing Figure 1: BroadVoice16 bit packing
3.2 Multiple BroadVoice16 Frames in an RTP Packet 3.2. Multiple BroadVoice16 Frames in an RTP Packet
More than one BroadVoice16 frame MAY be included in a single RTP More than one BroadVoice16 frame MAY be included in a single RTP
packet by a sender. Senders have the following additional packet by a sender. Senders have the following additional
restrictions: restrictions:
o SHOULD NOT include more BroadVoice16 frames in a single RTP o SHOULD NOT include more BroadVoice16 frames in a single RTP
packet than will fit in the MTU of the RTP transport protocol. packet than will fit in the MTU of the RTP.
o MUST NOT split a BroadVoice16 frame between RTP packets. o MUST NOT split a BroadVoice16 frame between RTP packets.
o BroadVoice16 frames in an RTP packet MUST be consecutive. o BroadVoice16 frames in an RTP packet MUST be consecutive.
Since multiple BroadVoice16 frames in an RTP packet MUST be Since multiple BroadVoice16 frames in an RTP packet MUST be
consecutive, and since BroadVoice16 has a fixed frame size of 5 ms, consecutive, and since BroadVoice16 has a fixed frame size of 5 ms,
recovering the timestamps of all frames within a packet is easy. recovering the timestamps of all frames within a packet is easy. The
The oldest frame within an RTP packet has the same timestamp as the oldest frame within an RTP packet has the same timestamp as the RTP
RTP packet, as mentioned above. To obtain the timestamp of the packet, as mentioned above. To obtain the timestamp of the frame
frame that is N frames later than the oldest frame in the packet, that is N frames later than the oldest frame in the packet, one
one simply adds 5*N ms worth of time units to the timestamp of the simply adds 5*N ms worth of time units to the timestamp of the RTP
RTP packet. packet.
It is RECOMMENDED that the number of frames contained within an RTP It is RECOMMENDED that the number of frames contained within an RTP
packet is consistent with the application. For example, in a packet be consistent with the application. For example, in a
telephony application where delay is important, the fewer frames per telephony application where delay is important, the fewer frames per
packet the lower the delay, whereas for a delay insensitive packet, the lower the delay; whereas, for a delay insensitive
streaming or messaging application, many frames per packet would be streaming or messaging application, many frames per packet would be
acceptable. acceptable.
Information describing the number of frames contained in an RTP Information describing the number of frames contained in an RTP
packet is not transmitted as part of the RTP payload. The only way 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 to determine the number of BroadVoice16 frames is to count the total
number of octets within the RTP payload, and divide the octet count number of octets within the RTP payload, and divide the octet count
by 10. by 10.
4. RTP Payload Format for BroadVoice32 Wideband Codec 4. RTP Payload Format for BroadVoice32 Wideband Codec
The BroadVoice32 uses 5 ms frames and a sampling frequency of 16 The BroadVoice32 uses 5 ms frames and a sampling frequency of 16 kHz,
kHz, so the RTP timestamp MUST be in units of 1/16000 of a second. so the RTP timestamp MUST be in units of 1/16000 of a second. The
The RTP timestamp indicates the sampling instant of the oldest RTP timestamp indicates the sampling instant of the oldest audio
audio sample represented by the frame(s) present in the payload. sample represented by the frame(s) present in the payload. The RTP
The RTP payload for the BroadVoice32 has the format shown in the payload for the BroadVoice32 has the format shown in the figure
figure below. No additional header specific to this payload format below. No additional header specific to this payload format is
is required. required.
0 1 2 3 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 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] | | RTP Header [1] |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
| | | |
| one or more frames of BroadVoice32 | | one or more frames of BroadVoice32 |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
If BroadVoice32 is used for applications with silence compression, If BroadVoice32 is used for applications with silence compression,
the first BroadVoice32 packet after a silence period during which the first BroadVoice32 packet after a silence period during which
packets have not been transmitted contiguously, SHOULD have the packets have not been transmitted contiguously SHOULD have the marker
marker bit in the RTP data header set to one. The marker bit bit in the RTP data header set to one. The marker bit in all other
in all other packets is zero. Applications without silence packets is zero. Applications without silence suppression MUST set
suppression MUST set the marker bit to zero. the marker bit to zero.
The assignment of an RTP payload type for this new packet format is 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. outside the scope of this document, and will not be specified here.
It is expected that the RTP profile for a particular class of It is expected that the RTP profile for a particular class of
applications will assign a payload type for this encoding, or if applications will assign a payload type for this encoding, or if that
that is not done then a payload type in the dynamic range shall be is not done, then a payload type in the dynamic range shall be
chosen. chosen.
4.1 BroadVoice32 Bit Stream Definition 4.1. BroadVoice32 Bit Stream Definition
The BroadVoice32 encoder operates on speech frames of 5 ms The BroadVoice32 encoder operates on speech frames of 5 ms
corresponding to 80 samples at a sampling rate of 16000 samples per corresponding to 80 samples at a sampling rate of 16000 samples per
second. For every 5 ms frame, the encoder encodes the 80 second. For every 5 ms frame, the encoder encodes the 80 consecutive
consecutive audio samples into 160 bits, or 20 octets. Thus, the audio samples into 160 bits, or 20 octets. Thus, the 160-bit bit
160-bit bit stream produced by the BroadVoice32 for each 5 ms frame stream produced by the BroadVoice32 for each 5 ms frame is octet-
is octet-aligned, and no padding bits are required. The bit aligned, and no padding bits are required. The bit allocation for
allocation for the encoded parameters of the BroadVoice32 codec the encoded parameters of the BroadVoice32 codec is listed in the
is listed in the following table. following table.
Number of bits Number of bits
Encoded Parameter Codeword per frame Encoded Parameter Codeword per frame
--------------------------------------------------------------- ---------------------------------------------------------------
Line Spectrum Pairs L0,L1,L2 7+5+5=17 Line Spectrum Pairs L0,L1,L2 7+5+5=17
Pitch Lag PL 8 Pitch Lag PL 8
Pitch Gain PG 5 Pitch Gain PG 5
Log-Gains (1st & 2nd subframes) LG0,LG1 5+5=10 Log-Gains (1st & 2nd subframes) LG0,LG1 5+5=10
Excitation Vectors (1st subframe) VA0,...,VA9 6*10=60 Excitation Vectors (1st subframe) VA0,...,VA9 6*10=60
Excitation Vectors (2nd subframe) VB0,...,VB9 6*10=60 Excitation Vectors (2nd subframe) VB0,...,VB9 6*10=60
--------------------------------------------------------------- ---------------------------------------------------------------
Total: 160 bits Total: 160 bits
The mapping of the encoded parameters in a 160-bit BroadVoice32 data The mapping of the encoded parameters in a 160-bit BroadVoice32 data
frame is defined in the following figure. This figure shows the bit frame is defined in the following figure. This figure shows the bit
packing in "network byte order", also known as big-endian order. packing in "network byte order", also known as big-endian order. The
The bits of each 32-bit word are numbered 0 to 31, with the most 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 significant bit on the left and numbered 0. The octets (bytes) of
each word are transmitted most significant octet first. The bits of each word are transmitted with the most significant octet first. The
data field for each encoded parameter are numbered in the same bits of the data field for each encoded parameter are numbered in the
order, with the most significant bit on the left. same order, with the most significant bit on the left.
0 1 2 3 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 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| | 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| |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 | | LG0 | LG1 | VA0 | VA1 | VA2 | VA3 |
| | | | | | | | | | | | | |
skipping to change at page 8, line 5 skipping to change at page 8, line 5
| | | | | | | | | | | | | |
|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| |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 | |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| |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 Figure 2: BroadVoice32 bit packing
4.2 Multiple BroadVoice32 Frames in an RTP Packet 4.2. Multiple BroadVoice32 Frames in an RTP Packet
More than one BroadVoice32 frame MAY be included in a single RTP More than one BroadVoice32 frame MAY be included in a single RTP
packet by a sender. Senders have the following additional packet by a sender. Senders have the following additional
restrictions: restrictions:
o SHOULD NOT include more BroadVoice32 frames in a single RTP o SHOULD NOT include more BroadVoice32 frames in a single RTP
packet than will fit in the MTU of the RTP transport protocol. packet than will fit in the MTU of the RTP.
o MUST NOT split a BroadVoice32 frame between RTP packets. o MUST NOT split a BroadVoice32 frame between RTP packets.
o BroadVoice32 frames in an RTP packet MUST be consecutive. o BroadVoice32 frames in an RTP packet MUST be consecutive.
Since multiple BroadVoice32 frames in an RTP packet MUST be Since multiple BroadVoice32 frames in an RTP packet MUST be
consecutive, and since BroadVoice32 has a fixed frame size of 5 ms, consecutive, and since BroadVoice32 has a fixed frame size of 5 ms,
recovering the timestamps of all frames within a packet is easy. recovering the timestamps of all frames within a packet is easy. The
The oldest frame within an RTP packet has the same timestamp as the oldest frame within an RTP packet has the same timestamp as the RTP
RTP packet, as mentioned above. To obtain the timestamp of the packet, as mentioned above. To obtain the timestamp of the frame
frame that is N frames later than the oldest frame in the packet, that is N frames later than the oldest frame in the packet, one
one simply adds 5*N ms worth of time units to the timestamp of the simply adds 5*N ms worth of time units to the timestamp of the RTP
RTP packet. packet.
It is RECOMMENDED that the number of frames contained within an RTP It is RECOMMENDED that the number of frames contained within an RTP
packet is consistent with the application. For example, in a packet be consistent with the application. For example, in a
telephony application where delay is important, the fewer frames per telephony application where delay is important, the fewer frames per
packet the lower the delay, whereas for a delay insensitive packet, the lower the delay; whereas, for a delay insensitive
streaming or messaging application, many frames per packet would be streaming or messaging application, many frames per packet would be
acceptable. acceptable.
Information describing the number of frames contained in an RTP Information describing the number of frames contained in an RTP
packet is not transmitted as part of the RTP payload. The only way 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 to determine the number of BroadVoice32 frames is to count the total
number of octets within the RTP payload, and divide the octet count number of octets within the RTP payload, and divide the octet count
by 20. by 20.
5. IANA Considerations 5. IANA Considerations
Two new MIME sub-types as described in this section are to be Two new MIME sub-types, as described in this section, have been
registered. registered.
The MIME names for the BV16 and BV32 codecs are to be allocated from 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 the IETF tree since these two codecs are expected to be widely used
for Voice-over-IP applications, especially in Voice over Cable for Voice-over-IP applications, especially in Voice over Cable
applications. applications.
5.1 MIME Registration of BroadVoice16 for RTP 5.1. MIME Registration of BroadVoice16 for RTP
MIME media type name: audio MIME media type name: audio
MIME media subtype name: BV16 MIME media subtype name: BV16
Required parameter: none Required parameter: none
Optional parameters: Optional parameters:
ptime: Defined as usual for RTP audio (see RFC 2327 [5]). ptime: Defined as usual for RTP audio (see RFC 2327 [4]).
maxptime: See RFC 2327 [5] for its definition. The maxptime maxptime: See RFC 3267 [7] for its definition. The maxptime
SHOULD be a multiple of the duration of a single codec data SHOULD be a multiple of the duration of a single codec data
frame (5 ms). frame (5 ms).
Encoding considerations: Encoding considerations:
This type is defined for transfer of BV16-encoded data via RTP This type is defined for transferring BV16-encoded data via RTP
using the payload format specified in Sections 3 of RFC XXXX. using the payload format specified in Section 3 of RFC 4298.
Audio data is binary data and must be encoded for non-binary Audio data is binary data and must be encoded for non-binary
transport; the Base64 encoding is suitable for Email. transport; the Base64 encoding is suitable for Email.
Security considerations: Security considerations:
See Section 7 "Security Considerations" of RFC XXXX. See Section 7 "Security Considerations" of RFC 4298.
Public specification: Public specification:
The BroadVoice16 codec has been specified in [3]. The BroadVoice16 codec has been specified in [3].
Intended usage: Intended usage:
COMMON. It is expected that many VoIP applications, especially COMMON. It is expected that many VoIP applications, especially
Voice over Cable applications, will use this type. Voice over Cable applications, will use this type.
Person & email address to contact for further information: Person & email address to contact for further information:
Juin-Hwey (Raymond) Chen Juin-Hwey (Raymond) Chen
rchen@broadcom.com rchen@broadcom.com
Author/Change controller: Author/Change controller:
Author: Juin-Hwey (Raymond) Chen, rchen@broadcom.com Author: Juin-Hwey (Raymond) Chen, rchen@broadcom.com
Change Controller: IETF Audio/Video Transport Working Group Change Controller: IETF Audio/Video Transport Working Group
delegated from the IESG delegated from the IESG
5.2 MIME Registration of BroadVoice32 for RTP 5.2. MIME Registration of BroadVoice32 for RTP
MIME media type name: audio MIME media type name: audio
MIME media subtype name: BV32 MIME media subtype name: BV32
Required parameter: none Required parameter: none
Optional parameters: Optional parameters:
ptime: Defined as usual for RTP audio (see RFC 2327 [5]). ptime: Defined as usual for RTP audio (see RFC 2327 [4]).
maxptime: See RFC 2327 [5] for its definition. The maxptime maxptime: See RFC 3267 [7] for its definition. The maxptime
SHOULD be a multiple of the duration of a single codec data SHOULD be a multiple of the duration of a single codec data
frame (5 ms). frame (5 ms).
Encoding considerations: Encoding considerations:
This type is defined for transfer of BV32-encoded data via RTP This type is defined for transferring BV32-encoded data via RTP
using the payload format specified in Sections 4 of RFC XXXX. using the payload format specified in Section 4 of RFC 4298.
Audio data is binary data and must be encoded for non-binary Audio data is binary data and must be encoded for non-binary
transport; the Base64 encoding is suitable for Email. transport; the Base64 encoding is suitable for Email.
Security considerations: Security considerations:
See Section 7 "Security Considerations" of RFC XXXX. See Section 7 "Security Considerations" of RFC 4298.
Intended usage: Intended usage:
COMMON. It is expected that many VoIP applications, especially COMMON. It is expected that many VoIP applications, especially
Voice over Cable applications, will use this type. Voice over Cable applications, will use this type.
Person & email address to contact for further information: Person & email address to contact for further information:
Juin-Hwey (Raymond) Chen Juin-Hwey (Raymond) Chen
rchen@broadcom.com rchen@broadcom.com
Author/Change controller: Author/Change controller:
Author: Juin-Hwey (Raymond) Chen, rchen@broadcom.com Author: Juin-Hwey (Raymond) Chen, rchen@broadcom.com
Change Controller: IETF Audio/Video Transport Working Group Change Controller: IETF Audio/Video Transport Working Group
delegated from the IESG delegated from the IESG
6. Mapping to SDP Parameters 6. Mapping to SDP Parameters
The information carried in the MIME media type specification has a The information carried in the MIME media type specification has a
specific mapping to fields in the Session Description Protocol (SDP) specific mapping to fields in the Session Description Protocol (SDP)
[5], which is commonly used to describe RTP sessions. When SDP is [4], which is commonly used to describe RTP sessions. When SDP is
used to specify sessions employing the BroadVoice16 or BroadVoice32 used to specify sessions employing the BroadVoice16 or BroadVoice32
codec, the mapping is as follows: codec, the mapping is as follows:
- The MIME type ("audio") goes in SDP "m=" as the media name. - The MIME type ("audio") goes in SDP "m=" as the media name.
- The MIME subtype (payload format name) goes in SDP "a=rtpmap" - The MIME subtype (payload format name) goes in SDP "a=rtpmap"
as the encoding name. The RTP clock rate in "a=rtpmap" MUST as the encoding name. The RTP clock rate in "a=rtpmap" MUST be
be 8000 for BV16 and 16000 for BV32. 8000 for BV16 and 16000 for BV32.
- The parameters "ptime" and "maxptime" go in the SDP "a=ptime" - The parameters "ptime" and "maxptime" go in the SDP "a=ptime"
and "a=maxptime" attributes, respectively. and "a=maxptime" attributes, respectively.
An example of the media representation in SDP for describing BV16 An example of the media representation in SDP for describing BV16
might be: might be:
m=audio 49120 RTP/AVP 97 m=audio 49120 RTP/AVP 97
a=rtpmap:97 BV16/8000 a=rtpmap:97 BV16/8000
An example of the media representation in SDP for describing BV32 An example of the media representation in SDP for describing BV32
might be: might be:
m=audio 49122 RTP/AVP 99 m=audio 49122 RTP/AVP 99
a=rtpmap:99 BV32/16000 a=rtpmap:99 BV32/16000
6.1 Offer-Answer Model Considerations 6.1. Offer-Answer Model Considerations
No special considerations are need for using the SDP Offer/Answer No special considerations are needed for using the SDP Offer/Answer
model [6] with the BV16 and BV32 RTP payload formats. model [5] with the BV16 and BV32 RTP payload formats.
7. Security Considerations 7. Security Considerations
RTP packets using the payload format defined in this specification RTP packets using the payload format defined in this specification
are subject to the security considerations discussed in the RTP are subject to the security considerations discussed in the RTP
specification [1] and any appropriate profile (for example, [7]). specification [1] and any appropriate profile (for example, [6]).
This implies that confidentiality of the media streams is achieved This implies that confidentiality of the media streams is achieved by
by encryption. Because the data compression used with this payload encryption.
format is applied end-to-end, encryption may be performed after
compression so there is no conflict between the two operations.
A potential denial-of-service threat exists for data encoding using A potential denial-of-service threat exists for data encoding using
compression techniques that have non-uniform receiver-end compression techniques that have non-uniform receiver-end
computational load. The attacker can inject pathological datagrams computational load. The attacker can inject pathological datagrams
into the stream which are complex to decode and cause the receiver into the stream that are complex to decode and cause the receiver to
to become overloaded. However, the encodings covered in this become overloaded. However, the encodings covered in this document
document do not exhibit any significant non-uniformity. do not exhibit any significant non-uniformity.
8. Congestion Control 8. Congestion Control
The general congestion control considerations for transporting RTP The general congestion control considerations for transporting RTP
data apply to BV16 and BV32 audio over RTP as well, see RTP [1] data apply to BV16 and BV32 audio over RTP as well (see RTP [1]) and
and any applicable RTP profile like AVP [7]. BV16 and BV32 do not any applicable RTP profile like AVP [6]. BV16 and BV32 do not have
have any built-in mechanism for reducing the bandwidth. Packing any built-in mechanism for reducing the bandwidth. Packing more
more frames in each RTP payload can reduce the number of packets frames in each RTP payload can reduce the number of packets sent, and
sent and hence the overhead from IP/UDP/RTP headers, at the hence the overhead from IP/UDP/RTP headers, at the expense of
expense of increased delay and reduced error robustness against increased delay and reduced error robustness against packet losses.
packet losses.
9. Acknowledgments 9. Acknowledgements
The authors would like to thank Magnus Westerlung, Colin Perkins, The authors would like to thank Magnus Westerlund, Colin Perkins,
Allison Mankin, and Jean-Francois Mule for their review of this Allison Mankin, and Jean-Francois Mule for their review of this
document. document.
10. References 10. References
10.1 Normative References 10.1. Normative References
[1] H. Schulzrinne, S. Casner, R. Frederick, and V. Jacobson, "RTP: [1] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
A Transport Protocol for Real-Time Applications", STD 64, "RTP: A Transport Protocol for Real-Time Applications", STD 64,
RFC 3550, Internet Engineering Task Force, July 2003. RFC 3550, July 2003.
[2] S. Bradner, "Key words for use in RFCs to Indicate requirement [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, Internet Engineering Task Force, Levels", BCP 14, RFC 2119, March 1997.
March 1997.
[3] Cable Television Laboratories, Inc., BroadVoice(TM)16 Speech [3] Cable Television Laboratories, Inc., BroadVoice(TM)16 Speech
Codec Specification, Revision 1.2, October 30, 2003. Codec Specification, Revision 1.2, October 30, 2003.
[5] M. Handley and V. Jacobson, "SDP: Session Description [4] Handley, M. and V. Jacobson, "SDP: Session Description Protocol",
Protocol", RC 2327, April 1998. RFC 2327, April 1998.
[6] J. Rosenberg and H. Schulzrinne, "An Offer/Answer Model with [5] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
the Session Description Protocol (SDP)", RFC 3264, Internet Session Description Protocol (SDP)", RFC 3264, June 2002.
Engineering Task Force, June 2002.
[7] H. Schulzrinne and S. Casner, "RTP Profile for Audio and Video [6] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
Conferences with Minimal Control", STD 65, RFC 3551, Internet Conferences with Minimal Control", STD 65, RFC 3551, July 2003.
Engineering Task Force, July 2003.
10.2 Informative References [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.
[4] Cable Television Laboratories, Inc., PacketCable(TM) 1.5 10.2. Informative References
[8] Cable Television Laboratories, Inc., PacketCable(TM) 1.5
Audio/Video Codecs Specification, PKT-SP-CODEC1.5-I01-050128, Audio/Video Codecs Specification, PKT-SP-CODEC1.5-I01-050128,
January 28, 2005. January 28, 2005.
http://www.cablelabs.com/specifications/archives/ http://www.cablelabs.com/specifications/archives/
11. Authors' Addresses Authors' Addresses
Juin-Hwey (Raymond) Chen Juin-Hwey (Raymond) Chen
Broadcom Corporation Broadcom Corporation
Room A3020 Room A3020
16215 Alton Parkway 16215 Alton Parkway
Irvine, CA 92618 Irvine, CA 92618
USA USA
Phone: +1 949 926 6288 Phone: +1 949 926 6288
Email: rchen@broadcom.com EMail: rchen@broadcom.com
Winnie Lee Winnie Lee
Broadcom Corporation Broadcom Corporation
Room A2012E Room A2012E
200-13711 International Place 200-13711 International Place
Richmond, British Columbia V6V 2Z8 Richmond, British Columbia V6V 2Z8
Canada Canada
Phone: +1 604 233 8605 Phone: +1 604 233 8605
Email: wlee@broadcom.com EMail: wlee@broadcom.com
Jes Thyssen Jes Thyssen
Broadcom Corporation Broadcom Corporation
Room A3018 Room A3018
16215 Alton Parkway 16215 Alton Parkway
Irvine, CA 92618 Irvine, CA 92618
USA USA
Phone: +1 949 926 5768
Email: jthyssen@broadcom.com
12. RFC-Editor Consideration
The RFC-editor is kindly requested to perform the following
modifications upon the publication of this specification:
- Replace all occurrences of RFC XXXX with the RFC number this Phone: +1 949 926 5768
specification receives when being published. EMail: jthyssen@broadcom.com
- Remove this Section. Full Copyright Statement
Expires: October 4, 2005 Copyright (C) The Internet Society (2005).
Copyright (C) The Internet Society (2005). This document is subject This document is subject to the rights, licenses and restrictions
to the rights, licenses and restrictions contained in BCP 78, and contained in BCP 78, and except as set forth therein, the authors
except as set forth therein, the authors retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
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