draft-ietf-avt-rtp-ipmr-01.txt   draft-ietf-avt-rtp-ipmr-02.txt 
Audio/Video Transport Working Group Audio/Video Transport Working Group
Internet Draft SPIRIT DSP Internet Draft SPIRIT DSP
Intended status: Informational February 10, 2009 Intended status: Informational February 25, 2009
RTP Payload Format for SPIRIT IP-MR Speech Codec Software draft-ietf-avt-rtp-ipmr-01.txt RTP Payload Format for IP-MR Speech Codec draft-ietf-avt-rtp-ipmr-02.txt
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Abstract Abstract
This document specifies the payload format for packetization of SPIRIT IP-MR encoded speech signals into the Real-time Transport Protocol (RTP). The payload format supports transmission of multiple frames per payload, introduced redundancy for robustness against packet loss, and payload format extension for future versions compatibility. This document specifies the payload format for packetization of SPIRIT IP-MR encoded speech
signals into the Real-time Transport Protocol (RTP). The payload format supports transmission
of multiple frames per payload and introduced redundancy for robustness against packet loss.
Table of Contents Table of Contents
1. Introduction 2 1. Introduction 2
2. IP-MR RTP Payload Formats 2 2. IP-MR Codec Description 2
2.1. Standard Payload Format 3 3. Payload Format 4
2.1.1. Payload Format Structure 3 3.1. Payload Format Structure 4
2.1.2. Payload Header 3 3.2. Payload Header 4
2.1.3. Speech Table of Contents 4 3.3. Speech Table of Contents 5
2.1.4. Speech Data 4 3.4. Speech Data 5
2.1.5. Redundancy Header 5 3.5. Redundancy Header 5
2.1.6. Redundancy Table of Contents 5 3.6. Redundancy Table of Contents 6
2.1.7. Redundancy Data 6 3.7. Redundancy Data 6
2.2. Payload Examples 6 4. Payload Examples 6
2.2.1. Standard Payload Carrying a Single Frame 6 4.1. Payload Carrying a Single Frame 6
2.2.2. Standard Payload Carrying Multiple Frames with Redundancy 7 4.2. Payload Carrying Multiple Frames with Redundancy 7
2.2.3. Extended Payload Carrying a Single Frame 8 5. Media Type Registration 8
3. Media Type Registration 8 5.1. Registration of media subtype audio/ip-mr_v2.5 8
3.1. Registration of MIME media type audio/ip-mr_v2.5 8 5.2. Mapping Media Type Parameters into SDP 9
3.2. Mapping Media Type Parameters into SDP 9 6. Security Considerations 9
4. Security Considerations 10 7. IANA Considerations 10
6. Normative References 10 8. Normative References 10
Author's Addresses 10 9. Author's Information 10
Expiration date 10 10. Expiration date 10
Legal Terms 10 11. Legal Terms 10
1. Introduction 1. Introduction
This document specifies the payload format for packetization of SPIRIT IP-MR encoded speech signals into the Real-time Transport Protocol (RTP). The payload format supports transmission of multiple frames per payload, introduced redundancy for robustness against packet loss, and payload format extension for future versions compatibility. This document specifies the payload format for packetization of SPIRIT IP-MR encoded speech
signals into the Real-time Transport Protocol (RTP). The payload format supports transmission
of multiple frames per payload and introduced redundancy for robustness against packet loss.
2. IP-MR RTP Payload Formats The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
The payload has two formats: standard optimized for current use-cases and extended for future versions compatibility. The payload format is defined by first bit of header. Both of these formats will be described bellow. "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119.
2.1. Standard Payload Format 2. IP-MR Codec Description
2.1.1. Payload Format Structure The IP-MR codec is scalable adaptive multi-rate wideband speech codec designed by SPIRIT for
use in IP based networks. These codec is suitable for real time communications such as
telephony and videoconferencing.
The standard payload consists of a payload header with general information about packet, a speech table of contents (TOC), and speech data. An optional redundancy section follows after speech data. The redundancy section consists of redundancy header, redundancy TOC and redundancy data payload. The codec operates on 20 ms frames at 16 kHz sampling rate and has an algorithmic delay of 25
ms.
The IP-MR supports six wide band speech coding modes with respective bit rates ranging from
about 7.7 to about 34.2 kbps. The coding mode can be changed at any 20 ms frame boundary
making possible to dynamically adjust the speech encoding rate during a session to adapt to the
varying transmission conditions.
The coded frame consists of multiple coding layers-base (or core) layer and several enhancement
layers which are coded independently. These enhancement layers can be omitted and remaining
base layer can be meaningfully decoded without artifacts. This making bit stream scalable and
allows reduce bit rate during transmission without re-encoding.
This memo specifies an optional form of redundancy coding within RTP for protection against
packet loss. It is based on commonly known scheme when previously transmitted frames are
aggregated together with new ones. Each frame is retransmitted once in the following RTP
payload packet. f(n-2)...f(n+4) denote a sequence of speech frames, and p(n-1)...p(n+4) a
sequence of payload packets:
--+--------+--------+--------+--------+--------+--------+--------+--
| f(n-2) | f(n-1) | f(n) | f(n+1) | f(n+2) | f(n+3) | f(n+4) |
--+--------+--------+--------+--------+--------+--------+--------+--
<---- p(n-1) ---->
<----- p(n) ----->
<---- p(n+1) ---->
<---- p(n+2) ---->
<---- p(n+3) ---->
<---- p(n+4) ---->
But because of scalable nature of IP-MR codec there is no need to duplicate a whole previous
frame - only core layer may be retransmitted. This reduces redundancy overhead while keeping
efficiency. Moreover, the speech bits encoded in core layer are divided on six classes (from A to
F) of perceptual sensitivity to errors. Using these classes as introduced redundancy make
possible to adjust trade-off between overhead and robustness against packet loss.
The mechanism described does not really require signaling at the session setup. The sender is
responsible for selecting an appropriate amount of redundancy based on feedback about the
channel conditions.
The main codec characteristics can be summarized as follows:
* Wideband, 16 kHz, speech codec
* Adaptive multi rate with six modes from about 7.7 to about 34.2 kbps
* Bit rate scalable
* Variable bit rate changing in accordance with actual speech content
* Discontinuous Transmission (DTX), silence suppression and comfort noise generation
* In-band redundancy scheme for protection against packet loss
3. Payload Format
3.1. Payload Format Structure
The IP-MR payload format consists of a payload header with general information about packet, a
speech table of contents (TOC), and speech data. An optional redundancy section follows after
speech data. The redundancy section consists of redundancy header, redundancy TOC and
redundancy data payload.
The following diagram shows the standard payload format layout: The following diagram shows the standard payload format layout:
+---------+--------+--------+- - - - - - +- - - - - - +- - - - - - + +---------+--------+--------+- - - - - - +- - - - - - +- - - - - - +
| payload | speech | speech | redundancy | redundancy | redundancy | | payload | speech | speech | redundancy | redundancy | redundancy |
| header | TOC | data | header | TOC | data | | header | TOC | data | header | TOC | data |
+---------+--------+--------+- - - - - - +- - - - - - +- - - - - - + +---------+--------+--------+- - - - - - +- - - - - - +- - - - - - +
2.1.2. Payload Header 3.2. Payload Header
The payload header has the following format: The payload header has the following format:
0 1 0 1
0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+
|T| CR | BR |D|A|GR |R| |T| CR | BR |D|A|GR |R|
+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+
o T (1 bit): Reserved compatibility with future extensions. Should be set to 0. * T (1 bit): Reserved compatibility with future extensions. SHOULD be set to 0.
o CR (3 bits): coding rate of frame(s) in this packet, as per the following table: * CR (3 bits): coding rate of frame(s) in this packet, as per the following table:
+-------+--------------+ +-------+--------------+
| CR | avg. bitrate | | CR | avg. bitrate |
+-------+--------------+ +-------+--------------+
| 0 | 7.7 kbps | | 0 | 7.7 kbps |
| 1 | 9.8 kbps | | 1 | 9.8 kbps |
| 2 | 14.3 kbps | | 2 | 14.3 kbps |
| 3 | 20.8 kbps | | 3 | 20.8 kbps |
| 4 | 27.9 kbps | | 4 | 27.9 kbps |
| 5 | 34.2 kbps | | 5 | 34.2 kbps |
| 6 | (reserved) | | 6 | (reserved) |
| 7 | NO_DATA | | 7 | NO_DATA |
+-------+--------------+ +-------+--------------+
Table 1 Coding rates of IP-MR codec
The CR value 7 (NO_DATA) indicates that there is no speech data (and speech TOC accordingly) in the payload. This MAY be used to transmit redundancy data only. The value 6 is reserved. If receiving this value the packet SHOULD be discarded. The CR value 7 (NO_DATA) indicates that there is no speech data (and speech TOC
accordingly) in the payload. This MAY be used to transmit redundancy data only. The value 6 is
reserved. If receiving this value the packet SHOULD be discarded.
o BR (3 bits): base rate for core layer of frame(s) in this packet. Values in the range 0-5 indicate bitrates for core layer, same as for CR. Values 6 and 7 are reserved. If one of these values is received the packet SHOULD be discarded. The base rate is the lowest rate for scalability, so speech payload can be scaled down not lower than BR value. If a received packet has BR > CR then during decoding it will be assumed that BR = CR. * BR (3 bits): base rate for core layer of frame(s) in this packet. Values in the range 0-5
indicate bitrates for core layer, same as for CR. Values 6 and 7 are reserved. If one of
these values is received the packet SHOULD be discarded. The base rate is the lowest
rate for scalability, so speech payload can be scaled down not lower than BR value. If a
received packet has BR > CR then during decoding it will be assumed that BR = CR.
o D (1 bit): indicates if the DTX mode is allowed or not. * D (1 bit): indicates if the DTX mode is allowed or not.
o A (1 bit): byte-aligned payload. If A=1 then all speech frames MUST be byte-aligned. This mode speeds up speech data access. The A=0 value specifies bandwidth-efficient mode with no byte alignment (including end of header). * A (1 bit): byte-aligned payload. If A=1 then all speech frames MUST be byte-aligned.
This mode speeds up speech data access. The A=0 value specifies bandwidth-efficient
mode with no byte alignment (including end of header).
o GR (2 bits): number of frames in packet (grouping size). Actual grouping size is GR + 1, thus maximum grouping supported is 4. If greater grouping size is required the extended payload format (sec. 2.2) MAY be used. * GR (2 bits): number of frames in packet (grouping size). Actual grouping size is GR + 1,
thus maximum grouping supported is 4.
o R (1 bit): redundancy presence bit. If R=1 then the packet contains redundancy information for lost packets recovery. In this case after speech TOC redundancy flags and TOC sections are present. If R=0 then speech TOC is the last section of payload header. * R (1 bit): redundancy presence bit. If R=1 then the packet contains redundancy
information for lost packets recovery. In this case after speech data the redundancy
section is present.
2.1.3. Speech Table of Contents 3.3. Speech Table of Contents
The speech TOC contains entries for each frame in packet (grouping size in total). Each entry contains a single field: The speech TOC contains entries for each frame in packet (grouping size in total). Each entry
contains a single field:
0 0
+-+ +-+
|E| |E|
+-+ +-+
o E (1 bit): frame existence indicator. If set to 0, this indicates the corresponding frame is absent and the receiver should set the teRxFrType to LOST_FRAME. This can be followed by the lost frame itself or by empty frames generated by the encoder during silence intervals in DTX mode. * E (1 bit): frame existence indicator. If set to 0, this indicates the corresponding frame is
absent and the receiver should set special LOST_FRAME flag for decoder. This can be
followed by the lost frame itself or by empty frames generated by the encoder during
silence intervals in DTX mode.
Note that if CR field from coding flags is 7 (NO_DATA) then speech TOC is empty. Note that if CR flag from payload header is 7 (NO_DATA) then speech TOC is empty.
2.1.4. Speech Data 3.4. Speech Data
Speech data of a payload contains one or more speech frames or comfort noise frames, as specified in the speech TOC of the payload. Speech data of a payload contains one or more speech frames or comfort noise frames, as
specified in the speech TOC of the payload.
Each speech frame represents 20 ms of speech encoded with the rate indicated in the CR and base rate indicated in BR field of the payload header. The length of the speech frame is variable due to the nature of the codec and can be calculated after decoding or by using GetFrameInfo function detailed in [1]. Each speech frame represents 20 ms of speech encoded with the rate indicated in the CR and
base rate indicated in BR field of the payload header. The length of the speech frame is variable
due to the nature of the codec and can be calculated after decoding.
2.1.5. Redundancy Header 3.5. Redundancy Header
If a packet contains redundancy (R field of payload header is 1) the speech data is followed by redundancy header: If a packet contains redundancy (R field of payload header is 1) the speech data is followed by
redundancy header:
0 1 2 3 4 5 0 1 2 3 4 5
+-+-+-+-+-+-+ +-+-+-+-+-+-+
| CL1 | CL2 | | CL1 | CL2 |
+-+-+-+-+-+-+ +-+-+-+-+-+-+
Redundancy header consists of two fields. Each field contains class specifier for redundancy partly taken from the preceding packet (CL1) and pre-preceding packet (CL2), e.g. distant from the current packet by 1 and 2 packets accordingly. The values are listed in the table below: Redundancy header consists of two fields. Each field contains class specifier for amount of
redundancy partly taken from the preceding packet (CL1) and pre-preceding packet (CL2), e.g.
distant from the current packet by 1 and 2 packets accordingly. The values are listed in the table
below:
+-------+-------------------+ +-------+-------------------+
| CL | amount redundancy | | CL | amount redundancy |
+-------+-------------------+ +-------+-------------------+
| 0 | NONE | | 0 | NONE |
| 1 | CLASS A | | 1 | CLASS A |
| 2 | CLASS B | | 2 | CLASS B |
| 3 | CLASS C | | 3 | CLASS C |
| 4 | CLASS D | | 4 | CLASS D |
| 5 | CLASS E | | 5 | CLASS E |
| 6 | CLASS F | | 6 | CLASS F |
| 7 | (reserved) | | 7 | (reserved) |
+-------+-------------------+ +-------+-------------------+
Each specifier takes 3 bits, thus the total redundancy header size is 6 bits. In case of redundancy usage followed by preceding (or pre- preceding) packet loss the receiver sets the special flag for decoder with CL class specifier. Each specifier takes 3 bits, thus the total redundancy header size is 6 bits.
2.1.6. Redundancy Table of Contents 3.6. Redundancy Table of Contents
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pkt1 Entries| Pkt2 Entries| | Pkt1 Entries| Pkt2 Entries|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The redundancy TOC contains entries for redundancy frames from preceding and pre-preceding packets. Each entry takes 1 bit like speech TOC entry (2.1.3): The redundancy TOC contains entries for redundancy frames from preceding and pre-preceding
packets. Each entry takes 1 bit like speech TOC entry (3.3):
0 0
+-+ +-+
|E| |E|
+-+ +-+
o E (1 bit): frame existence indicator. If set to 0, this indicates the corresponding frame is absent. * E (1 bit): frame existence indicator. If set to 0, this indicates the corresponding frame is
absent.
o For each preceding and pre-preceding packet the number of entries is equal to the grouping size of the current packet. E.g. maximum number of entries is 4*2 = 8.
o If class specifier in the redundancy header is CL=0 (NO_DATA) then there is no entries for corresponding packet redundancy. * For each preceding and pre-preceding packet the number of entries is equal to the
grouping size of the current packet. E.g. maximum number of entries is 4*2 = 8.
2.1.7. Redundancy Data * If class specifier in the redundancy header is CL=0 (NO_DATA) then there is no entries
for corresponding packet redundancy.
Redundancy data of a payload contains redundancy information for one or more speech frames or comfort noise frames that may be lost during transition, as specified in the redundancy TOC of the payload. Actually redundancy is the most important part of preceding frames representing 20 ms of speech. The length of redundancy frame is variable and can be calculated after decoding or by using GetFrameInfo function detailed in [1]. 3.7. Redundancy Data
2.2. Payload Examples Redundancy data of a payload contains redundancy information for one or more speech frames
or comfort noise frames that may be lost during transition, as specified in the redundancy TOC
of the payload. Actually redundancy is the most important part of preceding frames representing
20 ms of speech. This data MAY be used for partial reconstruction of lost frames. The amount of
available redundancy is specified by CL flag in redundancy header section (3.5). This flag
SHOULD be passed to decoder. The length of redundancy frame is variable and can be
calculated after decoding.
2.2.1. Standard Payload Carrying a Single Frame 4. Payload Examples
A few examples to highlight the payload format follow.
4.1. Payload Carrying a Single Frame
The following diagram shows a standard IP-MR payload carrying a The following diagram shows a standard IP-MR payload carrying a single speech frame without
single speech frame without redundancy: redundancy:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|CR=1 |BR=0 |0|0|0 0|0|1|sp(0) | |0|CR=1 |BR=0 |0|0|0 0|0|1|sp(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sp(193)|P| | sp(193)|P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In the payload the speech frame is not damaged at the IP origin (E=1), the coding rate is 9.7 kbps (CR=1), the base rate is 7.8 kbps (BR=0), and the DTX mode is off. There is no byte alignment (A=0) and no redundancy (R=0). The encoded speech bits - s(0) to s(193) - are placed immediately after TOC. Finally, one zero bit is added at the end as padding to make the payload byte aligned. In the payload the speech frame is not damaged at the IP origin (E=1), the coding rate is 9.7 kbps
(CR=1), the base rate is 7.8 kbps (BR=0), and the DTX mode is off. There is no byte alignment
(A=0) and no redundancy (R=0). The encoded speech bits - s(0) to s(193) - are placed
immediately after TOC. Finally, one zero bit is added at the end as padding to make the payload
byte aligned.
2.2.2. Standard Payload Carrying Multiple Frames with Redundancy 4.2. Payload Carrying Multiple Frames with Redundancy
The following diagram shows a payload that contains three frames, one of them with no speech data. The coding rate is 7.7 kbps (CR=0), the base rate is 7.7 kbps (BR=0), and the DTX mode is on. The speech frames are byte aligned (A=1), so 1 zero bit is added at the end of the header. Besides the speech frames the payload contains six redundancy frames (three per each delayed packet). The following diagram shows a payload that contains three frames, one of them with no speech
data. The coding rate is 7.7 kbps (CR=0), the base rate is 7.7 kbps (BR=0), and the DTX mode
is on. The speech frames are byte aligned (A=1), so 1 zero bit is added at the end of the header.
Besides the speech frames the payload contains six redundancy frames (three per each delayed
packet).
The first speech frame consists of bits sp1(0) to sp1(92). After that 3 bits are added for byte alignment. The second frame does not contain any speech information that is represented in the payload by its TOC entry. The third frame consists of bits sp3(0) to sp3(171). The first speech frame consists of bits sp1(0) to sp1(92). After that 3 bits are added for byte
alignment. The second frame does not contain any speech information that is represented in the
payload by its TOC entry. The third frame consists of bits sp3(0) to sp3(171).
The redundancy header follows after speech data. The one-packet- delayed redundancy contains class A+B bits (CL1=2), and two-packet- delayed redundancy contains class A bits (Cl2=1). The one-packet- delayed redundancy contains three frames with 20, 39 and 35 bits respectively. The first frame of two-packet-delayed redundancy is absent, it is represented in its TOC entry, and two other frames have sizes 15 and 19 bits. The redundancy header follows after speech data. The one-packet- delayed redundancy contains
class A+B bits (CL1=2), and two-packet- delayed redundancy contains class A bits (Cl2=1). The
one-packet- delayed redundancy contains three frames with 20, 39 and 35 bits respectively. The
first frame of two-packet-delayed redundancy is absent, it is represented in its TOC entry, and
two other frames have sizes 15 and 19 bits.
Note that all speech frames are padded with zero bits for byte alignment. Note that all speech frames are padded with zero bits for byte alignment.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|CR=2 |BR=1 |1|1|1 0|1|1 0 1|P|sp1(0) | |0|CR=0 |BR=0 |1|1|1 0|1|1 0 1|P|sp1(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sp1(92)|P|P|P| | sp1(92)|P|P|P|sp3(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|sp3(0) | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sp3(171)|P|P|P|P| | sp3(171)|P|P|P|P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|CL1=2|CL2=1|1 1 1|0 1 1|red1_1(0) red1_1(19)| |CL1=2|CL2=1|1 1 1|0 1 1|red1_1(0) red1_1(19)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|red1_2(0) |red1_2(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| red1_2(38)|red1_3(0) | | red1_2(38)|red1_3(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| red1_3(34)|red2_2(0) red2_2(14)|red2_3(0) | | red1_3(34)|red2_2(0) red2_2(14)|red2_3(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| red2_3(18)|P|P|P|P| | red2_3(18)|P|P|P|P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2.2.3. Extended Payload Carrying a Single Frame 5. Media Type Registration
The following diagram shows an extended IP-MR payload carrying a single speech frame without redundancy:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|CR=1 |BR=0 |0|0|0 0|0|1|P|P|P|0 1 1|0| header extension data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |sp(0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sp(193)| optional payload extenson ...
+-+-+-+-+-+-+-+-+-+-+ - - - - - - - - - - - - - - -
The standard header is the same as in example 2.3.1 except for the first bit that is set to 1 to reflect extended payload type. The standard header is padded with zeros to achieve byte alignment. After that the size of header extension follows (HESZ=3). Then the header extension data is placed. In 3 bytes (HESZ) from header extension beginning, the standard speech payload starts. After that, the optional payload extension MAY be added.
3. Media Type Registration
This section describes the media types and names associated with this payload format. This section describes the media types and names associated with this payload format.
3.1. Registration of MIME media type audio/ip-mr_v2.5 5.1. Registration of media subtype audio/ip-mr_v2.5
Type name: audio Type name: audio
Subtype name: ip-mr_v2.5 Subtype name: ip-mr_v2.5
Required parameters: none Required parameters: none
Optional parameters: Optional parameters:
o ptime: Gives the length of time in milliseconds represented by the media in a packet. Allowed values are: 20, 40, 60 and 80. * ptime: Gives the length of time in milliseconds represented by the media in a packet.
Allowed values are: 20, 40, 60 and 80.
Encoding considerations: Encoding considerations:
This media type is framed binary data (see RFC 4288, Section 4.8). This media type is framed binary data (see RFC 4288, Section 4.8).
Security considerations: See RFC 3550 Security considerations:
See RFC 3550
Applications that use this media type: Interoperability considerations: none
Audio and video streaming and conferencing tools. Published specification:
RFC XXXX
Applications that use this media type:
Real-time audio applications like voice over IP and teleconference, and multi-media
streaming.
Additional information: none Additional information: none
Person & email address to contact for further information:
Elena Berlizova
berlizova@spiritdsp.com
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: Restrictions on usage:
This media type depends on RTP framing, and hence is only defined for transfer via RTP
(RFC 3550).
This media type depends on RTP framing, and hence is only defined for transfer via RTP (RFC 3550). Author:
Sergey Ikonin <ikonin@spiritdsp.com>
3.2. Mapping Media Type Parameters into SDP Change controller:
IETF Audio/Video Transport working group delegated from the IESG.
The information carried in the media type specification has a specific mapping to fields in the Session Description Protocol (SDP) [RFC4566], which is commonly used to describe RTP sessions. When SDP is used to specify sessions employing the IP-MR codec, the mapping is as follows: 5.2. Mapping Media Type Parameters into SDP
The information carried in the media type specification has a specific mapping to fields in the
Session Description Protocol (SDP) [RFC4566], which is commonly used to describe RTP
sessions. When SDP is used to specify sessions employing the IP-MR codec, the mapping is as
follows:
* The media type ("audio") goes in SDP "m=" as the media name. * The media type ("audio") goes in SDP "m=" as the media name.
* The media subtype (payload format name) goes in SDP "a=rtpmap" as the encoding name. The RTP clock rate in "a=rtpmap" MUST 16000. * The media subtype (payload format name) goes in SDP "a=rtpmap" as the encoding name. The
RTP clock rate in "a=rtpmap" MUST 16000.
* The parameters "ptime" and "maxptime" go in the SDP "a=ptime" and "a=maxptime" attributes, respectively. * The parameter "ptime" goes in the SDP "a=ptime" attributes.
Any remaining parameters go in the SDP "a=fmtp" attribute by copying them directly from the media type parameter string as a semicolon- separated list of parameter=value pairs. Any remaining parameters go in the SDP "a=fmtp" attribute by copying them directly from the
media type parameter string as a semicolon- separated list of parameter=value pairs.
4. Security Considerations Note that the payload format (encoding) names are commonly shown in upper case. Media
subtypes are commonly shown in lower case. These names are case-insensitive in both places.
RTP packets using the payload format defined in this specification are subject to the security considerations discussed in the RTP specification [RFC3550], and any appropriate RTP profile. This implies that confidentiality of the media streams is achieved by encryption. Encryption may be performed after compression so there is no conflict between the two operations. 6. Security Considerations
This payload format does not exhibit any significant non-uniformity in the receiver side computational complexity for packet processing, and thus is unlikely to pose a denial-of-service threat due to the receipt of pathological data. RTP packets using the payload format defined in this specification are subject to the security
considerations discussed in the RTP specification [RFC3550], and any appropriate RTP profile.
This implies that confidentiality of the media streams is achieved by encryption. Encryption
may be performed after compression so there is no conflict between the two operations.
6. Normative References This payload format does not exhibit any significant non-uniformity in the receiver side
computational complexity for packet processing, and thus is unlikely to pose a denial-of-service
threat due to the receipt of pathological data.
[1] SPIRIT IP-MR v2.5 User Guide, website http://spiritdsp.com 7. IANA Considerations
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[3] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, One media type has been defined and needs registration in the media types registry.
8. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC
2119, March 1997.
[2] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003. "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003.
[4] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC 4566, July 2006. [3] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session Description Protocol", RFC
Author's Addresses 4566, July 2006.
9. Author's Information
Sergey Ikonin
SPIRIT DSP
Russia Russia
109004 B.Kommunisticheskaya st. 27 109004 B.Kommunisticheskaya st. 27
Tel: +7 495 661-2178 Tel: +7 495 661-2178
Fax: +7 495 912-6786 Fax: +7 495 912-6786
Email: Elena Berlizova berlizova@spiritdsp.com Email: ikonin@spiritdsp.com
Expiration date 10. Expiration date
This Internet-Draft will expire on August 09, 2009. This Internet-Draft will expire on August 25, 2009.
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For the avoidance of doubt, each Contributor to the IETF Standards Process licenses each
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