draft-ietf-avt-rtp-evrc-nw-10.txt   rfc6884.txt 
Network Working Group Z. Fang Internet Engineering Task Force (IETF) Z. Fang
Internet-Draft Qualcomm Incorporated Request for Comments: 6884 Qualcomm Incorporated
Intended status: Standards Track January 20, 2013 Category: Standards Track March 2013
Expires: July 24, 2013 ISSN: 2070-1721
RTP payload format for Enhanced Variable Rate Narrowband-Wideband Codec RTP Payload Format
(EVRC-NW) for the Enhanced Variable Rate Narrowband-Wideband Codec (EVRC-NW)
draft-ietf-avt-rtp-evrc-nw-10
Abstract Abstract
This document specifies real-time transport protocol (RTP) payload This document specifies Real-time Transport Protocol (RTP) payload
formats to be used for the Enhanced Variable Rate Narrowband-Wideband formats to be used for the Enhanced Variable Rate Narrowband-Wideband
Codec (EVRC-NW). Three media type registrations are included for Codec (EVRC-NW). Three media type registrations are included for
EVRC-NW RTP payload formats. In addition, a file format is specified EVRC-NW RTP payload formats. In addition, a file format is specified
for transport of EVRC-NW speech data in storage mode applications for transport of EVRC-NW speech data in storage mode applications
such as e-mail. such as email.
Status of this Memo
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ....................................................2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions .....................................................2
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Background ......................................................3
4. EVRC-NW codec . . . . . . . . . . . . . . . . . . . . . . . . 6 4. EVRC-NW Codec ...................................................3
5. RTP header usage . . . . . . . . . . . . . . . . . . . . . . . 7 5. RTP Header Usage ................................................4
6. Payload format . . . . . . . . . . . . . . . . . . . . . . . . 8 6. Payload Format ..................................................4
6.1. Encoding capability identification in EVRC-NW 6.1. Encoding Capability Identification in EVRC-NW
interleaved/bundled format . . . . . . . . . . . . . . . . 8 Interleaved/Bundled Format .................................5
7. Congestion Control Considerations . . . . . . . . . . . . . . 11 7. Congestion Control Considerations ...............................6
8. Storage format for the EVRC-NW Codec . . . . . . . . . . . . . 12 8. Storage Format for the EVRC-NW Codec ............................6
9. IANA considerations . . . . . . . . . . . . . . . . . . . . . 13 9. IANA Considerations .............................................7
9.1. Media Type Registrations . . . . . . . . . . . . . . . . . 13 9.1. Media Type Registrations ...................................7
9.1.1. Registration of Media Type audio/EVRCNW . . . . . . . 13 9.1.1. Registration of Media Type audio/EVRCNW .............7
9.1.2. Registration of Media Type audio/EVRCNW0 . . . . . . . 15 9.1.2. Registration of Media Type audio/EVRCNW0 ............9
9.1.3. Registration of Media Type audio/EVRCNW1 . . . . . . . 16 9.1.3. Registration of Media Type audio/EVRCNW1 ...........10
10. SDP mode attributes for EVRC-NW . . . . . . . . . . . . . . . 19 10. SDP Mode Attributes for EVRC-NW ...............................12
11. Mode Change Request/Response Considerations . . . . . . . . . 20 11. Mode Change Request/Response Considerations ...................13
12. Mapping EVRC-NW media type parameters into SDP . . . . . . . . 22 12. Mapping EVRC-NW Media Type Parameters into SDP ................14
13. Offer-Answer Model Considerations for EVRC-NW . . . . . . . . 23 13. Offer-Answer Model Considerations for EVRC-NW .................14
14. Declarative SDP Considerations . . . . . . . . . . . . . . . . 25 14. Declarative SDP Considerations ................................16
15. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 15. Examples ......................................................16
16. Security Considerations . . . . . . . . . . . . . . . . . . . 29 16. Security Considerations .......................................19
17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30 17. References ....................................................19
17.1. Normative References . . . . . . . . . . . . . . . . . . . 30 17.1. Normative References .....................................19
17.2. Informative References . . . . . . . . . . . . . . . . . . 31 17.2. Informative References ...................................20
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 32
1. Introduction 1. Introduction
This document specifies the payload formats for packetization of This document specifies the payload formats for packetization of
EVRC-NW encoded speech signals into the real-time transport protocol EVRC-NW encoded speech signals into the Real-time Transport Protocol
(RTP). It defines support for the header-free, interleaved/bundled, (RTP). It defines support for the header-free, interleaved/bundled,
and compact bundle packet formats for the EVRC-NW codec as well as and compact bundle packet formats for the EVRC-NW codec as well as
discontinuous transmission (DTX) support for EVRC-NW encoded speech discontinuous transmission (DTX) support for EVRC-NW encoded speech
transported via RTP. The EVRC-NW codec offers better speech quality transported via RTP. The EVRC-NW codec offers better speech quality
than the EVRC and EVRC-B codecs and better capacity than EVRC-WB than the EVRC and EVRC-B codecs and better capacity than the Enhanced
codec. EVRC-NW belongs to the EVRC family of codecs. Variable Rate Wideband Codec (EVRC-WB). EVRC-NW belongs to the EVRC
family of codecs.
2. Conventions 2. Conventions
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 this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [1]. document are to be interpreted as described in RFC 2119 [1].
3. Background 3. Background
EVRC-NW is an extension of both the EVRC-B [2] and EVRC-WB [3] speech EVRC-NW is an extension of both the EVRC-B [2] and EVRC-WB [3] speech
codecs developed in 3GPP2 with support for discontinuous transmission codecs developed in the Third Generation Partnership Project 2
(DTX). It provides enhanced voice quality and high spectral (3GPP2) with support for DTX. It provides enhanced voice quality and
efficiency. high spectral efficiency.
The EVRC-NW codec operates on 20 ms frames, and the default sampling The EVRC-NW codec operates on 20 ms frames, and the default sampling
rate is 16 kHz (wideband). Input and output at 8 kHz sampling rate rate is 16 kHz (wideband). Input and output at the 8 kHz sampling
(narrowband) is also supported. The EVRC-NW codec can operate in rate (narrowband) is also supported. The EVRC-NW codec can operate
eight modes (0 to 7) defined in [4]. EVRC-NW modes 0, 1, and 7 are in eight modes (0 to 7) as defined in 3GPP2 C.S0014-D [4]. EVRC-NW
interoperable with EVRC-WB. EVRC-NW modes 1 to 7 are interoperable modes 0, 1, and 7 are interoperable with EVRC-WB. EVRC-NW modes 1 to
with EVRC-B. EVRC-NW modes 0 to 6 use the full set or a subset of 7 are interoperable with EVRC-B. EVRC-NW modes 0 to 6 use the full
full rate, 1/2 rate, 1/4 rate and 1/8 rate frames. EVRC-NW mode 7 set or a subset of full rate, 1/2 rate, 1/4 rate, and 1/8 rate
uses only 1/2 rate and 1/8 rate frames. By default, EVRC-NW supports frames. EVRC-NW mode 7 uses only 1/2 rate and 1/8 rate frames. By
all narrowband modes (modes 1 to 7). The support of wideband mode default, EVRC-NW supports all narrowband modes (modes 1 to 7). The
(mode 0) is optional. Mode change among modes 1 to 7 (or among modes support of wideband mode (mode 0) is optional. Mode change among
0 to 7 if the receiver supports wideband mode) results in codec modes 1 to 7 (or among modes 0 to 7 if the receiver supports wideband
output bit-rate change but does not cause any decoding problems at mode) results in codec output bit-rate change but does not cause any
the receiver. EVRC-NW provides a standardized solution for decoding problems at the receiver. EVRC-NW provides a standardized
packetized voice applications that allow transitions between enhanced solution for packetized voice applications that allow transitions
quality and increased capacity. The most important service addressed between enhanced quality and increased capacity. The most important
is IP telephony. Target devices can be IP phones or VoIP handsets, service addressed is IP telephony. Target devices can be IP phones
media gateways, voice messaging servers, etc. or VoIP handsets, media gateways, voice messaging servers, etc.
4. EVRC-NW codec 4. EVRC-NW Codec
The EVRC-NW codec operates on 20 ms frames. It produces output The EVRC-NW codec operates on 20 ms frames. It produces output
frames of one of the four different sizes: 171 bits (Rate 1), 80 bits frames of one of the four different sizes: 171 bits (Rate 1), 80 bits
(Rate 1/2), 40 bits (Rate 1/4), or 16 bits (Rate 1/8). In addition, (Rate 1/2), 40 bits (Rate 1/4), or 16 bits (Rate 1/8). In addition,
there are two zero-bit codec frame types: blank (null) frames and there are two zero-bit codec frame types: blank (null) frames and
erasure frames. The default sampling rate is 16 kHz. Input and erasure frames. The default sampling rate is 16 kHz. Input and
output at 8 kHz sampling rate is also supported. output at the 8 kHz sampling rate is also supported.
The frame type values and sizes of the associated codec data frames The frame type values and sizes of the associated codec data frames
are listed in the table below: are listed in the table below:
Value Rate Total codec data frame size in bytes (and in bits) Value Rate Total codec data frame size in bytes (and in bits)
-------------------------------------------------------------------- --------------------------------------------------------------------
0 Blank (Null) 0 (0 bits) 0 Blank (Null) 0 (0 bits)
1 1/8 2 (16 bits) 1 1/8 2 (16 bits)
2 1/4 5 (40 bits) 2 1/4 5 (40 bits)
3 1/2 10 (80 bits) 3 1/2 10 (80 bits)
4 1 22 (171 bits; 5 bits padded at the end) 4 1 22 (171 bits; 5 bits padded at the end)
5 Erasure 0 (SHOULD NOT be transmitted by sender) 5 Erasure 0 (SHOULD NOT be transmitted by sender)
5. RTP header usage 5. RTP Header Usage
The format of the RTP header is specified in RFC 3550 [5]. The The format of the RTP header is specified in RFC 3550 [5]. The
EVRC-NW payload formats (Section 6) use the fields of the RTP header EVRC-NW payload formats (Section 6) use the fields of the RTP header
as specified in RFC 3550 [5]. as specified in RFC 3550 [5].
EVRC-NW has also the capability to operate with 8 kHz sampled input/ EVRC-NW also has the capability to operate with 8 kHz sampled input/
output signals. The decoder does not require a priori knowledge output signals. The decoder does not require a priori knowledge
about the sampling rate of the original signal at the input of the about the sampling rate of the original signal at the input of the
encoder. The decoder output can be at 8 kHz or 16 kHz regardless of encoder. The decoder output can be at 8 kHz or 16 kHz regardless of
the sampling rate used at the encoder. Therefore, depending on the the sampling rate used at the encoder. Therefore, depending on the
implementation and the electroacoustic audio capabilities of the implementation and the electroacoustic audio capabilities of the
devices, the input of the encoder and/or the output of the decoder devices, the input of the encoder and/or the output of the decoder
can be configured at 8 kHz; however, a 16 kHz RTP clock rate MUST can be configured at 8 kHz; however, a 16 kHz RTP clock rate MUST
always be used. The RTP timestamp is increased by 320 for each 20 always be used. The RTP timestamp is increased by 320 for each
milliseconds. 20 milliseconds.
The RTP header marker bit (M) SHALL be set to 1 if the first frame The RTP header marker bit (M) SHALL be set to 1 if the first frame
carried in the packet contains a speech frame which is the first in a carried in the packet contains a speech frame that is the first in a
talkspurt. For all other packets the marker bit SHALL be set to zero talkspurt. For all other packets, the marker bit SHALL be set to
(M=0). zero (M=0).
6. Payload format 6. Payload Format
Three RTP packet formats are supported for the EVRC-NW codec - the Three RTP packet formats are supported for the EVRC-NW codec -- the
interleaved/bundled packet format, the header-free packet format, and interleaved/bundled packet format, the header-free packet format, and
the compact bundled packet format. For all these formats, the the compact bundled packet format. For all these formats, the
operational details and capabilities, such as ToC, interleaving, DTX, operational details and capabilities of EVRC-NW, such as TOC,
and bundling, of EVRC-NW are exactly the same as those defined in interleaving, DTX, and bundling, are exactly the same as those
EVRC [6], EVRC-B [2] and EVRC-WB [3], except that defined in EVRC [6], EVRC-B [2], and EVRC-WB [3], except that
1. the mode change request field in the interleaved/bundled packet 1. the mode change request field in the interleaved/bundled packet
format MUST be interpreted according to the definition of the format MUST be interpreted according to the definition of the
RATE_REDUC parameter as defined in EVRC-NW [4]. RATE_REDUC parameter as described for EVRC-NW in
3GPP2 C.S0014-D [4].
2. the mode change request field in the interleaved/bundled packet 2. the mode change request field in the interleaved/bundled packet
format SHOULD be honored by an EVRCNW encoding end point in an format SHOULD be honored by an EVRC-NW encoding endpoint in a
one-to-one session with a dedicated EVRCNW decoding end point one-to-one session with a dedicated EVRC-NW decoding endpoint,
such as in a two-party call or in a conference leg. such as in a two-party call or in a conference leg.
3. the reserved bit field in the first octet of the interleaved/ 3. the reserved bit field in the first octet of the interleaved/
bundled format has only one bit. Bit 1 of the first octet is an bundled format has only one bit. Bit 1 of the first octet is an
EVRC-NW wideband/narrowband encoding capability identification EVRC-NW wideband/narrowband encoding capability identification
flag. flag.
The media type audio/EVRCNW maps to the interleaved/bundled packet The media type audio/EVRCNW maps to the interleaved/bundled packet
format, audio/EVRCNW0 maps to the header-free packet format, and format, audio/EVRCNW0 maps to the header-free packet format, and
audio/EVRCNW1 maps to the compact bundled packet format. audio/EVRCNW1 maps to the compact bundled packet format.
6.1. Encoding capability identification in EVRC-NW interleaved/bundled 6.1. Encoding Capability Identification in EVRC-NW Interleaved/Bundled
format Format
The EVRC-NW interleaved/bundled format defines an encoding capability The EVRC-NW interleaved/bundled format defines an encoding capability
identification flag, which is used to signal the local EVRC-NW identification flag, which is used to signal the local EVRC-NW
wideband/narrowband encoding capability at the time of construction wideband/narrowband encoding capability at the time of construction
of an RTP packet to the far end of a communication session. This of an RTP packet to the far end of a communication session. This
capability identification flag allows the far end to use the MMM capability identification flag allows the far end to use the MMM
field in its out-going (returning) EVRC-NW interleaved/bundled format field in its outgoing (returning) EVRC-NW interleaved/bundled format
packets to request the desired EVRC-NW wideband or narrowband packets to request the desired EVRC-NW wideband or narrowband
encoding mode in accordance with the dynamic/instantaneous encoding encoding mode in accordance with the dynamic/instantaneous encoding
capability information. See RFC 3558 [6] for the definition of MMM capability information. See RFC 3558 [6] for the definition of the
field. The following examples illustrate a few scenarios where the MMM field. The following examples illustrate a few scenarios where
encoding capability information is used: the encoding capability information is used:
o An end-to-end wideband communication is established first between o An end-to-end wideband communication is established first between
two communication end points using EVRC-NW interleaved/bundled two communication endpoints using the EVRC-NW interleaved/bundled
format. The called end point becomes wideband encoding incapable format. The called endpoint becomes wideband encoding incapable
during the call and makes the other end aware of this change using during the call and makes the other end aware of this change by
the encoding capability identification flag. Based on the new using the encoding capability identification flag. Based on the
information the calling end point could change the MMM value in new information, the calling endpoint could change the MMM value
its outgoing EVRC-NW packets from Mode-0 to Mode-4 to request in its outgoing EVRC-NW packets from mode 0 to mode 4 to request
narrowband encoded traffic for bandwidth efficiency or from Mode-0 narrowband encoded traffic for bandwidth efficiency or from mode 0
to Mode-1 for best perceptual quality. to mode 1 for best perceptual quality.
o An end-to-end narrowband communication is established between an o An end-to-end narrowband communication is established between a
EVRC-NW wideband encoding capable calling end point and an EVRC-NW calling endpoint that is EVRC-NW wideband encoding capable and a
wideband encoding incapable called end point. The called end called endpoint that is EVRC-NW wideband encoding incapable. The
point becomes EVRC-NW wideband encoding capable during the call called endpoint becomes EVRC-NW wideband encoding capable during
and makes the other end aware of this change using the encoding the call and makes the other end aware of this change using the
capability identification flag. Based on the new information the encoding capability identification flag. Based on the new
calling end point could change the MMM value in its outgoing information, the calling endpoint could change the MMM value in
EVRC-NW packets from non-Mode-0 to Mode-0 to request wideband its outgoing EVRC-NW packets from non-mode-0 to mode 0 to request
traffic. wideband traffic.
EVRC-NW interleaved/bundled format defines the encoding capability The EVRC-NW interleaved/bundled format defines the encoding
identification flag in bit 1 of the first octet, as illustrated in capability identification flag in bit 1 of the first octet, as
the figure below. The flag shall be set to zero (C=0) when the local illustrated in the figure below. The flag shall be set to zero (C=0)
EVRC-NW encoder is capable of Mode-0 wideband encoding. The flag when the local EVRC-NW encoder is capable of mode 0 wideband
shall be set to one (C=1) when the local EVRC-NW encoder is capable encoding. The flag shall be set to one (C=1) when the local EVRC-NW
of non-Mode-0 narrowband encoding only. See RFC 3558 [6] for encoder is capable of non-mode-0 narrowband encoding only. See
original definitions of other fields in the interleaved/bundled RFC 3558 [6] for original definitions of other fields in the
format. interleaved/bundled format.
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 | | RTP Header |
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
|R|C| LLL | NNN | MMM | Count | TOC | ... | TOC |padding| |R|C| LLL | NNN | MMM | Count | TOC | ... | TOC |padding|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| one or more codec data frames, one per TOC entry | | one or more codec data frames, one per TOC entry |
| .... | | .... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved (R): 1 bit Reserved (R): 1 bit
Reserved bit. MUST be set to zero by sender, SHOULD be ignored by Reserved bit. MUST be set to zero by sender; SHOULD be ignored by
receiver. receiver.
Encoding capability identification (C): 1 bit Encoding capability identification (C): 1 bit
Must be set to zero by sender to indicate wideband encoding Must be set to zero by sender to indicate wideband encoding
capable or set to one to indicate narrowband encoding capable capable or set to one to indicate narrowband encoding capable
only. only.
C = 0 : Mode-0 wideband encoding capable C = 0 : mode 0 wideband encoding capable
= 1 : Mode-0 wideband encoding incapable, i.e. narrowband = 1 : mode 0 wideband encoding incapable, i.e., narrowband
encoding only. encoding only.
7. Congestion Control Considerations 7. Congestion Control Considerations
Congestion control for RTP is discussed in RFC 3550 [5], and in Congestion control for RTP is discussed in RFC 3550 [5] and in
applicable RTP profiles, e.g., RFC3551 [7]. This document does not applicable RTP profiles, e.g., RFC3551 [7]. This document does not
change those considerations. change those considerations.
Due to the header overhead, the number of frames encapsulated in each Due to the header overhead, the number of frames encapsulated in each
RTP packet influences the overall bandwidth of the RTP stream. RTP packet influences the overall bandwidth of the RTP stream.
Packing more frames in each RTP packet can reduce the number of Packing more frames in each RTP packet can reduce the number of
packets sent and hence the header overhead, at the expense of packets sent and hence the header overhead, at the expense of
increased delay and reduced error robustness. increased delay and reduced error robustness.
8. Storage format for the EVRC-NW Codec 8. Storage Format for the EVRC-NW Codec
The storage format is used for storing EVRC-NW encoded speech frames, The storage format is used for storing EVRC-NW encoded speech frames,
e.g., as a file or e-mail attachment. e.g., as a file or email attachment.
The file begins with a magic number to identify the vocoder that is The file begins with a magic number to identify the vocoder that is
used. The magic number for EVRC-NW corresponds to the ASCII used. The magic number for EVRC-NW corresponds to the ASCII
character string "#!EVRCNW\n", i.e., "0x23 0x21 0x45 0x56 0x52 0x43 character string "#!EVRCNW\n", i.e., "0x23 0x21 0x45 0x56 0x52 0x43
0x4E 0x57 0x0A". 0x4E 0x57 0x0A".
The codec data frames are stored in consecutive order, with a single The codec data frames are stored in consecutive order, with a single
ToC entry field, extended to one octet, prefixing each codec data TOC entry field, extended to one octet, prefixing each codec data
frame. The ToC field is extended to one octet by setting the four frame. The TOC field is extended to one octet by setting the four
most significant bits of the octet to zero. For example, a ToC value most significant bits of the octet to zero. For example, a TOC value
of 4 (a full-rate frame) is stored as 0x04. The Value column in the of 4 (a full-rate frame) is stored as 0x04. The Value column in the
table in Section 4 provides the TOC values for corresponding frame table in Section 4 provides the TOC values for corresponding frame
types. types.
Speech frames lost in transmission and non-received frames MUST be Speech frames lost in transmission and non-received frames MUST be
stored as erasure frames (ToC value of 5) to maintain synchronization stored as erasure frames (TOC value of 5) to maintain synchronization
with the original media. with the original media.
9. IANA considerations 9. IANA Considerations
This document introduces a new EVRC-NW 'audio' media subtype. This document introduces a new EVRC-NW 'audio' media subtype.
9.1. Media Type Registrations 9.1. Media Type Registrations
Following the guidelines in RFC 4855 [8] and RFC 4288 [9], this Following the guidelines in RFC 4855 [8] and RFC 6838 [9], this
section registers new 'audio' media subtypes for EVRC-NW. section registers new 'audio' media subtypes for EVRC-NW.
9.1.1. Registration of Media Type audio/EVRCNW 9.1.1. Registration of Media Type audio/EVRCNW
Type name: audio Type name: audio
Subtype names: EVRCNW Subtype name: EVRCNW
Required parameters: None Required parameters: None
Optional parameters: Optional parameters: These parameters apply to RTP transfer only.
These parameters apply to RTP transfer only.
mode-set-recv: A subset of EVRC-NW modes. Possible values are a mode-set-recv: A subset of EVRC-NW modes. Possible values are a
comma separated list of modes from the set {0,1,2,3,4,5,6,7} (see comma-separated list of modes from the set {0,1,2,3,4,5,6,7}
Table 2.6.1.2-4 in 3GPP2 C.S0014-D). A decoder can use this (see Table 2.6.1.2-1 in 3GPP2 C.S0014-D [4]). A decoder can
attribute to inform an encoder of its preference to operate in a use this attribute to inform an encoder of its preference to
specified subset of modes. Absence of this parameter signals the operate in a specified subset of modes. Absence of this
mode set {1,2,3,4,5,6,7}. parameter signals the mode set {1,2,3,4,5,6,7}.
ptime: see RFC 4566 [10]. ptime: See RFC 4566 [10].
maxptime: see RFC 4566. maxptime: See RFC 4566.
maxinterleave: Maximum number for interleaving length (field LLL in maxinterleave: Maximum number for interleaving length (field LLL
the Interleaving Octet)[0..7]. The interleaving lengths used in the in the Interleaving Octet) [0..7]. The interleaving lengths
entire session MUST NOT exceed this maximum value. If not signaled, used in the entire session MUST NOT exceed this maximum value.
the maxinterleave length MUST be 5. If not signaled, the maxinterleave length MUST be 5.
silencesupp: see Section 6.1 in RFC 4788. silencesupp: See Section 6.1 in RFC 4788.
dtxmax: see Section 6.1 in RFC 4788. dtxmax: See Section 6.1 in RFC 4788.
dtxmin: see Section 6.1 in RFC 4788. dtxmin: See Section 6.1 in RFC 4788.
hangover: see Section 6.1 in RFC 4788. hangover: See Section 6.1 in RFC 4788.
Encoding considerations: Encoding considerations:
This media type is framed binary data (see RFC 6838, Section 4.8)
and is defined for transfer of EVRC-NW encoded data via RTP using
the interleaved/bundled packet format specified in RFC 3558 [6].
This media type is framed binary data (see RFC 4288, Section 4.8) and Security considerations: See Section 16.
is defined for transfer of EVRC-NW encoded data via RTP using the
interleaved/bundled packet format specified in RFC 3558 [6].
Security considerations: See Section 16.
Interoperability considerations: None Interoperability considerations: None
Published specification: Published specification:
The EVRC-NW vocoder is specified in 3GPP2 C.S0014-D [4]. The
The EVRC-NW vocoder is specified in 3GPP2 C.S0014-D. The transfer transfer method with the interleaved/bundled packet format via RTP
method with the interleaved/bundled packet format via RTP is is specified in RFC 3558 [6]. See Section 6 of RFC 6884 for
specified in RFC 3558 [6]. See Section 6 of RFC XXXX for details for details for EVRC-NW.
EVRC-NW. [Note to the RFC editor: please replace XXXX with the RFC
number of this document.]
Applications that use this media type: Applications that use this media type:
It is expected that many VoIP applications (as well as mobile
It is expected that many VoIP applications (as well as mobile applications) will use this type.
applications) will use this type.
Additional information: Additional information:
The following applies to stored-file transfer methods: The following applies to stored-file transfer methods:
Magic number: #!EVRCNW\n (see Section 8) Magic number: #!EVRCNW\n (see Section 8)
File extensions: enw, ENW File extensions: enw, ENW
Macintosh file type code: None Macintosh file type code: None
Object identifier or OID: None Object identifier or OID: None
EVRC-NW speech frames may also be stored in the file format "3g2" EVRC-NW speech frames may also be stored in the file format "3g2" as
defined in 3GPP2 C.S0050-B, which is identified using the media types defined in 3GPP2 C.S0050-B [14], which is identified using the media
"audio/3gpp2" or "video/3gpp2" registered by RFC 4393 [11]. types "audio/3gpp2" or "video/3gpp2" registered by RFC 4393 [11].
Person & email address to contact for further information: Person & email address to contact for further information:
Zheng Fang <zfang@qualcomm.com>
Zheng Fang <zfang@qualcomm.com> Intended usage: COMMON
Intended usage: COMMON
Restrictions on usage: Restrictions on usage:
This media type can be used with the file format defined in
Section 8 of RFC 6884 in contexts other than RTP. In the context
of transfers over RTP, the RTP payload format specified in
Section 4.1 of RFC 3558 [6] is used for this media type.
This media type can be used with the file format defined in Section 8 Author: Zheng Fang <zfang@qualcomm.com>
of RFC XXXX in contexts other than RTP. In context of transfers over
RTP, the RTP payload format specified in Section 4.1 of RFC 3558 [6]
is used for this media type. [Note to the RFC editor: please replace
XXXX with the RFC number of this document.]
Author:
Zheng Fang <zfang@qualcomm.com>
Change controller: Change controller:
IETF Payload working group delegated from the IESG.
IETF Payload working group delegated from the IESG.
9.1.2. Registration of Media Type audio/EVRCNW0 9.1.2. Registration of Media Type audio/EVRCNW0
Type name: audio Type name: audio
Subtype names: EVRCNW0 Subtype name: EVRCNW0
Required parameters: None Required parameters: None
Optional parameters: Optional parameters: These parameters apply to RTP transfer only.
These parameters apply to RTP transfer only.
mode-set-recv: A subset of EVRC-NW modes. Possible values are a mode-set-recv: A subset of EVRC-NW modes. Possible values are a
comma separated list of modes from the set {0,1,2,3,4,5,6,7} (see comma-separated list of modes from the set {0,1,2,3,4,5,6,7}
Table 2.6.1.2-4 in 3GPP2 C.S0014-D). A decoder can use this (see Table 2.6.1.2-1 in 3GPP2 C.S0014-D [4]). A decoder can
attribute to inform an encoder of its preference to operate in a use this attribute to inform an encoder of its preference to
specified subset of modes. Absence of this parameter signals the operate in a specified subset of modes. Absence of this
mode set {1,2,3,4,5,6,7}. parameter signals the mode set {1,2,3,4,5,6,7}.
ptime: see RFC 4566. ptime: See RFC 4566.
silencesupp: see Section 6.1 in RFC 4788. silencesupp: See Section 6.1 in RFC 4788.
dtxmax: see Section 6.1 in RFC 4788. dtxmax: See Section 6.1 in RFC 4788.
dtxmin: see Section 6.1 in RFC 4788. dtxmin: See Section 6.1 in RFC 4788.
hangover: see Section 6.1 in RFC 4788. hangover: See Section 6.1 in RFC 4788.
Encoding considerations: Encoding considerations:
This media type is framed binary data (see RFC 6838, Section 4.8)
and is defined for transfer of EVRC-NW encoded data via RTP using
the header-free packet format specified in RFC 3558 [6].
This media type is framed binary data (see RFC 4288, Section 4.8) and Security considerations: See Section 16.
is defined for transfer of EVRC-NW encoded data via RTP using the
header-free packet format specified in RFC 3558 [6].
Security considerations: See Section 16.
Interoperability considerations: None Interoperability considerations: None
Published specification: Published specification:
The EVRC-NW vocoder is specified in 3GPP2 C.S0014-D [4]. The
The EVRC-NW vocoder is specified in 3GPP2 C.S0014-D. The transfer transfer method with the header-free packet format via RTP is
method with the header-free packet format via RTP is specified in RFC specified in RFC 3558 [6].
3558 [6].
Applications that use this media type: Applications that use this media type:
It is expected that many VoIP applications (as well as mobile
It is expected that many VoIP applications (as well as mobile applications) will use this type.
applications) will use this type.
Additional information: None Additional information: None
Person & email address to contact for further information: Person & email address to contact for further information:
Zheng Fang <zfang@qualcomm.com>
Zheng Fang <zfang@qualcomm.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 [5]. The RTP payload format specified in
Section 4.2 of RFC 3558 [6] SHALL be used. This media type SHALL
NOT be used for storage or file transfer; instead, audio/EVRCNW
SHALL be used.
This media type depends on RTP framing, and hence is only defined for Author: Zheng Fang <zfang@qualcomm.com>
transfer via RTP [5], the RTP payload format specified in Section 4.2
of RFC 3558 [6] SHALL be used. This media type SHALL NOT be used for
storage or file transfer, instead audio/EVRCNW SHALL be used.
Author:
Zheng Fang <zfang@qualcomm.com>
Change controller: Change controller:
IETF Payload working group delegated from the IESG.
IETF Payload working group delegated from the IESG.
9.1.3. Registration of Media Type audio/EVRCNW1 9.1.3. Registration of Media Type audio/EVRCNW1
Type name: audio Type name: audio
Subtype names: EVRCNW1 Subtype name: EVRCNW1
Required parameters: None Required parameters: None
Optional parameters: Optional parameters: These parameters apply to RTP transfer only.
These parameters apply to RTP transfer only.
mode-set-recv: A subset of EVRC-NW modes. Possible values are a mode-set-recv: A subset of EVRC-NW modes. Possible values are a
comma separated list of modes from the set {0,1} (see Table 2.6.1.2-4 comma-separated list of modes from the set {0,1} (see Table
in 3GPP2 C.S0014-D). A decoder can use this attribute to inform an 2.6.1.2-1 in 3GPP2 C.S0014-D [4]). A decoder can use this
encoder of its preference to operate in a specified subset of modes. attribute to inform an encoder of its preference to operate in
A value of 0 signals the support for wideband fixed rate (full or a specified subset of modes. A value of 0 signals support for
half rate, depending on the value of 'fixedrate' parameter). A value wideband fixed rate (full or half rate, depending on the value
of 1 signals narrowband fixed rate (full or half rate, depending on of the 'fixedrate' parameter). A value of 1 signals narrowband
the value of 'fixedrate' parameter). Absence of this parameter fixed rate (full or half rate, depending on the value of the
signals the mode 1. 'fixedrate' parameter). Absence of this parameter signals
mode 1.
ptime: see RFC 4566. ptime: See RFC 4566.
maxptime: see RFC 4566. maxptime: See RFC 4566.
fixedrate: Indicates the EVRC-NW rate of the session while in single fixedrate: Indicates the EVRC-NW rate of the session while in
rate operation. Valid values include: 0.5 and 1, where a value of single rate operation. Valid values include 0.5 and 1, where a
0.5 indicates the 1/2 rate while a value of 1 indicates the full value of 0.5 indicates the 1/2 rate while a value of 1
rate. If this parameter is not present, 1/2 rate is assumed. indicates the full rate. If this parameter is not present, 1/2
rate is assumed.
silencesupp: see Section 6.1 in RFC 4788. silencesupp: See Section 6.1 in RFC 4788.
dtxmax: see Section 6.1 in RFC 4788. dtxmax: See Section 6.1 in RFC 4788.
dtxmin: see Section 6.1 in RFC 4788. dtxmin: See Section 6.1 in RFC 4788.
hangover: see Section 6.1 in RFC 4788. hangover: See Section 6.1 in RFC 4788.
Encoding considerations: Encoding considerations:
This media type is framed binary data (see RFC 6838, Section 4.8)
and is defined for transfer of EVRC-NW encoded data via RTP using
the compact bundled packet format specified in RFC 4788.
This media type is framed binary data (see RFC 4288, Section 4.8) and Security considerations: See Section 16.
is defined for transfer of EVRC-NW encoded data via RTP using the
compact bundled packet format specified in RFC 4788.
Security considerations: See Section 16
Interoperability considerations: None Interoperability considerations: None
Published specification: Published specification:
The EVRC-NW vocoder is specified in 3GPP2 C.S0014-D [4]. The
The EVRC-NW vocoder is specified in 3GPP2 C.S0014-D. The transfer transfer method with the compact bundled packet format via RTP is
method with the compact bundled packet format via RTP is specified in specified in RFC 4788.
RFC 4788.
Applications that use this media type: Applications that use this media type:
It is expected that many VoIP applications (as well as mobile
It is expected that many VoIP applications (as well as mobile applications) will use this type.
applications) will use this type.
Additional information: None Additional information: None
Person & email address to contact for further information:
Zheng Fang <zfang@qualcomm.com>
Intended usage: COMMON Person & email address to contact for further information:
Zheng Fang <zfang@qualcomm.com>
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 [5]. The RTP payload format specified in
Section 4 of RFC 4788 SHALL be used. This media type SHALL NOT be
used for storage or file transfer; instead, audio/EVRCNW SHALL be
used.
This media type depends on RTP framing, and hence is only defined for Author: Zheng Fang <zfang@qualcomm.com>
transfer via RTP [5], the RTP payload format specified in Section 4
of RFC 4788 SHALL be used. This media type SHALL NOT be used for
storage or file transfer, instead audio/EVRCNW SHALL be used.
Author:
Zheng Fang <zfang@qualcomm.com>
Change controller: Change controller:
IETF Payload working group delegated from the IESG.
IETF Payload working group delegated from the IESG. 10. SDP Mode Attributes for EVRC-NW
10. SDP mode attributes for EVRC-NW
'mode-set-recv' can be used by a decoder to inform an encoder of its 'mode-set-recv' can be used by a decoder to inform an encoder of its
preference to operate in a specified subset of modes. Note that preference to operate in a specified subset of modes. Note that
indicating a preference implicitly indicates support for that indicating a preference implicitly indicates support for that
capability. If mode 0 is not preferred for media type EVRCNW0 or capability. If mode 0 is not preferred for media type EVRCNW0 or
EVRCNW1, then there is no indication that mode 0 is supported. EVRCNW1, then there is no indication that mode 0 is supported.
However absence of this parameter or absence of mode 0 in this However, absence of this parameter or absence of mode 0 in this
parameter for media type EVRCNW shall not preclude mode 0 support parameter for media type EVRCNW shall not preclude mode 0 support
during a call where mode 0 may be requested via the MMM field. during a call where mode 0 may be requested via the MMM field.
To inform the capability for wideband mode support, a decoder can 1. To inform other nodes of its capability for wideband mode
always decode all the narrowband modes (modes 1 to 7). Unless the support: a decoder can always decode all the narrowband modes
decoder indicates the support of mode 0 (i.e., preference) in this (modes 1 to 7). Unless the decoder indicates support of mode 0
parameter or in the MMM mode request field in interleaved/bundled (i.e., preference) in this parameter or in the MMM mode request
payload format, an encoder at the other side shall not operate in field in the interleaved/bundled payload format, an encoder at
mode 0. the other side shall not operate in mode 0.
To indicate a preference to operate in a subset of modes, a set has 2. To indicate a preference to operate in a subset of modes: a set
been defined so that several modes can be expressed as a preference has been defined so that several modes can be expressed as a
in one attempt. For instance, the set {4,5,6,7} signals that the preference in one attempt. For instance, the set {4,5,6,7}
receiver prefers the sender to operate in bandwidth-efficient signals that the receiver prefers that the sender operate in
narrowband modes of EVRC-NW. bandwidth-efficient narrowband modes of EVRC-NW.
Note, during an active call session using the interleaved/bundled Note that during an active call session using the interleaved/bundled
packet format, the MMM mode request received from a communication packet format, the MMM mode request received from a communication
partner can contain a mode request different than the values in the partner can contain a mode request different than the values in the
last mode-set-recv attribute. The partner's EVRC-NW wideband last mode-set-recv attribute. The partner's EVRC-NW wideband
decoding capability is determined by the latest mode-set-recv decoding capability is determined by the latest mode-set-recv
attribute or MMM mode request field. For example, a mode request attribute or MMM mode request field. For example, a mode request
with MMM=0 from a communication partner is an implicit indication of with MMM=0 from a communication partner is an implicit indication of
the partner's EVRCNW wideband decoding capability and preference. An the partner's EVRC-NW wideband decoding capability and preference.
EVRCNW wideband capable node receiving the request can operate in An EVRC-NW wideband-capable node receiving the request can operate in
wideband mode. A mode request with MMM=1, 2, ..., or 7 from a wideband mode. A mode request with MMM=1, 2, ..., or 7 from a
communication partner is an implicit indication of the partner's communication partner is an implicit indication of the partner's
EVRCNW narrowband decoding preference. The encoder of an EVRCNW node EVRC-NW narrowband decoding preference. The encoder of an EVRC-NW
receiving the request shall honor the request and operate in node receiving the request shall honor the request and operate in
narrowband mode. narrowband mode.
'sendmode' is used as a SDP mode attribute in EVRC [6], EVRC-B [2] 'sendmode' is used as a Session Description Protocol (SDP) mode
and EVRC-WB [3]. However it is deprecated in EVRC-NW. attribute in EVRC [6], EVRC-B [2], and EVRC-WB [3]. However, it is
deprecated in EVRC-NW.
11. Mode Change Request/Response Considerations 11. Mode Change Request/Response Considerations
The interleaved/bundled packet format for the EVRC family of vocoders The interleaved/bundled packet format for the EVRC family of vocoders
supports a 3-bit field (MMM) that a communication node can use to supports a 3-bit field (MMM) that a communication node can use to
indicate its preferred compression mode to an opposite node. The indicate its preferred compression mode to an opposite node. The
concept of the compression mode (also known as Capacity Operating concept of the compression mode (also known as Capacity Operating
Point) was introduced to allow a controlled trade-off between voice Point) was introduced to allow a controlled trade-off between voice
quality and channel capacity. The notion makes it possible to quality and channel capacity. The notion makes it possible to
exercise vocoders at the highest possible (average) bit-rate (hence, exercise vocoders at the highest possible (average) bit-rate (hence,
highest voice quality) when the network is lightly loaded. highest voice quality) when the network is lightly loaded.
Conversely, once the network load increases the vocoders can be Conversely, once the network load increases, the vocoders can be
requested to operate at lower average bit-rates so as to absorb the requested to operate at lower average bit-rates so as to absorb the
additional network load without causing an undue increase in the additional network load without causing an undue increase in the
frame-erasure rates; the underlying premise is that while a higher frame-erasure rates; the underlying premise is that while a higher
bit-rate improves the vocoder performance, it also increases the bit-rate improves vocoder performance, it also increases the network
network loading, risking a sharp decline in voice quality should the load, risking a sharp decline in voice quality should the frame-
frame-erasure rate be too high. By contrast, a lower bit-rate mode erasure rate be too high. By contrast, a lower bit-rate mode of
of operation can result in accommodation of the additional network operation can result in accommodation of the additional network load
load without causing unduly high frame-erasure rates, resulting in without causing unduly high frame-erasure rates, resulting in better
better overall quality despite the inherently lower voice quality of overall quality despite the inherently lower voice quality of the
the lower bit-rate mode of the vocoder. lower bit-rate mode of the vocoder.
Accordingly, the MMM field should be used to request the far-end to Accordingly, the MMM field should be used to request the far end to
transmit compressed-speech using a mode that provides the best transmit compressed speech using a mode that provides the best
balance between voice quality and capacity. However, in the case of balance between voice quality and capacity. However, in the case of
mobile-mobile calls, for example, there are two wireless sides mobile-mobile calls, for example, there are two wireless sides
involved, each with a potentially different network load level and involved, each with a potentially different network load level and
hence a different preferred mode. In such cases, achieving optimal hence a different preferred mode. In such cases, achieving optimal
end-to-end performance depends on coherent management of the end-to-end performance depends on coherent management of the
operative mode by the two sides. This requires that even if the operative mode by the two sides. This requires that even if the
local node prefers a higher bit-rate vocoder mode, it should adjust local node prefers a higher bit-rate vocoder mode, it should adjust
to a lower bit-rate mode if requested by the far end, in order to to a lower bit-rate mode if requested by the far end, in order to
avoid potentially high frame erasure rates due to heavy load at the avoid potentially high frame-erasure rates due to heavy load at the
far end network. For similar reasons, in cases where a mode far-end network. For similar reasons, in cases where a mode
requested by the far end should not be supported, it might still be requested by the far end should not be supported, it might still be
beneficial to consider switching to a supported vocoder mode beneficial to consider switching to a supported vocoder mode
corresponding to a lower average bit-rate than requested. It is corresponding to a lower average bit-rate than requested. It is
recommended that the next lower average bit-rate supported vocoder recommended that the next lower average bit-rate supported vocoder
mode be used for encoding when a mode requested by the far end is not mode be used for encoding when a mode requested by the far end is not
supported. supported.
A wideband-capable endpoint can use the information conveyed by the A wideband-capable endpoint can use the information conveyed by the
C-bit of the RTP payload header to determine the optimal mode to C-bit of the RTP payload header to determine the optimal mode to
request of the far end. If the far end cannot provide Mode0 packets request of the far end. If the far end cannot provide mode 0 packets
(C-bit=1), then the choice of MMM can be based strictly on the local (C-bit=1), then the choice of MMM can be based strictly on the local
network load. If the C-bit indicates remote end's Mode0 encoding network load. If the C-bit indicates the remote end's mode 0
capability (C-bit=0), then even if the local network load is not encoding capability (C-bit=0), then even if the local network load is
light, Mode0 can be requested knowing definitively that it will be not light, mode 0 can be requested knowing definitively that it will
supported. This will permit operators to treat wideband-capable be supported. This will permit operators to treat wideband-capable
mobiles preferentially, should they wish to adopt such policy. mobiles preferentially, should they wish to adopt such policy.
12. Mapping EVRC-NW media type parameters into SDP 12. Mapping EVRC-NW Media Type Parameters into SDP
Information carried in the media type specification has a specific Information carried in the media type specification has a specific
mapping to fields in the Session Description Protocol (SDP) [10], mapping to fields in the Session Description Protocol (SDP) [10],
which is commonly used to describe RTP sessions. When SDP is used to which is commonly used to describe RTP sessions. When SDP is used to
specify sessions employing EVRC-NW encoded speech, the mapping is as specify sessions employing EVRC-NW encoded speech, the mapping is as
follows. follows.
o The media type ("audio") goes in SDP "m=" as the media name. o The media type ("audio") goes in SDP "m=" as the media name.
o The media subtype ("EVRCNW", "EVRCNW0" or "EVRCNW1") goes in SDP o The media subtype ("EVRCNW", "EVRCNW0", or "EVRCNW1") goes in SDP
"a=rtpmap" as the encoding name. "a=rtpmap" as the encoding name.
o The optional parameters 'ptime and 'maxptime' (for subtypes o The optional parameters 'ptime and 'maxptime' (for subtypes EVRCNW
EVRCNW, EVRCNW1) go in the SDP "a=ptime" and "a=maxptime" and EVRCNW1) go in the SDP "a=ptime" and "a=maxptime" attributes,
attributes, respectively. respectively.
o Any remaining parameters (for subtypes EVRCNW, EVRCNW0 and o Any remaining parameters (for subtypes EVRCNW, EVRCNW0, and
EVRCNW1) go in the SDP "a=fmtp" attribute by copying them from the EVRCNW1) go in the SDP "a=fmtp" attribute by copying them from the
media type string as a semicolon separated list of parameter=value media type string as a semicolon-separated list of parameter=value
pairs. pairs.
13. Offer-Answer Model Considerations for EVRC-NW 13. Offer-Answer Model Considerations for EVRC-NW
The following considerations apply when using the SDP offer-answer The following considerations apply when using the SDP offer-answer
procedures of RFC 3264 [12] to negotiate the use of EVRC-NW payload procedures of RFC 3264 [12] to negotiate the use of EVRC-NW payload
in RTP: in RTP:
o Since EVRC-NW is an extension of both EVRC-B and EVRC-WB, the o Since EVRC-NW is an extension of both EVRC-B and EVRC-WB, the
offerer SHOULD also announce EVRC-B and EVRC-WB support in its offerer SHOULD also announce EVRC-B and EVRC-WB support in its
"m=audio" lines, with EVRC-NW as the preferred codec. This will "m=audio" lines, with EVRC-NW as the preferred codec. This will
allow interoperability with an answerer which supports only EVRC-B allow interoperability with an answerer that supports only EVRC-B
and/or EVRC-WB. and/or EVRC-WB.
Below is an example of such an offer: Below is an example of such an offer:
m=audio 55954 RTP/AVP 98 99 100 m=audio 55954 RTP/AVP 98 99 100
a=rtpmap:98 EVRCNW0/16000 a=rtpmap:98 EVRCNW0/16000
a=rtpmap:99 EVRCWB0/16000 a=rtpmap:99 EVRCWB0/16000
a=rtpmap:100 EVRCB0/8000 a=rtpmap:100 EVRCB0/8000
a=fmtp:98 mode-set-recv=0,1,2,3,4,5,6 a=fmtp:98 mode-set-recv=0,1,2,3,4,5,6
a=fmtp:99 mode-set-recv=0,4 a=fmtp:99 mode-set-recv=0,4
a=fmtp:100 recvmode=0 a=fmtp:100 recvmode=0
If the answerer supports EVRC-NW then the answerer can keep the If the answerer supports EVRC-NW, then the answerer can keep the
payload type 98 in its answer and the conversation can be done using payload type 98 in its answer and the conversation can be done using
EVRC-NW. Else, if the answerer supports only EVRC-WB and/or EVRC-B EVRC-NW. Otherwise, if the answerer supports only EVRC-WB and/or
then the answerer will leave only the payload type 99 and/or 100 EVRC-B, then the answerer will leave only the payload type 99 and/or
respectively in its answer and the conversation will be done using 100, respectively, in its answer and the conversation will be done
EVRC-WB and/or EVRC-B respectively. using EVRC-WB and/or EVRC-B, respectively.
An example answer for the above offer: An example answer for the above offer:
m=audio 55954 RTP/AVP 98 m=audio 55954 RTP/AVP 98
a=rtpmap:98 EVRCNW0/16000 a=rtpmap:98 EVRCNW0/16000
a=fmtp:98 mode-set-recv=4 a=fmtp:98 mode-set-recv=4
o 'mode-set-recv' is a uni-directional receive only parameter. o 'mode-set-recv' is a unidirectional receive-only parameter.
o An offerer can use 'mode-set-recv' to request that the remote o An offerer can use 'mode-set-recv' to request that the remote
sender's encoder be limited to the list of modes signaled in sender's encoder be limited to the list of modes signaled in
'mode-set-recv'. A remote sender MAY ignore 'mode-set-recv' 'mode-set-recv'. A remote sender MAY ignore 'mode-set-recv'
requests. However, a remote sender shall not assume the other requests. However, a remote sender shall not assume the other
side can support mode 0, unless the offer includes mode 0 side can support mode 0, unless the offer includes mode 0
explicitly in 'mode-set-recv' or the remote sender receives mode explicitly in 'mode-set-recv' or the remote sender receives mode
requests with MMM = 0 from the communication partner during an requests with MMM=0 from the communication partner during an
active call using EVRC-NW interleaved/bundled format. active call using the EVRC-NW interleaved/bundled format.
o The parameters 'maxptime' and 'ptime' will in most cases not o The parameters 'maxptime' and 'ptime' will in most cases not
affect interoperability, however the setting of the parameters can affect interoperability; however, the setting of the parameters
affect the performance of the application. The SDP offer-answer can affect the performance of the application. The SDP offer-
handling of the 'ptime' parameter is described in RFC 3264 [12]. answer handling of the 'ptime' parameter is described in RFC 3264
The 'maxptime' parameter MUST be handled in the same way. [12]. The 'maxptime' parameter MUST be handled in the same way.
o For a sendonly stream, the 'mode-set-recv' parameter is not useful o For a sendonly stream, the 'mode-set-recv' parameter is not useful
and SHOULD NOT be used. and SHOULD NOT be used.
o When using EVRCNW1, the entire session MUST use the same fixed o When using EVRCNW1, the entire session MUST use the same fixed
rate and mode (0-Wideband or 1-Narrowband). rate and mode (0-Wideband or 1-Narrowband).
o For additional rules which MUST be followed while negotiating DTX o For additional rules that MUST be followed while negotiating DTX
parameters, see Section 6.8 in RFC 4788 [2]. parameters, see Section 6.8 in RFC 4788 [2].
o Any unknown parameter in an SDP offer MUST be ignored by the o Any unknown parameter in an SDP offer MUST be ignored by the
receiver and MUST NOT be included in the SDP answer. receiver and MUST NOT be included in the SDP answer.
14. Declarative SDP Considerations 14. Declarative SDP Considerations
For declarative use of SDP in SAP [14] and RTSP [15], the following For declarative use of SDP in the Session Announcement Protocol (SAP)
[15] and the Real Time Streaming Protocol (RTSP) [16], the following
considerations apply: considerations apply:
o Any 'maxptime' and 'ptime' values should be selected with care to o Any 'maxptime' and 'ptime' values should be selected with care to
ensure that the session's participants can achieve reasonable ensure that the session's participants can achieve reasonable
performance. performance.
o The payload format configuration parameters are all declarative o The payload format configuration parameters are all declarative,
and a participant MUST use the configuration(s) that is provided and a participant MUST use the configuration(s) that is provided
for the session. More than one configuration MAY be provided if for the session. More than one configuration MAY be provided if
necessary by declaring multiple RTP payload types, however the necessary by declaring multiple RTP payload types; however, the
number of types SHOULD be kept small. For declarative examples, number of types SHOULD be kept small. For declarative examples,
see Section 15. see Section 15.
o The usage of unidirectional receive-only parameters, such as o The usage of unidirectional receive-only parameters, such as
'mode-set-recv', should be excluded in any declarations, since 'mode-set-recv', should be excluded in any declarations, since
these parameters are meaningless in one-way streaming these parameters are meaningless in one-way streaming
applications. applications.
15. Examples 15. Examples
skipping to change at page 27, line 29 skipping to change at page 18, line 18
a=rtpmap:97 EVRCNW/16000 a=rtpmap:97 EVRCNW/16000
a=rtpmap:98 EVRCWB/16000 a=rtpmap:98 EVRCWB/16000
a=rtpmap:99 EVRCB/8000 a=rtpmap:99 EVRCB/8000
a=fmtp:97 silencesupp=1;dtxmax=32;dtxmin=12;hangover=1; \ a=fmtp:97 silencesupp=1;dtxmax=32;dtxmin=12;hangover=1; \
mode-set-recv=0,1,2,3,4,5,6 mode-set-recv=0,1,2,3,4,5,6
a=fmtp:98 silencesupp=1;dtxmax=32;dtxmin=12;hangover=1; \ a=fmtp:98 silencesupp=1;dtxmax=32;dtxmin=12;hangover=1; \
mode-set-recv=0,4 mode-set-recv=0,4
a=fmtp:99 recvmode=0 a=fmtp:99 recvmode=0
a=maxptime:120 a=maxptime:120
Examples usage of EVRCNW with DTX with silencesupp=0: Example usage of EVRCNW with DTX with silencesupp=0:
m=audio 49120 RTP/AVP 97 98 99 m=audio 49120 RTP/AVP 97 98 99
a=rtpmap:97 EVRCNW/16000 a=rtpmap:97 EVRCNW/16000
a=rtpmap:98 EVRCWB/16000 a=rtpmap:98 EVRCWB/16000
a=rtpmap:99 EVRCB/8000 a=rtpmap:99 EVRCB/8000
a=fmtp:97 silencesupp=0;dtxmax=32;dtxmin=12;hangover=1; \ a=fmtp:97 silencesupp=0;dtxmax=32;dtxmin=12;hangover=1; \
mode-set-recv=0,1,2,3,4,5,6 mode-set-recv=0,1,2,3,4,5,6
a=fmtp:98 silencesupp=0;dtxmax=32;dtxmin=12;hangover=1; \ a=fmtp:98 silencesupp=0;dtxmax=32;dtxmin=12;hangover=1; \
mode-set-recv=0,4 mode-set-recv=0,4
a=fmtp:99 recvmode=0 a=fmtp:99 recvmode=0
a=maxptime:120 a=maxptime:120
Example offer answer exchange between EVRC-NW and legacy EVRC-B (RFC Example offer-answer exchange between EVRC-NW and legacy EVRC-B
4788): (RFC 4788):
Offer: Offer:
m=audio 55954 RTP/AVP 97 98 99 m=audio 55954 RTP/AVP 97 98 99
a=rtpmap:97 EVRCNW0/16000 a=rtpmap:97 EVRCNW0/16000
a=rtpmap:98 EVRCWB0/16000 a=rtpmap:98 EVRCWB0/16000
a=rtpmap:99 EVRCB0/8000 a=rtpmap:99 EVRCB0/8000
a=rtpmap:97 mode-set-recv=0,1,2,3,4,5,6 a=rtpmap:97 mode-set-recv=0,1,2,3,4,5,6
a=fmtp:98 mode-set-recv=0,4 a=fmtp:98 mode-set-recv=0,4
a=fmtp:99 recvmode=0 a=fmtp:99 recvmode=0
Answer: Answer:
m=audio 55954 RTP/AVP 99 m=audio 55954 RTP/AVP 99
a=rtpmap:99 EVRCB0/8000 a=rtpmap:99 EVRCB0/8000
Example offer answer exchange between EVRC-NW and legacy EVRC-WB (RFC Example offer-answer exchange between EVRC-NW and legacy EVRC-WB
5188): (RFC 5188):
Offer: Offer:
m=audio 55954 RTP/AVP 97 98 99 m=audio 55954 RTP/AVP 97 98 99
a=rtpmap:97 EVRCNW0/16000 a=rtpmap:97 EVRCNW0/16000
a=rtpmap:98 EVRCWB0/16000 a=rtpmap:98 EVRCWB0/16000
a=rtpmap:99 EVRCB0/8000 a=rtpmap:99 EVRCB0/8000
a=rtpmap:97 mode-set-recv=0,1,2,3,4,5,6 a=rtpmap:97 mode-set-recv=0,1,2,3,4,5,6
a=fmtp:98 mode-set-recv=0,4 a=fmtp:98 mode-set-recv=0,4
a=fmtp:99 recvmode=0 a=fmtp:99 recvmode=0
skipping to change at page 29, line 13 skipping to change at page 19, line 31
a=rtpmap:98 EVRCWB0/16000 a=rtpmap:98 EVRCWB0/16000
16. Security Considerations 16. Security Considerations
Since compression is applied to the payload formats end-to-end, and Since compression is applied to the payload formats end-to-end, and
the encodings do not exhibit significant non-uniformity, the encodings do not exhibit significant non-uniformity,
implementations of this specification are subject to all the security implementations of this specification are subject to all the security
considerations specified in RFC 3558 [6]. Implementations using the considerations specified in RFC 3558 [6]. Implementations using the
payload defined in this specification are subject to the security payload defined in this specification are subject to the security
considerations discussed in RFC 3558 [6], RFC 3550 [5], and any considerations discussed in RFC 3558 [6], RFC 3550 [5], and any
appropriate profile (for example RFC 3551 [7]). Additional security appropriate profile (for example, RFC 3551 [7]). Additional security
considerations are described in RFC 6562 [13]. considerations are described in RFC 6562 [13].
17. References 17. References
17.1. Normative References 17.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Xie, Q. and R. Kapoor, "Enhancements to RTP Payload Formats for [2] Xie, Q. and R. Kapoor, "Enhancements to RTP Payload Formats for
EVRC Family Codecs", RFC 4788, January 2007. EVRC Family Codecs", RFC 4788, January 2007.
[3] Desineni, H. and Q. Xie, "RTP Payload Format for the Enhanced [3] Desineni, H. and Q. Xie, "RTP Payload Format for the Enhanced
Variable Rate Wideband Codec (EVRC-WB) and the Media Subtype Variable Rate Wideband Codec (EVRC-WB) and the Media Subtype
Updates for EVRC-B Codec", RFC 5188, February 2008. Updates for EVRC-B Codec", RFC 5188, February 2008.
[4] "Enhanced Variable Rate Codec, Speech Service Options 3, 68, [4] "Enhanced Variable Rate Codec, Speech Service Options 3, 68,
70, and 73 for Wideband Spread Spectrum Digital Systems", 70, and 73 for Wideband Spread Spectrum Digital Systems",
3GPP2 C.S0014-D v3.0, October 2010. 3GPP2 C.S0014-D v3.0, October 2010, <http://www.3gpp2.org/
public_html/specs/C.S0014-D_v3.0_EVRC.pdf>.
[5] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, [5] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
"RTP: A Transport Protocol for Real-Time Applications", STD 64, "RTP: A Transport Protocol for Real-Time Applications", STD 64,
RFC 3550, July 2003. RFC 3550, July 2003.
[6] Li, A., "RTP Payload Format for Enhanced Variable Rate Codecs [6] Li, A., "RTP Payload Format for Enhanced Variable Rate Codecs
(EVRC) and Selectable Mode Vocoders (SMV)", RFC 3558, (EVRC) and Selectable Mode Vocoders (SMV)", RFC 3558,
July 2003. July 2003.
[7] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video [7] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
Conferences with Minimal Control", STD 65, RFC 3551, July 2003. Conferences with Minimal Control", STD 65, RFC 3551, July 2003.
[8] Casner, S., "Media Type Registration of RTP Payload Formats", [8] Casner, S., "Media Type Registration of RTP Payload Formats",
RFC 4855, February 2007. RFC 4855, February 2007.
[9] Freed, N. and J. Klensin, "Media Type Specifications and [9] Freed, N., Klensin, J., and T. Hansen, "Media Type
Registration Procedures", BCP 13, RFC 4288, December 2005. Specifications and Registration Procedures", BCP 13, RFC 6838,
January 2013.
[10] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session [10] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006. Description Protocol", RFC 4566, July 2006.
[11] Garudadri, H., "MIME Type Registrations for 3GPP2 Multimedia [11] Garudadri, H., "MIME Type Registrations for 3GPP2 Multimedia
Files", RFC 4393, March 2006. Files", RFC 4393, March 2006.
[12] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with [12] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
Session Description Protocol (SDP)", RFC 3264, June 2002. Session Description Protocol (SDP)", RFC 3264, June 2002.
[13] Perkins, C. and JM. Valin, "Guidelines for the Use of Variable [13] Perkins, C. and JM. Valin, "Guidelines for the Use of Variable
Bit Rate Audio with Secure RTP", RFC 6562, March 2012. Bit Rate Audio with Secure RTP", RFC 6562, March 2012.
17.2. Informative References 17.2. Informative References
[14] Handley, M., Perkins, C., and E. Whelan, "Session Announcement [14] "3GPP2 File Formats for Multimedia Services", 3GPP2 C.S0050-B
v1.0, May 2007, <http://www.3gpp2.org/public_html/specs/
C.S0050-B_v1.0_070521.pdf>.
[15] Handley, M., Perkins, C., and E. Whelan, "Session Announcement
Protocol", RFC 2974, October 2000. Protocol", RFC 2974, October 2000.
[15] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time Streaming [16] Schulzrinne, H., Rao, A., and R. Lanphier, "Real Time Streaming
Protocol (RTSP)", RFC 2326, April 1998. Protocol (RTSP)", RFC 2326, April 1998.
Author's Address Author's Address
Zheng Fang Zheng Fang
Qualcomm Incorporated Qualcomm Incorporated
5775 Morehouse Drive 5775 Morehouse Drive
San Diego, CA 92126 San Diego, CA 92126
USA USA
Phone: +1 858 651 9484 Phone: +1 858 651 9484
Email: zfang@qualcomm.com EMail: zfang@qualcomm.com
URI: http://www.qualcomm.com URI: http://www.qualcomm.com
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