draft-ietf-avt-rtp-evrc-wb-04.txt   draft-ietf-avt-rtp-evrc-wb-05.txt 
Network Working Group H. Desineni Network Working Group H. Desineni
Internet-Draft Qualcomm Internet-Draft Qualcomm
Updates: 4788 (if approved) Q. Xie Updates: 4788 (if approved) Q. Xie
Intended status: Standards Track Motorola Intended status: Standards Track Motorola
Expires: April 25, 2008 October 23, 2007 Expires: May 3, 2008 October 31, 2007
RTP payload format for EVRC-WB codec and media subtype updates for RTP payload format for EVRC-WB codec and media subtype updates for
EVRC-B codec EVRC-B codec
draft-ietf-avt-rtp-evrc-wb-04.txt draft-ietf-avt-rtp-evrc-wb-05.txt
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Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
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 EVRC wideband codec (EVRC-WB) and updates formats to be used for the EVRC wideband codec (EVRC-WB) and updates
the media type registrations for EVRC-B codec. Several media type the media type registrations for EVRC-B codec. Several media type
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. EVRC-WB codec . . . . . . . . . . . . . . . . . . . . . . . . 6 4. EVRC-WB codec . . . . . . . . . . . . . . . . . . . . . . . . 6
5. RTP header usage . . . . . . . . . . . . . . . . . . . . . . . 7 5. RTP header usage . . . . . . . . . . . . . . . . . . . . . . . 7
6. Payload format . . . . . . . . . . . . . . . . . . . . . . . . 8 6. Payload format . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Congestion Control Considerations . . . . . . . . . . . . . . 9 7. Congestion Control Considerations . . . . . . . . . . . . . . 9
8. Storage format for EVRC-WB Codec . . . . . . . . . . . . . . . 10 8. Storage format for the EVRC-WB Codec . . . . . . . . . . . . . 10
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9.1. Media Type Registration . . . . . . . . . . . . . . . . . 11 9.1. Media Type Registrations . . . . . . . . . . . . . . . . . 11
9.1.1. Registration of Media Type EVRCWB . . . . . . . . . . 11 9.1.1. Registration of Media Type audio/EVRCWB . . . . . . . 11
9.1.2. Registration of Media Type EVRCWB0 . . . . . . . . . . 13 9.1.2. Registration of Media Type audio/EVRCWB0 . . . . . . . 13
9.1.3. Registration of Media Type EVRCWB1 . . . . . . . . . . 15 9.1.3. Registration of Media Type audio/EVRCWB1 . . . . . . . 15
9.1.4. Updated Registration of Media Type EVRCB . . . . . . . 17 9.1.4. Updated Registration of Media Type audio/EVRCB . . . . 17
9.1.5. Updated Registration of Media Type EVRCB0 . . . . . . 19 9.1.5. Updated Registration of Media Type audio/EVRCB0 . . . 19
10. SDP mode attributes for EVRC-WB and EVRC-B . . . . . . . . . . 21 10. SDP mode attributes for EVRC-WB and EVRC-B . . . . . . . . . . 21
11. EVRC-B RFC XXXX Interoperability with legacy EVRC-B (RFC 11. EVRC-B RFC XXXX Interoperability with legacy EVRC-B (RFC
4788) implementations . . . . . . . . . . . . . . . . . . . . 22 4788) implementations . . . . . . . . . . . . . . . . . . . . 22
12. Mapping EVRC-WB media type parameters into SDP . . . . . . . . 23 12. Mapping EVRC-WB media type parameters into SDP . . . . . . . . 23
13. Mapping EVRC-B media type parameters into SDP . . . . . . . . 24 13. Mapping EVRC-B media type parameters into SDP . . . . . . . . 24
14. Offer-Answer Model Considerations for EVRC-WB . . . . . . . . 25 14. Offer-Answer Model Considerations for EVRC-WB . . . . . . . . 25
15. Offer-Answer Model Considerations for EVRC-B . . . . . . . . . 27 15. Offer-Answer Model Considerations for EVRC-B . . . . . . . . . 27
16. Declarative SDP Considerations . . . . . . . . . . . . . . . . 28 16. Declarative SDP Considerations . . . . . . . . . . . . . . . . 28
17. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 17. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
18. Security Considerations . . . . . . . . . . . . . . . . . . . 33 18. Security Considerations . . . . . . . . . . . . . . . . . . . 33
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registrations for EVRC-B codec. registrations for EVRC-B codec.
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-WB is a wideband extension of EVRC-B [4] speech codec developed EVRC-WB is a wideband extension of the EVRC-B [4] speech codec
in 3GPP2 with support for discontinuous transmission (DTX). It developed in 3GPP2 with support for discontinuous transmission (DTX).
provides enhanced (wideband) voice quality. It provides enhanced (wideband) voice quality.
EVRC-WB codec operates on 20 ms frames, and the default sampling rate The EVRC-WB codec operates on 20 ms frames, and the default sampling
is 16 kHz. Input and output at 8 kHz sampling rate is also rate is 16 kHz. Input and output at 8 kHz sampling rate is also
supported. EVRC-WB codec can operate in three modes (0,4 and 7) supported. The EVRC-WB codec can operate in three modes (0,4 and 7)
defined in [5]. EVRC-WB modes 4,7 are interoperable with EVRC-B. defined in [5]. EVRC-WB modes 4 and 7 are interoperable with EVRC-B.
EVRC-WB mode 4 uses full rate, 1/2 rate and 1/8 rate frames. EVRC-WB EVRC-WB mode 4 uses full rate, 1/2 rate and 1/8 rate frames. EVRC-WB
mode 7 uses only 1/2 rate and 1/8 rate frames. Mode change results mode 7 uses only 1/2 rate and 1/8 rate frames. Mode change results
in codec output bit-rate but does not cause any decoding problems at in codec output bit-rate change but does not cause any decoding
the receiver. For successful decoding, the decoder does not need to problems at the receiver. For successful decoding, the decoder does
know the encoder's current mode of operation. EVRC-WB provides a not need to know the encoder's current mode of operation. EVRC-WB
standardized solution for packetized voice applications that allow provides a standardized solution for packetized voice applications
transitions between narrowband and wideband telephony. The most that allow transitions between narrowband and wideband telephony.
important service addressed is IP telephony. Target devices can be The most important service addressed is IP telephony. Target devices
IP phones or VoIP handsets, media gateways, voice messaging servers, can be IP phones or VoIP handsets, media gateways, voice messaging
etc. servers, etc.
4. EVRC-WB codec 4. EVRC-WB codec
EVRC-WB codec operates on 20 ms frames. It produces output frames of The EVRC-WB codec operates on 20 ms frames. It produces output
one of the three different sizes: 171 bits, 80 bits or 16 bits. In frames of one of the three different sizes: 171 bits, 80 bits, or 16
addition, there are two zero bit codec frame types: blank (null) bits. In addition, there are two zero bit codec frame types: blank
frames and erasure frames. The default sampling rate is 16 kHz. (null) frames and erasure frames. The default sampling rate is 16
Input and output at 8 kHz sampling rate is also supported. kHz. Input and output at 8 kHz sampling rate is also supported.
The frame type values and size of the associated codec data frame are The frame type values and sizes of the associated codec data frames
listed in the table below: are listed in the table below:
Value Rate Total codec data frame size (in octets) Value Rate Total codec data frame size in bytes (and in bits)
-------------------------------------------------------------------- --------------------------------------------------------------------
0 Blank 0 (0 bit) 0 Blank 0 (0 bit)
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 [6]. The The format of the RTP header is specified in RFC 3550 [6]. The
EVRC-WB payload formats (Section 6) use the fields of the RTP header EVRC-WB payload formats (Section 6) use the fields of the RTP header
in a manner consistent with RFC 3550. in a manner consistent with RFC 3550.
EVRC-WB has also the capability to operate with 8 kHz sampled input/ EVRC-WB has also 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 8kHz or 16kHz regardless of encoder. The decoder output can be at 8kHz or 16kHz 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 audio electro acoustic capabilities of the implementation and the electro acoustic 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 20
milliseconds. 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 which 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 zero
(M=0). (M=0).
skipping to change at page 10, line 5 skipping to change at page 10, line 5
Congestion control for RTP SHALL be used in accordance with RFC 3550 Congestion control for RTP SHALL be used in accordance with RFC 3550
[6], and with any applicable RTP profile; e.g., RFC 3551 [10]. [6], and with any applicable RTP profile; e.g., RFC 3551 [10].
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 EVRC-WB Codec 8. Storage format for the EVRC-WB Codec
The storage format is used for storing EVRC-WB encoded speech frames, The storage format is used for storing EVRC-WB encoded speech frames,
e.g., as a file or e-mail attachment. e.g., as a file or e-mail 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-WB corresponds to the ASCII used. The magic number for EVRC-WB corresponds to the ASCII
character string "#!EVCWB\n", i.e., "0x23 0x21 0x45 0x56 0x43 0x57 character string "#!EVCWB\n", i.e., "0x23 0x21 0x45 0x56 0x43 0x57
0x42 0x0A". 0x42 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
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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. See Section 4 for the of 4 (a full-rate frame) is stored as 0x04. See Section 4 for the
mapping from frame type to ToC value. mapping from frame type to ToC value.
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 updates EVRCB and EVRCB0 media subtypes defined in RFC This document updates the audio/EVRCB and audio/EVRCB0 media types
4788 [3] and adds new EVRC-WB media subtypes. defined in RFC 4788 [3] and adds new EVRC-WB 'audio' media subtypes.
[-- RFC Editor: Please replace all instances of "RFC XXXX" in this [-- RFC Editor: Please replace all instances of "RFC XXXX" in this
document with the RFC number of this document prior to IANA document with the RFC number of this document prior to IANA
registration and RFC publication, and remove this note.] registration and RFC publication, and remove this note.]
9.1. Media Type Registration 9.1. Media Type Registrations
Following the guidelines in RFC 4288 [9], this section registers new Following the guidelines in RFC 4288 [9], this section registers new
media subtypes for EVRC-WB and updates EVRCB, EVRCB0 media subtypes 'audio' media subtypes for EVRC-WB and updates audio/EVRCB and audio/
defined in RFC 4788 [3]. EVRCB0 media types defined in RFC 4788 [3].
9.1.1. Registration of Media Type EVRCWB 9.1.1. Registration of Media Type audio/EVRCWB
Type name: audio Type name: audio
Subtype names: EVRCWB Subtype names: EVRCWB
Required parameters: none Required parameters: none
Optional parameters: Optional parameters:
mode-set-recv: A subset of EVRC-WB modes. Possible values are a mode-set-recv: A subset of EVRC-WB modes. Possible values are a
comma separated list of modes from the set: 0,4,7 (see Table comma separated list of modes from the set {0,4,7} (see Table
2.5.1.2-1 [5]). A decoder can use this attribute to inform its 2.5.1.2-1 in 3GPP2 C.S0014-C). A decoder can use this attribute to
preference to an encoder to operate in a specified subset of modes. inform its preference to an encoder to operate in a specified subset
Absence of this parameter signals the mode set {0,4,7}. of modes. Absence of this parameter signals the mode set {0,4,7}.
sendmode: A mode of EVRC-WB codec. Encoder can use this to signal sendmode: A mode of the EVRC-WB codec. An encoder can use this to
its current mode of operation. Possible values are 0,4,7 (see Table signal its current mode of operation. Possible values are 0,4,7 (see
2.5.1.2-1 [5]). Absence of this parameter signals mode 0. Table 2.5.1.2-1 in 3GPP2 C.S0014-C). Absence of this parameter
signals mode 0.
ptime: see RFC 4566 [8]. ptime: see RFC 4566.
maxptime: see RFC 4566 [8]. maxptime: see RFC 4566.
maxinterleave: Maximum number for interleaving length (field LLL in maxinterleave: Maximum number for interleaving length (field LLL in
the Interleaving Octet). The interleaving lengths used in the entire the Interleaving Octet). The interleaving lengths used in the entire
session MUST NOT exceed this maximum value. If not signaled, the session MUST NOT exceed this maximum value. If not signaled, the
maxinterleave length MUST be 5. maxinterleave length MUST be 5.
silencesupp: see Section 6.1 in [3] silencesupp: see Section 6.1 in RFC 4788.
dtxmax: see Section 6.1 in [3] dtxmax: see Section 6.1 in RFC 4788.
dtxmin: see Section 6.1 in [3]
hangover: see Section 6.1 in [3] dtxmin: see Section 6.1 in in RFC 4788.
hangover: see Section 6.1 in in RFC 4788.
Encoding considerations: Encoding considerations:
This media type is framed binary data (see RFC 4288, Section 4.8) and This media type is framed binary data (see RFC 4288, Section 4.8) and
is defined for transfer of EVRC-WB encoded data via RTP using the is defined for transfer of EVRC-WB encoded data via RTP using the
Interleaved/Bundled packet format specified in RFC 3558 [2]. Interleaved/Bundled packet format specified in RFC 3558 [2].
Security considerations: See Section 18 of RFC XXXX. Security considerations: See Section 18 of RFC XXXX.
Interoperability considerations: none Interoperability considerations: none
Published specification: Published specification:
The EVRC-WB vocoder is specified in 3GPP2 C.S0014-C [5]. Transfer The EVRC-WB vocoder is specified in 3GPP2 C.S0014-C. The transfer
method with Interleaved/Bundled packet format via RTP is specified in method with the Interleaved/Bundled packet format via RTP is
RFC 3558 and RFC XXXX. specified in RFC 3558 and RFC XXXX.
3GPP2 C.S0050-B, 3GPP2 File Formats for Multimedia Services. 3GPP2 C.S0050-B, 3GPP2 File Formats for Multimedia Services.
3GPP2 specifications are publicly accessible at http://www.3gpp2.org 3GPP2 specifications are publicly accessible at http://www.3gpp2.org
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 information applies for storage format only. The following information applies for the storage format only.
Magic number: #!EVCWB\n (see Section 8 of RFC XXXX) Magic number: #!EVCWB\n (see Section 8 of RFC XXXX)
File extensions: evw, EVW File extensions: evw, EVW
Macintosh file type code: none Macintosh file type code: none
Object identifier or OID: none Object identifier or OID: none
EVRC-WB speech frames may also be stored in the file format "3g2" EVRC-WB speech frames may also be stored in the file format "3g2"
defined in 3GPP2 C.S0050-B, which is identified using the media types defined in 3GPP2 C.S0050-B, which is identified using the media types
"audio/3gpp2" or "video/3gpp2" registered by RFC4393. "audio/3gpp2" or "video/3gpp2" registered by RFC4393.
Person & email address to contact for further information: Person & email address to contact for further information:
Harikishan Desineni <hd@qualcomm.com> Harikishan Desineni <hd@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 This basic form of this media type depends on RTP framing, and hence
transfer via RTP (RFC 3550). Transfer within other framing protocols is only defined for transfer via RTP (RFC 3550). For storage and/or
is not defined at this time. transfer within other protocols, the storage format according to the
Additional Information clause above must be used.
Author: Author:
Harikishan Desineni Harikishan Desineni
Change controller: Change controller:
IETF Audio/Video Transport working group delegated from the IESG. IETF Audio/Video Transport working group delegated from the IESG.
9.1.2. Registration of Media Type EVRCWB0 9.1.2. Registration of Media Type audio/EVRCWB0
Type name: audio Type name: audio
Subtype names: EVRCWB0 Subtype names: EVRCWB0
Required parameters: Required parameters:
Optional parameters: Optional parameters:
mode-set-recv: A subset of EVRC-WB modes. Possible values are a mode-set-recv: A subset of EVRC-WB modes. Possible values are a
comma separated list of modes from the set: 0,4,7 (see Table comma separated list of modes from the set {0,4,7} (see Table
2.5.1.2-1 [5]). A decoder can use this attribute to inform its 2.5.1.2-1 [5]). A decoder can use this attribute to inform its
preference to an encoder to operate in a specified subset of modes. preference to an encoder to operate in a specified subset of modes.
Absence of this parameter signals the mode set {0,4,7}. Absence of this parameter signals the mode set {0,4,7}.
sendmode: A mode of EVRC-WB codec. Encoder can use this to signal sendmode: A mode of the EVRC-WB codec. An encoder can use this to
its current mode of operation. Possible values are 0,4,7 (see Table signal its current mode of operation. Possible values are 0,4,7 (see
2.5.1.2-1 [5]). Absence of this parameter signals mode 0. Table 2.5.1.2-1 in 3GPP2 C.S0014-C). Absence of this parameter
signals mode 0.
ptime: see RFC 4566 [8]. ptime: see RFC 4566 [8].
silencesupp: see Section 6.1 in [3] silencesupp: see Section 6.1 in RFC 4788.
dtxmax: see Section 6.1 in [3] dtxmax: see Section 6.1 in RFC 4788.
dtxmin: see Section 6.1 in [3] dtxmin: see Section 6.1 in RFC 4788.
hangover: see Section 6.1 in [3] hangover: see Section 6.1 in RFC 4788.
Encoding considerations: Encoding considerations:
This media type is framed binary data (see RFC 4288, Section 4.8) and This media type is framed binary data (see RFC 4288, Section 4.8) and
is defined for transfer of EVRC-WB encoded data via RTP using the is defined for transfer of EVRC-WB encoded data via RTP using the
Header-Free packet format specified in RFC 3558. Header-Free packet format specified in RFC 3558.
Security considerations: See Section 18 of RFC XXXX. Security considerations: See Section 18 of RFC XXXX.
Interoperability considerations: none Interoperability considerations: none
Published specification: Published specification:
The EVRC-WB vocoder is specified in 3GPP2 C.S0014-C [5]. Transfer The EVRC-WB vocoder is specified in 3GPP2 C.S0014-C. The transfer
method with header free packet format via RTP is specified in RFC method with header free packet format via RTP is specified in RFC
3558 and RFC XXXX. 3558 and RFC XXXX.
3GPP2 C.S0050-B, 3GPP2 File Formats for Multimedia Services. 3GPP2 C.S0050-B, 3GPP2 File Formats for Multimedia Services.
3GPP2 specifications are publicly accessible at http://www.3gpp2.org 3GPP2 specifications are publicly accessible at http://www.3gpp2.org
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 information applies for storage format only. The following information applies for the storage format only.
Magic number: #!EVCWB\n (see Section 8 of RFC XXXX) Magic number: #!EVCWB\n (see Section 8 of RFC XXXX)
File extensions: evw, EVW File extensions: evw, EVW
Macintosh file type code: none Macintosh file type code: none
Object identifier or OID: none Object identifier or OID: none
EVRC-WB speech frames may also be stored in the file format "3g2" EVRC-WB speech frames may also be stored in the file format "3g2"
skipping to change at page 14, line 52 skipping to change at page 15, line 5
"audio/3gpp2" or "video/3gpp2" registered by RFC4393. "audio/3gpp2" or "video/3gpp2" registered by RFC4393.
Person & email address to contact for further information: Person & email address to contact for further information:
Harikishan Desineni <hd@qualcomm.com> Harikishan Desineni <hd@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 This basic form of this media type depends on RTP framing, and hence
transfer via RTP (RFC 3550). Transfer within other framing protocols is only defined for transfer via RTP (RFC 3550). For storage and/or
is not defined at this time. transfer within other protocols, the storage format according to the
Additional Information clause above must be used.
Author: Author:
Harikishan Desineni Harikishan Desineni
Change controller: Change controller:
IETF Audio/Video Transport working group delegated from the IESG. IETF Audio/Video Transport working group delegated from the IESG.
9.1.3. Registration of Media Type EVRCWB1 9.1.3. Registration of Media Type audio/EVRCWB1
Type name: audio Type name: audio
Subtype names: EVRCWB1 Subtype names: EVRCWB1
Required parameters: Required parameters:
Optional parameters: Optional parameters:
mode-set-recv: A subset of EVRC-WB modes. Possible values are a mode-set-recv: A subset of EVRC-WB modes. Possible values are a
comma separated list of modes from the set: 0,4,7 (see Table comma separated list of modes from the set {0,4,7} (see Table
2.5.1.2-1 [5]). A decoder can use this attribute to inform its 2.5.1.2-1 [5]). A decoder can use this attribute to inform its
preference to an encoder to operate in a specified subset of modes. preference to an encoder to operate in a specified subset of modes.
Value of 0 signals the support for wideband fixed rate (full or half A value of 0 signals the support for wideband fixed rate (full or
rate, depending on the value of 'fixedrate' parameter). Value of 4 half rate, depending on the value of 'fixedrate' parameter). A value
signals narroband fixed full rate. Value of 7 signals narrowband of 4 signals narroband fixed full rate. A value of 7 signals
fixed half rate. Absence of this parameter signals mode 0. narrowband fixed half rate. Absence of this parameter signals mode
0.
sendmode: A mode of EVRC-WB codec. Encoder can use this to signal sendmode: A mode of the EVRC-WB codec. An encoder can use this to
its current mode of operation. Possible values are a comma separated signal its current mode of operation. Possible values are 0,4,7 (see
list of modes from the set: 0,4,7 (see Table 2.5.1.2-1 [5]). Table 2.5.1.2-1 in 3GPP2 C.S0014-C). 'sendmode' with value 0 signals
'sendmode' with value 0 signals wideband fixed rate (full or half wideband fixed rate operation (full or half rate, depending on the
rate, depending on the value of 'fixedrate' parameter) operation. value of the 'fixedrate' parameter). 'sendmode' with value 4 signals
'sendmode' with value 4 signals narrowband fixed full rate operation. narrowband fixed full rate operation. 'sendmode' with value 7 signals
'sendmode' with value 7 signals narrowband fixed half rate operation. narrowband fixed half rate operation. The 'fixedrate' parameter MUST
'fixedrate' parameter MUST not be present when 'sendmode' value is 4 not be present when the 'sendmode' value is 4 or 7. Absence of this
or 7. Absence of this parameter signals mode 0. parameter signals mode 0.
ptime: see RFC 4566 [8]. ptime: see RFC 4566 [8].
maxptime: see RFC 4566 [8]. maxptime: see RFC 4566 [8].
fixedrate: Indicates the EVRC-WB rate of the session while in single fixedrate: Indicates the EVRC-WB rate of the session while in single
rate operation. Valid values include: 0.5 and 1, where a value of rate operation. Valid values include: 0.5 and 1, where a value of
0.5 indicates the 1/2 rate while a value of 1 indicates the full 0.5 indicates the 1/2 rate while a value of 1 indicates the full
rate. If this parameter is not present, 1/2 rate is assumed. rate. If this parameter is not present, 1/2 rate is assumed.
silencesupp: see Section 6.1 in [3] silencesupp: see Section 6.1 in RFC 4788.
dtxmax: see Section 6.1 in [3] dtxmax: see Section 6.1 in RFC 4788.
dtxmin: see Section 6.1 in [3] dtxmin: see Section 6.1 in RFC 4788.
hangover: see Section 6.1 in [3] hangover: see Section 6.1 in RFC 4788.
Encoding considerations: Encoding considerations:
This media type is framed binary data (see RFC 4288, Section 4.8) and This media type is framed binary data (see RFC 4288, Section 4.8) and
is defined for transfer of EVRC-WB encoded data via RTP using the is defined for transfer of EVRC-WB encoded data via RTP using the
compact bundle packet format specified in RFC 4788. compact bundle packet format specified in RFC 4788.
Security considerations: See Section 18 of RFC XXXX. Security considerations: See Section 18 of RFC XXXX.
Interoperability considerations: none Interoperability considerations: none
Published specification: Published specification:
The EVRC-WB vocoder is specified in 3GPP2 C.S0014-C. Transfer method The EVRC-WB vocoder is specified in 3GPP2 C.S0014-C. The transfer
with compact bundled packet format via RTP is specified in RFC 4788 method with the compact bundled packet format via RTP is specified in
and RFC XXXX. RFC 4788 and RFC XXXX.
3GPP2 C.S0050-B, 3GPP2 File Formats for Multimedia Services. 3GPP2 C.S0050-B, 3GPP2 File Formats for Multimedia Services.
3GPP2 specifications are publicly accessible at http://www.3gpp2.org 3GPP2 specifications are publicly accessible at http://www.3gpp2.org
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 information applies for storage format only. The following information applies for the storage format only.
Magic number: #!EVCWB\n (see Section 8 of RFC XXXX) Magic number: #!EVCWB\n (see Section 8 of RFC XXXX)
File extensions: evw, EVW File extensions: evw, EVW
Macintosh file type code: none Macintosh file type code: none
Object identifier or OID: none Object identifier or OID: none
EVRC-WB speech frames may also be stored in the file format "3g2" EVRC-WB speech frames may also be stored in the file format "3g2"
defined in 3GPP2 C.S0050-B, which is identified using the media types defined in 3GPP2 C.S0050-B, which is identified using the media types
"audio/3gpp2" or "video/3gpp2" registered by RFC 4393. "audio/3gpp2" or "video/3gpp2" registered by RFC 4393.
Person & email address to contact for further information: Person & email address to contact for further information:
Harikishan Desineni <hd@qualcomm.com> Harikishan Desineni <hd@qualcomm.com>
Intended usage: COMMON Intended usage: COMMON
skipping to change at page 17, line 13 skipping to change at page 17, line 16
"audio/3gpp2" or "video/3gpp2" registered by RFC 4393. "audio/3gpp2" or "video/3gpp2" registered by RFC 4393.
Person & email address to contact for further information: Person & email address to contact for further information:
Harikishan Desineni <hd@qualcomm.com> Harikishan Desineni <hd@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 This basic form of this media type depends on RTP framing, and hence
transfer via RTP (RFC 3550). Transfer within other framing protocols is only defined for transfer via RTP (RFC 3550). For storage and/or
is not defined at this time. transfer within other protocols, the storage format according to the
Additional Information clause above must be used.
Author: Author:
Harikishan Desineni Harikishan Desineni
Change controller: Change controller:
IETF Audio/Video Transport working group delegated from the IESG. IETF Audio/Video Transport working group delegated from the IESG.
9.1.4. Updated Registration of Media Type EVRCB 9.1.4. Updated Registration of Media Type audio/EVRCB
Type name: audio Type name: audio
Subtype names: EVRCB Subtype names: EVRCB
Required parameters: none Required parameters: none
Optional parameters: Optional parameters:
recvmode: A mode of EVRC-B codec. A decoder can use this attribute recvmode: A mode of EVRC-B codec. A decoder can use this attribute
to inform its preference to an encoder to operate in a specified to inform its preference to an encoder to operate in a specified
mode. Possible values are a comma separated list of modes from the mode. Possible values are 0..7 (see the encoder operating point
set: 0..7 (see encoder operating point column in Table 2-6 [4]). column in Table 2-6 of 3GPP2 C.S0014-B).
sendmode: A mode of EVRC-B codec. An encoder can use this to signal sendmode: A mode of EVRC-B codec. An encoder can use this to signal
its current mode of operation. Possible values are a comma separated its current mode of operation. Possible values are 0..7 (see encoder
list of modes from the set: 0..7 (see encoder operating point column operating point column in Table 2-6 of 3GPP2 C.S0014-B).
in Table 2-6 [4]).
ptime: see RFC 4566 ptime: see RFC 4566
maxptime: see RFC 4566 [8]. maxptime: see RFC 4566 [8].
maxinterleave: Maximum number for interleaving length (field LLL in maxinterleave: Maximum number for interleaving length (field LLL in
the Interleaving Octet). The interleaving lengths used in the entire the Interleaving Octet). The interleaving lengths used in the entire
session MUST NOT exceed this maximum value. If not signaled, the session MUST NOT exceed this maximum value. If not signaled, the
maxinterleave length MUST be 5. maxinterleave length MUST be 5.
silencesupp: see Section 6.1 for definition. If this parameter is silencesupp: see Section 6.1 of RFC 4788 for a definition. If this
not present, the default value 1 MUST be assumed. parameter is not present, the default value 1 MUST be assumed.
dtxmax: see Section 6.1 of [3] dtxmax: see Section 6.1 of [3]
dtxmin: see Section 6.1 of [3] dtxmin: see Section 6.1 of [3]
hangover: see Section 6.1 of [3] hangover: see Section 6.1 of [3]
Encoding considerations: Encoding considerations:
This media type is framed binary data (see RFC 4288, Section 4.8) and This media type is framed binary data (see RFC 4288, Section 4.8) and
skipping to change at page 18, line 28 skipping to change at page 18, line 33
Interleaved/Bundled packet format specified in RFC 3558. Interleaved/Bundled packet format specified in RFC 3558.
Security considerations: See Section 9 of RFC 4788. Security considerations: See Section 9 of RFC 4788.
Interoperability considerations: none Interoperability considerations: none
Published specification: Published specification:
The EVRC-B vocoder is specified in 3GPP2 C.S0014-B. Transfer method The EVRC-B vocoder is specified in 3GPP2 C.S0014-B. Transfer method
with Interleaved/Bundled packet format via RTP is specified in RFC with Interleaved/Bundled packet format via RTP is specified in RFC
3558,RFC XXXX and RFC 4788. 3558, RFC 4788 and RFC XXXX.
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: The following information applies for storage Additional information: The following information applies for the
format only. Magic number: #!EVRC-B\n (see Section 5 of RFC 4788) storage format only.
File extensions: evb, EVB Macintosh file type code: none Object
identifier or OID: none Magic number: #!EVRC-B\n (see Section 5 of RFC 4788)
File extensions: evb, EVB
Macintosh file type code: none
Object identifier or OID: none
Person & email address to contact for further information: Person & email address to contact for further information:
Harikishan Desineni <hd@qualcomm.com> Harikishan Desineni <hd@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 This basic form of this media type depends on RTP framing, and hence
transfer via RTP (RFC 3550). Transfer within other framing protocols is only defined for transfer via RTP (RFC 3550). For storage and/or
is not defined at this time. transfer within other protocols, the storage format according to the
Additional Information clause above must be used.
Author: Author:
Qiaobing Xie / Harikishan Desineni Qiaobing Xie / Harikishan Desineni
Change controller: Change controller:
IETF Audio/Video Transport working group delegated from the IESG. IETF Audio/Video Transport working group delegated from the IESG.
9.1.5. Updated Registration of Media Type EVRCB0 9.1.5. Updated Registration of Media Type audio/EVRCB0
Type name: audio Type name: audio
Subtype names: EVRCB0 Subtype names: EVRCB0
Required parameters: none Required parameters: none
Optional parameters: Optional parameters:
recvmode: A mode of EVRC-B codec. A decoder can use this attribute recvmode: A mode of the EVRC-B codec. A decoder can use this
to inform its preference to an encoder to operate in a specified attribute to inform its preference to an encoder to operate in a
mode. Possible values are a comma separated list of modes from the specified mode. Possible values are 0..7 (see the encoder operating
set: 0..7 (see encoder operating point column in Table 2-6 [4]). point column in Table 2-6 of 3GPP2 C.S0014-B).
sendmode: A mode of EVRC-B codec. An encoder can use this to signal sendmode: A mode of EVRC-B codec. An encoder can use this to signal
its current mode of operation. Possible values are a comma separated its current mode of operation. Possible values are a comma separated
list of modes from the set: 0..7 (see encoder operating point column list of modes from the set: 0..7 (see encoder operating point column
in Table 2-6 [4]). in Table 2-6 [4]).
silencesupp: see Section 6.1 for definition. If this parameter is silencesupp: see Section 6.1 of RFC 4788 for a definition. If this
not present, the default value 1 MUST be assumed. parameter is not present, the default value 1 MUST be assumed.
dtxmax: see Section 6.1 of [3] dtxmax: see Section 6.1 of RFC 4788.
dtxmin: see Section 6.1 of [3] dtxmin: see Section 6.1 of RFC 4788.
hangover: see Section 6.1 of [3] hangover: see Section 6.1 of RFC 4788.
Encoding considerations: Encoding considerations:
This media type is framed binary data (see RFC 4288, Section 4.8) and This media type is framed binary data (see RFC 4288, Section 4.8) and
is defined for transfer of EVRC-B encoded data via RTP using the is defined for transfer of EVRC-B encoded data via RTP using the
Header-Free packet format specified in RFC 3558. Header-Free packet format specified in RFC 3558.
Security considerations: See Section 9 of RFC 4788. Security considerations: See Section 9 of RFC 4788.
Interoperability considerations: none Interoperability considerations: none
skipping to change at page 20, line 22 skipping to change at page 20, line 36
Additional information: none Additional information: none
Person & email address to contact for further information: Person & email address to contact for further information:
Harikishan Desineni <hd@qualcomm.com> Harikishan Desineni <hd@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 This basic form of this media type depends on RTP framing, and hence
transfer via RTP (RFC 3550). Transfer within other framing protocols is only defined for transfer via RTP (RFC 3550). For storage and/or
is not defined at this time. transfer within other protocols, the storage format according to the
Additional Information clause above must be used.
Author: Author:
Qiaobing Xie / Harikishan Desineni Qiaobing Xie / Harikishan Desineni
Change controller: Change controller:
IETF Audio/Video Transport working group delegated from the IESG. IETF Audio/Video Transport working group delegated from the IESG.
10. SDP mode attributes for EVRC-WB and EVRC-B 10. SDP mode attributes for EVRC-WB and EVRC-B
'sendmode' can be used by a sender (EVRC-WB or EVRC-B) to announce 'sendmode' can be used by a sender (EVRC-WB or EVRC-B) to announce
its encoder's current mode of operation. Sender can change its mode its encoder's current mode of operation. A sender can change its
anytime and it does not cause any decoding problems at the receiver. mode anytime and this does not cause any decoding problems at the
receiver.
'recvmode' is defined for use with EVRC-B. A decoder can use this 'recvmode' is defined for use with EVRC-B. A decoder can use this
attribute to inform its preference to an encoder to operate in a attribute to inform an encoder of its preference to operate in a
specified mode. Receiver will continue to decode properly even if specified mode. The receiver will continue to decode properly even
the sender does not operate in the preferred mode. if the sender does not operate in the preferred mode.
'mode-set-recv' is defined for use with EVRC-WB. A decoder can use 'mode-set-recv' is defined for use with EVRC-WB. A decoder can use
this attribute to inform its preference to an encoder to operate in a this attribute to inform an encoder of its preference to operate in a
specified subset of modes. Receiver will continue to decode properly specified subset of modes. The receiver will continue to decode
even if the sender does not operate in one of the preferred modes. A properly even if the sender does not operate in one of the preferred
set has been defiend so that several modes can be expressed as a modes. A set has been defined so that several modes can be expressed
preference in one attempt. For ex., the set {4,7} signals that the as a preference in one attempt. For instance, the set {4,7} signals
receiver prefers the sender to operate in narrowband modes of that the receiver prefers the sender to operate in narrowband modes
EVRC-WB. of EVRC-WB.
11. EVRC-B RFC XXXX Interoperability with legacy EVRC-B (RFC 4788) 11. EVRC-B RFC XXXX Interoperability with legacy EVRC-B (RFC 4788)
implementations implementations
This document adds new optional parameters "recvmode" and "sendmode" This document adds new optional parameters "recvmode" and "sendmode"
to the original EVRC-B payload subtypes "EVRCB" and "EVRCB0" defined to the original EVRC-B Media types "audio/EVRCB" and "audio/EVRCB0"
in RFC 4788. The existing RFC 4788 implementations will not send defined in RFC 4788. Existing RFC 4788 implementations will not send
these parameters in SDP and will ignore if they are received. This these parameters in SDP and will ignore them if they are received.
will allow interoperability between RFC 4788 and RFC XXXX This will allow interoperability between RFC 4788 and RFC XXXX
implementations of EVRC-B. For an example offer and answer exchange, implementations of EVRC-B. For an example offer and answer exchange,
see Section 17. see Section 17.
12. Mapping EVRC-WB media type parameters into SDP 12. Mapping EVRC-WB 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) [8], mapping to fields in the Session Description Protocol (SDP) [8],
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-WB encoded speech, the mapping is as specify sessions employing EVRC-WB encoded speech, the mapping is as
follows. follows.
skipping to change at page 24, line 7 skipping to change at page 24, line 7
EVRCWB, EVRCWB1) go in the SDP "a=ptime" and "a=maxptime" EVRCWB, EVRCWB1) go in the SDP "a=ptime" and "a=maxptime"
attributes, respectively. attributes, respectively.
o Any remaining parameters (for subtypes EVRCWB, EVRCWB0 and o Any remaining parameters (for subtypes EVRCWB, EVRCWB0 and
EVRCWB1) go in the SDP "a=fmtp" attribute by copying them from the EVRCWB1) 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. Mapping EVRC-B media type parameters into SDP 13. Mapping EVRC-B media type parameters into SDP
The optional parameters "recvmode" and "sendmode" (for subtypes EVRCB The new optional parameters "recvmode" and "sendmode" (for 'audio'
and EVRCB0) go in the SDP "a=fmtp" attribute by copying them directly subtypes EVRCB and EVRCB0) go in the SDP "a=fmtp" attribute by
from the media type string. copying them directly from the media type string.
For all other Media Type parameteres, the specification in Section
6.7 of RFC 4788 [3] still applies.
14. Offer-Answer Model Considerations for EVRC-WB 14. Offer-Answer Model Considerations for EVRC-WB
The following considerations apply when using SDP offer-answer The following considerations apply when using the SDP offer-answer
procedures [7] to negotiate the use of EVRC-WB payload in RTP: procedures [7] to negotiate the use of EVRC-WB payload in RTP:
o Since EVRC-WB is an extension of EVRC-B, the offerer SHOULD o Since EVRC-WB is an extension of EVRC-B, the offerer SHOULD
announce EVRC-B support in its "m=audio" line, with EVRC-WB as the announce EVRC-B support in its "m=audio" line, with EVRC-WB as the
preferred codec. This will allow interoperability with an preferred codec. This will allow interoperability with an
answerer which supports only EVRC-B. answerer which supports only EVRC-B.
Below is an example of such an offer: Below is an example of such an offer:
m=audio 55954 RTP/AVP 98 99 m=audio 55954 RTP/AVP 98 99
skipping to change at page 25, line 39 skipping to change at page 25, line 39
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 EVRCWB0/16000 a=rtpmap:98 EVRCWB0/16000
a=fmtp:98 mode-set-recv=4;sendmode=4 a=fmtp:98 mode-set-recv=4;sendmode=4
o "mode-set-recv" is a uni-directional receive only parameter. o "mode-set-recv" is a uni-directional receive only parameter.
o "sendmode" is a uni-directional send only parameter. o "sendmode" is a uni-directional send only parameter.
o Using "sendmode", a sender can signal its current mode of o Using 'sendmode', a sender can signal its current mode of
operation. Note that a receiver may receive RTP media well before operation. Note that a receiver may receive RTP media well before
the arrival of SDP with 'sendmode' parameter. the arrival of SDP with a (first time, or updated) 'sendmode'
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. requests.
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 can
affect the performance of the application. The SDP offer-answer affect the performance of the application. The SDP offer-answer
handling of the "ptime" parameter is described in RFC3264 [7]. handling of the "ptime" parameter is described in RFC3264 [7].
The "maxptime" parameter MUST be handled in the same way. The "maxptime" parameter MUST be handled in the same way.
o For a sendonly stream, "mode-set-recv" parameter is not useful and o For a sendonly stream, the 'mode-set-recv' parameter is not useful
SHOULD NOT be used. and SHOULD NOT be used.
o For a recvonly stream, "sendmode" parameter is not useful and o For a recvonly stream, the 'sendmode' parameter is not useful and
SHOULD NOT be used. SHOULD NOT be used.
o When using EVRCWB1, the entire session MUST use the same fixed o When using EVRCWB1, the entire session MUST use the same fixed
rate and mode (0-Wideband or 4,7-Narrowband). rate and mode (0-Wideband or 4,7-Narrowband).
o For additional rules which MUST be followed while negotiating DTX o For additional rules which MUST be followed while negotiating DTX
parameters, see Section 6.8 in [3]. parameters, see Section 6.8 in [3].
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.
15. Offer-Answer Model Considerations for EVRC-B 15. Offer-Answer Model Considerations for EVRC-B
See Section 6.8 of [3] for offer-answer usage of EVRC-B. The See Section 6.8 of [3] for offer-answer usage of EVRC-B. The
following are several additional considerations for EVRC-B. following are several additional considerations for EVRC-B.
o "recvmode" is a uni-directional receive only parameter. o "recvmode" is a uni-directional receive only parameter.
o "sendmode" is a uni-directional send only parameter. o "sendmode" is a uni-directional send only parameter.
o Using "recvmode", a receiver can signal the remote sender to o Using 'recvmode', a receiver can signal the remote sender to
operate its encoder in the specified mode. A remote sender MAY operate its encoder in the specified mode. A remote sender MAY
ignore "recvmode" requests. ignore "recvmode" requests.
o Using "sendmode", a sender can signal its current mode of o Using 'sendmode', a sender can signal its current mode of
operation. Note that a receiver may receive RTP media well before operation. Note that a receiver may receive RTP media well before
the arrival of SDP with 'sendmode' parameter. the arrival of SDP with a (first time, or updated)'sendmode'
parameter.
o For a sendonly stream, "recvmode" parameter is not useful and o For a sendonly stream, the 'recvmode' parameter is not useful and
SHOULD NOT be used. SHOULD NOT be used.
o For a recvonly stream, "sendmode" parameter is not useful and o For a recvonly stream, the 'sendmode' parameter is not useful and
SHOULD NOT be used. SHOULD NOT be used.
16. Declarative SDP Considerations 16. Declarative SDP Considerations
For declarative use of SDP in SAP [11] and RTSP [12] , the following For declarative use of SDP in SAP [11] and RTSP [12] , 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.
skipping to change at page 34, line 10 skipping to change at page 34, line 10
Implementations using the payload defined in this specification are Implementations using the payload defined in this specification are
subject to the security considerations discussed in RFC3558 [2], subject to the security considerations discussed in RFC3558 [2],
RFC3550 [6], and any appropriate profile (for example RFC3551 [10]). RFC3550 [6], and any appropriate profile (for example RFC3551 [10]).
This payload does not specify any different security services. This payload does not specify any different security services.
19. Changes to RFC4788 19. Changes to RFC4788
This document updates RFC 4788 and the updates are summarized below: This document updates RFC 4788 and the updates are summarized below:
o Added new media type attribute "sendmode" to media sub-types EVRCB o Added new media type attribute "sendmode" to media sub-types EVRCB
and EVRCB0. This attribute can be used to signal EVRC-B encoder's and EVRCB0. This attribute can be used to signal the EVRC-B
current mode of operation. encoder's current mode of operation.
o Added new media type attribute "recvmode" to media sub-types EVRCB o Added new media type attribute "recvmode" to media sub-types EVRCB
and EVRCB0. This attribute can be used to signal EVRC-B decoder's and EVRCB0. This attribute can be used to signal the EVRC-B
preferred operating mode to a remote sender. decoder's preferred operating mode to a remote sender.
20. References 20. References
20.1. Normative References 20.1. 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] Li, A., "RTP Payload Format for Enhanced Variable Rate Codecs [2] 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,
 End of changes. 83 change blocks. 
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