[xiph-commits] r8560 - trunk/speex/doc
philkerr at motherfish-iii.xiph.org
philkerr at motherfish-iii.xiph.org
Thu Dec 30 13:29:41 PST 2004
Author: philkerr
Date: 2004-12-30 13:29:40 -0800 (Thu, 30 Dec 2004)
New Revision: 8560
Added:
trunk/speex/doc/draft-herlein-speex-rtp-profile-03.txt
Log:
Added: trunk/speex/doc/draft-herlein-speex-rtp-profile-03.txt
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--- trunk/speex/doc/draft-herlein-speex-rtp-profile-03.txt 2004-12-30 21:29:26 UTC (rev 8559)
+++ trunk/speex/doc/draft-herlein-speex-rtp-profile-03.txt 2004-12-30 21:29:40 UTC (rev 8560)
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+AVT Working Group G. Herlein
+Internet-Draft S. Morlat
+Expires: July 2, 2005 J. Jean-Marc
+ R. Hardiman
+ P. Kerr
+ January 01, 2005
+
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+ draft-herlein-speex-rtp-profile-03
+ RTP Payload Format for the Speex Codec
+
+Status of this Memo
+
+ This document is an Internet-Draft and is subject to all provisions
+ of section 3 of RFC 3667. By submitting this Internet-Draft, each
+ author represents that any applicable patent or other IPR claims of
+ which he or she is aware have been or will be disclosed, and any of
+ which he or she become aware will be disclosed, in accordance with
+ RFC 3668.
+
+ Internet-Drafts are working documents of the Internet Engineering
+ Task Force (IETF), its areas, and its working groups. Note that
+ other groups may also distribute working documents as
+ Internet-Drafts.
+
+ Internet-Drafts are draft documents valid for a maximum of six months
+ and may be updated, replaced, or obsoleted by other documents at any
+ time. It is inappropriate to use Internet-Drafts as reference
+ material or to cite them other than as "work in progress."
+
+ The list of current Internet-Drafts can be accessed at
+ http://www.ietf.org/ietf/1id-abstracts.txt.
+
+ The list of Internet-Draft Shadow Directories can be accessed at
+ http://www.ietf.org/shadow.html.
+
+ This Internet-Draft will expire on July 2, 2005.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2005).
+
+Abstract
+
+ Speex is an open-source voice codec suitable for use in Voice over IP
+ (VoIP) type applications. This document describes the payload format
+ for Speex generated bit streams within an RTP packet. Also included
+ here are the necessary details for the use of Speex with the Session
+ Description Protocol (SDP) and a preliminary method of using Speex
+
+
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+Herlein, et al. Expires July 2, 2005 [Page 1]
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
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+ within H.323 applications.
+
+Table of Contents
+
+ 1. Conventions used in this document . . . . . . . . . . . . . 3
+ 2. Overview of the Speex Codec . . . . . . . . . . . . . . . . 4
+ 3. RTP payload format for Speex . . . . . . . . . . . . . . . . 5
+ 4. RTP Header . . . . . . . . . . . . . . . . . . . . . . . . . 6
+ 5. Speex payload . . . . . . . . . . . . . . . . . . . . . . . 8
+ 6. Example Speex packet . . . . . . . . . . . . . . . . . . . . 9
+ 7. Multiple Speex frames in a RTP packet . . . . . . . . . . . 10
+ 8. MIME registration of Speex . . . . . . . . . . . . . . . . . 11
+ 9. SDP usage of Speex . . . . . . . . . . . . . . . . . . . . . 12
+ 10. ITU H.323/H.245 Use of Speex . . . . . . . . . . . . . . . . 15
+ 11. NonStandardMessage format . . . . . . . . . . . . . . . . . 16
+ 12. RTP Payload Types . . . . . . . . . . . . . . . . . . . . . 17
+ 13. Security Considerations . . . . . . . . . . . . . . . . . . 18
+ 14. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 19
+ 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
+ 15.1 Normative References . . . . . . . . . . . . . . . . . . . 20
+ 15.2 Informative References . . . . . . . . . . . . . . . . . . 20
+ Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 20
+ Intellectual Property and Copyright Statements . . . . . . . 22
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+Herlein, et al. Expires July 2, 2005 [Page 2]
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
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+1. Conventions used in this document
+
+ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
+ "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
+ document are to be interpreted as described in RFC 2119 [1].
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+Herlein, et al. Expires July 2, 2005 [Page 3]
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
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+2. Overview of the Speex Codec
+
+ Speex is based on the CELP [10] encoding technique with support for
+ either narrowband (nominal 8kHz), wideband (nominal 16kHz) or
+ ultra-wideband (nominal 32kHz), and (non-optimal) rates up to 48 kHz
+ sampling also available. The main characteristics can be summarized
+ as follows:
+
+ o Free software/open-source
+ o Integration of wideband and narrowband in the same bit-stream
+ o Wide range of bit-rates available
+ o Dynamic bit-rate switching and variable bit-rate (VBR)
+ o Voice Activity Detection (VAD, integrated with VBR)
+ o Variable complexity
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+3. RTP payload format for Speex
+
+ For RTP based transportation of Speex encoded audio the standard RTP
+ header [2] is followed by one or more payload data blocks. An
+ optional padding terminator may also be used.
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | RTP Header |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | one or more frames of Speex .... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | one or more frames of Speex .... | padding |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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+4. RTP Header
+
+ 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
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | sequence number |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | timestamp |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ The RTP header begins with an octet of fields (V, P, X, and CC) to
+ support specialized RTP uses (see [2] and [7] for details). For
+ Speex the following values are used.
+
+ Version (V): 2 bits
+
+ This field identifies the version of RTP. The version used by this
+ specification is two [2].
+
+ Padding (P): 1 bit
+
+ If the padding bit is set, the packet contains one or more additional
+ padding octets at the end which are not part of the payload. P is
+ set if the total packet size is less than the MTU.
+
+ Extension (X): 1 bit
+
+ If the extension, X, bit is set, the fixed header MUST be followed by
+ exactly one header extension, with a format defined in Section 5.3.1.
+ of [2].
+
+ CSRC count (CC): 4 bits
+
+ The CSRC count contains the number of CSRC identifiers.
+
+ Marker (M): 1 bit
+
+ The M bit indicates if the packet contains comfort noise. This field
+ is used in conjunction with the cng SDP attribute and is detailed
+ further in section 5 below. In normal usage this bit is set if the
+ packet contains comfort noise.
+
+ Payload Type (PT): 7 bits
+
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+
+Herlein, et al. Expires July 2, 2005 [Page 6]
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
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+ An RTP profile for a class of applications is expected to assign a
+ payload type for this format, or a dynamically allocated payload type
+ SHOULD be chosen which designates the payload as Speex.
+
+ Sequence number: 16 bits
+
+ The sequence number increments by one for each RTP data packet sent,
+ and may be used by the receiver to detect packet loss and to restore
+ packet sequence. This field is detailed further in [2].
+
+ Timestamp: 32 bits
+
+ A timestamp representing the sampling time of the first sample of the
+ first Speex packet in the RTP packet. The clock frequency MUST be
+ set to the sample rate of the encoded audio data. Speex uses 20 msec
+ frames and a variable sampling rate clock. The RTP timestamp MUST be
+ in units of 1/X of a second where X is the sample rate used. Speex
+ uses a nominal 8kHz sampling rate for narrowband use, a nominal 16kHz
+ sampling rate for wideband use, and a nominal 32kHz sampling rate for
+ ultra-wideband use.
+
+ SSRC/CSRC identifiers:
+
+ These two fields, 32 bits each with one SSRC field and a maximum of
+ 16 CSRC fields, are as defined in [2].
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+Herlein, et al. Expires July 2, 2005 [Page 7]
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
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+5. Speex payload
+
+ For the purposes of packetizing the bit stream in RTP, it is only
+ necessary to consider the sequence of bits as output by the Speex
+ encoder [9], and present the same sequence to the decoder. The
+ payload format described here maintains this sequence.
+
+ A typical Speex frame, encoded at the maximum bitrate, is approx.
+ 110 octets and the total number of Speex frames SHOULD be kept less
+ than the path MTU to prevent fragmentation. Speex frames MUST NOT be
+ fragmented across multiple RTP packets,
+
+ An RTP packet MAY contain Speex frames of the same bit rate or of
+ varying bit rates, since the bit-rate for a frame is conveyed in band
+ with the signal.
+
+ The encoding and decoding algorithm can change the bit rate at any 20
+ msec frame boundary, with the bit rate change notification provided
+ in-band with the bit stream. Each frame contains both "mode"
+ (narrowband, wideband or ultra-wideband) and "sub-mode" (bit-rate)
+ information in the bit stream. No out-of-band notification is
+ required for the decoder to process changes in the bit rate sent by
+ the encoder.
+
+ It is RECOMMENDED that values of 8000, 16000 and 32000 be used for
+ normal internet telephony applications, though the sample rate is
+ supported at rates as low as 6000 Hz and as high as 48 kHz.
+
+ The RTP payload MUST be padded to provide an integer number of octets
+ as the payload length. These padding bits are LSB aligned in network
+ octet order and consist of a 0 followed by all ones (until the end of
+ the octet). This padding is only required for the last frame in the
+ packet, and only to ensure the packet contents ends on an octet
+ boundary.
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+Herlein, et al. Expires July 2, 2005 [Page 8]
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+6. Example Speex packet
+
+ In the example below we have a single Speex frame with 5 bits of
+ padding to ensure the packet size falls on an octet boundary.
+
+ 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
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | sequence number |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | timestamp |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+
+ 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
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | ..speex data.. |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | ..speex data.. |0 1 1 1 1|
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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+7. Multiple Speex frames in a RTP packet
+
+ Below is an example of two Speex frames contained within one RTP
+ packet. The Speex frame length in this example fall on an octet
+ boundary so there is no padding.
+
+ Speex codecs [9] are able to detect the the bitrate from the payload
+ and are responsible for detecting the 20 msec boundaries between each
+ frame.
+
+ 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
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ |V=2|P|X| CC |M| PT | sequence number |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | timestamp |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | synchronization source (SSRC) identifier |
+ +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ | contributing source (CSRC) identifiers |
+ | ... |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | ..speex data.. |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | ..speex data.. | ..speex data.. |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ | ..speex data.. |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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+8. MIME registration of Speex
+
+ Full definition of the MIME [3] type for Speex will be part of the
+ Ogg Vorbis MIME type definition application [8].
+
+ MIME media type name: audio
+
+ MIME subtype: speex
+
+ Optional parameters:
+
+ Required parameters: to be included in the Ogg MIME specification.
+
+ Encoding considerations:
+
+ Security Considerations:
+
+ See Section 6 of RFC 3047.
+
+ Interoperability considerations: none
+
+ Published specification:
+
+ Applications which use this media type:
+
+ Additional information: none
+
+ Person & email address to contact for further information:
+
+ Greg Herlein <gherlein at herlein.com>
+ Jean-Marc Valin <jean-marc.valin at hermes.usherb.ca>
+
+ Intended usage: COMMON
+
+ Author/Change controller:
+
+ Author: Greg Herlein <gherlein at herlein.com>
+ Change controller: Greg Herlein <gherlein at herlein.com>
+ Change controller: IETF AVT Working Group
+
+ This transport type signifies that the content is to be interpreted
+ according to this document if the contents are transmitted over RTP.
+ Should this transport type appear over a lossless streaming protocol
+ such as TCP, the content encapsulation should be interpreted as an
+ Ogg Stream in accordance with [8], with the exception that the
+ content of the Ogg Stream may be assumed to be Speex audio and Speex
+ audio only.
+
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+Herlein, et al. Expires July 2, 2005 [Page 11]
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
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+9. SDP usage of Speex
+
+ When conveying information by SDP [4], the encoding name MUST be set
+ to "speex". An example of the media representation in SDP for
+ offering a single channel of Speex at 8000 samples per second might
+ be:
+
+ m=audio 8088 RTP/AVP 97
+ a=rtpmap:97 speex/8000
+
+ Note that the RTP payload type code of 97 is defined in this media
+ definition to be 'mapped' to the speex codec at an 8kHz sampling
+ frequency using the 'a=rtpmap' line. Any number from 96 to 127 could
+ have been chosen (the allowed range for dynamic types).
+
+ The value of the sampling frequency is typically 8000 for narrow band
+ operation, 16000 for wide band operation, and 32000 for ultra-wide
+ band operation.
+
+ If for some reason the offerer has bandwidth limitations, the client
+ may use the "b=" header, as explained in SDP [4]. The following
+ example illustrates the case where the offerer cannot receive more
+ than 10 kbit/s.
+
+ m=audio 8088 RTP/AVP 97
+ b=AS:10
+ a=rtmap:97 speex/8000
+
+ In this case, if the remote part agrees, it should configure its
+ Speex encoder so that it does not use modes that produce more than 10
+ kbit/s. Note that the "b=" constraint also applies on all payload
+ types that may be proposed in the media line ("m=").
+
+ An other way to make recommendations to the remote Speex encoder is
+ to use its specific parameters via the a=fmtp: directive. The
+ following parameters are defined for use in this way:
+
+ ptime: duration of each packet in milliseconds.
+
+ sr: actual sample rate in Hz.
+
+ ebw: encoding bandwidth - either 'narrow' or 'wide' or 'ultra'
+ (corresponds to nominal 8000, 16000, and 32000 Hz sampling rates).
+
+ vbr: variable bit rate - either 'on' 'off' or 'vad' (defaults
+ to off). If on, variable bit rate is enabled. If off, disabled.
+ If set to 'vad' then constant bit rate is used but silence will be
+ encoded with special short frames to indicate a lack of voice for
+
+
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+Herlein, et al. Expires July 2, 2005 [Page 12]
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
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+ that period.
+
+ cng: comfort noise generation - either 'on' or 'off'. If off
+ then silence frames will be silent; if 'on' then those frames will
+ be filled with comfort noise.
+
+ mode: Speex encoding mode. Can be {1,2,3,4,5,6,any} defaults to
+ 3 in narrowband, 6 in wide and ultra-wide.
+
+ penh: use of perceptual enhancement. 1 indicates to the decoder
+ that perceptual enhancement is recommended, 0 indicates that it is
+ not. Defaults to on (1).
+
+
+ Examples:
+
+ m=audio 8008 RTP/AVP 97
+ a=rtpmap:97 speex/8000
+ a=fmtp:97 mode=4
+
+ This examples illustrate an offerer that wishes to receive a Speex
+ stream at 8000Hz, but only using speex mode 3.
+
+ The offerer may suggest to the remote decoder to activate its
+ perceptual enhancement filter like this:
+
+ m=audio 8088 RTP/AVP 97
+ a=rtmap:97 speex/8000
+ a=fmtp:97 penh=1
+
+ Several Speex specific parameters can be given in a single a=fmtp
+ line provided that they are separated by a semi-colon:
+
+ a=fmtp:97 mode=any;penh=1
+
+ The offerer may indicate that it wishes to send variable bit rate
+ frames with comfort noise:
+
+ m=audio 8088 RTP/AVP 97
+ a=rtmap:97 speex/8000
+ a=fmtp:97 vbr=on;cng=on
+
+ The "ptime" attribute is used to denote the packetization interval
+ (ie, how many milliseconds of audio is encoded in a single RTP
+ packet). Since Speex uses 20 msec frames, ptime values of multiples
+ of 20 denote multiple Speex frames per packet. Values of ptime which
+ are not multiples of 20 MUST be ignored and clients MUST use the
+ default value of 20 instead.
+
+
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+Herlein, et al. Expires July 2, 2005 [Page 13]
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
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+ In the example below the ptime value is set to 40, indicating that
+ there are 2 frames in each packet.
+
+ m=audio 8008 RTP/AVP 97
+ a=rtpmap:97 speex/8000
+ a=ptime:40
+
+ Note that the ptime parameter applies to all payloads listed in the
+ media line and is not used as part of an a=fmtp directive.
+
+ Values of ptime not multiple of 20 msec are meaningless, so the
+ receiver of such ptime values MUST ignore them. If during the life
+ of an RTP session the ptime value changes, when there are multiple
+ Speex frames for example, the SDP value must also reflect the new
+ value.
+
+ Care must be taken when setting the value of ptime so that the RTP
+ packet size does not exceed the path MTU.
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+10. ITU H.323/H.245 Use of Speex
+
+ Application is underway to make Speex a standard ITU codec. However,
+ until that is finalized, Speex MAY be used in H.323 [5] by using a
+ non-standard codec block definition in the H.245 [6] codec capability
+ negotiations.
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+11. NonStandardMessage format
+
+ For Speex use in H.245 [6] based systems, the fields in the
+ NonStandardMessage should be:
+
+ t35CountryCode = Hex: B5
+ t35Extension = Hex: 00
+ manufacturerCode = Hex: 0026
+ [Length of the Binary Sequence (8 bit number)]
+ [Binary Sequence consisting of an ASCII string, no NULL
+ terminator]
+
+ The binary sequence is an ascii string merely for ease of use. The
+ string is not null terminated. The format of this string is
+
+ speex [optional variables]
+
+ The optional variables are identical to those used for the SDP a=fmtp
+ strings discussed in section 5 above. The string is built to be all
+ on one line, each key-value pair separated by a semi-colon. The
+ optional variables MAY be omitted, which causes the default values to
+ be assumed. They are:
+
+ ebw=narrow;mode=3;vbr=off;cng=off;ptime=20;sr=8000;penh=no;
+
+ The fifth octet of the block is the length of the binary sequence.
+
+ NOTE: this method can result in the advertising of a large number of
+ Speex 'codecs' based on the number of variables possible. For most
+ VoIP applications, use of the default binary sequence of 'speex' is
+ RECOMMENDED to be used in addition to all other options. This
+ maximizes the chances that two H.323 based applications that support
+ Speex can find a mutual codec.
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
+
+
+12. RTP Payload Types
+
+ Dynamic payload type codes MUST be negotiated 'out-of-band' for the
+ assignment of a dynamic payload type from the range of 96-127. H.323
+ applications MUST use the H.245 H2250LogicalChannelParameters
+ encoding to accomplish this.
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
+
+
+13. Security Considerations
+
+ RTP packets using the payload format defined in this specification
+ are subject to the security considerations discussed in the RTP
+ specification [2], and any appropriate RTP profile. This implies
+ that confidentiality of the media streams is achieved by encryption.
+ Because the data compression used with this payload format is applied
+ end-to-end, encryption may be performed after compression so there is
+ no conflict between the two operations.
+
+ A potential denial-of-service threat exists for data encodings using
+ compression techniques that have non-uniform receiver-end
+ computational load. The attacker can inject pathological datagrams
+ into the stream which are complex to decode and cause the receiver to
+ be overloaded. However, this encoding does not exhibit any
+ significant non-uniformity.
+
+ As with any IP-based protocol, in some circumstances a receiver may
+ be overloaded simply by the receipt of too many packets, either
+ desired or undesired. Network-layer authentication may be used to
+ discard packets from undesired sources, but the processing cost of
+ the authentication itself may be too high.
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
+
+
+14. Acknowledgments
+
+ The authors would like to thank Equivalence Pty Ltd of Australia for
+ their assistance in attempting to standardize the use of Speex in
+ H.323 applications, and for implementing Speex in their open source
+ OpenH323 stack. The authors would also like to thank Brian C. Wiles
+ <brian at streamcomm.com> of StreamComm for his assistance in developing
+ the proposed standard for Speex use in H.323 applications.
+
+ The authors would also like to thank the following members of the
+ Speex and AVT communities for their input: Ross Finlayson, Federico
+ Montesino Pouzols, Henning Schulzrinne, Magnus Westerlund.
+
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+Herlein, et al. Expires July 2, 2005 [Page 19]
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
+
+
+15. References
+
+15.1 Normative References
+
+ [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
+ Levels", RFC 2119.
+
+ [2] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
+ "RTP: A Transport Protocol for real-time applications", RFC
+ 3550.
+
+ [3] "Multipurpose Internet Mail Extensions (MIME) Part One: Format
+ of Internet Message Bodies", RFC 2045.
+
+ [4] Jacobson, V. and M. Handley, "SDP: Session Description
+ Protocol", RFC 2327.
+
+ [5] "Packet-based Multimedia Communications Systems", ITU-T
+ Recommendation H.323.
+
+ [6] "Control of communications between Visual Telephone Systems and
+ Terminal Equipment", ITU-T Recommendation H.245.
+
+ [7] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
+ Conferences with Minimal Control.", RFC 3551.
+
+ [8] Walleij, L., "The application/ogg Media Type", RFC 3534.
+
+15.2 Informative References
+
+ [9] "Speexenc/speexdec, reference command-line encoder/decoder",
+ Speex website http://www.speex.org/.
+
+ [10] "CELP, U.S. Federal Standard 1016.", National Technical
+ Information Service (NTIS) website http://www.ntis.gov/.
+
+
+Authors' Addresses
+
+ Greg Herlein
+ 2034 Filbert Street
+ San Francisco, California 94123
+ United States
+
+ EMail: gherlein at herlein.com
+
+
+
+
+
+
+Herlein, et al. Expires July 2, 2005 [Page 20]
+
+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
+
+
+ Simon Morlat
+ 35, av de Vizille App 42
+ Grenoble 38000
+ France
+
+ EMail: simon.morlat at linphone.org
+
+
+ Jean-Marc Valin
+ Department of Electrical and Computer Engineering
+ University of Sherbrooke
+ 2500 blvd Universite
+ Sherbrooke, Quebec J1K 2R1
+ Canada
+
+ EMail: jean-marc.valin at hermes.usherb.ca
+
+
+ Roger Hardiman
+ 49 Nettleton Road
+ Cheltenham, Gloucestershire GL51 6NR
+ England
+
+ EMail: roger at freebsd.org
+
+
+ Phil Kerr
+ England
+
+ EMail: phil at plus24.com
+
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+Herlein, et al. Expires July 2, 2005 [Page 21]
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+Internet-Draft draft-herlein-speex-rtp-profile-03 January 2005
+
+
+Intellectual Property Statement
+
+ The IETF takes no position regarding the validity or scope of any
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+ The IETF invites any interested party to bring to its attention any
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+
+Disclaimer of Validity
+
+ This document and the information contained herein are provided on an
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+Copyright Statement
+
+ Copyright (C) The Internet Society (2005). This document is subject
+ to the rights, licenses and restrictions contained in BCP 78, and
+ except as set forth therein, the authors retain all their rights.
+
+
+Acknowledgment
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
+
+
+
+
+Herlein, et al. Expires July 2, 2005 [Page 22]
+
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