Internet DRAFT - draft-xie-avt-xadsr-es202212

draft-xie-avt-xadsr-es202212





Audio Video Transport WG                                          Q. Xie
Internet-Draft                                                 D. Pearce
Expires: April 18, 2004                                         Motorola
                                                        October 19, 2003


      RTP Payload Format for European Telecommunications Standards
    Institute (ETSI) European Standard ES 202 212 Extended Advanced
             Distributed Speech Recognition Encoding (XAFE)
                  draft-xie-avt-xadsr-es202212-00.txt

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

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Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   This document specifies an RTP payload format for encapsulating ETSI
   Standard ES 202 212 extended advanced front-end (XAFE) signal
   processing feature streams for distributed speech recognition (DSR)
   systems.









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Table of Contents

   1.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  ES 202 212 DSR RTP Payload Format  . . . . . . . . . . . . . .  4
   3.1 Consideration on Number of FPs in Each RTP Packet  . . . . . .  4
   3.2 Support for Discontinuous Transmission . . . . . . . . . . . .  4
   4.  Frame Pair Formats . . . . . . . . . . . . . . . . . . . . . .  4
   4.1 Format of Speech and Non-speech FPs  . . . . . . . . . . . . .  4
   4.2 Format of Null FP  . . . . . . . . . . . . . . . . . . . . . .  6
   4.3 RTP header usage . . . . . . . . . . . . . . . . . . . . . . .  6
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   5.1 Mapping MIME Parameters into SDP . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   7.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  9
       Normative References . . . . . . . . . . . . . . . . . . . . .  9
       Informative References . . . . . . . . . . . . . . . . . . . .  9
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 10
       Intellectual Property and Copyright Statements . . . . . . . . 11
































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1. Conventions

   The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
   SHOULD NOT, RECOMMENDED, NOT RECOMMENDED, MAY, and OPTIONAL, when
   they appear in this document, are to be interpreted as described in
   [3].

   The following acronyms are used in this document:

      DSR  - Distributed Speech Recognition
      ETSI - the European Telecommunications Standards Institute
      FP   - Frame Pair
      DTX  - Discontinuous Transmission
      VAD  - Voice Activity Detection


2. Introduction

   Distributed speech recognition (DSR) technology is intended for a
   remote device acting as a thin client, also known as the front-end,
   to communicate with a speech recognition server, also called a speech
   engine, over a network connection to obtain speech recognition
   services. More details on DSR over Internet can be found in [7].

   To achieve interoperability with different client devices and speech
   engines, ETSI has issued several standards (or draft standards) for
   DSR front-end encoding schemes with different capabilities and
   characteristics, including the ES 201 108 DSR front-end, ES 202 050
   Advanced front-end (AFE), ES 202 211 Extended front-end (XFE), and
   the ES 202 212 Extended Advanced front-end (XAFE).

   The first DSR front-end encoding scheme ES 201 108 was published by
   ETSI in early 2000 [8] and an RTP packetization for ES 201 108 frames
   is defined in [7] in IETF.

   This document defines the RTP packetization for the ES 202 212
   Extended Advanced front-end (XAFE) [1]. The ES 202 212 XAFE is
   designed for use with discontinuous transmission and to support the
   transmission of Voice Activity information. XAFE also incorporates
   tonal information, viz., fundamental frequency F0 and voicing class,
   as additional parameters. This information can be used for enhancing
   the recognition accuracy of tonal languages, e.g., Mandarin,
   Cantonese, and Thai.

   More discussion about the different capabilities, characteristics,
   and applicabilities of the various ETSI DSR front-end encoding
   schemes can be found in [1].




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   The RTP packetization for ES 202 212 front-end defined in this
   document uses the same RTP packet format layout as that defined in
   [7] but with slightly different bit definition and with the addition
   of the compressed information for the extension in the frame bit
   definition for the payload. It also has a different payload type MIME
   registration.

3. ES 202 212 DSR RTP Payload Format

   Similar to other ETSI DSR front-end encoding schemes, the encoded DSR
   feature stream of ES 202 212 is transmitted in a sequence of frame
   pairs (FPs), where each FP represents two consecutive original voice
   frames.

   An ES 202 212 DSR RTP payload datagram is very similar to that
   defined in Section 3 of [7], i.e., a standard RTP header followed by
   a DSR payload containing a series of DSR FPs.

   The size of each ES 202 212 FP is 112 bits or 14 octets (see Sections
   3 below). This ensures that an ES 202 212 DSR RTP payload will always
   end on an octet boundary.

3.1 Consideration on Number of FPs in Each RTP Packet

   Same considerations described in Section 3.1 of [7] apply to ES 202
   212 RTP payload.

3.2 Support for Discontinuous Transmission

   Same considerations described in Section 3.2 of [7] apply to ES 202
   212 RTP payload.

4. Frame Pair Formats

4.1 Format of Speech and Non-speech FPs

   The following mel-cepstral frame MUST be used, as defined in Section
   7.2.4 in [1]:

   As defined in Section 7.2.4 in [1], after two frames (Frame #1 and
   Frame #2) worth of codebook indices, or 88 bits, a 4-bit CRC
   calculated on these 88 bits immediately follows it. The pitch indices
   of the first frame (Pidx1: 7 bits) and the second frame (Pidx2: 5
   bits) of the frame pair then follow. The class indices of the two
   frames in the frame pair worth 1 bit each next follow (Cidx1 and
   Cidx2). Finally, a 2-bit CRC (PC-CRC) calculated on the pitch and
   class bits (total: 14 bits) of the frame pair using the binary
   polynomial g(X) = 1 + X + X2 is included. The total number of bits in



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   frame pair packet is therefore 44 + 44 + 4 + 7 + 5 + 1 + 1 + 2 = 108.
   At the end, each FP MUST be padded with 4 zeros to the MSB 4 bits of
   the last octet in order to make the FP aligned to the 32-bit word
   boundary. The padding brings the total size of a FP to 112 bits, or
   14 octets. Note, this padding is separate from padding indicated by
   the P bit in the RTP header.

   The following diagram shows a complete ES 202 212 FP:

     Frame #1 in FP:
     ===============
        (MSB)                                     (LSB)
          0     1     2     3     4     5     6     7
       +-----+-----+-----+-----+-----+-----+-----+-----+
       :  idx(2,3) |            idx(0,1)               |    Octet 1
       +-----+-----+-----+-----+-----+-----+-----+-----+
       :       idx(4,5)        |     idx(2,3) (cont)   :    Octet 2
       +-----+-----+-----+-----+-----+-----+-----+-----+
       |             idx(6,7)              |idx(4,5)(cont)  Octet 3
       +-----+-----+-----+-----+-----+-----+-----+-----+
   idx(10,11)| VAD |              idx(8,9)             |    Octet 4
       +-----+-----+-----+-----+-----+-----+-----+-----+
       :       idx(12,13)      |   idx(10,11) (cont)   :    Octet 5
       +-----+-----+-----+-----+-----+-----+-----+-----+
                               |   idx(12,13) (cont)   :    Octet 6/1
                               +-----+-----+-----+-----+


    Frame #2 in FP:
    ===============
        (MSB)                                     (LSB)
          0     1     2     3     4     5     6     7
       +-----+-----+-----+-----+
       :        idx(0,1)       |                            Octet 6/2
       +-----+-----+-----+-----+-----+-----+-----+-----+
       |              idx(2,3)             |idx(0,1)(cont)  Octet 7
       +-----+-----+-----+-----+-----+-----+-----+-----+
       :  idx(6,7) |              idx(4,5)             |    Octet 8
       +-----+-----+-----+-----+-----+-----+-----+-----+
       :        idx(8,9)       |      idx(6,7) (cont)  :    Octet 9
       +-----+-----+-----+-----+-----+-----+-----+-----+
       |          idx(10,11)         | VAD |idx(8,9)(cont)  Octet 10
       +-----+-----+-----+-----+-----+-----+-----+-----+
       |                   idx(12,13)                  |    Octet 11
       +-----+-----+-----+-----+-----+-----+-----+-----+






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    CRC for Frame #1 and Frame #2 in FP:
    ====================================
        (MSB)                                     (LSB)
          0     1     2     3     4     5     6     7
                               +-----+-----+-----+-----+
                               |          CRC          |    Octet 12/1
                               +-----+-----+-----+-----+


    Extension information and padding in FP:
    ========================================
        (MSB)                                     (LSB)
          0     1     2     3     4     5     6     7
       +-----+-----+-----+-----+
       :       Pidx1           |                            Octet 12/2
       +-----+-----+-----+-----+-----+-----+-----+-----+
       |            Pidx2            |   Pidx1 (cont)  :    Octet 13
       +-----+-----+-----+-----+-----+-----+-----+-----+
       |  0  |  0  |  0  |  0  |  PC-CRC   |Cidx2|Cidx1|    Octet 14
       +-----+-----+-----+-----+-----+-----+-----+-----+

   The codebook indices, VAD flag, pitch index, and class index are
   specified in Section 6 of [1]. The 4-bit CRC and the 2-bit PC-CRC in
   the FP MUST be calculated using the formula (including the bit-order
   rules) defined in 7.2.4 in [1].

   Any number of FPs MAY be aggregate together in an RTP payload and
   they MUST be consecutive in time. However, one SHOULD always keep the
   RTP payload size smaller than the MTU in order to avoid IP
   fragmentation and SHOULD follow the recommendations given in Section
   3.1 in [7] when determining the proper number of FPs in an RTP
   payload.

4.2 Format of Null FP

   A Null FP for the ES 202 212 front-end codec is defined by setting
   all the 112 bits of the FP with 0's.

4.3 RTP header usage

   The format of the RTP header is specified in [5]. This payload format
   uses the fields of the header in a manner consistent with that
   specification.

   The RTP timestamp corresponds to the sampling instant of the first
   sample encoded for the first FP in the packet. The timestamp clock
   frequency is the same as the sampling frequency, so the timestamp
   unit is in samples.



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   As defined by ES 202 212 front-end codec, the duration of one FP is
   20 ms, corresponding to 160, 220, or 320 encoded samples with
   sampling rate of 8, 11, or 16 kHz being used at the front-end,
   respectively.  Thus, the timestamp is increased by 160, 220, or 320
   for each consecutive FP, respectively.

   The DSR payload for ES 202 212 front-end codes is always an integral
   number of octets. If additional padding is required for some other
   purpose, then the P bit in the RTP in the header may be set and
   padding appended as specified in [5].

   The RTP header marker bit (M) should be set following the general
   rules for audio codecs as defined in Section 4.1 in [6].

   The assignment of an RTP payload type for this new packet format is
   outside the scope of this document, and will not be specified here.
   It is expected that the RTP profile under which this payload format
   is being used will assign a payload type for this encoding or specify
   that the payload type is to be bound dynamically.

5. IANA Considerations

   One new MIME subtype registration is required for this payload type,
   as described below.

   Media Type name: audio

   Media subtype name: dsr-es202212

   Required parameters: none

   Optional parameters:

   rate: Indicates the sample rate of the speech.  Valid values include:
      8000, 11000, and 16000.  If this parameter is not present, 8000
      sample rate is assumed.

   maxptime: The maximum amount of media which can be encapsulated in
      each packet, expressed as time in milliseconds. The time shall be
      calculated as the sum of the time the media present in the packet
      represents.  The time SHOULD be a multiple of the frame pair size
      (i.e., one FP => 20ms).

      If this parameter is not present, maxptime is assumed to be 80ms.

      Note, since the performance of most speech recognizers are
      extremely sensitive to consecutive FP losses, if the user of the
      payload format expects a high packet loss ratio for the session,



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      it MAY consider to explicitly choose a maxptime value for the
      session that is shorter than the default value.

   ptime: see RFC2327 [4].

   Encoding considerations: This type is defined for transfer via RTP
      [5] as described in Sections 3 and 4 of RFC XXXX.

   Security considerations: See Section 6 of RFC XXXX.

   Person & email address to contact for further information:
      Qiaobing.Xie@motorola.com

   Intended usage: COMMON. It is expected that many VoIP applications
      (as well as mobile applications) will use this type.

   Author/Change controller:

      *  Qiaobing.Xie@motorola.com

      *  IETF Audio/Video transport working group


5.1 Mapping MIME Parameters into SDP

   The information carried in the MIME media type specification has a
   specific mapping to fields in the Session Description Protocol (SDP)
   [4], which is commonly used to describe RTP sessions. When SDP is
   used to specify sessions employing ES 202 050 DSR codec, the mapping
   is as follows:

   o  The MIME type ("audio") goes in SDP "m=" as the media name.

   o  The MIME subtype ("dsr-es202212") goes in SDP "a=rtpmap" as the
      encoding name.

   o  The optional parameter "rate" also goes in "a=rtpmap" as clock
      rate.

   o  The optional parameters "ptime" and "maxptime" go in the SDP
      "a=ptime" and "a=maxptime" attributes, respectively.

   Example of usage of ES 202 212 DSR:

     m=audio 49120 RTP/AVP 101
     a=rtpmap:101 dsr-es202212/8000
     a=maxptime:40




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6. Security Considerations

   Implementations using the payload defined in this specification are
   subject to the security considerations discussed in the RTP
   specification [5] and the RTP profile [6]. This payload does not
   specify any different security services.

7. Acknowledgments

   The design presented here is based on that of [7].

Normative References

   [1]  European Telecommunications Standards Institute (ETSI) Standard
        ES 202 212 v0.1.1, "Speech Processing, Transmission and Quality
        aspects (STQ); Distributed speech recognition; Extended advanced
        front-end feature extraction algorithm; Compression algorithms;
        Back-end speech reconstruction algorithm", (http://pda.etsi.org/
        pda/home.asp?wki_id=??) , April 2003.

   [2]  Bradner, S., "The Internet Standards Process -- Revision 3", BCP
        9, RFC 2026, October 1996.

   [3]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [4]  Handley, M. and V. Jacobson, "SDP: Session Description
        Protocol", RFC 2327, April 1998.

   [5]  Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson,
        "RTP: A Transport Protocol for Real-Time Applications", RFC
        3550, July 2003.

   [6]  Schulzrinne, H. and S. Casner, "RTP Profile for Audio and Video
        Conferences with Minimal Control", RFC 3551, July 2003.

   [7]  Xie, Q., "RTP Payload Format for European Telecommunications
        Standards Institute (ETSI) European Standard ES 201 108
        Distributed Speech Recognition Encoding", RFC 3557, July 2003.

Informative References

   [8]  European Telecommunications Standards Institute (ETSI) Standard
        ES 201 108, "Speech Processing, Transmission and Quality Aspects
        (STQ); Distributed Speech Recognition; Front-end Feature
        Extraction Algorithm; Compression Algorithms", http://
        webapp.etsi.org/pda/home.asp?wki_id=9948 , April 2000.




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Authors' Addresses

   Qiaobing Xie
   Motorola, Inc.
   1501 W. Shure Drive, 2-F9
   Arlington Heights, IL  60004
   US

   Phone: +1-847-632-3028
   EMail: qxie1@email.mot.com


   David Pearce
   Motorola Labs
   UK Research Laboratory
   Jays Close
   Viables Industrial Estate
   Basingstoke, HANTS  RG22 4PD
   UK

   Phone: +44 (0)1256 484 436
   EMail: bdp003@motorola.com





























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Intellectual Property Statement

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   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.











































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