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Versions: (draft-edwards-avt-rtp-jpeg2000) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 RFC 5371

INTERNET-DRAFT                                             Eric Edwards
draft-ietf-avt-rtp-jpeg2000-04.txt                      Satoshi Futemma
                                                       Nobuyoshi Tomita
                                                       Eisaburo Itakura
                                                       Sony Corporation
                                                       October 27, 2003
                                                Expires: April 26, 2004


              RTP Payload Format for JPEG 2000 Video Streams

Status of this Memo

    This document is an Internet-Draft and is in subject to all
    provisions of Section 10 of RFC2026.

    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 materials 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-Drafts Shadow Directories can be accessed at
    http://www.ietf.org/shadow.html.

Abstract

    This document describes a payload format for transporting JPEG
    2000 video streams using RTP (Real-time Transport Protocol). JPEG
    2000 video streams are formed as a continuous series of JPEG 2000
    still images. This payload format will allow for JPEG 2000's
    scalability and robustness to be maximized in streaming
    applications.


Table of Contents

    1.      Introduction ..........................................  2
    1.1     Conventions Used in this Document .....................  3
    2.      JPEG 2000 Video Features ..............................  4
    3.      Payload Design ........................................  4
    4.      Payload Format ........................................  4
    4.1     RTP fixed header usage ................................  4
    4.2     RTP Payload header format .............................  5
    5.      RTP Packetization .....................................  7
    5.1     Non-intelligent mode ..................................  8
    5.2     Intelligent mode  .....................................  9
    6.      Scalable Delivery and Priority field .................. 10

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    6.1     Priority mapping table ................................ 11
    6.1.1   Default priority mapping .............................. 11
    6.1.2   User-defined priority table ........................... 11
    6.2     Sender's Action   ..................................... 12
    6.3     Receiver's Action ..................................... 12
    7.      JPEG 2000 main header compensation .................... 13
    7.1     Sender processing ..................................... 13
    7.2     Receiver processing ................................... 14
    8.      Optional Payload Header ............................... 14
    9.      Security Consideration ................................ 15
    10.     IANA Consideration .................................... 16
    10.1    MIME Registration ..................................... 16
    10.2    SDP Parameters ........................................ 17
    11.     Intellectual Property Right Statement ................. 17
    12.     Informative Appendix - Recommended Practices .......... 18
    13.     References  ........................................... 18
    14.     Authors' Addresses .................................... 19
    15.     Full Copyright Statement .............................. 20


1. Introduction

    This document specifies payload formats for JPEG 2000 video
    streams over the Real-time Transport Protocol (RTP). JPEG 2000 is
    an ISO/IEC International Standard developed for next-generation
    still image encoding.  Its basic encoding technology is described
    in [1][6].

    Part 3 of the JPEG 2000 standard defines Motion JPEG 2000[6].
    However, Part 3 defines only the file format but not the
    transmission format for streaming on the Internet.  For this
    reason, it is necessary to define the RTP format for JPEG 2000
    video streams.

    JPEG 2000 supports many powerful features that are not supported
    in the current JPEG standard [1][7][8]:

        o Higher compression efficiency than JPEG with less visual
          loss especially at extreme compression ratios.

        o A single codestream that offers both lossy and superior
          lossless compression.

        o Robust transmission over noisy environments.

        o Progressive transmission by pixel accuracy (SNR Scalability)
          and resolution.

        o Random codestream access and processing.

    The JPEG-2000 algorithm is briefly explained below. Fig. 1
    shows a block diagram of JPEG 2000 encoding method.



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                                                     +-----+
                                                     | ROI |
                                                     +-----+
                                                        |
                                                        V
                   +----------+   +----------+   +------------+
                   |DC, comp. |   | Wavelet  |   |            |
    raw image  ==> |transform-|==>|transform-|==>|Quantization|==+
                   |  ation   |   |  ation   |   |            |  |
                   +----------+   +----------+   +------------+  |
                                                                 |
                  +-----------+   +----------+   +------------+  |
                  |           |   |          |   |            |  |
     JPEG 2000 <==| Data      |<==|Arithmetic|<==|Coefficient |<=+
     codestream   | Ordering  |   |  coding  |   |bit modeling|
                  +-----------+   +----------+   +------------+

                  Fig. 1: Block diagram of the JPEG 2000 encoder


    Each color component or tile is transformed into wavelet
    coefficients.  The component or tile is sub-sampled into various
    levels usually vertically and horizontally from high frequencies
    (which contains all the sharp details) to the low frequencies
    (which contains all the flat areas.)  Quantization is performed on
    the coefficients within each sub-band.  The wavelet coefficient is
    divided by the quantization step size and the result is truncated.
    After quantization, code blocks are formed from within the
    precincts within the tiles.  Precincts are a finer separation than
    tiles and code blocks are the smallest separation of the image
    data.  Entropy coding is performed within each code block and
    arithmetically encoded by bit plane.  After the coefficients of
    all code blocks have been coded into a short bit stream, a header
    is added turning it into a packet.  The header has all the
    information needed to decompress the packet into code blocks.  A
    group of packets are called layers.

    The standard has four ways to transmit and decode a compressed
    image: by resolution, quality, position, or component.  Packets
    can be ordered in any way to maximize these features.

    This is only to serve as an introduction to JPEG 2000 and to aid
    in understanding the rest of this document.  Further details of
    the encoder can be found in various texts on JPEG 2000 [1].

    To decompress a JPEG 2000 codestream, one would follow the
    reverse order of the encoding order, minus the quantization step.
    It is outside the scope of this document to describe in detail
    this procedure.  Please refer to various JPEG 2000 texts for
    details [1].

1.1 Conventions Used in this Document

    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL

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    NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
    in this document are to be interpreted as described in RFC2119
    [2].

2. JPEG 2000 Video Features

    JPEG 2000 video streams are formed as a continuous series of JPEG
    2000 still images.  The previously described features of JPEG 2000
    can be used effectively in a streaming application.  A JPEG 2000
    video stream has the following merits:

    In JPEG 2000 SNR is improved dramatically over classic JPEG at a
    low bit rates.

    This is a Full Intra format- each frame is independently
    compressed - and therefore has a low encoding and decoding delay.

    JPEG 2000 has flexible and accurate rate control.  This is
    suitable for traffic control and congestion control during network
    transmission.

    JPEG 2000 can provide its own codestream error resilience markers
    to aid in codestream recovery.

3. Payload Design

    To provide a payload format that exploits the JPEG 2000 video
    stream, described in the previous section, the following must be
    taken into consideration:

    - Provisions for packet loss

        On the Internet, 5% packet loss is common and this percentage
        may sometimes come to 20% or more.  To split JPEG 2000 video
        streams into RTP packets, efficient packetization of the code
        stream is required to minimize the effects of problems in
        decoding due to missing code-blocks in error prone
        environments.  If the main header is lost in transmission, the
        image cannot be decoded.  Accordingly, a system to compensate
        for the loss of the main header is required.

    - A packetizing scheme that exploits JPEG 2000 functionality.

        A packetizing scheme so that an image can be progressively
        transmitted and reconstructed progressively by the receiver
        using JPEG 2000 functionality would be very powerful.  It
        would allow for maximizing performance over various network
        conditions and variations in computing power of receiving
        platforms.

4. Payload Format

4.1 RTP fixed header usage


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    For each RTP packet, the RTP fixed header is followed by the JPEG
    2000 payload header, which is followed by JPEG 2000 codestream.
    The RTP header fields that have a meaning specific to a JPEG
    2000 video stream are described as follows:

    Marker bit (M): The marker bit of the RTP fixed header MUST be set
      to 1 on the last RTP packet of a video frame, and otherwise, it
      must be 0.  When transmission is performed by multiple RTP
      sessions, the bit is set in the last packet of the frame in each
      session.

    Payload type (PT): The payload type is dynamically assigned by
      means outside the scope of this document. A payload type in the
      dynamic range shall be chosen by means of an out of band
      signaling protocol (e.g., RTSP, SIP, etc.)

    Timestamp: The RTP timestamp is in units of 90 kHz. The same
      timestamp must appear in each fragment of a given frame.  When a
      JPEG 2000 image is an interlaced, the odd field and the
      corresponding even field have the same timestamps.  The initial
      value of the timestamp is random to make known plaintext attacks
      on encryption more difficult, even if the source itself does not
      encrypt, as the packets may flow through a translator that does.


4.2 RTP Payload header format

    The RTP payload header format for JPEG 2000 video stream is as
    follows:

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |X|E|MHF|mh_id|T|     priority  |           tile number         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | reserved  |tp |             fragment offset                   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Fig. 2:  RTP payload header format for JPEG 2000


    X : 1 bit

        Extension bit flag.  This bit MUST be set to 1 when a JPEG
        2000 optional payload header follows this header, the JPEG
        2000 payload header, otherwise it MUST be set to 0.  The
        details of optional payload headers are described in Section 8
        of this document.

    E : 1 bit

        Enable bit flag.  If this bit is set to 1, it means
        "intelligent packetization" described in Section 5.2.  If E
        bit is 0, it means non-intelligent packetization" and a

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        receiver MUST ignore any other payload header information
        other than extension bit flag and fragment offset.


    MHF (Main Header Flag) : 2 bits

        MHF shows whether the main header is packed into the RTP
        packet or not.  When the main header exists in the RTP packet,
        the sender MUST set the first bit to 1, otherwise this field
        MUST set to 0.  If the first bit is 1, the second bit is
        valid, and if the last part of the main header is included
        (either whole or fragmented), the sender MUST set the second
        bit to 1. In other words, this field is either 3(=0b11) or
        2(=0b10) if the main header exists in the RTP packet,
        otherwise 0. Table of MHF usage is below:

        +----+-------------------------------------------------------+
        |MHF | Description                                           |
        +----+-------------------------------------------------------+
        | 00 | no main header is packed at all                       |
        | 01 | reserved for future use.                              |
        | 10 | the fragmented main header (not last part) is packed. |
        | 11 | a whole main header or the last part of the           |
        |    | fragmented main header is packed.                     |
        +----+-------------------------------------------------------+

                           Table 1: MHF usage values


        The receiver checks MHF to determine the main header range and
        may perform main header compensation described in Section 7 if
        the main header is lost.

    mh_id : 3 bits

        Main header identification value.  This is used for  JPEG
        2000 main header recovery.  The same mh_id is used as long as
        the coding parameters described in the main header remain
        unchanged.  The initial value of mh_id is random. Mh_id value
        must increase by 1 every time a new main header is
        transmitted.  Once the mh_id value is greater than 7, it must
        roll over and start at 1 again.  Usage of this header is
        described in Section 7 of this document. This field is only
        valid when E bit is 1.  If the E bit is 0, then this field
        SHOULD be zero.

    T (Tile field invalidation flag) : 1 bit

        T bit indicates whether the tile number field is invalid or
        not. A sender MUST set T bit when the tile number field is
        invalid.

        There are two cases where the tile number field is invalid.
        One is the case that an RTP packet holds only the JPEG 2000

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        main header. In this case, a sender can not set any number in
        the tile number field because no JPEG 2000 tile-part bitstream
        is included in the RTP packet.

        The other case is that multiple tile-part bitstreams are
        packed together in an RTP packet. In general, it is advisable
        to pack only one tile bitstream in an RTP packet, but if the
        tile-part length is too small it is efficient to pack together
        multiple tile-parts in one RTP packet.  In this case it is
        meaningless to assign a number (e.g. the smallest tile number)
        because the number is designed for decoding an arbitrary tile
        easily, which is not valid when multiple tile parts are
        combined in a single packet. Therefore, T bit indication is
        needed.

    priority : 8 bits

        The priority field indicates the importance of the JPEG 2000
        packet included in the payload.  Typically, a higher priority
        is set in the packets containing JPEG 2000 packets containing
        the lower sub-bands.

    tile number : 16 bits

        This field shows the tile number that a bitstream belongs to
        only when the T bit is 0. A receiver can easily decode an
        arbitrary tile by checking this field. If T bit is set to 1, a
        receiver MUST ignore this field.

    tp (type) : 2 bits

        This field indicates how a JPEG 2000 image is scanned (meaning
        - progressive or interlace).

        0: The image is progressively scanned. On a computer monitor,
           it should be displayed as-is at the specified width and
           height in the JPEG 2000 main header.

        1: The image is an odd field of an interlaced video signal.
           The height specified in the JPEG 2000 main header is half
           of the height of the entire displayed image.  In a
           receiver, an odd field should be de-interlaced with the
           even field following it so that lines from each image can
           alternate.

        2: The image is an even field of an interlaced video signal.

        3: The image is a single field from an interlaced video
           signal, intended to be displayed full frame as if it were
           received as both the odd & even field of the frame.  On a
           computer monitor, each line in the image should be
           displayed twice, doubling the height of the image.

    fragment offset : 24 bits

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        This value must be set to the byte offset in the JPEG 2000
        data stream contained in this RTP packet.

        JPEG 2000 frames are typically larger than the underlying
        network's maximum transfer units (MTU), therefore frames might be
        fragmented into several packets.  The fragment offset is the
        data offset in bytes of the current packet from the start of
        the JPEG 2000 codestream.  This field helps the receiver to
        reassemble the JPEG 2000 codestream.

        To perform scalable video delivery by using multiple RTP
        sessions, the offset value from the first byte of the same
        frame is set for fragment offset.  It is possible, in scalable
        video delivery using multiple RTP sessions, the fragment
        offset may not start with 0 in some RTP sessions even if the
        packet is the first one of the frame.

5. RTP Packetization

    As shown in Fig. 3, a JPEG 2000 codestream is structured from the
    main header beginning with the SOC marker, one or more tiles (only
    one tile for no tile division), and the EOC marker to indicate the
    end of the codestream.  Each tile consists of a tile-part header
    that starts with the SOT marker and ends with the SOD marker, and
    bitstream (a series of jp2-packet).

          +--  +------------+
    Main  |    |     SOC    |  Required as the first marker.
    header|    +------------+
          |    |    main    |  Main header marker segments
          +--  +------------+
          |    |    SOT     |  Required at the beginning of each
    Tile- |    +------------+    tile-part header.
    part  |    |   T0,TP0   |  Tile 0, tile-part 0 header marker
    header|    +------------+    segments
          |    |    SOD     |  Required at the end of each tile-part
          +--  +------------+    header
               | bitstream  |  Tile-part bitstream
          +--  +------------+
          |    |    SOT     |
    Tile- |    +------------+
    part  |    |   T1,TP0   |
    header|    +------------+
          |    |    SOD     |
          +--  +------------+
               | bit stream |
               +------------+
               |    EOC     |  Required as the last marker in the code
               +------------+  stream

              Fig. 3: Construction of the JPEG 2000 codestream



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    Two packetization modes can be used for a JPEG 2000 RTP packet:
    non-intelligent mode and intelligent mode.

    A sender is allowed to packetize the JPEG 2000 codestream in
    either mode, but MUST not change the mode within the same JPEG
    2000 codestream. A sender may implement only one mode, but a
    receiver MUST interpret both modes. A receiver identifies the
    packetization mode with E bit flag in the payload header to
    process the RTP packet properly.

    In both modes, a sender usually partitions the JPEG 2000 codestream
    in the way that IP fragmentation never occurs. Any packets larger
    than the MTU size might be fragmented into multiple smaller IP
    packets by the IP layer.  Therefore, if one fragment is lost
    during transmission, a receiver might not be able to reassemble
    the IP packet, so that it is recognized as a loss of the whole
    fragmented packet.

5.1 Non-intelligent mode

    This mode is prepared for a thin sender, which has insufficient CPU
    power to parse the JPEG 2000 codestream syntax and to partition
    the codestream per jp2-packet.

    In this mode, a sender segments the JPEG 2000 codestream along
    arbitrary lengths into RTP packets, and E bit flag in the payload
    header MUST be set to 0.

    Typically, a sender fragments a JPEG 2000 codestream in a fixed
    length.  An example of this packetization is below:

    +------+-------+-------------------------------+
    |RTP   |payload| JPEG 2000 codestream fragment |
    |header|header |                               |
    +------+-------+-------------------------------+
    +------+-------+-------------------------------+
    |RTP   |payload| JPEG 2000 codestream fragment |
    |header|header |                               |
    +------+-------+-------------------------------+
                     ...
    +------+-------+-------------------------------+
    |RTP   |payload| JPEG 2000 codestream fragment |
    |header|header |                               |
    +------+-------+-------------------------------+

        Fig. 4: Example of non-intelligent mode packetization


    A receiver recognizes that the codestream is packetized in
    non-intelligent mode by checking E bit flag, then RTP packets with
    same RTP timestamps are de-packetized to the JPEG 2000 codestream
    using fragment offset in the payload header.
    In this mode, X bit and fragment offset are interpreted and any
    other fields are ignored.

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    If a receiver receives the RTP packets in both modes and both RTP
    timestamps are the same, then it SHOULD ignore the all RTP packets
    with the timestamp.


5.2 Intelligent mode

    In this mode, a new concept for a packetization unit is
    introduced. A packetization unit is defined as either a JPEG 2000
    main header, a tile-part header, or a jp2-packet.

    First, a sender divides the JPEG 2000 codestream into
    packetization units by parsing the codestream or by getting any
    indexing informations from encoder, and then packs the
    packetization units into RTP packets.  A sender can put an
    arbitrary number of packetization units into an RTP packet, but it
    MUST preserve the codestream order.  An example of this kind of
    RTP packet format is below:

    +------+-------+---------------+---------------+
    |RTP   |payload| packetization | packetization |
    |header|header | unit          | unit          |
    +------+-------+---------------+---------------+

    Fig. 5 An Example of RTP packet format with multiple
           packetization units

    Sometimes, packetization units may be not 32-bits aligned, so
    additional padding octets are needed.  In an RTP packet with
    multiple packetization units, any required paddings MUST be added
    at the end of concatenated packetization units.

    If a packetization unit is larger than MTU size, it can be
    fragmented.  To pack a fragmented packetization unit, the
    fragmented unit MUST NOT be packed with the succeeding
    packetization unit into the same RTP packet. An example of this
    kind of RTP packet format is below:

    +------+-------+-----------------------------+
    |RTP   |payload| packetization unit fragment |
    |header|header |                             |
    +------+-------+-----------------------------+
    +------+-------+-----------------------------+
    |RTP   |payload| packetization unit fragment |
    |header|header |                             |
    +------+-------+-----------------------------+
                     ...
    +------+-------+-----------------------------+
    |RTP   |payload| packetization unit fragment |
    |header|header |                             |
    +------+-------+-----------------------------+

    Fig. 6 An Example of RTP packet format with a fragmented

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           packetization unit


6. Scalable Delivery and Priority field

    JPEG 2000 codestream has rich functionality built into it so
    decoders can easily handle scalable delivery or progressive
    transmission.  Progressive transmission that allows images to be
    reconstructed with increasing pixel accuracy or spatial resolution
    is essential for many applications.  This feature allows the
    reconstruction of images with different resolutions and pixel
    accuracy, as needed or desired, for different target devices.  The
    largest image source devices can provide a code stream that is
    easily processed for the smallest image display device.

    The jp2-packets contain all compressed image data from a
    specific layer, a specific component, a specific resolution level,
    and a specific precinct.  The order in which these jp2-packets are
    found in the codestream is called the "progression order".  The
    ordering of the jp2-packets can progress along four axes: layer,
    component, resolution level and precinct.

    Providing a priority field to indicate importance of data contained
    in a given RTP packet can exploit JPEG 2000 progressive and
    scalable functions.

    The lower the number of priority value is the higher priority.  In
    other words, the priority value 0 is the highest priority and 255
    is the lowest priority.  We define the priority value 0 as special
    priorities for the headers (the main header or tile-part header)
    When any headers (the main header or tile-part header) are packed
    into the RTP packet, the sender MUST set the priority value to 0.

6.1 Priority mapping table

    For the progression order, the priority value for each jp2-packet
    is given by the priority mapping table.  There are two types of
    priority mapping: default priority mapping and user-defined
    priority mapping. In principle, the priority mapping table is
    negotiated between the sender and the receiver through external
    protocols (such as: RTSP, SIP, etc), which not within the scope of
    this document.  However, in some environments such as a multicast
    video-conference environment, it might be difficult to negotiate
    the priority-mapping table between senders and receivers.  We
    define the default priority mapping for such a situation.  The
    receiver interprets the priority as a user-defined priority value
    only when the priority-mapping table has been negotiated and
    otherwise the receiver interprets as the default priority.

6.1.1 Default priority mapping

    The JPEG 2000 codestream is ordered in some progression order and
    in the most cases the foremost jp2-packets are more important
    than the latter ones.

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    In default priority mapping, a priority value is defined as
    jp2-packet sequence number, in which the first jp2-packet in a
    tile MUST be assigned the value 1. For every successive packet
    this number is incremented by one.  When the maximum number (=255)
    is reached, the number remains at 255.  A jp2-packet sequence
    number is also hinted from Nsop of SOP marker segment (Annex A.8.1
    [1]) in the JPEG 2000 codestream.

6.1.2 User-defined priority table

    The user-defined priority table is freely defined by users, but
    priority value 0 MUST be used for the headers (the main header and
    tile-part headers).

    For example, in the LRCP order codestream with 3 layers and 3
    resolutions, the user-defined priority table can be defined below
    (the format is not significant).  4 level priorities is defined
    in the below example.

                priority 1: L=0,R=0, C=any, P=any
                priority 2: L=0,R=1-2, C=any, P=any
                priority 3: L=1,R=any, C=any, P=any
                priority 4: L=2,R=any, C=any, P=any

    As another example, the resolution-based priority table can be
    defined as below:

                Priority 1: R=0, L=0, C=any, P=any
                Priority 2: R=0, L=1-2, C=any, P=any
                Priority 3: R=1, L=any, C=any, P=any
                Priority 4: R=2, L=any, C=any, P=any

    As another example, the component-based priority table can be
    defined as below:

                Priority 1: C=0, L=0, R=0, P=any
                Priority 2: C=0, L=0, R=any, P=any
                            C=0, L=any, R=0, P=any
                Priority 3: C=1-2, L=any, R=any, P=any

    To change the priority-mapping table, a new priority-mapping table
    must be sent from the sender to the receiver as needed.

6.2 Sender's Action

    A priority value is given in accordance with the priority mapping
    table. If multiple jp2-packets are packed into the same RTP
    packet, the lowest priority value is set.

    Accordingly, a sender can transmit each priority using separate
    multiple RTP sessions. For example, in layered multicast a sender
    can transmit each priority through each multicast group.


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6.3 Receiver's Action

    Progressive transmission that allows images to be reconstructed
    with increasing pixel accuracy or spatial resolution is essential
    for many applications.  This feature allows the reconstruction of
    images with different resolutions and pixel accuracy, as needed or
    desired, for different target devices.  The image architecture
    provides for the efficient delivery of image data in many
    applications such as client/server applications.  The receiver
    should decode packets above a certain priority to obtain maximum
    performance depending on the receiver's platform.

    The receiver can determine on its own (using or not using the
    mapping table or other variables) the priority value level the RTP
    packets it should decode.

    For example, when a less powerful CPU is used or the terminal has
    only a low-resolution display, decoding only RTP packets below a
    certain priority permits obtaining optimal performance.

    If any high-priority RTP packet is not received when a packet loss
    occurs, frame(s) can be skipped because no significant visual loss
    may be perceived even if decoding can be successfully performed.

    When the priority value is uninterpreted or unexpected,
    a receiver MUST ignore the priority field of this RTP packet.

7. JPEG 2000 main header compensation

    The JPEG 2000 main header has various encoding parameters.  A
    decoder decodes the JPEG 2000 codestream by using the parameters
    described in the JPEG 2000 main header.  If an RTP packet is lost
    with the JPEG 2000 main header, the corresponding JPEG 2000
    codestream cannot be decoded, even if all of the following RTP
    packets has been successfully received.

    A recovery of the main header that has been lost is very simple
    with this procedure.  In the case of JPEG 2000 video, it is common
    that encode parameters will not vary greatly from each successive
    frame. Even if the RTP packet including the main header of a frame
    has dropped, decoding processing may be performed by using the
    main header of the previous frame if this previous frame is
    already encoded by the same encode parameters.

    The mh_id field of the payload header is used to recognize whether
    the encoding parameters of the main header are the same as the
    encoding parameters of the previous frame. The same value is set
    in mh_id of the RTP packet in the same frame.  Mh_id and encode
    parameters are not associated with each other as 1:1 but they are
    used to recognize whether the encode parameters of the previous
    frame are the same or not.

    The mh_id field value SHOULD be saved from previous frames to be
    used to recover the current frame's main header, if lost.  If the

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    mh_id of the current frame has the same value as the mh_id value
    of the previous frame, the previous frame's main header SHOULD be
    used to decode the current frame, in case of a lost header.

    The sender MUST increment mh_id when parameters in the header
    change and send a new main header accordingly.

    The receiver MAY use the mh_id and MAY retain the header for such
    compensation.

7.1 Sender processing

    The sender must transmit RTP packets with the same mh_id value
    unless the encoder parameters are different from the previous
    frame.  The encode parameters are the fixed information marker
    segment (SIZ marker) and functional marker segments (COD, COC,
    RGN, QCD, QCC, and POC) specified in JPEG 2000 Part 1 Annex A [1].
    If the encode parameters have been changed, the sender
    transmitting RTP packets MUST increment the mh_id value by one.
    The initial mh_id value should be 1.  When the mh_id value exceeds
    7, the value MUST return to 1 again.

    If the mh_id field is set to 0, the receiver MUST not save the
    main header and MUST NOT compensate for lost headers using the
    above method.

7.2 Receiver processing

    When the receiver has received the main header correctly, the RTP
    sequence number, the mh_id and main header should be saved except
    when the mh_id value is 0.  Only the last main header that was
    received correctly SHOULD be saved.  That is, if there has been a
    saved main header, the previous one is deleted and the new main
    header is saved.

    When the main header is not received, the receiver compares the
    current mh_id value (this mh_id can be known by receiving at least
    one RTP packet) with the saved mh_id value.  When the values are
    the same, decoding may be performed by using the saved main
    header.

    Knowing whether the main header is lost or not maybe difficult,
    especially when the main header is fragmented.

    In all cases, the main header will start with fragment offset = 0.
    In the case of fragmented main header, only the first fragment
    will have the fragment offset = 0.

8. Optional Payload Header

    An optional payload header is intended for sending application
    specific data.  When X bit in the payload header is set, an
    optional payload header follows the payload header. The JPEG 2000
    video stream payload comes after the optional payload header.

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    When X bit in payload header is set, a receiver MUST process the
    optional payload header.  An optional payload header that a
    receiver cannot recognize MUST be skipped in specified length.

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |    optype   |X|             length            |               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
    |                   option specific format .....                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Fig. 7 : JPEG 2000 video stream optional payload header generic
                 format


    Optype : 7 bits

        Optype describes the optional payload header type.  Optypes
        0-63 are reserved as fixed, well-known mappings to be defined
        by future revisions of this document. Optypes 64-127 can be
        freely used for an application's own definition. If some
        options would be fully tested and widely used, they shall be
        registered with the Internet Assigned Number Authority (IANA).


    X : 1 bit

        Further extension bit. This must be set to 1 if another
        optional payload header follows this optional payload header;
        otherwise it must be set to 0.

        When the extension bit of the optional header is 1, another
        optional payload header MUST come immediately after this
        optional payload header.

    length : 16 bits

        This value must be the length of optional header in bytes
        (including optype, X, length field). The receiver shall
        perform processing for the optional header when the extension
        bit of the JPEG 2000 payload header is 1.


9. Security Consideration

    RTP packets using the payload format defined in this specification
    are subject to the security considerations discussed in the RTP
    specifications[3]. 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 on the compressed data so there is no conflict
    between the two operations.

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    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, JPEG 2000 coding does not
    exhibit any significant non-uniformity.

    If QoS enhanced service is used, RTP receivers SHOULD monitor
    packet loss to ensure that the service that was requested is
    actually being delivered.  If it is not, then they SHOULD assume
    that they are receiving best-effort service and behave accordingly.

    If best-effort service is being used, users of this payload format
    MUST monitor packet loss to ensure that the packet loss rate is
    within acceptable parameters.  Packet loss is considered
    acceptable if a TCP flow across the same network path,
    experiencing the same network conditions, would achieve an average
    throughput, measured on a reasonable timescale, that is not less
    than the RTP flow is achieving.  This condition can be satisfied
    by implementing congestion control mechanisms to adapt the
    transmission rate (or the number of layers subscribed for a
    layered multicast session), or by arranging for a receiver to
    leave the session if the loss rate is unacceptably high.

    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.  In a multicast
    environment, pruning of specific sources may be implemented in
    future versions of IGMP [9] and in multicast routing protocols to
    allow a receiver to select which sources are allowed to reach it.


10. IANA Consideration

10.1 MIME Registration

    This document defines a new RTP payload name and associated MIME
    type, jpeg2000. The MIME registration form for JPEG 2000 video
    stream is enclosed below:

    MIME media type name:  video

    MIME subtype name: jpeg2000

    Required parameters: none

    Optional parameters: none

    Encoding considerations:
        JPEG 2000 video stream can be transmitted
        with RTP as specified in RFC XXXX.

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    Security considerations: see section 9 of RFC XXXX.

    Interoperability considerations:
        JPEG 2000 video stream is a sequence of JPEG 2000 still
        images. An implementation in compliant with [1] can decode and
        attempt to display the encoded JPEG 2000 video stream.

    Published specification: ISO/IEC 15444-1, RFC XXXX

    Applications which use this media type:
        video streaming and communication.

    Additional information: none

    Magic number(s): none

    File extension(s): none

    Macintosh File Type Code(s): none

    Person & email address to contact for further information:
        Eric Edwards
        Email: Eric.Edwards@am.sony.com

    Intended usage: COMMON

    Author/Change controller:
        Eric Edwards
        Email: Eric.Edwards@am.sony.com


10.2 SDP Parameters

    The MIME media type video/jpeg2000 string is mapped to fields in
    the Session Description Protocol (SDP) [4] as follows:

    o The media name in the "m=" line of SDP MUST be video.

    o The encoding name in the "a=rtpmap" line of SDP MUSE be jpeg2000
      (the MIME subtype).

    o The clock rate in the "a=rtpmap" line MUSE be 90000.

    Therefore, an example of media representation in SDP is as
    follows:

        m=video 49170/2 RTP/AVP 98
        a=rtpmap:98 jpeg2000/90000


11. Intellectual Property Right Statement

    The IETF takes no position regarding the validity or scope of any

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    intellectual property or other rights that might be claimed to
    pertain to the implementation or use of the technology described
    in this document or the extent to which any license under such
    rights might or might not be available; neither does it represent
    that it has made any effort to identify any such rights.
    Information on the IETF's procedures with respect to rights in
    standards-track and standards-related documentation can be found
    in BCP-11.  Copies of claims of rights made available for
    publication and any assurances of licenses to be made available,
    or the result of an attempt made to obtain a general license or
    permission for the use of such proprietary rights by implementors
    or users of this specification can be obtained from the IETF
    Secretariat.

    The IETF invites any interested party to bring to its attention
    any copyrights, patents or patent applications, or other
    proprietary rights which may cover technology that may be required
    to practice this standard.  Please address the information to the
    IETF Executive Director.

    The IETF has been notified of intellectual property rights claimed
    in regard to some or all of the specification contained in this
    document.  For more information consult the online list of claimed
    rights.


12. Informative Appendix - Recommended Practices

    As the JPEG 2000 coding standard is highly flexible, many
    different but compliant data streams can be produced and still be
    labeled as a JPEG 2000 data stream.

    The following is a set of recommendations set forth from our
    experience in developing JPEG 2000 and this payload
    specification. Implementations of this standard must handle all
    possibilities mentioned in this specification.  The following is a
    listing of items an implementation could optimize.


    Error Resilience Markers

        The use of error resilience markers in the JPEG 2000 data
        stream is highly recommended in all situations.  Error
        recovery with these markers is helpful to the decoder and save
        external resources.  Markers such as: RESET, RESTART, and
        ERTERM.

    YPbPr Color space

        The YPbPr color space provides the greatest amount of
        compression in color with respect to the human visual
        system. When used with JPEG 2000, the usage of this color
        space can provide excellent visual results at extreme bit
        rates.

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    Progression Ordering

        JPEG 2000 offers many different ways to order the final code
        stream to optimize the transfer with the presentation.  The
        most useful ordering in our usage cases have been for layer
        progression and resolution progression ordering.

    Tiling and Packets

        JPEG 2000 packets are formed regardless of the encoding
        method. The encoder has little control over the size of these
        JPEG 2000 packets as they maybe large or small.

        Tiling splits the image up into smaller areas and each are
        encoded separately.  With tiles, the JPEG 2000 packet sizes
        are also reduced.  When using tiling, almost all JPEG 2000
        packet sizes are an acceptable size (i.e. smaller than the MTU
        size of most networks.)


13. References

Normative References

    [1] ISO/IEC JTC1/SC29, ISO/IEC 15444-1 "Information technology -
        JPEG 2000 image coding system - Part 1: Core coding system",
        July 2002.

    [2] S. Bradner, "Key words for use in RFCs to Indicate Requirement
        Levels", BCP14, RFC2119, March 1997.

    [3] H. Schulzrinne, S. Casner, R. Frederick, and V. Jacobson,
        "RTP: A Transport Protocol for Real Time Applications", RFC
        1889, January 1996.

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

Informative References

    [5] ISO/IEC JTC1/SC29/WG1, "JPEG2000 Part I Final Committe Draft
        Version 1.0", http://www.jpeg.org/public/fcd15444-1.pdf, March
        2000.

    [6] ISO/IEC JTC1/SC29/WG1, "Motion JPEG 2000 Final Committee Draft
        1.0", http://www.jpeg.org/public/fcd15444-3.doc, March, 2001.

    [7] ISO/IEC JTC1/SC29/WG1, "JPEG2000 requirements and profiles
        version 6.3", draft in progress,
        http://www.jpeg.org/public/wg1n1803.pdf

    [8] Diego Santa-Cruz, Touradj Ebrahimi, Joel Askelof, Mathias
        Larsson and Charilaos Christopoulos, "JPEG 2000 still image

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        coding versus other standards", In Proc. of SPIE's 45th annual
        meeting, Application of Digital Image Processing XXIII,
        vol.4115, pp.446-454, July 2000.

    [9] Deering, S., "Host Extensions for IP Multicasting", STD 5,
        RFC 1112, August 1989.

14. Authors' Addresses

    Eric Edwards
    Sony Corporation
    Media Processing Division
    Platform Technology Center of America
    3300 Zanker Road, MD: SJ2C4
    San Jose, CA 95134
    Phone: +1 408 955 6462
    Fax: +1 408 955 5724
    Email: Eric.Edwards@am.sony.com

    Satoshi Futemma/Nobuyoshi Tomita/Eisaburo Itakura
    Sony Corporation
    6-7-35 Kitashinagawa Shinagawa-ku
    Tokyo 141-0001 JAPAN
    Phone: +81 3 5448 3096
    Fax: +81 3 5448 4622
    Email: {satosi-f|n-tomita|itakura}@sm.sony.co.jp


15. Full Copyright Statement

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

    This document and translations of it may be copied and furnished
    to others, and derivative works that comment on or otherwise
    explain it or assist in its implementation may be prepared, copied,
    published and distributed, in whole or in part, without
    restriction of any kind, provided that the above copyright notice
    and this paragraph are included on all such copies and derivative
    works.  However, this document itself may not be modified in any
    way, such as by removing the copyright notice or references to the
    Internet Society or other Internet organizations, except as needed
    for the purpose of developing Internet standards in which case the
    procedures for copyrights defined in the Internet Standards
    process must be followed, or as required to translate it into
    languages other than English.

    The limited permissions granted above are perpetual and will not
    be revoked by the Internet Society or its successors or assigns.

    This document and the information contained herein is provided on
    an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
    ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
    THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED

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    WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.






















































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