qcp.txt

详细说明了高通QCP音频的文件格式

Internet Draft: The Audio/QCP Media Type and File Format    H. Garudadri
Document: draft-garudadri-qcp-00.txt                          R. Gellens
Expires: August 2003                                            Qualcomm
                                                        23 February 2003
    
    
                The Audio/QCP Media Type and File Format
    
    
Status of this Memo
    
    This document is an Internet-Draft and is in full conformance with
    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 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>.
    
    
Copyright Notice
    
    Copyright (C) The Internet Society (2003).  All Rights Reserved.
    
    
Abstract
    
    RFC 2658 specifies the streaming format for QCELP 13K vocoder, but
    did not specify the storage format for QCELP 13K vocoder.  Many
    implementations have been using the qcp file format for exchanging
    QCELP 13K data and EVRC data. (For example, Eudora, QuickTime and
    CDMA 2000 handsets).  This document specifies the qcp fileformat and
    registers the audio/qcp MIME media type.  This format has parameters
    to support QCELP 13K and EVRC data.  Note that this is different
    from the EVRC storage format specified in
    draft-ietf-avt-evrc-smv-03.txt (for EVRC and SMV vocoders).





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    1.  Conventions Used in this Document . . . . . . . . . . . . . .  2
    2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . .   2
    3.  QCP FILE FORMAT . . . . . . . . . . . . . . . . . . . . . . .  2
      3.1.  RIFF subchunks . . . . . . . . . . . . . . . . . . . . .   2
      3.2.  General view of qcp subchunks . . . . . . . . . . . . . .  3
      3.3.  Detailed view of qcp subchunks . . . . . . . . . . . . .   4
      3.4.  Optional Chunks . . . . . . . . . . . . . . . . . . . . .  6
    4.  READING A QCP FILE . . . . . . . . . . . . . . . . . . . . .   7
    5.  WRITING A QCP FILE  . . . . . . . . . . . . . . . . . . . . .  8
    6.  Registration of Media Type Audio/qcp . . . . . . . . . . . .   8
    7.  Security Considerations . . . . . . . . . . . . . . . . . . .  9
    8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . .   9
    9.  Normative References  . . . . . . . . . . . . . . . . . . . . 10
     10.  Authors Address  . . . . . . . . . . . . . . . . . . . . .  10
      Intellectual Property Statement . . . . . . . . . . . . . . . . 10
      Full Copyright Statement . . . . . . . . . . . . . . . . . . .  11
    
1.  Conventions Used in this Document
    
    The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD
    NOT", and "MAY" in this document are to be interpreted as described
    in "Key words for use in RFCs to Indicate Requirement Levels"
    [KEYWORDS].
    
2.  Introduction
    
    This document specifies a format for storage of [QCELP] 13K and
    [EVRC] vocoder packets in files which may residing on network
    elements (e.g., media servers, Mulimedia Messaging System (MMS)
    centers, etc.) and third-generation (3G) handsets or be transmitted
    via email or other mechanisms.  The vocoder packets read from a file
    may be streamed using [QCELP] or delivered to an [EVRC] or [QCELP]
    13K decoder.
    
3.  QCP FILE FORMAT
    
    The QCP file format uses the RIFF (Resource Interchange File Format)
    specification.  It contains:
    o   RIFF chunk with the identifying code QLCM
        o   Chunks within the RIFF chunk:
                o    Three required chunks fmt, vrat, and data
                o    Four optional chunks labl, offs, cnfg, and text
    
    The RIFF (Resource Interchange File Format) specification is
    published in [TBD].
    





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3.1.  RIFF subchunks
    
    In this section, various RIFF subchunks are described.
    
    fmt:  This subchunk is of type "Format".  It defines which speech
    codec is being used.  Both QCELP 13K and EVRC are supported.  This
    is a required chunk.
    
    vrat:  This subchunk is of type "variable-rate".  It is used to
    determine whether the data chunk is comprised of variable-rate or
    fixed-rate packets, and to determine the size of the data chunk in
    numbers of packets.  This information can be used to determine the
    length of the data chunk in seconds without reading the whole file
    in the case of variable-rate packets.  This is a required chunk.
    
    data:  This subchunk contains the packetized speech data, generatd
    by the speech codec.  This is a required chunk.  Note:  The size of
    the data chunk MUST be word (16-bits) aligned.  If the data chunk
    happens to be of an odd size, then a zero pad byte MUST be added at
    the end to make it word aligned.
    
    labl:  This subchunk is of type "Label".  It is used for generic
    storage for applications use.  This is an optional chunk.
    
    Offs:  This subchunk contains byte offsets into data chunk in (t *
    100 ms) increments.  This is useful for fast-forward and rewind
    features for files containing variable rate packets.  This is an
    optional chunk.
    
    cnfg:  This is of type "File configuration".  It contains
    configuration information about the file that an application may
    need to know.  This is an optional chunk.
    
    text:  This subchunk is used to for any generic storage for
    applications use.  This is an optional chunk.
    
    All data is in little-endian format, and all structs are padding
    neutral, that is, they have no padding.  The chunks are word (16
    bits) aligned.
    
3.2.  General view of qcp subchunks
    

    <QLCM-form>
    RIFF( 'QLCM'
        <format chunk 'fmt'>                       // required
        [<variable rate chunk - 'vrat'>]           // required
        [<label chunk 'labl'>]                     // optional
        [<offsets in increments chunk - 'offs'>]   // optional


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        <codec packet data chunk - 'data'>         // required
        [<configuration chunk - 'cnfg'>]           // optional
        [<text chunk - 'text'>]                    //  optional
    )

    
3.3.  Detailed view of qcp subchunks
    
    RIFF 'QLCM' {
        BYTE[4] id    = {'R', 'I', 'F', 'F'}
        UINT32 size   = size of RIFF chunk excluding id and size
        BYTE[4]       = {'Q', 'L', 'C', 'M'}
    
        <format chunk - 'fmt '>  {
            BYTE[4] id     = {'f', 'm', 't', ' '}
            UINT32 size    = size of 'fmt ' subchunk excluding id and
                             size
            BYTE mjv       = major version of this format (see note 1)
            BYTE mnv       = minor version of this format (see note 1)
            struct type_qpl_info {
                struct GUID {
                    UINT32    Data1;
                    UINT16    Data2;
                    UINT16    Data3;
                    BYTE      Data4[ 8 ];
                } = Id;                          // unique ID of this
                                                 //    codec
                UINT16    Version;               // version # of the
                                                 //    codec
                BYTE      Name[80];              // proper name of the
                                                 //    codec
                UINT16    avgBitsPerSec;         // avg bps of the
                                                 //    codec
                UINT16    bytesPerPacket;        // size of a packet in
                                                 //    bytes (max rate)
                                                 // including header
                                                 //    byte for that
                                                 //    packet
                UINT16    samplesPerBlock;       // size of a block in
                                                 //    samples
                                                 // encoder encodes one
                                                 //    block into one
                                                 //    packet
                                                 // decoder decodes one
                                                 //    packet into one
                                                 //    block
                UINT16    samplesPerSec;         // sps of input needed
                                                 //    for the encoder
                                                 // and output from the


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                                                 //    decoder
                UINT16    bitsPerSample;         // bits per sample of
                                                 //    the above
    
                // contains rate header format info
                struct type_qpl_variable_rate {
                    UINT32    numOfRates;         // # of rates
                    // high byte = rate, low byte = size of following
                    // packet
                    UINT16    bytesPerPacket[8]; 
                } = variableRate;
    
                UINT32    reserved[5];            // reserved
            } = codec info
        }
    
        <variable rate chunk - 'vrat'> {
            BYTE[4]   id         = {'v', 'r', 'a', 't'}
            UINT32    size       = size of 'vrat' subchunk excluding
                                   id and size
            UINT32    variableRate;
                // if ( == 0 ) packet data is fixed rate 
                // else if ( < 0xFFFF0000 ) variable rate
            UINT32    sizeInPackets;
                // the data chunk size in packets
        }
    
        [<label chunk - 'labl'>]
                // see Optional chunks
    
        [<offsets in increments chunk - 'offs'>]
                // see Optional chunks
    
        <codec packet data chunk - 'data'> {
            BYTE[4] id    = {'d', 'a', 't', 'a'}
            UINT32 size   = size of 'data' subchunk excluding id and
                            size
            BYTE[ ]       = actual packet data (see note 2)
        }
    
        [<configuration chunk - 'cnfg'>] // see Optional chunks
    
        [<text chunk - 'text'>]          // see Optional chunks
    }







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    Note 1:  The current format version is (major = 1, minor = 0)
    
    Note 2: 
    If ( variableRate of 'vrat' == 0 OR 'vrat' doesn't exist ) then
        BYTE[bytesPerPacket] = packet1
        BYTE[bytesPerPacket] = packet2
                *
                *
                *
    else if ( variableRate of 'vrat' < 0xFFFF0000 ) then
        packet1 {
            BYTE = rate
            BYTE[ LOBYTE(variableRate.bytesPerPacket[n]) ] where
                n = index to bytesPerPacket
            array that contains the rate in the high byte of
                bytesPerPacket.
        }
        packet2 {
            BYTE  = rate
            BYTE[ LOBYTE(variableRate.bytesPerPacket[n]) ] where
                n = index to bytesPerPacket
            array that contains the rate in the high byte of
                bytesPerPacket.
        }
                *
                *
                *
    
    Note 3:  The fmt chunk MUST appear before the data chunk.
    
    
3.4.  Optional Chunks
    
    Positioning of the optional chunks is as follows:
    
    o    The position of the labl chunk MUST follow the vrat chunk.
    
    o    The offs chunk MAY be positioned anywhere after the lablvrat
    chunk.
    
    o    The cnfg and text chunks MAY appear anywhere.
    
    o    The optional chunks cannot be subchunks of other chunks.
    
    <label chunk - 'labl'> {
        BYTE[4]  id        = {'l', 'a', 'b', 'l'}
        UINT32   size      = size of 'labl' subchunk excluding id and
                             size
        BYTE[48]           = generic storage for applications' use;


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