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        <b><u>Encapsulation of Opus in ISO Base Media File Format</u></b><br>
        <font size="2">last updated: August 28, 2018</font><br>
        <br>
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                                Encapsulation of Opus in ISO Base Media File Format
                                        Version 0.8.1 (incomplete)


Table of Contents
<a href="#1">1</a> Scope
<a href="#2">2</a> Normative References
<a href="#3">3</a> Terms and Definitions
<a href="#4">4</a> Design Rules of Encapsulation
    <a href="#4.1">4.1</a> File Type Identification
    <a href="#4.2">4.2</a> Overview of Track Structure
    <a href="#4.3">4.3</a> Definitions of Opus sample
        <a href="#4.3.1">4.3.1</a> Sample entry format
        <a href="#4.3.2">4.3.2</a> Opus Specific Box
        <a href="#4.3.3">4.3.3</a> Sample format
        <a href="#4.3.4">4.3.4</a> Duration of Opus sample
        <a href="#4.3.5">4.3.5</a> Sub-sample
        <a href="#4.3.6">4.3.6</a> Random Access
            <a href="#4.3.6.1">4.3.6.1</a> Random Access Point
            <a href="#4.3.6.2">4.3.6.2</a> Pre-roll
    <a href="#4.4">4.4</a> Trimming of Actual Duration
    <a href="#4.5">4.5</a> Channel Mapping
        <a href="#4.5.1">4.5.1</a> ISO Base Media native Channel Mapping
        <a href="#4.5.2">4.5.2</a> Composition on all active tracks (informative)
    <a href="#4.6">4.6</a> Basic Structure (informative)
        <a href="#4.6.1">4.6.2</a> Initial Movie
        <a href="#4.6.2">4.6.3</a> Movie Fragments
    <a href="#4.7">4.7</a> Example of Encapsulation (informative)
<a href="#5">5</a> Author's Address

<a name="1"></a>
1 Scope
    This specification specifies the fundamental way of the encapsulation of Opus coded bitstreams in ISO Base Media
    file format and its derivatives. The encapsulation of Opus coded bitstreams in QuickTime file format is outside
    the scope of this specification.

<a name="2"></a>
2 Normative References
    [1] ISO/IEC 14496-12:2015 Corrected version
        Information technology — Coding of audio-visual objects — Part 12: ISO base media file format

    [2] RFC 6716
        Definition of the Opus Audio Codec

    [3] RFC 7845
        Ogg Encapsulation for the Opus Audio Codec

<a name="3"></a>
3 Terms and Definitions
    3.1 active track
        enabled track from the non-alternate group or selected track from alternate group

    3.2 actual duration
        duration constructed from valid samples

    3.3 edit
        entry in the Edit List Box

    3.4 padded samples
        PCM samples after decoding Opus sample(s) which are not valid samples
        An Opus bitstream always contains them partially at the beginning and may contain them in part at the end, as
        long as not physically removed yet at the beginning and/or the end.

    3.5 priming samples
        padded samples at the beginning of the Opus bitstream

    3.6 sample-accurate
        for any PCM sample, a timestamp exactly matching its sampling timestamp is present in the media timeline.

    3.7 valid samples
        PCM samples after decoding Opus sample(s) corresponding to input PCM samples

<a name="4"></a>
4 Design Rules of Encapsulation
    4.1 File Type Identification<a name="4.1"></a>
        This specification defines the brand 'Opus' to declare files are conformant to this specification. Additionally,
        files conformant to this specification shall contain at least one brand, which supports the requirements and the
        requirements described in this clause without contradiction, in the compatible brands list of the File Type Box.
        As an example, the minimal support of the encapsulation of Opus bitstreams in ISO Base Media file format requires
        the 'iso2' brand in the compatible brands list since support of roll groups is required.
<a name="4.2"></a>
    4.2 Overview of Track Structure
        This clause summarizes requirements of the encapsulation of Opus coded bitstream as media data in audio tracks
        in file formats compliant with the ISO Base Media File Format. The details are described in clauses after this
        clause.
            + The handler_type field in the Handler Reference Box shall be set to 'soun'.
            + The Media Information Box shall contain the Sound Media Header Box.
            + The codingname of the sample entry is 'Opus'.
                This specification does not define any encapsulation using MP4AudioSampleEntry with objectTypeIndication
                specified by the MPEG-4 Registration Authority (http://www.mp4ra.org/).
                See 4.3.1 Sample entry format to get the details about the sample entry.
            + The 'dOps' box is added to the sample entry to convey initializing information for the decoder.
                See 4.3.2 Opus Specific Box to get the details.
            + An Opus sample is exactly one Opus packet for each of different Opus bitstreams.
                See 4.3.3 Sample format to get the details.
            + Every Opus sample is a sync sample but requires pre-roll for every random access to get correct output.
                See 4.3.6 Random Access to get the details.
<a name="4.3"></a>
    4.3 Definitions of Opus sample
        4.3.1 Sample entry format<a name="4.3.1"></a>
            For any track containing Opus bitstreams, at least one sample entry describing corresponding Opus bitstream
            shall be present inside the Sample Table Box. This version of the specification defines only one sample
            entry format named OpusSampleEntry whose codingname is 'Opus'. This sample entry includes exactly one Opus
            Specific Box defined in 4.3.2 as a mandatory box and indicates that Opus samples described by this sample
            entry are stored by the sample format described in 4.3.3.

            The syntax and semantics of the OpusSampleEntry is shown as follows.

            class OpusSampleEntry() extends AudioSampleEntry ('Opus') {
                OpusSpecificBox();
            }

            + channelcount:
                The channelcount field indicates the number of output channels and shall be set to the same value of
                the OutputChannelCount in the OpusDecoderConfigurationRecord. The value of this field may be used in
                the ChannelLayout if any as described in 4.5.1.
            + samplesize:
                The samplesize field shall be set to 16.
            + samplerate:
                The samplerate field shall be set to 48000&lt&lt16.
            + OpusSpecificBox
                This box contains initializing information for the decoder as defined in 4.3.2.

        4.3.2 Opus Specific Box<a name="4.3.2"></a>
            Exactly one Opus Specific Box shall be present in each OpusSampleEntry.
            The Opus Specific Box contains an OpusDecoderConfigurationRecord which contains the Version field and
            this specification defines version 0 of this record. If incompatible changes occured in the fields after
            the Version field within the OpusDecoderConfigurationRecord in the future versions of this specification,
            another version will be defined.
            This box refers to Ogg Opus [3] at many parts but all the data are stored as big-endian format.

            The syntax and semantics of the Opus Specific Box is shown as follows.

            class ChannelMappingTable (unsigned int(8) OutputChannelCount) {
                unsigned int(8) StreamCount;
                unsigned int(8) CoupledCount;
                unsigned int(8 * OutputChannelCount) ChannelMapping;
            }

            aligned(8) class OpusDecoderConfigurationRecord {
                unsigned int(8) Version;
                unsigned int(8) OutputChannelCount;
                unsigned int(16) PreSkip;
                unsigned int(32) InputSampleRate;
                signed int(16) OutputGain;
                unsigned int(8) ChannelMappingFamily;
                if (ChannelMappingFamily != 0) {
                    ChannelMappingTable(OutputChannelCount);
                }
            }

            class OpusSpecificBox extends Box('dOps') {
                OpusDecoderConfigurationRecord() OpusConfig;
            }

            + Version:
                The Version field shall be set to 0.
                In the future versions of this specification, this field may be set to other values. And without support
                of those values, the reader shall not read the fields after this within the OpusSpecificBox.
            + OutputChannelCount:
                The OutputChannelCount field shall be set to the same value as the *Output Channel Count* field in the
                identification header defined in Ogg Opus [3].
            + PreSkip:
                The PreSkip field indicates the number of the priming samples, that is, the number of samples at 48000 Hz
                to discard from the decoder output when starting playback. The value of the PreSkip field shall be at least
                80 milliseconds' worth of PCM samples even when removing any number of Opus samples which may or may not
                contain the priming samples. The PreSkip field is not used for discarding the priming samples at the whole
                playback at all since it is informative only, and that task falls on the Edit List Box.
            + InputSampleRate:
                The InputSampleRate field shall be set to the same value as the *Input Sample Rate* field in the
                identification header defined in Ogg Opus [3].
            + OutputGain:
                The OutputGain field shall be set to the same value as the *Output Gain* field in the identification
                header define in Ogg Opus [3]. Note that the value is stored as 8.8 fixed-point.
            + ChannelMappingFamily:
                The ChannelMappingFamily field shall be set to the same value as the *Channel Mapping Family* field in
                the identification header defined in Ogg Opus [3]. Note that the value 255 may be used for an alternative
                to map channels by ISO Base Media native mapping. The details are described in 4.5.1.
            + StreamCount:
                The StreamCount field shall be set to the same value as the *Stream Count* field in the identification
                header defined in Ogg Opus [3].
            + CoupledCount:
                The CoupledCount field shall be set to the same value as the *Coupled Count* field in the identification
                header defined in Ogg Opus [3].
            + ChannelMapping:
                The ChannelMapping field shall be set to the same octet string as *Channel Mapping* field in the identi-
                fication header defined in Ogg Opus [3].

        4.3.3 Sample format<a name="4.3.3"></a>
            An Opus sample is exactly one Opus packet for each of different Opus bitstreams. Due to support more than
            two channels, an Opus sample can contain frames from multiple Opus bitstreams but all Opus packets shall
            share with the total of frame sizes in a single Opus sample. The way of how to pack an Opus packet from
            each of Opus bitstreams into a single Opus sample follows Appendix B. in RFC 6716 [2].
            The endianness has nothing to do with any Opus sample since every Opus packet is processed byte-by-byte.
            In this specification, 'sample' means 'Opus sample' except for 'padded samples', 'priming samples', 'valid
            sample' and 'sample-accurate', i.e. 'sample' is 'sample' in the term defined in ISO/IEC 14496-12 [1].

                +-----------------------------------------+-------------------------------------+
                | Opus packet 0 (self-delimiting framing) | Opus packet 1 (undelimited framing) |
                +-----------------------------------------+-------------------------------------+
                |<---------------------------- the size of Opus sample ------------------------>|

                    Figure 1 - Example structure of an Opus sample containing two Opus bitstreams

        4.3.4 Duration of Opus sample<a name="4.3.4"></a>
            The duration of Opus sample is given by multiplying the total of frame sizes for a single Opus bitstream
            expressed in seconds by the value of the timescale field in the Media Header Box.
            Let's say an Opus sample consists of two Opus bitstreams, where the frame size of one bitstream is 40 milli-
            seconds and the frame size of another is 60 milliseconds, and the timescale field in the Media Header Box
            is set to 48000, then the duration of that Opus sample shall be 120 milliseconds since three 40 millisecond
            frame and two 60 millisecond frames shall be contained because of the maximum duration of Opus packet, 120
            milliseconds, and 5760 in the timescale indicated in the Media Header Box.

            To indicate the valid samples excluding the padded samples at the end of Opus bitstream, the duration of
            the last Opus sample of an Opus bitstream is given by multiplying the number of the valid samples by the
            value produced by dividing the value of the timescale field in the Media Header Box by 48000.

        4.3.5 Sub-sample<a name="4.3.5"></a>
            The structure of the last Opus packet in an Opus sample is different from the others in the same Opus sample,
            and the others are invalid Opus packets as an Opus sample because of self-delimiting framing. To avoid
            complexities, sub-sample is not defined for Opus sample in this specification.

        4.3.6 Random Access<a name="4.3.6"></a>
            This subclause describes the nature of the random access of Opus sample.

            4.3.6.1 Random Access Point<a name="4.3.6.1"></a>
                All Opus samples can be independently decoded i.e. every Opus sample is a sync sample. Therefore, the
                Sync Sample Box shall not be present as long as there are no samples other than Opus samples in the same
                track. And the sample_is_non_sync_sample field for Opus samples shall be set to 0.

            4.3.6.2 Pre-roll<a name="4.3.6.2"></a>
                Opus bitstream requires at least 80 millisecond pre-roll after each random access to get correct output.
                Pre-roll is indicated by the roll_distance field in AudioRollRecoveryEntry. AudioPreRollEntry shall not
                be used since every Opus sample is a sync sample in Opus bitstream. Note that roll_distance is expressed
                in sample units in a term of ISO Base Media File Format, and always takes negative values.

                For any track containing Opus bitstreams, at least one Sample Group Description Box and at least one
                Sample to Group Box within the Sample Table Box shall be present and these have the grouping_type field
                set to 'roll'. If any Opus sample is contained in a track fragment, the Sample to Group Box with the
                grouping_type field set to 'roll' shall be present for that track fragment.

                For the requirement of AudioRollRecoveryEntry, the compatible_brands field in the File Type Box shall
                contain at least one brand which requires support for roll groups.
<a name="4.4"></a>
    4.4 Trimming of Actual Duration
        Due to the priming samples (or the padding at the beginning) derived from the pre-roll for the startup and the
        padded samples at the end, we need trim from media to get the actual duration. An edit in the Edit List Box can
        achieve this demand, and the Edit Box and the Edit List Box shall be present.

        For sample-accurate trimming, proper timescale should be set to the timescale field in the Movie Header Box
        and the Media Header Box inside Track Box(es) for Opus bitstream. The timescale field in the Media Header Box is
        typically set to 48000. It is recommended that the timescale field in the Movie Header Box be set to the same
        value of the timescale field in the Media Header Box in order to avoid the rounding problem when specifying
        duration of edit if the timescales in all of the Media Header Boxes are set to the same value.

        For example, to indicate the actual duration of an Opus bitstream in a track with the timescale fields of both
        the Movie Header Box and the Media Header Box set to 48000, we would use the following edit:
            segment_duration = the number of the valid samples
            media_time = the number of the priming samples
            media_rate = 1 &lt&lt 16

        The Edit List Box is applied to whole movie including all movie fragments. Therefore, it is impossible to tell
        the actual duration in the case producing movie fragments on the fly such as live-streaming. In such cases,
        the duration of the last Opus sample may be helpful by setting zero to the segment_duration field since the
        value 0 represents implicit duration equal to the sum of the duration of all samples.
<a name="4.5"></a>
    4.5 Channel Mapping
        4.5.1 ISO Base Media native Channel Mapping<a name="4.5.1"></a>
            ISO Base Media File Format, that is ISO/IEC 14496-12 [1], defines an extension ChannelLayout to the
            AudioSampleEntry, which conveys information of mapping channels to loudspeaker positions. The ChannelLayout
            enables to specify the channel layout more flexibly than the predefined layouts of the ChannelMappingFamily.

            To utilize the ChannelLayout for OpusSampleEntry, the ChannelMappingFamily field should be set to 255.
            Even when the ChannelMappingFamily field is set to another value, the assignment of each output channel to
            loudspeaker position specified by the ChannelMappingFamily would be changed as specified by the ChannelLayout.
            The procedure of the assignment is the following.

                1. Decoded channels are mapped to output channels according to the ChannelMappingTable.
                2. Output channels are mapped to loudspeaker positions according to the ChannelLayout.

            In this way, the parameters of the Opus Specific Box are processed before the ChannelLayout, and the
            ChannelLayout shall follow the Opus Specific Box.

        4.5.2 Composition on all active tracks (informative)<a name="4.5.2"></a>
            By the application of alternate_group in the Track Header Box, whole audio channels in all active tracks from
            non-alternate group and/or different alternate group from each other are composited into the presentation. If
            an Opus sample consists of multiple Opus bitstreams, it can be splitted into individual Opus bitstreams and
            reconstructed into new Opus samples as long as every Opus bitstream has the same total duration in each Opus
            sample. This nature can be utilized to encapsulate a single Opus bitstream in each track without breaking the
            original channel layout.

            As an example, let's say there is a following track:
                OutputChannelCount = 6;
                StreamCount        = 4;
                CoupledCount       = 2;
                ChannelMapping     = {0, 4, 1, 2, 3, 5}; // front left, front center, front right,
                                                         // rear left, rear right, LFE
            Here, to couple front left to front right channels into the first stream, and couple rear left to rear right
            channels into the second stream, reordering is needed since coupled streams must precede any non-coupled
            stream. You extract the four Opus bitstreams from this track and you encapsulate two of the four into a track
            and the others into another track. The former track is as follows.
                OutputChannelCount = 6;
                StreamCount        = 2;
                CoupledCount       = 2;
                ChannelMapping     = {0, 255, 1, 2, 3, 255}; // front left, front center, front right,
                                                             // rear left, rear right, LFE
            And the latter track is as follows.
                OutputChannelCount = 6;
                StreamCount        = 2;
                CoupledCount       = 0;
                ChannelMapping     = {255, 0, 255, 255, 255, 1}; // front left, front center, front right,
                                                                 // rear left, rear right, LFE
            In addition, the value of the alternate_group field in the both tracks is set to 0. As the result, the player
            may play as if channels with 255 are not present, and play the presentation constructed from the both tracks
            in the same channel layout as the one of the original track. Keep in mind that the way of the composition, i.e.
            the mixing for playback, is not defined here, and maybe different results could occur except for the channel
            layout of the original, depending on an implementation or the definition of a derived file format.

            Note that some derived file formats may specify the restriction to ignore alternate grouping. In the context
            of such file formats, this application is not available. This unavailability does not mean incompatibilities
            among file formats unless the restriction to the value of the alternate_group field is specified and brings
            about any conflict among their definitions.
<a name="4.6"></a>
    4.6 Basic Structure (informative)
        4.6.1 Initial Movie<a name="4.6.1"></a>
            This subclause shows a basic structure of the Movie Box as follows:

            +----+----+----+----+----+----+----+----+------------------------------+
            |moov|    |    |    |    |    |    |    | Movie Box                    |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |mvhd|    |    |    |    |    |    | Movie Header Box             |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |trak|    |    |    |    |    |    | Track Box                    |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |tkhd|    |    |    |    |    | Track Header Box             |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |edts|    |    |    |    |    | Edit Box                     |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |elst|    |    |    |    | Edit List Box                |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |mdia|    |    |    |    |    | Media Box                    |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |mdhd|    |    |    |    | Media Header Box             |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |hdlr|    |    |    |    | Handler Reference Box        |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |minf|    |    |    |    | Media Information Box        |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |smhd|    |    |    | Sound Media Header Box       |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |dinf|    |    |    | Data Information Box         |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |    |dref|    |    | Data Reference Box           |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |    |    |url |    | DataEntryUrlBox              |
            +----+----+----+----+----+----+ or +----+------------------------------+
            |    |    |    |    |    |    |urn |    | DataEntryUrnBox              |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |stbl|    |    |    | Sample Table                 |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |    |stsd|    |    | Sample Description Box       |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |    |    |Opus|    | OpusSampleEntry              |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |    |    |    |dOps| Opus Specific Box            |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |    |stts|    |    | Decoding Time to Sample Box  |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |    |stsc|    |    | Sample To Chunk Box          |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |    |stsz|    |    | Sample Size Box              |
            +----+----+----+----+----+ or +----+----+------------------------------+
            |    |    |    |    |    |stz2|    |    | Compact Sample Size Box      |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |    |stco|    |    | Chunk Offset Box             |
            +----+----+----+----+----+ or +----+----+------------------------------+
            |    |    |    |    |    |co64|    |    | Chunk Large Offset Box       |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |    |sgpd|    |    | Sample Group Description Box |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |    |    |    |sbgp|    |    | Sample to Group Box          |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |mvex|*   |    |    |    |    |    | Movie Extends Box            |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |trex|*   |    |    |    |    | Track Extends Box            |
            +----+----+----+----+----+----+----+----+------------------------------+

                    Figure 2 - Basic structure of Movie Box

            It is strongly recommended that the order of boxes should follow the above structure.
            Boxes marked with an asterisk (*) may be present.
            For most boxes listed above, the definition is as is defined in ISO/IEC 14496-12 [1]. The additional boxes
            and the additional requirements, restrictions and recommendations to the other boxes are described in this
            specification.

        4.6.2 Movie Fragments<a name="4.6.2"></a>
            This subclause shows a basic structure of the Movie Fragment Box as follows:

            +----+----+----+----+----+----+----+----+------------------------------+
            |moof|    |    |    |    |    |    |    | Movie Fragment Box           |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |mfhd|    |    |    |    |    |    | Movie Fragment Header Box    |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |traf|    |    |    |    |    |    | Track Fragment Box           |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |tfhd|    |    |    |    |    | Track Fragment Header Box    |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |trun|    |    |    |    |    | Track Fragment Run Box       |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |sgpd|*   |    |    |    |    | Sample Group Description Box |
            +----+----+----+----+----+----+----+----+------------------------------+
            |    |    |sbgp|    |    |    |    |    | Sample to Group Box          |
            +----+----+----+----+----+----+----+----+------------------------------+

                    Figure 3 - Basic structure of Movie Fragment Box

            It is strongly recommended that the Movie Fragment Header Box and the Track Fragment Header Box be
            placed first in their container.
            Boxes marked with an asterisk (*) may be present.
            For the boxes listed above, the definition is as is defined in ISO/IEC 14496-12 [1].
<a name="4.7"></a>
    4.7 Example of Encapsulation (informative)
        [File]
            size = 17757
            [ftyp: File Type Box]
                position = 0
                size = 24
                major_brand = Opus : Opus audio coding
                minor_version = 0
                compatible_brands
                    brand[0] = Opus : Opus audio coding
                    brand[1] = iso2 : ISO Base Media file format version 2
            [moov: Movie Box]
                position = 24
                size = 757
                [mvhd: Movie Header Box]
                    position = 32
                    size = 108
                    version = 0
                    flags = 0x000000
                    creation_time = UTC 2014/12/12, 18:41:19
                    modification_time = UTC 2014/12/12, 18:41:19
                    timescale = 48000
                    duration = 33600 (00:00:00.700)
                    rate = 1.000000
                    volume = 1.000000
                    reserved = 0x0000
                    reserved = 0x00000000
                    reserved = 0x00000000
                    transformation matrix
                        | a, b, u |   | 1.000000, 0.000000, 0.000000 |
                        | c, d, v | = | 0.000000, 1.000000, 0.000000 |
                        | x, y, w |   | 0.000000, 0.000000, 1.000000 |
                    pre_defined = 0x00000000
                    pre_defined = 0x00000000
                    pre_defined = 0x00000000
                    pre_defined = 0x00000000
                    pre_defined = 0x00000000
                    pre_defined = 0x00000000
                    next_track_ID = 2
                [trak: Track Box]
                    position = 140
                    size = 608
                    [tkhd: Track Header Box]
                        position = 148
                        size = 92
                        version = 0
                        flags = 0x000007
                            Track enabled
                            Track in movie
                            Track in preview
                        creation_time = UTC 2014/12/12, 18:41:19
                        modification_time = UTC 2014/12/12, 18:41:19
                        track_ID = 1
                        reserved = 0x00000000
                        duration = 33600 (00:00:00.700)
                        reserved = 0x00000000
                        reserved = 0x00000000
                        layer = 0
                        alternate_group = 0
                        volume = 1.000000
                        reserved = 0x0000
                        transformation matrix
                            | a, b, u |   | 1.000000, 0.000000, 0.000000 |
                            | c, d, v | = | 0.000000, 1.000000, 0.000000 |
                            | x, y, w |   | 0.000000, 0.000000, 1.000000 |
                        width = 0.000000
                        height = 0.000000
                    [edts: Edit Box]
                        position = 240
                        size = 36
                        [elst: Edit List Box]
                            position = 281
                            size = 28
                            version = 0
                            flags = 0x000000
                            entry_count = 1
                            entry[0]
                                segment_duration = 33600
                                media_time = 312
                                media_rate = 1.000000
                    [mdia: Media Box]
                        position = 276
                        size = 472
                        [mdhd: Media Header Box]
                            position = 284
                            size = 32
                            version = 0
                            flags = 0x000000
                            creation_time = UTC 2014/12/12, 18:41:19
                            modification_time = UTC 2014/12/12, 18:41:19
                            timescale = 48000
                            duration = 34560 (00:00:00.720)
                            language = und
                            pre_defined = 0x0000
                        [hdlr: Handler Reference Box]
                            position = 316
                            size = 51
                            version = 0
                            flags = 0x000000
                            pre_defined = 0x00000000
                            handler_type = soun
                            reserved = 0x00000000
                            reserved = 0x00000000
                            reserved = 0x00000000
                            name = Xiph Audio Handler
                        [minf: Media Information Box]
                            position = 367
                            size = 381
                            [smhd: Sound Media Header Box]
                                position = 375
                                size = 16
                                version = 0
                                flags = 0x000000
                                balance = 0.000000
                                reserved = 0x0000
                            [dinf: Data Information Box]
                                position = 391
                                size = 36
                                [dref: Data Reference Box]
                                    position = 399
                                    size = 28
                                    version = 0
                                    flags = 0x000000
                                    entry_count = 1
                                    [url : Data Entry Url Box]
                                        position = 415
                                        size = 12
                                        version = 0
                                        flags = 0x000001
                                        location = in the same file
                            [stbl: Sample Table Box]
                                position = 427
                                size = 321
                                [stsd: Sample Description Box]
                                    position = 435
                                    size = 79
                                    version = 0
                                    flags = 0x000000
                                    entry_count = 1
                                    [Opus: Audio Description]
                                        position = 451
                                        size = 63
                                        reserved = 0x000000000000
                                        data_reference_index = 1
                                        reserved = 0x0000
                                        reserved = 0x0000
                                        reserved = 0x00000000
                                        channelcount = 6
                                        samplesize = 16
                                        pre_defined = 0
                                        reserved = 0
                                        samplerate = 48000.000000
                                        [dOps: Opus Specific Box]
                                            position = 487
                                            size = 27
                                            Version = 0
                                            OutputChannelCount = 6
                                            PreSkip = 312
                                            InputSampleRate = 48000
                                            OutputGain = 0
                                            ChannelMappingFamily = 1
                                            StreamCount = 4
                                            CoupledCount = 2
                                            ChannelMapping
                                                0 -> 0: front left
                                                1 -> 4: fron center
                                                2 -> 1: front right
                                                3 -> 2: side left
                                                4 -> 3: side right
                                                5 -> 5: rear center
                                [stts: Decoding Time to Sample Box]
                                    position = 514
                                    size = 24
                                    version = 0
                                    flags = 0x000000
                                    entry_count = 1
                                    entry[0]
                                        sample_count = 18
                                        sample_delta = 1920
                                [stsc: Sample To Chunk Box]
                                    position = 538
                                    size = 40
                                    version = 0
                                    flags = 0x000000
                                    entry_count = 2
                                    entry[0]
                                        first_chunk = 1
                                        samples_per_chunk = 13
                                        sample_description_index = 1
                                    entry[1]
                                        first_chunk = 2
                                        samples_per_chunk = 5
                                        sample_description_index = 1
                                [stsz: Sample Size Box]
                                    position = 578
                                    size = 92
                                    version = 0
                                    flags = 0x000000
                                    sample_size = 0 (variable)
                                    sample_count = 18
                                    entry_size[0] = 977
                                    entry_size[1] = 938
                                    entry_size[2] = 939
                                    entry_size[3] = 938
                                    entry_size[4] = 934
                                    entry_size[5] = 945
                                    entry_size[6] = 948
                                    entry_size[7] = 956
                                    entry_size[8] = 955
                                    entry_size[9] = 930
                                    entry_size[10] = 933
                                    entry_size[11] = 934
                                    entry_size[12] = 972
                                    entry_size[13] = 977
                                    entry_size[14] = 958
                                    entry_size[15] = 949
                                    entry_size[16] = 962
                                    entry_size[17] = 848
                                [stco: Chunk Offset Box]
                                    position = 670
                                    size = 24
                                    version = 0
                                    flags = 0x000000
                                    entry_count = 2
                                    chunk_offset[0] = 797
                                    chunk_offset[1] = 13096
                                [sgpd: Sample Group Description Box]
                                    position = 694
                                    size = 26
                                    version = 1
                                    flags = 0x000000
                                    grouping_type = roll
                                    default_length = 2 (constant)
                                    entry_count = 1
                                    roll_distance[0] = -2
                                [sbgp: Sample to Group Box]
                                    position = 720
                                    size = 28
                                    version = 0
                                    flags = 0x000000
                                    grouping_type = roll
                                    entry_count = 1
                                    entry[0]
                                        sample_count = 18
                                        group_description_index = 1
            [free: Free Space Box]
                position = 748
                size = 8
            [mdat: Media Data Box]
                position = 756
                size = 17001
<a name="5"></a>
5 Authors' Address
    Yusuke Nakamura
        Email: muken.the.vfrmaniac |at| gmail.com
        </div>
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