Description

This use case demonstrates the use of dynamic objects. It contains two moving objects that appear at different times, and share the same track. It also contains a channel-based stereo bed.

Approach

The two dynamic objects are both of the Objects typeDefinition. Each object contains three audioBlockFormats, with the first one of zero duration to initialise the position at the start of the channel. The audioObjects that reference each of these two objects have different start times, and do not overlap in time. Therefore the two audioTrackUIDs (ATU_00000001 and ATU_00000002) can share the same track in the BW64 file, as shown in the diagram:

This can be defined in the 'chna' chunk as shown:

TrackNum	audioTrackUID	audioTrackFormatID	audioPackFormatID
1	ATU_00000001	AT_00031001_01	AP_00031001
1	ATU_00000002	AT_00031002_01	AP_00031002
2	ATU_00000003	AT_00010001_01	AP_00010002
3	ATU_00000004	AT_00010002_01	AP_00010002

As well as the two dynamic objects, there is a stereo channel-based audioObject, which uses audioTrackUIDs ATU_00000003 and ATU_00000004. As this object uses a common definition format (AP_00010002), then the metadata for those elements do not have to be included in this file. Unlike the two dynamic objects, the channel-based object is not time restricted, so lasts the duration of the programme.

Example XML

<?xml version="1.0" encoding="utf-8"?>
<ebuCoreMain xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns="urn:ebu:metadata-schema:ebuCore_2014" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" schema="EBU_CORE_20140201.xsd" xml:lang="en">
  <coreMetadata>
    <format>
      <audioFormatExtended version="ITU-R_BS.2076-1">
        <audioProgramme audioProgrammeID="APR_1001" audioProgrammeName="Dynamic Mixed">
          <audioContentIDRef>ACO_1001</audioContentIDRef>
          <audioContentIDRef>ACO_1002</audioContentIDRef>
          <audioContentIDRef>ACO_1003</audioContentIDRef>
        </audioProgramme>

        <audioContent audioContentID="ACO_1001" audioContentName="Object 1">
          <audioObjectIDRef>AO_1001</audioObjectIDRef>
        </audioContent>
        <audioContent audioContentID="ACO_1002" audioContentName="Object 2">
          <audioObjectIDRef>AO_1002</audioObjectIDRef>
        </audioContent>
        <audioContent audioContentID="ACO_1003" audioContentName="Background">
          <audioObjectIDRef>AO_1003</audioObjectIDRef>
        </audioContent>

        <audioObject audioObjectID="AO_1001" audioObjectName="Object 1" start="00:00:05.00000" duration="00:00:55.00000">
          <audioPackFormatIDRef>AP_00031001</audioPackFormatIDRef>
          <audioTrackUIDRef>ATU_00000001</audioTrackUIDRef>
        </audioObject>
        <audioObject audioObjectID="AO_1002" audioObjectName="Object 2" start="00:01:05.00000" duration="00:00:25.00000">
          <audioPackFormatIDRef>AP_00031002</audioPackFormatIDRef>
          <audioTrackUIDRef>ATU_00000002</audioTrackUIDRef>
        </audioObject>
        <audioObject audioObjectID="AO_1003" audioObjectName="Background">
          <audioPackFormatIDRef>AP_00010002</audioPackFormatIDRef>
          <audioTrackUIDRef>ATU_00000003</audioTrackUIDRef>
          <audioTrackUIDRef>ATU_00000004</audioTrackUIDRef>
        </audioObject>

        <audioPackFormat audioPackFormatID="AP_00031001" audioPackFormatName="Object 1" typeLabel="0003" typeDefinition="Objects">
          <audioChannelFormatIDRef>AC_00031001</audioChannelFormatIDRef>
        </audioPackFormat>
        <audioPackFormat audioPackFormatID="AP_00031002" audioPackFormatName="Object 2" typeLabel="0003" typeDefinition="Objects">
          <audioChannelFormatIDRef>AC_00031002</audioChannelFormatIDRef>
        </audioPackFormat>

        <audioChannelFormat audioChannelFormatID="AC_00031001" audioChannelFormatName="Object 1" typeLabel="0003" typeDefinition="Objects">
          <audioBlockFormat audioBlockFormatID="AB_00031001_00000001" rtime="00:00:00.00000" duration="00:00:00.00000">
            <position coordinate="azimuth">80.000000</position>
            <position coordinate="elevation">10.000000</position>
          </audioBlockFormat>
          <audioBlockFormat audioBlockFormatID="AB_00031001_00000002" rtime="00:00:00.00000" duration="00:00:35.00000">
            <position coordinate="azimuth">60.000000</position>
            <position coordinate="elevation">15.000000</position>
          </audioBlockFormat>
          <audioBlockFormat audioBlockFormatID="AB_00031001_00000003" rtime="00:00:35.00000" duration="00:00:20.00000">
            <position coordinate="azimuth">50.000000</position>
            <position coordinate="elevation">30.000000</position>
          </audioBlockFormat>
        </audioChannelFormat>
        <audioChannelFormat audioChannelFormatID="AC_00031002" audioChannelFormatName="Object 2" typeLabel="0003" typeDefinition="Objects">
          <audioBlockFormat audioBlockFormatID="AB_00031002_00000001" rtime="00:00:00.00000" duration="00:00:00.00000">
            <position coordinate="azimuth">-110.000000</position>
            <position coordinate="elevation">-20.000000</position>
          </audioBlockFormat>
          <audioBlockFormat audioBlockFormatID="AB_00031002_00000002" rtime="00:00:00.00000" duration="00:00:15.00000">
            <position coordinate="azimuth">-80.000000</position>
            <position coordinate="elevation">0.000000</position>
          </audioBlockFormat>
          <audioBlockFormat audioBlockFormatID="AB_00031002_00000003" rtime="00:00:15.00000" duration="00:00:10.00000">
            <position coordinate="azimuth">-20.000000</position>
            <position coordinate="elevation">10.000000</position>
          </audioBlockFormat>
        </audioChannelFormat>

        <audioStreamFormat audioStreamFormatID="AS_00031001" audioStreamFormatName="Object 1" formatLabel="0001" formatDefinition="PCM">
          <audioChannelFormatIDRef>AC_00031001</audioChannelFormatIDRef>
          <audioTrackFormatIDRef>AT_00031001_01</audioTrackFormatIDRef>
        </audioStreamFormat>
        <audioStreamFormat audioStreamFormatID="AS_00031002" audioStreamFormatName="Object 2" formatLabel="0001" formatDefinition="PCM">
          <audioChannelFormatIDRef>AC_00031002</audioChannelFormatIDRef>
          <audioTrackFormatIDRef>AT_00031002_01</audioTrackFormatIDRef>
        </audioStreamFormat>

        <audioTrackFormat audioTrackFormatID="AT_00031001_01" audioTrackFormatName="Object 1" formatLabel="0001" formatDefinition="PCM">
          <audioStreamFormatIDRef>AS_00031001</audioStreamFormatIDRef>
        </audioTrackFormat>
        <audioTrackFormat audioTrackFormatID="AT_00031002_01" audioTrackFormatName="Object 2" formatLabel="0001" formatDefinition="PCM">
          <audioStreamFormatIDRef>AS_00031002</audioStreamFormatIDRef>
        </audioTrackFormat>

        <audioTrackUID UID="ATU_00000001">
          <audioTrackFormatIDRef>AT_00031001_01</audioTrackFormatIDRef>
          <audioPackFormatIDRef>AP_00031001</audioPackFormatIDRef>
        </audioTrackUID>
        <audioTrackUID UID="ATU_00000002">
          <audioTrackFormatIDRef>AT_00031002_01</audioTrackFormatIDRef>
          <audioPackFormatIDRef>AP_00031002</audioPackFormatIDRef>
        </audioTrackUID>
        <audioTrackUID UID="ATU_00000003">
          <audioTrackFormatIDRef>AT_00010001_01</audioTrackFormatIDRef>
          <audioPackFormatIDRef>AP_00010002</audioPackFormatIDRef>
        </audioTrackUID>
        <audioTrackUID UID="ATU_00000004">
          <audioTrackFormatIDRef>AT_00010002_01</audioTrackFormatIDRef>
          <audioPackFormatIDRef>AP_00010002</audioPackFormatIDRef>
        </audioTrackUID>
      </audioFormatExtended>
    </format>
  </coreMetadata>
</ebuCoreMain>