libcmml: Multitrack annotations in CMML

# Multitrack annotations in CMML

The default case for CMML is to have one annotation track with temporally non-overlapping clips of annotations. This is the case when the "track" attribute of the clip tag is not used.

It is however possible to specify several tracks of annotations within one CMML file. To that end, you need to give each track that you're using a name. This name needs to be written into the "track" attribute of the clip tags which belong onto that track. Not providing a track attribute attaches the clip to the default track.

Take care that the clips in one annotation track do not overlap in time.

This is an example of such a multi-track annotation specification:

    <clip track="german" lang="de" id="intro_ge" start="npt:0">
      <a href="http://www.blah.au/fish.html">Lesen Sie mehr &#252;ber Fische.</a>
      <desc>Dies ist die Einleitung zum Film &#252;ber Fische von Joe.</desc>
    </clip>

    <clip track="default" lang="en" id="intro" start="npt:0">
      <a href="http://www.blah.au/fish.html">Read more about fish.</a>
      <desc>This is the introduction to the film Joe made about fish.</desc>
    </clip>

    <clip track="german" id="dolphin_ge" start="npt:3.5">
      <desc>Joe hat einen Delphin im Meer entdeckt.</desc>
      <meta name="Thema" content="Delphin"/>
    </clip>

    <clip id="dolphin" start="npt:3.5">
      <desc>Here, Joe caught sight of a dolphin in the ocean.</desc>
      <meta name="Subject" content="dolphin"/>
    </clip>