]>
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- appears only to affect PDF output. HTML scaling is done in the
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--->
-
<bookinfo>
<title>DCP-o-matic users' manual</title>
<author><firstname>Carl</firstname><surname>Hetherington</surname></author>
</section>
+
<section>
<title>Decrypting encrypted DCPs</title>
</section>
+<section>
+<title>Making a DCP from a DCP</title>
+
+<para>
+In many ways, using DCPs as <emphasis>content</emphasis> in
+DCP-o-matic is the same as using any other content. There are a few
+things to note, though.
+</para>
+
+
+<section>
+<title>Re-use of existing data</title>
+
+<para>
+Where possible DCP-o-matic will re-use existing JPEG2000-compressed
+data from DCP content without modification. This has the advantage
+that creation of the new DCP will be quick, as the time-consuming
+JPEG2000 encoding is not necessary.
+</para>
+
+<para>
+DCP-o-matic can do this if you avoid changes to the following content
+settings:
+</para>
+
+<itemizedlist>
+<listitem>Crop</listitem>
+<listitem>Scaling</listitem>
+<listitem>Subtitle burn-in</listitem>
+<listitem>Fades</listitem>
+<listitem>Colour conversion</listitem>
+</itemizedlist>
+
+<para>
+If you do change any of these settings on a piece of DCP content
+DCP-o-matic will decode and then re-encode the JPEG2000 data.
+</para>
+
+</section>
+
+
+<section>
+<title>Making overlay files</title>
+
+<para>
+With its default settings, DCP-o-matic will take any data from DCP
+content and copy it into the DCP that it creates. See <xref linkend="fig-dcp-copy"/>.
+</para>
+
+<figure id="fig-dcp-copy">
+<title>Creating a new DCP by copying an existing one</title>
+<mediaobject><imageobject><imagedata scale="100" fileref="diagrams/dcp-copy&dia;"/></imageobject></mediaobject>
+</figure>
+
+<para>
+This can be inefficient in some cases. Consider, for example, a film
+which has ten different translations for which the subtitles are
+different but video and audio are the same. If the video and audio
+content takes up, say, 100Gb this means that the set of DCPs for every
+translation would be about 1Tb with a lot of duplicated data.
+</para>
+
+<para>
+The DCP format has a solution to this problem. One DCP can refer to
+the ‘assets’ (picture, sound or subtitle) of another DCP.
+For our translation example this means that we could have a
+‘base’ DCP (often called the OV or Original Version)
+containing video, audio and one set of subtitles and then any number
+of overlay DCPs (often called VF or Version Files) which refer to the
+base version and replace the original subtitles with their own. <xref
+linkend="fig-dcp-refer"/> shows this principle for one of our
+translations. The DCP that we make refers to the original content
+DCP's video and audio rather than containing a copy.
+</para>
+
+<figure id="fig-dcp-refer">
+<title>Creating a new DCP by referring to an existing one</title>
+<mediaobject><imageobject><imagedata scale="100" fileref="diagrams/dcp-refer&dia;"/></imageobject></mediaobject>
+</figure>
+
+<para>
+To play back the subtitled DCP the projectionist ingests both the base
+(OV) DCP and the overlay (VF) DCP, then plays the VF one.
+</para>
+
+</section>
+
+</section>
+
+
</chapter>
<!-- ============================================================== -->
<title>Burnt-in subtitles</title>
<mediaobject>
<imageobject>
- <imagedata scale="80" fileref="diagrams/burn-in&dia;"/>
+ <imagedata scale="100" fileref="diagrams/burn-in&dia;"/>
</imageobject>
</mediaobject>
</figure>
<title>Separate subtitles</title>
<mediaobject>
<imageobject>
- <imagedata scale="80" fileref="diagrams/discrete&dia;"/>
+ <imagedata scale="100" fileref="diagrams/discrete&dia;"/>
</imageobject>
</mediaobject>
</figure>
<title>Timecode</title>
<mediaobject>
<imageobject>
- <imagedata fileref="diagrams/timecode&dia;"/>
+ <imagedata scale="100" fileref="diagrams/timecode&dia;"/>
</imageobject>
</mediaobject>
</figure>
<title>Creating a new film</title>
<mediaobject>
<imageobject>
- <imagedata fileref="diagrams/file-structure&dia;"/>
+ <imagedata scale="100" fileref="diagrams/file-structure&dia;"/>
</imageobject>
</mediaobject>
</figure>