+<!-- ============================================================== -->
+<chapter xmlns="http://docbook.org/ns/docbook" version="5.0" xml:lang="en">
+<title>Manipulating existing DCPs</title>
+
+<para>
+Frequently DCP-o-matic is used to take content in formats such as MP4
+and convert it to JPEG2000 for a DCP. Alternatively, it can be used
+to take existing DCPs and modify them in various ways.
+</para>
+
+<section>
+<title>Importing a DCP into DCP-o-matic</title>
+
+<para>
+If you want to do something to an existing DCP the first step is to
+import it. Click <guilabel>Add folder...</guilabel> and select your
+DCP's folder. It will be added to the DCP-o-matic project. If the
+DCP is unencrypted you can preview it in the normal way, though
+playback will be very slow as decoding of DCPs is almost as
+computationally intensive as encoding them.
+</para>
+
+</section>
+
+
+<section>
+<title>Decrypting encrypted DCPs</title>
+
+<para>
+DCPs can be encrypted (see <xref linkend="ch-encryption"/> for
+details). If you import an encrypted DCP you will need a key, in the
+form of a Key Delivery Message (KDM), to decrypt it.
+</para>
+
+<para>
+KDMs must be prepared by the organisation which created the DCP. They
+contain the keys to decrypt the DCP wrapped up in such a way that only
+the intended recipient can read them. You will need to provide the
+organisation with a certificate which identifies your copy of
+DCP-o-matic and allows them to create a KDM for you.
+</para>
+
+<para>
+To get DCP-o-matic's decryption certificate, open the Preferences
+dialogue (see <xref linkend="ch-preferences"/>) and go to the
+<guilabel>Keys</guilabel> tab. Click the <guilabel>Export DCP
+decryption certificate...</guilabel> button at the bottom of this tab
+and save the certificate. Send this certificate to the DCP creators
+and they can create a KDM to allow DCP-o-matic to decrypt their DCP.
+</para>
+
+<para>
+Once you have your KDM, right-click the DCP's name in DCP-o-matic and
+choose <guilabel>Add KDM...</guilabel>. Specify your KDM and (all
+being well) the DCP will be decrypted and become available for preview.
+</para>
+
+</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>
+
+<para>
+To make a DCP like this:
+</para>
+
+<itemizedlist>
+<listitem>Import your ‘Content DCP’ to a DCP-o-matic project.</listitem>
+<listitem>Add whatever replacement you want in your new DCP (replacement subtitles or audio files, for example).</listitem>
+<listitem>Select the DCP in the content list</listitem>
+<listitem>Tick the <guilabel>Refer to existing DCP</guilabel> checkbox
+in the tabs for the parts of the DCP that you want to refer to in your
+new DCP. For example, to refer to the ‘Content DCP’'s video and audio you would select the <guilabel>Video</guilabel> tab, click <guilabel>Refer to existing DCP</guilabel> then select the <guilabel>Audio</guilabel> tab and do the same.</listitem>
+<listitem>Do <guilabel>Make DCP</guilabel> as usual and your VF DCP will be created.</listitem>
+</itemizedlist>
+
+</section>
+
+</section>
+
+
+
+</chapter>
+<!-- ============================================================== -->
+
+
projects / dcpomatic.git / blobdiff