+<guilabel>Audio Delay</guilabel> is used to adjust the synchronisation
+between audio and video. A positive delay will move the audio later
+with respect to the video, and a negative delay will move it earlier.
+</para>
+
+</section>
+</section>
+
+
+<!-- ============================================================== -->
+<section>
+<title>Subtitles</title>
+
+<para>
+The subtitles tab contains settings related to subtitles in your
+content, as shown in <xref linkend="fig-subtitles-tab"/>.
+</para>
+
+<figure id="fig-subtitles-tab">
+ <title>Subtitle settings tab</title>
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="screenshots/subtitles-tab&scs;"/>
+ </imageobject>
+ </mediaobject>
+</figure>
+
+<para>
+DCP-o-matic will extract subtitles from the content, if present, and
+they can be ‘burnt into’ the DCP (that is, they are
+included in the image and not overlaid by the projector) or included
+as a separate subtitle ‘asset’ within your DCP (in which
+case the projector overlays them onto the image on playback). The
+difference between these two arrangements is illustrated by <xref
+linkend="fig-burn-in"/> and <xref linkend="fig-discrete"/>
+</para>
+
+<figure id="fig-burn-in">
+ <title>Burnt-in subtitles</title>
+ <mediaobject>
+ <imageobject>
+ <imagedata scale="100" fileref="diagrams/burn-in&dia;"/>
+ </imageobject>
+ </mediaobject>
+</figure>
+
+<figure id="fig-discrete">
+ <title>Separate subtitles</title>
+ <mediaobject>
+ <imageobject>
+ <imagedata scale="100" fileref="diagrams/discrete&dia;"/>
+ </imageobject>
+ </mediaobject>
+</figure>
+
+<para>
+The advantage of separate subtitles is that the same video content can
+be used for DCPs in many different languages. This means that only a
+small text file needs to be changed for each target language, rather
+than a large video file. It also means that the time-consuming video
+encoding need only be done once for the project rather than once for
+every language.
+</para>
+
+<para>
+Note that subtitles come in two types: text and bitmap. Text
+subtitles are expressed as plain text and can be either burnt into the
+image or included as a separate subtitle asset within the DCP. Bitmap
+subtitles, on the other hand, are expressed as pre-rendered bitmaps.
+They cannot (yet) be added to the DCP as a separate asset and must be
+burnt into the image.
+</para>
+
+<para>
+Select the <guilabel>Use Subtitles</guilabel> check-box to enable
+these subtitles.
+</para>
+
+<para>
+Select the <guilabel>Burn subtitles into image</guilabel> check-box to
+burn these subtitles into the image; if this is not ticked the
+subtitles will be included separately in the DCP to be rendered by the
+projector.
+</para>
+
+<para>
+The <guilabel>X Offset</guilabel> and <guilabel>Y Offset</guilabel>
+controls move the subtitles around within the image. The offsets are
+expressed as a percentage of the video frame size; 100% X offset is
+the entire width of the frame, and 100% Y offset is the entire height.
+Hence, to move the subtitles down by half the frame height you would
+use a Y offset of 50%.
+</para>
+
+<para>
+The <guilabel>X Scale</guilabel> and <guilabel>Y Scale</guilabel>
+controls scale the subtitles. Scale values of 1 make the subtitles
+the same size (relative to the size of the image) as they are on the
+original. Values lower than 1 make them smaller, and values higher
+make them larger. You can stretch the subtitles in either direction
+by specifying different values for X and Y scale. Subtitles from DVD
+and Blu Ray sources are frequently larger (relative to the video
+frame) than those typically used for DCP, so it is often useful to
+scale such subtitles down using these controls.
+</para>
+
+<para>
+The <guilabel>Stream</guilabel> control changes the subtitle stream
+that is used when the content has more than one.
+</para>
+
+</section>
+
+
+<!-- ============================================================== -->
+<section>
+<title>Timing</title>
+
+<para>
+The timing tab contains settings related to the timing of your
+content, as shown in <xref linkend="fig-timing-tab-detail"/>.
+</para>
+
+<figure id="fig-timing-tab-detail">
+ <title>Timing settings tab</title>
+ <mediaobject>
+ <imageobject>
+ <imagedata fileref="screenshots/timing-tab&scs;"/>
+ </imageobject>
+ </mediaobject>
+</figure>
+
+<para>
+Most of the timing tab's entries are <emphasis>time-codes</emphasis>.
+These are expressed as four numbers, as shown in <xref
+linkend="fig-timecode"/>.
+</para>
+
+<figure id="fig-timecode">
+ <title>Timecode</title>
+ <mediaobject>
+ <imageobject>
+ <imagedata scale="100" fileref="diagrams/timecode&dia;"/>
+ </imageobject>
+ </mediaobject>
+</figure>
+
+<para>
+<guilabel>Position</guilabel> is the time at which this piece of
+content should start within the DCP. In most cases, this will be
+<code>0:0:0:0</code> to make the content start at the beginning of the
+DCP.
+</para>
+
+<para>
+<guilabel>Full length</guilabel> is the length of the piece of
+content. This can only be set for still-image content: for video or
+sound content, it is fixed by the nature of the content file. If
+still-image content is being used you can set the length for which it
+should be displayed using this control.
+</para>
+
+<para>
+<guilabel>Trim from start</guilabel> specifies the amount that should be trimmed from the start of the content.
+</para>
+
+<para>
+<guilabel>Trim from end</guilabel> specifies the amount that should be trimmed from the end of the content.
+</para>
+
+<para>
+<guilabel>Play length</guilabel> indicates how long this piece of
+content will be once the trims have been applied. This will be equal
+to the full length minus <guilabel>trim-from-start</guilabel> and minus <guilabel>trim-from-end</guilabel>.
+</para>
+
+<para>
+<guilabel>Video frame rate</guilabel> specifies the frame rate for
+still-image content. It can also be used to override the detected
+frame rate of other content if DCP-o-matic has got it wrong.
+</para>
+
+<para>
+Each timecode control has a <guilabel>Set</guilabel> which you should
+click when you have entered a new value for a timecode. The
+<guilabel>Set</guilabel> button will make DCP-o-matic take account of
+any changes to the corresponding timecode.
+</para>
+
+</section>
+
+
+<!-- ============================================================== -->
+<section>
+<title>Video processing pipeline</title>
+
+<para>
+This section gives a little more detail about how DCP-o-matic process
+video as it takes it from a source and puts it into a DCP.
+</para>
+
+<para>
+Consider, as a somewhat over-the-top example, that we have a 720 x 576
+image which is letterboxed with 36 black pixels each at the top and
+bottom, and the video content within the letterbox should be presented
+in the DCP at ratio of 2.39:1 within a 1.85:1 frame (such as might
+happen with a trailer). The source image is shown in <xref
+linkend="fig-pipeline1"/>.
+</para>
+
+<figure id="fig-pipeline1">
+ <title>Example image to demonstrate video processing</title>
+ <mediaobject>
+ <imageobject>
+ <imagedata scale="100" fileref="diagrams/pipeline1&dia;"/>
+ </imageobject>
+ </mediaobject>
+</figure>
+
+<para>
+DCP-o-matic runs through the following steps when preparing an image for a DCP:
+</para>
+
+<itemizedlist>
+<listitem>Crop</listitem>
+<listitem>Scale</listitem>
+<listitem>Place in container</listitem>
+</itemizedlist>
+
+<para>
+First, some amount of the image can be cropped. This is almost always
+used to remove black borders (letterboxing and/or pillarboxing) around
+images.
+</para>
+
+<para>
+In our example image, we would use 36 pixels of crop from the top and
+bottom. This would give the new image shown in <xref
+linkend="fig-pipeline2"/>.