placed between all producers and the consumer).
TODO: transition example
+
+
+Flexibility:
+
+ The information presented above is considered the MLT Westley "normal"
+ form. This is the output generated by the westley consumer, for example,
+ when used with inigo. It is the output generated when you use the
+ "Westley to File" consumer in the demo script, which beginners will find
+ most useful for learning to use westley XML. This section describes
+ alternative forms the westley producer accepts.
+
+ First of all, the normal form is more of a linear format with producers
+ and playlists defined prior to their usage in a multitrack. Westley
+ also accepts a hierarchical format with producers as children of tracks
+ or playlist entries and with playlists as children of tracks:
+
+ <westley>
+ <tractor>
+ <multitrack>
+ <track>
+ <playlist>
+ <entry>
+ <producer>
+ <property name="resource">clip1.dv</property>
+ </producer>
+ </entry>
+ </playlist>
+ </track>
+ </multitrack>
+ </tractor>
+ </westley>
+
+ Obviously, this example is meant to demonstrate hierarchy and not effective
+ use of playlist or multitrack!
+
+ Secondly, as part of error handling, westley is forgiving if you fail to
+ supply <tractor>, <track>, and <entry> where one can be understood. This
+ affords an abbreviated syntax that is less verbose and perhaps less
+ intimidating for a human to read and understand. One can simplify the
+ above example as:
+
+ <westley>
+ <multitrack>
+ <playlist>
+ <producer>
+ <property name="resource">clip1.dv</property>
+ </producer>
+ </playlist>
+ </multitrack>
+ </westley>
+
+ Yes, filters and transitions can be added to the above example after the
+ closing multitrack tag (</multitrack>) because it is still enclosed within
+ the westley body tags.
+
+ If you specify in and out on a producer and it has been enclosed within
+ an <entry> or <playlist>, then the edit points apply to the playlist
+ entry and not to the producer itself. This facilitates re-use of media:
+
+ <playlist>
+ <producer id="clip1" in="25" out="78">
+ <property name="resource">clip1.dv</property>
+ </producer>
+ <entry producer="clip1" in="119" out="347"/>
+ </playlist>
+
+ In the above example, the producer attribute of the entry element is
+ a reference to the preceding producer. All references must follow the
+ definition. The edit points supplied on the producer above will not affect
+ the entry that references it below because westley knows the clip is a
+ playlist entry and optimises this situation. The advantage is that one
+ does not need to determine every clip to be included ahead of time
+ and specify them outside the context of the mutlitrack timeline.
+
+ This form of authoring will be easier for many to visualise as a non-linear
+ editor's timeline. Here is a more complex example:
+
+ <westley>
+ <multitrack>
+ <playlist>
+ <producer id="foo" in="100" out="149">
+ <property name="resource">clip2.mpeg</property>
+ </producer>
+ <blank length="25"/>
+ <entry producer="foo" in="10" out="59"/>
+ </playlist>
+ <playlist>
+ <blank length="25"/>
+ <producer id="bar" in="100" out="199">
+ <property name="resource">clip3.mpeg</property>
+ </producer>
+ <entry out="99" producer="bar"/>
+ </playlist>
+ </multitrack>
+ <filter mlt_service="greyscale" track="0"/>
+ <transition mlt_service="luma" in="25" out="49" a_track="0" b_track="1"/>
+ <transition mlt_service="luma" in="75" out="99" a_track="0" b_track="1">
+ <property name="reverse" value="1"/>
+ </transition>
+ </westley>
+
+ Did you notice something different in the last example? Properties can be
+ expressed using XML attributes on the element as well. However, only
+ non-service-specific properties are supported in this way. For example,
+ "mlt_service" is available to any producer, filter, or transition. However,
+ "resource" is actually service-specific. Notice the syntax of the last
+ property, on the last transition. Westley accepts property values using
+ the "value" attribute as well as using element text.
+
+ We have seen a few different ways of expressing property values. There are
+ a couple more for properties that can accept XML data. For example, the
+ GDK pixbuf producer with librsvg can handle embedded SVG, and the Pango
+ producer can handle embedded Pango markup. You can enclose the embedded XML
+ using a CDATA section:
+
+ <property name="resource"><![CDATA[ <svg>...</svg> ]]></property>
+
+ Please ensure the opening CDATA tag immediately follows the opening
+ property tag and that the section closing tag immediately precedes the
+ closing property tag.
+
+ However, westley can also accept inline embedded XML:
+
+ <property name="resource">
+ <svg>
+ </svg>
+ </property>
+
+ Currently, there is no namespace handling so a conflict will occur only on
+ any embedded XML that contains an element named "property" because
+ westley collects embedded XML until it reaches a closing property tag.
+
+ TODO: xml entities
+
+
+Technique:
+
+ If one finds the above hierarchical, abbreviated format intuitive,
+ start with a simple template and fill and extend as needed:
+ <westley>
+ <multitrack>
+ <playlist>
+ </playlist>
+ ...add a playlist for each track...
+ </multitrack>
+ ...add filters and transitions...
+ </westley>
+
+ By using a playlist for each track, it is easier to iteratively add new
+ clips and blank regions as you develop the project. You will not have to
+ use <track> or later add <playlist> when necessary.
+
+ A more advanced template that allows sequencing multitracks is:
+ <playlist>
+ <entry>
+ <multitrack>
+ <playlist>
+ </playlist>
+ ...add a playlist for each track...
+ </multitrack>
+ ...add filters and transitions...
+ </entry>
+
+ <entry>
+ <multitrack>
+ <playlist>
+ </playlist>
+ ...add a playlist for each track...
+ </multitrack>
+ ...add filters and transitions...
+ </entry>
+ </playlist>
+
+ If you want to have a silent, black background for audio and video fades,
+ then make the last track simply <producer mlt_service="colour"/>. Then,
+ use composite and volume key-framable properties.
+ TODO: to be continued
+
+ TODO: considerations with mixing multiple audio layers
projects / mlt / blobdiff