David Robillard
99904735e0
git-svn-id: svn://localhost/ardour2/branches/midi@1614 d708f5d6-7413-0410-9779-e7cbd77b26cf
225 lines
9.0 KiB
XML
225 lines
9.0 KiB
XML
<?xml version="1.0" standalone="no"?>
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<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN" "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
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]>
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<section id="sn-working-with-crossfades">
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<title>Working with Crossfades</title>
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<para>
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Whenever you arrange any two audio regions so that they overlap in any
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way, you create the potential for a
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<link linkend="gt-crossfade">crossfade</link> between them: a smooth
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transition from one region to the other. Crossfades in Ardour are
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generated in realtime, and are not stored on disk. They are objects
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within a playlist just like regions, except that the only way to create
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a crossfade is by overlapping two regions, and the only way to remove a
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crossfade is to move one or both of the regions so that they no longer
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overlap. Note that crossfades are not always audible (they can be muted
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and unmuted at will), and can be edited in a variety of ways. We think
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of a crossfade as consisting of an overlap between two regions, plus two
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gain control curves that control the volume of the incoming and outgoing
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regions during the crossfade.
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</para>
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<section id="crossfade-types">
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<title>Types of crossfades</title>
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<para>
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Ardour comes with two basic kinds of crossfades, termed
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<emphasis>short crossfades</emphasis> and <emphasis>full
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crossfades</emphasis> . A full crossfade is a transition between two
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regions that spans the entire overlap between them. If the overlap is
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2 seconds long, then the crossfade is 2 seconds long. A short
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crossfade is a transition between two regions that lasts a fixed
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amount of time and serves simply to avoid audio glitches at the
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boundary of the two regions. The length of a short crossfade is a
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session-wide parameter than can be set via the <emphasis>option
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editor</emphasis> . The default is 15ms, and the length can vary from
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1 milliseconds to 0.5 seconds. In the current version of Ardour, it is
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not possible to change the length of a short becrossfade after it has
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been created, but it is possible to change most short crossfades to a
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full crossfade and vice versa. Full crossfades can have their length
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altered by changing the extent of the overlap between the two regions.
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</para>
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<para>
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Note that even though the absolute length of the crossfade is fixed,
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crossfades can be <emphasis>edited</emphasis> with complete freedom,
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allowing you change the effective length of a crossfade by altering
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the shapes of the fade in and fade out curves.
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</para>
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</section>
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<section id="crossfade-overlaps">
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<title>Overlaps</title>
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<para>
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There are several different ways to overlap two regions, and they
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result in different kinds of crossfades being placed at the boundaries
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of the two regions:
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</para>
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<section id="external-overlaps">
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<title>External overlaps</title>
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<para>
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An "external" overlap occurs when a region starts within another
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region, but extends beyond the other's end.
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</para>
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<mediaobject>
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<imageobject>
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<imagedata fileref="images/overlaplaterhigher.png"/>
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</imageobject>
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</mediaobject>
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<para>
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Overlaps like this will cause an xfade to be placed at the start of
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the later region. Whether it is a full or short crossfade is
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controlled by the current crossfade type preference. If short
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crossfades have been chosen, the crossfade will last for the current
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short crossfade duration; otherwise the full crossfade will last for
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the entire overlap. The mute status of the crossfade will depend on
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the current state of the "New crossfades are muted" setting.
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</para>
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<para>
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In the example above, the later region is above the earlier one. It
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is also possible to create an overlap where the earlier region is in
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a higher layer:
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</para>
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<mediaobject>
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<imageobject>
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<imagedata fileref="images/overlapearlyhigher.png"/>
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</imageobject>
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</mediaobject>
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<para>
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For an overlap of this type, the current crossfade type preference
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affects the placement of the crossfade. If full crossfades have been
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chosen, the crossfade will be placed at the start of the later
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region and will last for the entire overlap. If short crossfades
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have been chosen, the crossfade will start just before the end of
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the earlier region and will last for the chosen short crossfade
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duration. The mute status of the crossfade will depend on the
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current state of the "New crossfades are muted" setting.
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</para>
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</section>
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<section id="internal-overlaps">
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<title>Internal overlaps</title>
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<para>
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An "internal" overlap occurs when the start and end of one region
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both occur within the duration of another.
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</para>
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<mediaobject>
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<imageobject>
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<imagedata fileref="images/internalhigheroverlap.png"/>
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</imageobject>
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</mediaobject>
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<para>
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Overlaps of this type will cause two short crossfades to be place at
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the start of the later region and close to its end. Both crossfades
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will last for the current short crossfade duration, and are created
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in an un-muted state. These crossfades <emphasis>cannot</emphasis>
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be converted to full crossfades. It is important to realize that the
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purpose of these two crossfades is a little different than those
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created for the single-ended overlap cases above. They are created
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solely to avoid audio glitches at the transitions between the two
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regions, and are not intended to facilitate interesting crossfades
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between the upper and lower region.
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</para>
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<para>
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Notice that in the example above, the shorter region is above the
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longer one. It is also possible to create the following type of
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overlap, where the shorter region is below the longer one:
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</para>
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<mediaobject>
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<imageobject>
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<imagedata fileref="images/internalloweroverlap.png"/>
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</imageobject>
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</mediaobject>
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<para>
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Overlaps of this type will not cause any crossfades to be created.
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The uppermost region will be audible throughout its duration; the
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lowermost region will not be audible at all.
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</para>
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</section>
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</section>
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<section id="creating-crossfades">
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<title>Creating Crossfades</title>
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<para>
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To create a crossfade between two regions, move them so that they
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overlap. A crossfade is automatically created within the overlap
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(possibly two, dependening on the type of overlap, as explained
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above). Whether the crossfade is muted or not depends on two things:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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if the current crossfade type is set to "Short", the new crossfade
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will be created in an un-muted state
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</para>
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</listitem>
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<listitem>
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<para>
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if the current crossfade type is set to "Full", the mute status of
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the new crossfade is controlled from the <emphasis>option
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editor</emphasis> on the "Layers&Fades" control panel. If "New
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crossfades are unmuted", the new crossfade will be unmuted.
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</para>
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</listitem>
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</itemizedlist>
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<para>
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A muted crossfade is not directly visible in the editor window, but
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can be accessed by context clicking within the overlap that it relates
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to. An unmuted crossfade has a yellow background that covers the
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entire overlap (to make its presence obvious at all times), and a pair
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of visible curves that show the gain control curves for the fade.
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These curves may not be visible at a particular zoom level, especially
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for short crossfades.
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</para>
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</section>
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<section id="editing-crossfades">
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<title>Editing Crossfades</title>
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<para>
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To carry out operations on a crossfade, context click anywhere in the
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overlap. For the short crossfades in the "internal" overlap case, you
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will need to zoom in until the crossfade becomes visible, and then
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context click on it. Each crossfade under the mouse pointer (there is
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normally only one) will appear in the context menu, and will lead to a
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submenu offering the following options:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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Mute/Unmute the crossfade
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</para>
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</listitem>
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<listitem>
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<para>
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Edit the crossfade
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</para>
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</listitem>
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<listitem>
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<para>
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change the crossfade from short to full or vice versa
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</para>
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</listitem>
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</itemizedlist>
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<para>
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The last option is not available for the short crossfades in the
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"internal" overlap case.
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</para>
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</section>
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<!--
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<xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
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href="Some_Subsection.xml" />
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-->
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</section>
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