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