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<?xml version="1.0" standalone="no"?>
<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN" "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
]>
<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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