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+<p>Every Region has a fade-in and fade-out. By default, the region fade
+is very short, and serves to de-click the transitions at the start and
+end of the region. By adjusting the regions fade length, a more
+gradual transition can be accomplished.<br></p>
+
+<h2>Region Fades</h2>
+<p> <dfn>Region fades</dfn> are possible at the beginning and end of
+all audio regions. In object mode, a grip appears at the top left and
+top right of an audio region when the cursor hovers over it. Placing
+the cursor over the top of the grip displays the region fade cursor
+tip. Click and drag the grip left or right in the timeline to
+adjust the length of the fade.<br>
+</p>
+<h2>Crossfades</h2>
+<p> <dfn>Crossfades</dfn> refer to the behavior when you want to make
+a smooth transition (mix) from one audio region to another on the same
+track. Historically, this was done by splicing 2 pieces of analog
+tape together, and this concept was carried forward into digital
+editing. Each track is a sequence of sound files (regions). If
+two regions are butted against each other, there needs to be a method
+to splice them smoothly together. The crossfade allows one region
+to fade smoothly out, while the next region fades smoothly in, like 2
+pieces of tape that have been cut at and angle, and overlapped.<br>
+</p>
+<p>But Ardour uses a more refined "layered" editing model, and
+therefore it is possible for multiple regions to be stacked on a single
+location with arbitrary overlaps between different layers. For
+this reason, crossfades must be implemented differently. We can't
+assume that a crossfade is an entitry that exists between 2 regions;
+instead each region must have its own associated crossfades at each
+end, and the topmost region must always crossfade down to the
+underlying region(s), if any.<br>
+</p>
+<p>Ardour solves this problem by putting a crossfade at the beginning
+and end of every region. The fades of the bottom-most region are
+first rendered, and then each region is rendered on top of the one
+below it, with fades at the end of each region providing a crossfade to
+the region(s) beneath it. <br>
+</p>
+<p>It is important to understand that region fades <em>are</em> crossfades. When one region has
+another region or multiple regions beneath its fade area, then you will
+hear the topmost region fade-out be mirrored as a fade-in on the
+underlying region(s). The grip for the topmost region will allow
+changing the length and type of the crossfade into the underlying
+region(s). In this way you can create a complicated series of
+crossfades, and then layer another region atop the others, and fade
+into _that_ complicated series. <em>An image here would
+probably help.</em><br>
+</p>
+<p>If a region doesn't have any region(s) under it, then the region is
+crossfaded to silence; for convenience we call this a "fade"
+rather than a crossfade.<br>
+</p>
+<h2>Fade Shapes<br>
+</h2>
+<p>To activate/deactivate or change the shape of a region's fadein or
+fade-out, hover the cursor over the regionfade grip till the cursor tip
+indicates region fade editing and context-click to bring up a context
+menu. In the context menu there is a list of options for the
+regionfade. <kbd class="menu">Activate/Deactivate</kbd> enables and
+disables the regionfade.<br>
+</p>
+<p>Because each fade is also a crossfade, it has an inverse fade shape
+for the audio beneath the fade. It is important to know how the
+shapes differ, and which are most suitable for various editing tasks.<br>
+</p>
+<p>The different types of fades are:<br>
+</p>
+<ul>
+ <li><kbd class="menu">Linear</kbd> : A simple linear coefficient decrease, and its
+mathematical inverse. A Linear fade starts attentuating quickly
+and then cuts off even more abruptly at lower levels. When used
+as a crossfade, the signals are each -6dB attenuated at the midpoint.
+This is the correct crossfade to use with highly-correlated signals for
+a smooth transition.<br>
+ </li>
+ <li><kbd class="menu">Constant Power</kbd> : The constant power curve starts fading
+slowly and then cuts off abruptly. When used as a crossfade
+between 2 audio regions, the signals are symetrically attenuated, and
+they each reach -3dB at the midpoint. This is the correct crossfade to
+use when you want to splice audio in the general ( uncorrelated ) case.<br>
+ </li>
+ <li><kbd class="menu">Symmetric</kbd> : The Symmetric fade starts slowly, then
+attenuates significantly before transitioning to a slower fade-out near
+the end of the fade. When used as a crossfade, the Symmetric
+curve is not mathematically correct like the Equal Power or Linear
+curves, but it provides a slower fade-out at low volumes. This is
+sometimes useful when editing 2 entire music works together so that the
+transition is more gradual.<br>
+ </li>
+ <li><kbd class="menu">Fast</kbd> : The Fast curve is a linear decibel fade; It sounds
+like a perfectly smooth fader or knob moved to silence. This shape is
+excellent as a general-purpose fade-in. When used as a
+crossfade, the inverse fade curve maintains constant power but is
+therefore non-symmetric; so its use is limited to those cases where the
+user finds it appropriate.</li>
+ <li><kbd class="menu">Slow</kbd> : The Slow curve is a modified linear decibel fade.
+The initial curve starts more gradually so that it has a less
+abrupt transition near unity. After that, it sounds like a
+perfectly smooth fader or knob moved to silence. This shape is excellent as
+a general-purpose fade-out. When used as a crossfade, the
+inverse fade curve maintains constant power but is therefore
+non-symmetric; so its use is limited to those cases where the user
+finds it appropriate.<br>
+ </li>
+</ul>
+<p>Although these fade shapes serve specific purposes, you might find that
+any of the shapes is usable in your situation. The final decision
+is an artistic choice rather than a <br></p>
+<br>
+<p>These fade curves are developed to provide a range of common uses, and
+are developed with the least possible amount of changes in the "slope"
+of the line. This provides artifact-free crossfades. Some
+DAWs provide complicated fade editors with parametric "spline" controls
+of the fade curves. While it might be interesting to develop a
+fade curve with a faster cutoff, the mathematical difference between
+this and simply shortening the fade is vanishingly small; and the
+amount of effort to shorten the fade is much easier than messing with a
+crossfade editor dialog.<br></p>
+
projects / ardour-manual / blobdiff