2 Every Region has a fade-in and fade-out. By default, the region fade
3 is very short, and serves to de-click the transitions at the start and
4 end of the region. By adjusting the regions fade length, a more
5 gradual transition can be accomplished.
10 <dfn>Region fades</dfn> are possible at the beginning and end of
11 all audio regions. In object mode, a grip appears at the top left and
12 top right of an audio region when the cursor hovers over it. Placing
13 the cursor over the top of the grip displays the region fade cursor
14 tip. Clicking and dragging the grip left or right in the timeline adjusts the
21 <dfn>Crossfades</dfn> refer to the behavior of two audio regions transitioning
22 smoothly (mixing) from one to another on the same
23 track. Historically, this was done by splicing two pieces of analog
24 tape together, and this concept was carried forward into digital
25 editing. Each track is a sequence of sound files (regions). If
26 two regions are butted against each other, there needs to be a method
27 to splice them smoothly together. The crossfade allows one region
28 to fade smoothly out, while the next region fades smoothly in, like two
29 pieces of tape that have been cut at an angle, and overlapped.
32 But Ardour uses a more refined "layered" editing model, and
33 therefore it is possible for multiple regions to be stacked on a single
34 location with arbitrary overlaps between different layers. For
35 this reason, crossfades must be implemented differently. It can't be
36 assumed that a crossfade is an entity that exists between two regions;
37 instead each region must have its own associated crossfades at each
38 end, and the topmost region must always crossfade down to the
39 underlying region(s), if any.
42 Ardour solves this problem by putting a crossfade at the beginning
43 and end of every region. The fades of the bottom-most region are
44 first rendered, and then each region is rendered on top of the one
45 below it, with fades at the end of each region providing a crossfade to
46 the region(s) beneath it.
49 It is important to understand that region fades <em>are</em> crossfades.
50 When one region has another region or multiple regions beneath its fade area,
51 then what will be heard is the topmost region fade-out mirrored as a fade-in
52 on the underlying region(s). The grip for the topmost region will allow
53 changing the length and type of the crossfade into the underlying
54 region(s). In this way complicated series of crossfades can be created, and
55 then another region layered atop the others, and faded into a complicated
59 If a region doesn't have any region(s) under it, then the region is
60 crossfaded to silence; for convenience this is called a "fade"
61 rather than a crossfade.
67 <img src="/images/crossfade_menu.png">
68 <figcaption class=center>The fade shape context menu.</figcaption>
72 To activate/deactivate or change the shape of a region's fadein or
73 fade-out, the cursor has to be hovered over the region fade grip until the
74 cursor tip indicates region fade editing, then <kbd class="mouse">right</kbd>
75 clicked to bring up a context menu. In the context menu is a list of options
76 for the region fade. <kbd class="menu">Activate/Deactivate</kbd> enables and
77 disables the region fade.
80 Because each fade is also a crossfade, it has an inverse fade shape
81 for the audio beneath the fade. It is important to know how the
82 shapes differ, and which are most suitable for various editing tasks.
85 The different types of fades are:
88 <tr><th><kbd class="menu">Linear</kbd></th><td>A simple linear coefficient
89 decrease, and its mathematical inverse. A Linear fade starts attenuating
90 quickly, and then cuts off even more abruptly at lower levels. When used as a
91 crossfade, the signals are each -6dB attenuated at the midpoint. This is the
92 correct crossfade to use with highly-correlated signals for a smooth
94 <tr><th><kbd class="menu">Constant Power</kbd></th><td>The constant power
95 curve starts fading slowly and then cuts off abruptly. When used as a
96 crossfade between 2 audio regions, the signals are symmetrically attenuated,
97 and they each reach -3dB at the midpoint. This is the correct crossfade to
98 use when splicing audio in the general (uncorrelated) case.</td></tr>
99 <tr><th><kbd class="menu">Symmetric</kbd></th><td>The Symmetric fade starts
100 slowly, then attenuates significantly before transitioning to a slower
101 fade-out near the end of the fade. When used as a crossfade, the Symmetric
102 curve is not mathematically correct like the Constant Power or Linear curves,
103 but it provides a slower fade-out at low volumes. This is sometimes useful
104 when editing 2 entire music works together so that the transition is more
106 <tr><th><kbd class="menu">Slow</kbd></th><td>The Slow curve is a modified
107 linear decibel fade. The initial curve starts more gradually so that it has
108 a less abrupt transition near unity. After that, it sounds like a perfectly
109 smooth fader or knob moved to silence. This shape is excellent as a
110 general-purpose fade-out. When used as a crossfade, the inverse fade curve
111 maintains constant power but is therefore non-symmetric; so its use is
112 limited to those cases where the user finds it appropriate.</td></tr>
113 <tr><th><kbd class="menu">Fast</kbd></th><td>The Fast curve is a linear
114 decibel fade; It sounds like a perfectly smooth fader or knob moved to
115 silence. This shape is excellent as a general-purpose fade-in. When used as
116 a crossfade, the inverse fade curve maintains constant power but is
117 therefore non-symmetric; so its use is limited to those cases where the
118 user finds it appropriate.</td></tr>
122 Although these fade shapes serve specific purposes, any of the shapes is
123 usable in any situation, so the final decision is mostly an artistic choice.
127 These fade curves are developed to provide a range of common uses, and
128 are developed with the least possible amount of changes in the "slope"
129 of the line. This provides artefact-free crossfades. Some
130 DAWs provide complicated fade editors with parametric "spline" controls
131 of the fade curves. While it might be interesting to develop a
132 fade curve with a faster cutoff, the mathematical difference between
133 this and simply shortening the fade is vanishingly small; and the
134 amount of effort to shorten the fade is much easier than messing with a
135 crossfade editor dialog.