3 title: Create Region Fades and Crossfades
6 <p class="fixme">Add images--an image is worth more than 1,000 words</p>
8 Every Region has a fade-in and fade-out. By default, the region fade
9 is very short, and serves to de-click the transitions at the start and
10 end of the region. By adjusting the regions fade length, a more
11 gradual transition can be accomplished.
16 <dfn>Region fades</dfn> are possible at the beginning and end of
17 all audio regions. In object mode, a grip appears at the top left and
18 top right of an audio region when the cursor hovers over it. Placing
19 the cursor over the top of the grip displays the region fade cursor
20 tip. Click and drag the grip left or right in the timeline to
21 adjust the length of the fade.
26 <dfn>Crossfades</dfn> refer to the behavior when you want to make
27 a smooth transition (mix) from one audio region to another on the same
28 track. Historically, this was done by splicing 2 pieces of analog
29 tape together, and this concept was carried forward into digital
30 editing. Each track is a sequence of sound files (regions). If
31 two regions are butted against each other, there needs to be a method
32 to splice them smoothly together. The crossfade allows one region
33 to fade smoothly out, while the next region fades smoothly in, like 2
34 pieces of tape that have been cut at and angle, and overlapped.
38 But Ardour uses a more refined "layered" editing model, and
39 therefore it is possible for multiple regions to be stacked on a single
40 location with arbitrary overlaps between different layers. For
41 this reason, crossfades must be implemented differently. We can't
42 assume that a crossfade is an entitry that exists between 2 regions;
43 instead each region must have its own associated crossfades at each
44 end, and the topmost region must always crossfade down to the
45 underlying region(s), if any.
49 Ardour solves this problem by putting a crossfade at the beginning
50 and end of every region. The fades of the bottom-most region are
51 first rendered, and then each region is rendered on top of the one
52 below it, with fades at the end of each region providing a crossfade to
53 the region(s) beneath it.
57 It is important to understand that region fades <em>are</em> crossfades. When one region has
58 another region or multiple regions beneath its fade area, then you will
59 hear the topmost region fade-out be mirrored as a fade-in on the
60 underlying region(s). The grip for the topmost region will allow
61 changing the length and type of the crossfade into the underlying
62 region(s). In this way you can create a complicated series of
63 crossfades, and then layer another region atop the others, and fade
64 into <em>that</em> complicated series.
66 <p class="fixme">An image here would probably help.</p>
69 If a region doesn't have any region(s) under it, then the region is
70 crossfaded to silence; for convenience we call this a "fade"
71 rather than a crossfade.
76 To activate/deactivate or change the shape of a region's fade-in or
77 fade-out, hover the cursor over the region fade grip till the cursor tip
78 indicates region fade editing and context-click to bring up a context
79 menu. In the context menu there is a list of options for the
80 region fade. <kbd class="menu">Activate/Deactivate</kbd> enables and
81 disables the region fade.
85 Because each fade is also a crossfade, it has an inverse fade shape
86 for the audio beneath the fade. It is important to know how the
87 shapes differ, and which are most suitable for various editing tasks.
91 The different types of fades are:
94 <dl class="narrower-table">
95 <dt><kbd class="menu">Linear</kbd></dt>
96 <dd>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.</dd>
97 <dt><kbd class="menu">Constant Power</kbd></dt>
98 <dd>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.</dd>
99 <dt><kbd class="menu">Symmetric</kbd></dt>
100 <dd>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 two entire works of music together so that the transition is more gradual.</dd>
101 <dt><kbd class="menu">Fast</kbd></dt>
102 <dd>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.</dd>
103 <dt><kbd class="menu">Slow</kbd></dt>
104 <dd>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.</dd>
108 Although these fade shapes serve specific purposes, any of the shapes is usable in certain situations. The final decision is an artistic choice rather than a rigidly prescribed one.
112 These fade curves are developed to provide a range of common uses, and
113 are developed with the least possible amount of changes in the "slope"
114 of the line. This provides artifact-free crossfades. Some
115 DAWs provide complicated fade editors with parametric "spline" controls
116 of the fade curves. While it might be interesting to develop a
117 fade curve with a faster cutoff, the mathematical difference between
118 this and simply shortening the fade is vanishingly small; the
119 amount of effort to shorten the fade is much easier than fooling around with a
120 crossfade editor dialog.