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