76 lines
2.4 KiB
Plaintext
76 lines
2.4 KiB
Plaintext
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# Crossfade between tracks,
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# taking the respective volume levels
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# into account in the choice of the
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# transition.
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# @category Source / Track Processing
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# @param ~start_next Crossing duration, if any.
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# @param ~fade_in Fade-in duration, if any.
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# @param ~fade_out Fade-out duration, if any.
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# @param ~width Width of the volume analysis window.
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# @param ~conservative Always prepare for
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# a premature end-of-track.
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# @param s The input source.
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def smart_crossfade (~start_next=5.,~fade_in=3.,
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~fade_out=3., ~width=2.,
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~conservative=false,s)
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high = -20.
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medium = -32.
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margin = 4.
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fade.out = fade.out(type="sin",duration=fade_out)
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fade.in = fade.in(type="sin",duration=fade_in)
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add = fun (a,b) -> add(normalize=false,[b,a])
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log = log(label="smart_crossfade")
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def transition(a,b,ma,mb,sa,sb)
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list.iter(fun(x)->
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log(level=4,"Before: #{x}"),ma)
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list.iter(fun(x)->
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log(level=4,"After : #{x}"),mb)
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if
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# If A and B and not too loud and close,
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# fully cross-fade them.
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a <= medium and
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b <= medium and
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abs(a - b) <= margin
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then
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log("Transition: crossed, fade-in, fade-out.")
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add(fade.out(sa),fade.in(sb))
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elsif
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# If B is significantly louder than A,
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# only fade-out A.
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# We don't want to fade almost silent things,
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# ask for >medium.
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b >= a + margin and a >= medium and b <= high
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then
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log("Transition: crossed, fade-out.")
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add(fade.out(sa),sb)
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elsif
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# Do not fade if it's already very low.
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b >= a + margin and a <= medium and b <= high
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then
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log("Transition: crossed, no fade-out.")
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add(sa,sb)
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elsif
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# Opposite as the previous one.
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a >= b + margin and b >= medium and a <= high
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then
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log("Transition: crossed, fade-in.")
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add(sa,fade.in(sb))
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# What to do with a loud end and
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# a quiet beginning ?
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# A good idea is to use a jingle to separate
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# the two tracks, but that's another story.
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else
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# Otherwise, A and B are just too loud
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# to overlap nicely, or the difference
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# between them is too large and
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# overlapping would completely mask one
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# of them.
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log("No transition: just sequencing.")
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sequence([sa, sb])
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end
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end
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cross(width=width, duration=start_next,
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conservative=conservative,
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transition,s)
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end
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