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