Le dimanche 20 septembre 2009 10:30:07, David Baelde a écrit :
> Hi,
Hi !
> The smart_cross() operator takes a transition function of type (float,
> float, [(string*string)], [(string*string)], source, source)->source).
> This means that it is of the form fun (v1,v2,m1,m2,s1,s2) -> ... where
> v1/v2 are the volumes before/after the track change, m1/m2 the
> metadata before/after the track change, and s1/s2 the source
> before/after the change.
>
> So, you can read the metadata attached to the next track using for
> example m2["cross"]=="no".
Just to add more details. If you want an example of the use of a function for
smart_cross, you can look for the definition of smart_crossfading in utils.liq.
Now, if you want a metadata to prevent any transition, you could do:
def smart_crossfade (~start_next=5.,~fade_in=3.,~fade_out=3.,
~default=(fun (a,b) -> sequence([a, b])),
~high=-15., ~medium=-32., ~margin=4.,
~width=2.,~conservative=false,s)
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 mb["cross"]=="no" # <<<<<<<<<<<<<<<<<<<<<<<<<
# no transitions # <<<<<<<<<<<<<<<<<<<<<<<<<
then # <<<<<<<<<<<<<<<<<<<<<<<<<
sequence([a, b]) # <<<<<<<<<<<<<<<<<<<<<<<<<
elsif
# If A and B are not too loud and close, fully cross-fade them.
a <= medium and b <= medium and abs(a - b) <= margin
then
log("Old <= medium, new <= medium and |old-new| <= margin.")
log("Old and new source are not too loud and close.")
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("new >= old + margin, old >= medium and new <= high.")
log("New source is significantly louder than old one.")
log("Transition: crossed, fade-out.")
add(fade.out(sa),sb)
elsif
# Opposite as the previous one.
a >= b + margin and b >= medium and a <= high
then
log("old >= new + margin, new >= medium and old <= high")
log("Old source is significantly louder than new one.")
log("Transition: crossed, fade-in.")
add(sa,fade.in(sb))
elsif
# Do not fade if it's already very low.
b >= a + margin and a <= medium and b <= high
then
log("new >= old + margin, old <= medium and new <= high.")
log("Do not fade if it's already very low.")
log("Transition: crossed, no fade.")
add(sa,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: using default.")
default(sa, sb)
end
end
smart_cross(width=width, duration=start_next, conservative=conservative,
transition,s)
end
Not tested by it should work...
Romain
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