45 lines
1.2 KiB
Python
45 lines
1.2 KiB
Python
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def f_accel_decel(t, old_d, new_d, abruptness=1, soonness=1.0):
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"""
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abruptness
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negative abruptness (>-1): speed up down up
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zero abruptness : no effect
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positive abruptness: speed down up down
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soonness
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for positive abruptness, determines how soon the
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speedup occurs (0<soonness < inf)
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"""
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a = 1.0+abruptness
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def _f(t):
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f1 = lambda t: (0.5)**(1-a)*(t**a)
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f2 = lambda t: (1-f1(1-t))
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return (t<.5)*f1(t) + (t>=.5)*f2(t)
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return old_d*_f((t/new_d)**soonness)
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def accel_decel(clip, new_duration=None, abruptness=1.0, soonness=1.0):
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"""
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new_duration
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If None, will be that of the current clip.
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abruptness
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negative abruptness (>-1): speed up down up
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zero abruptness : no effect
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positive abruptness: speed down up down
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soonness
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for positive abruptness, determines how soon the
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speedup occurs (0<soonness < inf)
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"""
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if new_duration is None:
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new_duration = clip.duration
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fl = lambda t : f_accel_decel(t, clip.duration, new_duration,
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abruptness, soonness)
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return clip.fl_time(fl).set_duration(new_duration)
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