1 files changed, 32 insertions, 0 deletions
diff --git a/lib/dtas/fadefx.rb b/lib/dtas/fadefx.rb
new file mode 100644
index 0000000..7e0e65f
--- /dev/null
+++ b/lib/dtas/fadefx.rb
@@ -0,0 +1,32 @@
+# Copyright (C) 2013, Eric Wong <normalperson@yhbt.net> and all contributors
+# License: GPLv3 or later (https://www.gnu.org/licenses/gpl-3.0.txt)
+require_relative '../dtas'
+require_relative 'parse_time'
+
+class DTAS::FadeFX
+  include DTAS::ParseTime
+  attr_reader :out_prev, :in_main, :out_main, :in_next
+  F = Struct.new(:type, :len)
+
+  def initialize(args)
+    args =~ /\Afade=([^,]*),([^,]*);([^,]*),([^,]*)\z/ or
+      raise ArgumentError, "bad fade format"
+    fades = [ $1, $2, $3, $4 ]
+    %w(out_prev in_main out_main in_next).each do |iv|
+      instance_variable_set("@#{iv}", parse!(fades.shift))
+    end
+  end
+
+  # q - quarter of a sine wave
+  # h - half a sine wave
+  # t - linear (`triangular') slope
+  # l - logarithmic
+  # p - inverted parabola
+  # default is 't' (sox defaults to 'l', but triangular makes more sense
+  # when concatenating
+  def parse!(str)
+    type = "t"
+    str.sub!(/\A([a-z])/, "") and type = $1
+    F[type, parse_time(str)]
+  end
+end