From bbd2a006152cce4e5fa28bb2793d239ebdfdb491 Mon Sep 17 00:00:00 2001
From: Eric Wong <normalperson@yhbt.net>
Date: Sun, 13 Oct 2013 08:54:05 +0000
Subject: trimfx: initial bits

This will allow editing individual portions of audio of
a larger file while creating cross fade effects to join
them.
---
 examples/trimfx.sample.yml | 30 +++++++++++++++++++++
 lib/dtas/trimfx.rb         | 67 ++++++++++++++++++++++++++++++++++++++++++++++
 test/test_trimfx.rb        | 35 ++++++++++++++++++++++++
 3 files changed, 132 insertions(+)
 create mode 100644 examples/trimfx.sample.yml
 create mode 100644 lib/dtas/trimfx.rb
 create mode 100644 test/test_trimfx.rb

diff --git a/examples/trimfx.sample.yml b/examples/trimfx.sample.yml
new file mode 100644
index 0000000..e205b03
--- /dev/null
+++ b/examples/trimfx.sample.yml
@@ -0,0 +1,30 @@
+# To the extent possible under law, Eric Wong has waived all copyright and
+# related or neighboring rights to this example.
+# Note: be sure to update test/test_trimfx.rb if you change this,
+# test_trimfx.rb relies on this.
+---
+infile: foo.flac
+env:
+  PATH: $PATH
+  SOX_OPTS: $SOX_OPTS -R
+  I2: second.flac
+  I3: third.flac
+comments:
+  ARTIST: John Smith
+  ALBUM: Hello World
+  YEAR: 2013
+track_start: 1
+effects:
+# the fade parameter sets the default fade for every subsequent effect
+- fade=t1,t1;t1,t1 # fade-out-orig,fade-in-new;fade-out-orig;fade-in-new
+
+# the following commands are equivalent
+- trim 52 =53 sh sox $SOXIN $SOXOUT $TRIMFX vol -6dB $FADEFX
+- trim 52 1 sox vol -6dB # shorthand
+
+# as are the following (for little endian machines)
+- trim 52 1 eca -eadb:-6
+- trim 52 1 sh sox $SOXIN $SOX2ECA $TRIMFX | ecasound $ECAFMT
+  -i stdin -o stdout -eadb:-6 | sox $ECA2SOX - $SOXOUT $FADEFX
+# SOX2ECA='-tf32 -c$CHANNELS -r$RATE'
+# ECAFMT='-f32_le,$CHANNELS,$RATE
diff --git a/lib/dtas/trimfx.rb b/lib/dtas/trimfx.rb
new file mode 100644
index 0000000..5cfac26
--- /dev/null
+++ b/lib/dtas/trimfx.rb
@@ -0,0 +1,67 @@
+# 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 'shellwords'
+
+class DTAS::TrimFX
+  attr_reader :tbeg
+  attr_reader :tlen
+
+  def initialize(args)
+    args = args.dup
+    case args.shift
+    when "trim"
+      parse_trim!(args)
+    when "all"
+      @tbeg = 0
+      @tlen = nil
+    else
+      raise ArgumentError, "#{args.inspect} not understood"
+    end
+  end
+
+  def to_sox_arg(format)
+    if @tbeg && @tlen
+      %W(trim #{@tbeg * format.rate}s #{@tlen * format.rate}s)
+    else
+      []
+    end
+  end
+
+  def parse_time(tbeg)
+    case tbeg
+    when /\A\d+\z/
+      tbeg.to_i
+    when /\A[\d\.]+\z/
+      tbeg.to_f
+    when /\A[:\d\.]+\z/
+      hhmmss = tbeg.dup
+      rv = hhmmss.sub!(/\.(\d+)\z/, "") ? "0.#$1".to_f : 0
+
+      # deal with HH:MM:SS
+      t = hhmmss.split(/:/)
+      raise ArgumentError, "Bad time format: #{hhmmss}" if t.size > 3
+
+      mult = 1
+      while part = t.pop
+        rv += part.to_i * mult
+        mult *= 60
+      end
+      rv
+    else
+      raise ArgumentError, "unparseable: #{tbeg.inspect}"
+    end
+  end
+
+  def parse_trim!(args)
+    tbeg = parse_time(args.shift)
+    tlen = args.shift
+    is_stop_time = tlen.sub!(/\A=/, "") ? true : false
+    tlen = parse_time(tlen)
+    if is_stop_time
+      tlen = tlen - tbeg
+    end
+    @tbeg = tbeg
+    @tlen = tlen
+  end
+end
diff --git a/test/test_trimfx.rb b/test/test_trimfx.rb
new file mode 100644
index 0000000..107946f
--- /dev/null
+++ b/test/test_trimfx.rb
@@ -0,0 +1,35 @@
+# 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 './test/helper'
+require 'dtas/trimfx'
+require 'yaml'
+
+class TestTrimFX < Testcase
+  def test_example
+    ex = YAML.load(File.read("examples/trimfx.sample.yml"))
+    effects = []
+    ex["effects"].each do |line|
+      words = Shellwords.split(line)
+      case words[0]
+      when "trim"
+        tfx = DTAS::TrimFX.new(words)
+        assert_equal 52.0, tfx.tbeg
+        assert_equal 1.0, tfx.tlen
+        effects << tfx
+      end
+    end
+    assert_equal 4, effects.size
+  end
+
+  def test_all
+    tfx = DTAS::TrimFX.new(%w(all))
+    assert_equal 0, tfx.tbeg
+    assert_nil tfx.tlen
+  end
+
+  def test_time
+    tfx = DTAS::TrimFX.new(%w(trim 2:30 3.1))
+    assert_equal 150, tfx.tbeg
+    assert_equal 3.1, tfx.tlen
+  end
+end
-- 
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