Create my audiobook, 88 chapters with 9 ingredients to each chapter, using Ruby + sox

audiobook.rb

#!/usr/bin/env ruby

# if limiting to one chapter, ./audiobook.rb 05
LIMIT = (ARGV[0] =~ /\A[0-9][0-9]\Z/) ? ARGV[0] : false

BASE = Dir.pwd + '/'
NUMS = BASE + 'ChapterNums/'
DRUM = BASE + 'DrumFills/'
GUIT = BASE + 'GuitarChords/'
URLS = BASE + 'URLs/'
TALK = BASE + 'YourMusicAndPeople/clean/'
TEMP = BASE + 'tmp/'
OUT  = BASE + 'out/'

def seconds(filename)
  %x(soxi -D #{filename}).to_f
end

def pad(filename, seconds, outfile)
  fullout = OUT + outfile + '.wav'
  %x(sox #{filename} #{fullout} pad #{seconds} 0)
  fullout
end

drum_in = 'drumch-37.wav'
drum_x = 'drumch-48.wav'
drum_out = 'drumch-80.wav'
File.readlines('ymap.txt').each do |line|
  title, body, guitar, chapter_n, url = line.strip.split("\t")
  next if (LIMIT && LIMIT != title[0,2])
  puts body

  # start with the drum
  pad(DRUM + drum_in, 0, 'drum_in')

  # guitar comes in at final drum hit
  pad(GUIT + guitar, 0.8, 'guitar_in')

  # chapter number at set time
  nu = pad(NUMS + chapter_n, 2.3, 'chapter_n')

  # title after chapter
  nu = pad(TALK + title, seconds(nu) + 0.7, 'title')

  # drum_x after title
  nu = pad(DRUM + drum_x, seconds(nu) + 0.5, 'drum_x')

  # body after drum_x
  nu = pad(TALK + body, seconds(nu) - 1, 'body')

  # url after body
  nu = pad(URLS + url, seconds(nu) + 1, 'url')

  # reverse guitar : ends after url
  rguit = TEMP + guitar
  %x(sox #{GUIT + guitar} #{rguit} reverse)
  nu = pad(rguit, (seconds(nu) - seconds(rguit)) + 2, 'guitar_out')
  %x(rm #{rguit})

  # final drum ends at same time as reverse guitar
  pad(DRUM + drum_out, (seconds(nu) - seconds(DRUM + drum_out)) + 2.2, 'drum_out')

  # move it all to a subdir
  subdir = OUT + title[0,2]
  %x(mkdir -p #{subdir})
  %x(mv #{OUT + '*.wav'} #{subdir + '/'})
end