Assemble m4a files into audio books

AssembleAudioBook.rb

require 'pp'
require 'fileutils'
require 'escape'

@TARGET = ARGV[0]
File.delete(@TARGET) if File.exists?(@TARGET)


def formatTime(dur)
    ms = ((dur.round(3) - dur.truncate())*1000).to_i
    totalss = dur.truncate().to_i
    ss = totalss.modulo(60)
    mm = (totalss.-(ss)/60).modulo(60)
    hh = (totalss/3600)
    "%02d:%02d:%02d.%03d" % [hh,mm,ss,ms]
end

def getLengthMP4(f)
  cmd = Escape.shell_command [ :mp4info , f]
  /(\d*.\d{3}) secs/ =~ `#{cmd}`
  $1.to_f
end

class Chapter
  def initialize(filepath)
    @filepath = filepath
    @length   = getLengthMP4(self.filepath)
    @offset   = @@offset 
    @@offset += @length
    @name     = self.name()
  end
  attr_reader :offset , :filepath
  def name
    @filepath.gsub( /.m..$/,'')
  end
  def formatted_offset
    formatTime(@offset)
  end
  def chapter_entry
    formatted_offset + ' ' + name
  end
end


def append
  0.step(@chlst.size-1,20) do |i|
     ubound = [i+19,@chlst.size-1].min
     iflag = i.upto(ubound).map do |j|
        [ '-cat', @chlst.at(j).filepath ]
     end.flatten
     cmda = [:mp4box, iflag].flatten
     cmda+=["-new"] if i < 20
     cmda+=[@TARGET]
     cmd = Escape.shell_command cmda
     p cmd
     puts `#{cmd}`
   end
end


def chapterFile
   chfilename = @TARGET.gsub(/\.m..$/i,'.chapters.txt')
   File.open(chfilename,'w+') do |cf| 
     cf.puts @chlst.map{ |f| f.chapter_entry }.*("\n")
   end
end

glob_pattern = '**/*.m4a'
@@offset     = 0.0
@chlst       = Dir.glob( glob_pattern ).sort.map{ |f| Chapter.new f}
pp @chlst
append
markChapters = Escape.shell_command [:mp4chaps,  "-i" , "-Q",  @TARGET]
chapterFile
puts `#{markChapters}`