gistfile1.txt

#!/bin/env ruby

# Quick and dirty script to merge N small mp3 files in the current directory into files with duration ~30 minutes
# The power of Unix + the power of Ruby :)

# Question: how to reduce the number of used tools (mplayer, sox, and lame) ?

i = 1
threshold = 60 * 30

merge = lambda{|tuple|
  duration, list = tuple
  list = list.map{|f| "'#{f}'"}.join(' ')
  STDERR.puts "#{list} => out/#{i}.mp3 (#{duration} seconds, #{duration*10/60} minutes)"
  `sox #{list} -t wavpcm - | lame --silent - > out/#{i}.mp3`
  i += 1
}

merge.call Dir['*.mp3'].map{|fn|
  [fn, `mplayer -identify -ao null -vo null -frames 0 #{fn}  | grep ^ID_LENGTH= | cut -d = -f 2`.to_f] 
}.inject([0, []]){|memo, tuple|

  res = [memo[0] + tuple[1], memo[1] + [tuple[0]]]

  if res[0] > threshold
    merge.call res
    [0, []]
  else
    res
  end
}