Mute the audio of certain parts of a video with ffmpeg via Ruby CLI script

muteaudio.rb

require "optparse"
require "active_support/all"

options = []
input   = nil
output  = nil

has_two_timestamps= ->(arg) {
  if arg.split(",").count == 2
    nil
  else
    "Needs to have two timestamps (e.g. '01:46:48,01:48:46')"
  end
}

intervals_are_delimited_with_colons = ->(arg) {
  start_interval, end_interval = arg.split(",")
  if /\d{2}:\d{2}:\d{2}/.match?(start_interval.to_s) && /\d{2}:\d{2}:\d{2}/.match?(end_interval.to_s)
    nil
  else
    "Intervals must be separated by colons (e.g. 01:48:46')"
  end
}

intervals_have_proper_start_and_end = ->(arg) {
  # start should not be greater than end
  intervals = arg.split(",").map { |interval| interval.split(":") }
  start_interval = intervals[0] || []
  end_interval = intervals[1] || []

  start_in_seconds = (start_interval[0].to_i.hours + start_interval[1].to_i.minutes + start_interval[2].to_i.seconds).to_i
  end_in_seconds   = (end_interval[0].to_i.hours + end_interval[1].to_i.minutes + end_interval[2].to_i.seconds).to_i

  if start_in_seconds > end_in_seconds
    nil
  else
    "The end interval must be greater than the start interval"
  end
}

checks = [
  has_two_timestamps,
  intervals_are_delimited_with_colons,
  intervals_have_proper_start_and_end
]

option_parser = OptionParser.new do |opts|
  opts.on("-t", "--interval INTERVAL", "Specify time interval to be muted") do |t|
    # Check if interval is in the following format
    # 1:46:48,1:48:46
    errors = checks.map { |check| check.call(t) }.compact

    options << [t, errors]
  end

  opts.on("-i", "--input INPUT", "Name of the input file") do |i|
    if o.empty?
      fail "Input file must be provided"
    else
      input = i
    end
  end

  opts.on("-o", "--output OUTPUT", "Name of the output file") do |o|
    if o.empty?
      fail "Output file must be provided"
    else
      output = o
    end
  end
end

option_parser.parse!

# See if there are any errors
option_errors = options.select { |interval| _t, errors = interval; errors.any? }
option_errors << ["", ["An input file was not detected"]]  if input.nil?
option_errors << ["", ["An output file was not detected, you need to put an "]] if output.nil?

if option_errors.any?
  puts "\n\n"
  error_message = option_errors.inject("Some of the timestamps given were found to have the following errors:\n\n") do |message, interval|
    timestamp, errors = interval

    message << timestamp + "\n"
    message << errors.join("\n")
    message << "\n\n"

    message
  end

  puts error_message
else
  af = options.map do |set|
    timestamps, _errors = set
    start_time, end_time = timestamps.split(",").map { |timestamp| timestamp.split(":").map(&:to_i) }
    
    start_time_in_seconds = start_time[0].hours + start_time[1].minutes + start_time[2].seconds
    end_time_in_seconds   = end_time[0].hours + end_time[1].minutes + end_time[2].seconds

    "volume=enable='between(t,#{start_time_in_seconds},#{end_time_in_seconds})':volume=0"
  end.join(", ")

# ffmpeg -i 20170608004526_SHOWROOM_AKB48のオールナイトニッポン.flv -af "volume=enable='between(t,1720, 1852)':volume=0, volume=enable='between(t,5822,5940)':volume=0, volume=enable='between(t,6479,6597)':volume=0, volume=enable='between(t,7964,8088)':volume=0" -vcodec copy 20170608004526_SHOWROOM_AKB48のオ ールナイトニッポンmaster.mp4
  `ffmpeg -i #{input} -af "#{af}" -vcodec copy #{output}`
end