flv_meta.rb

# parse the duration of a FLV file from the metadata
def duration(file_name)

  return -1 unless FileTest.exist?(file_name)

  metadata = File.open(file_name, 'rb') do |file|
    file.read(400) # bytes
  end
  
  offset = metadata =~ /duration/
  
  if offset
    start = offset + "duration".size + 1
    size = 8 # bytes
  
    buffer = metadata[start...(start + size)]
    seconds = buffer.unpack('G').first unless buffer.nil?
    "#{sprintf("%02i", seconds / 60)}:#{sprintf("%02i", seconds % 60)}" unless seconds.nil?
  end
    
end