Use CoreAudio with Ruby to make a real time CLI level meter and frequency response chart

audio.rb

require "thread"
require "fftw3"
require "coreaudio"
require 'ruby-progressbar'

# progressbar = ProgressBar.create
# progressbar.total = 100

Thread.abort_on_exception = true

BUF_SIZE=1024*4

inbuf = CoreAudio.default_input_device.input_buffer(BUF_SIZE)
PEAK = 65535.0

@mutex = Mutex.new
@db = nil
@f  = nil
run = true
th = Thread.start do
  loop do
    wav = inbuf.read(BUF_SIZE)
    amp = wav.abs.max.to_f
    @mutex.synchronize do
      @db = 20 * Math.log(amp / PEAK)
      @f = FFTW3.fft(wav, 1).abs/wav.length
    end
  end
end

inbuf.start
Signal.trap("SIGINT") { run = false}
sleep 1
while run
  db = nil
  f  = nil
  
  @mutex.synchronize do
    db = @db
    f = @f
  end
  system("clear")
  print "#{db.to_i} dB |"
  (db.to_i + 100).times { print "=" }
  puts
  puts "frequency:"
  freq = f.to_a.map(&:first)[0...300].map{|i| i.to_i }
  freq.each_with_index{|i, idx| puts(("%3d |"%idx)+("D"*[360,i].min)) if idx % 2 == 0 }
  puts freq.length
  sleep 0.1
end


inbuf.stop
th.kill.join
#
#
#
puts "#{inbuf.dropped_frame} frame dropped at input buffer."