ASCII equalizer.

ascii_eq.rb

require 'ffi'

module FFI::PortAudio
  module API
    extend FFI::Library

    ffi_lib 'portaudio'

    Int16 = 0x8
    FramesPerBufferUnspecified = 0

    class PaStreamParameters < FFI::Struct
      layout(
        :device, :int,
        :channelCount, :int,
        :sampleFormat, :ulong,
        :suggestedLatency, :double,
        :hostApiSpecificStreamInfo, :pointer)
    end

    callback :PaStreamCallback, [:pointer, :pointer, :ulong, :pointer, :ulong, :pointer], :int

    attach_function :Pa_Initialize, [], :int
    attach_function :Pa_Terminate, [], :int
    attach_function :Pa_GetDefaultInputDevice, [], :int
    attach_function :Pa_OpenStream, [:pointer, :pointer, :pointer, :double, :ulong, :ulong, :PaStreamCallback, :pointer], :int
    attach_function :Pa_CloseStream, [:pointer], :int
    attach_function :Pa_StartStream, [:pointer], :int
    attach_function :Pa_StopStream, [:pointer], :int
    attach_function :Pa_Sleep, [:long], :void
  end
end

include FFI::PortAudio

API.Pa_Initialize

input = API::PaStreamParameters.new

input[:device] = API.Pa_GetDefaultInputDevice
input[:channelCount] = 1
input[:sampleFormat] = API::Int16

maxmin = [nil, nil]

callback = lambda {|input, _, frameCount, _, _, _|
  v = input.read_array_of_int16(frameCount).inject(0){|r, i| r + i.abs }

  maxmin = [
    [maxmin[0] || v, v].max,
    [maxmin[1] || v, v].min
  ]
  max, min = maxmin
  v = (max - min) == 0 ? 1 : (v - min).quo(max - min)
  print "¥e[#{31 + (6 * v).to_i}m"
  puts "*" * (v * 80).to_i
}

stream = FFI::Buffer.new(:pointer)
API.Pa_OpenStream(stream, input, nil, 44100, 700, 0, callback, nil)

API.Pa_StartStream stream.read_pointer

at_exit do
  API.Pa_CloseStream(stream)
  API.Pa_Terminate
end

loop { sleep 1 }