Matlab script to equalize a song.

equalizer.matlab

#! /usr/bin/octave -qf 

pkg load signal
% read the file name
fprintf('\n\nInitializing equalizer ...\n');
% setting default values for Equalizer
Equalizer.type = 'Custom';
Equalizer.amps  = [7 7 2 0.25 0];
Equalizer.freqs = [100 500 1000 5000 10000];

varargin = argv();
wav_file_name = varargin{1};

% parse command line arguments
if nargin == 4
	saving_file_name = varargin{2};
	amps = strsplit(varargin{3},':');
	freqs = strsplit(varargin{4},':');

	for i=1:length(amps)
		Equalizer.amps(i) = str2num(cell2mat(amps(1,i)));
		Equalizer.freqs(i) = str2num(cell2mat(freqs(1,i)));
	end

elseif nargin == 3
	saving_file_name = varargin{2};
	Equalizer.type = varargin{3};

	if length(Equalizer.type) == 2
	
		if Equalizer.type == 'XB'
			Equalizer.amps = [8 8 6 5 5];
		elseif Equalizer.type == 'BP'
			Equalizer.amps = [7 8 5 6 7];
		elseif Equalizer.type == 'BL'
			Equalizer.amps = [5 5 5 5 5];
		elseif Equalizer.type == 'BT'
			Equalizer.amps = [5 5 6 7 8];
		elseif Equalizer.type == 'VL'
			Equalizer.amps = [5 5 6 7 6];
		end 

	else
		cells = strsplit(varargin{3},':');
		Equalizer.type = 'Custom';
		if length(cells) ~= 5
			fprintf('Invalid option for equalizer.Must be one of the following. ');
			fprintf('\n\tXB --> eXtreme Bass');
			fprintf('\n\tBP --> Bass Punch');
			fprintf('\n\tBL --> BaLanced');
			fprintf('\n\tBT --> Brilliant Treble');
			fprintf('\n\tVL --> Vocalizer\n');
			exit
		end

		for i=1:length(cells)
			Equalizer.amps(i) = str2num(cell2mat(cells(1,i)));
		end
	end

elseif nargin == 2
	saving_file_name = varargin{2};
else
	saving_file_name = 'out.wav';
end

% change the scale from dB to ratio of intensities
Equalizer.amps = 10 .^ ((Equalizer.amps - 1)/4) / 10;

% compute file size and sampling rate 
[siz, channels] = wavread(wav_file_name,'size');
[_, Fs, nbits] = wavread(wav_file_name,1);

% set equalization time duration
window_time_duration = 2000 ;%milliseconds

window_length =  window_time_duration / 1000 * Fs;
num_frames = floor(siz / window_length);

% compute equalization amplitudes
amplitudes = ones(Equalizer.freqs(1),1) * Equalizer.amps(1);

for i=2:length(Equalizer.freqs)

	bandwidth = Equalizer.freqs(i) - Equalizer.freqs(i-1) - 1;
	step = (Equalizer.amps(i) - Equalizer.amps(i-1)) / bandwidth; 
	
	amps = [Equalizer.amps(i-1): step : Equalizer.amps(i)];
	amplitudes = [amplitudes ; amps'];
end
if (window_length > length(amplitudes))
	amps = ones(window_length - length(amplitudes),1) * Equalizer.amps(end) ;
	amplitudes = [amplitudes ; amps];
else
	amplitudes = amplitudes(1:window_length);
end

%[amplitudes , [1:length(amplitudes)]']; % just for debugging

amplitudes = amplitudes * ones(1,channels);

%amplitudes(1:20,:) = zeros(size(amplitudes(1:20,:))); % ingnore 0-20Hz

half_amplitudes = amplitudes(1:ceil(length(amplitudes) / 2),:)';
amplitudes = [half_amplitudes'; fliplr(half_amplitudes)'];

% equalize the song window by window
equalized_song = [];
equalized_song2 = [];
dump = [];
dump2 = [];

fprintf('Equalizer settings: %s\n', Equalizer.type)
fprintf('\tFrequency | Amplitude\n')
fprintf('\t----------+-----------\n');
for i=1:length(Equalizer.freqs);
	fprintf('\t%d\t  |\t%.2f\n', Equalizer.freqs(i), Equalizer.amps(i) );
end
fprintf('\nEqualizing song %s ...\n', wav_file_name);

for i=0:num_frames-2
	% print progress
	fprintf('\tProgress %d / %d [%.2f%%]\r', ...
		i, num_frames-2, 100 * i / (num_frames-2)); 

	% extract the window
	window_start = round(i*window_length + 1);
	window_stop = round((i+1) * window_length);
	window = wavread(wav_file_name,[window_start window_stop]);
	window2 = wavread(wav_file_name,[window_start + window_length / 2 , ...
		window_stop + window_length / 2]);
	% compute fft of the window
	FFT = fft(window);
	FFT2 = fft(window2);

	% equalize the frame
	FFT = FFT .* amplitudes;
	FFT2 = FFT2 .* amplitudes;

	% compute amplified window
	equalized_window = ifft(FFT);
	equalized_window2 = ifft(FFT2);

	equalized_song = [equalized_song ; equalized_window];
	equalized_song2 = [equalized_song2; equalized_window2];

	% dump once every 20 frames, to optimize concatenation 
	if mod(i, 20) == 0 && i ~= 0
		dump = [dump; equalized_song];
		dump2 = [dump2; equalized_song2];
		equalized_song = [];
		equalized_song2 = [];
	end 

end

%dump rest of the song
dump = [dump; equalized_song];
dump2 = [dump2; equalized_song2];

equalized_song = dump;
equalized_song2 = dump2;

fprintf('\nRemoving abrupt changes in audio,\n');
fprintf('by Triangular filter ...\n');

step = 2 / window_length; 
sawtooth = repmat([[0:step:1]' ; [1:-step:0]'],1,channels);
sawtooth2 = repmat([[1:-step:0]' ; [0:step:1]'],1,channels);
start_ = 1;

equalized_song = [ equalized_song ; 
				   zeros(window_length / 2, channels) ];
equalized_song2 = [ zeros(window_length / 2,channels); 
					equalized_song2 ];


for i=1:num_frames-1

	fprintf('\tProgress %d / %d [%.2f%%]\r', ...
		i-1, num_frames-2, 100 * (i-1) / (num_frames-2));

	stop_ = start_ + length(sawtooth) - 1;
	equalized_song(start_:stop_,:) = equalized_song(start_:stop_,:) .* sawtooth;
	equalized_song2(start_:stop_,:) = equalized_song2(start_:stop_,:) ...
		.* sawtooth2;
	start_ = start_ + length(sawtooth);

end 

fprintf('\nMultiplexing audio streams ...\n');
merged_song = equalized_song + equalized_song2;

%save the song
fprintf('Saving song as %s ...\n', saving_file_name);
wavwrite(merged_song, Fs, nbits, saving_file_name);
fprintf('Done\n\n');