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authMultimediaAssignment2018
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Apostolos Fanakis 6 years ago
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  1. 57
      Level_1/AACoder1.m
  2. BIN
      Level_1/LicorDeCalandraca.wav
  3. 82
      Level_1/SSC.m
  4. 19
      Level_1/demoAAC1.m
  5. 103
      Level_1/filterbank.m
  6. 30
      Level_1/iAACoder1.m
  7. 103
      Level_1/iFilterbank.m
  8. 61
      Level_1/imdct4.m
  9. 75
      Level_1/mdct4.m

57
Level_1/AACoder1.m
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function AACSeq1 = AACoder1(fNameIn)
%Implementation of WHAT?? //TODO!!
% Usage AACSeq1 = AACoder1(fNameIn), where:
% Inputs
% - fNameIn is the filename and path of the file to encode
%
% Output
% - AACSeq1 is an array of structs containing K structs, where K is
% the number of computed frames. Every struct of the array consists
% of a frameType, a winType, chl.frameF which are the MDCT
% coefficients of this frame's left channel, chr.frameF which are
% the MDCT coefficients of this frame's right channel
% Reads the audio file
[originalAudioData, ~] = audioread(fNameIn);
% Splits the audio in frames and determines the type of each frame
frameTypes{fix((length(originalAudioData) - 1025) / 1024)} = 'OLS';
frameTypes{1} = 'OLS';
for i = 1:length(frameTypes) - 2
nextFrameStart = (i + 1) * 1024 + 1;
nextFrameStop = nextFrameStart + 2047;
frameTypes{i+1} = SSC(1, originalAudioData(nextFrameStart:nextFrameStop, :), frameTypes{i});
end
% Assignes a type to the last frame
if strcmp(frameTypes{length(frameTypes) - 1}, 'LSS')
frameTypes{length(frameTypes)} = 'ESH';
elseif strcmp(frameTypes{length(frameTypes) - 1}, 'ESH')
frameTypes{length(frameTypes)} = 'ESH';
else
frameTypes{length(frameTypes)} = 'OLS';
end
AACSeq1(length(frameTypes)) = struct;
for i = 0:length(frameTypes)-1
currFrameStart = i * 1024 + 1;
currFrameStop = currFrameStart + 2047;
frameF = filterbank(originalAudioData(currFrameStart:currFrameStop, :), frameTypes{i+1}, 'SIN');
AACSeq1(i + 1).frameType = frameTypes(i + 1);
AACSeq1(i + 1).winType = 'KBD';
AACSeq1(i + 1).chl.frameF = frameF(:, 1);
AACSeq1(i + 1).chr.frameF = frameF(:, 2);
end
if true
[idx,label] = grp2idx(sort(frameTypes));
hist(idx,unique(idx));
set(gca,'xTickLabel',label)
sum(idx(:) == 1)
sum(idx(:) == 2)
sum(idx(:) == 3)
sum(idx(:) == 4)
end
end

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Level_1/LicorDeCalandraca.wav
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82
Level_1/SSC.m
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function frameType = SSC(~, nextFrameT, prevFrameType)
%Implementation of the SSC step
% Usage frameType = SSC(frameT, nextFrameT, prevFrameType), where:
% Inputs
% - frameT is a frame in the time domain, containing both channels of
% the audio stored in an array of dimensions 2048X2
% - nextFrameT is the next frame in the time domain, containing both
% channels of the audio stored in an array of dimensions 2048X2
% - prevFrameType is the type of the previous frame in string
% representation, can be one of "OLS" (ONLY_LONG_SEQUENCE), "LSS"
% (LONG_START_SEQUENCE), "ESH" (EIGHT_SHORT_SEQUENCE), "LPS"
% (LONG_STOP_SEQUENCE)
%
% Output
% - frameType is the type of the current frame in string
% representation, can be one of "OLS" (ONLY_LONG_SEQUENCE), "LSS"
% (LONG_START_SEQUENCE), "ESH" (EIGHT_SHORT_SEQUENCE), "LPS"
% (LONG_STOP_SEQUENCE)
% Examines the cases where the determination of the type of the next
% frame isn't needed for
if strcmp(prevFrameType, 'LSS')
frameType = 'ESH';
return;
elseif strcmp(prevFrameType, 'LPS')
frameType = 'OLS';
return;
end
% Determines the type of the next frame
% Filters frame
nextFrameT = filter([0.7548, -0.7548], [1, -0.5095], nextFrameT, [], 2);
channelFrameType = {'OLS', 'OLS'};
for channel = 1:2
% Calculates sub-frame energy estimation
[subFrames, ~] = buffer(nextFrameT(449:end-448, channel), 256, 128, 'nodelay');
energyEstimations = sum(subFrames.^2, 1);
% Calculates the ratio of the sub-frame energy to the average energy of
% the previous sub-frames
nextIsESH = 0;
for subFrameIndex = 1:8
energyRatio = energyEstimations(subFrameIndex) / ...
mean(energyEstimations(1:subFrameIndex-1));
if (energyEstimations(subFrameIndex) > 10^(-3)) && (energyRatio > 10)
nextIsESH = 1;
break;
end
end
if nextIsESH == 1
if strcmp(prevFrameType, 'ESH')
% This frame of this channel is an EIGHT_SHORT_SEQUENCE type
% frame. This means the frames of both channels will be encoded
% as EIGHT_SHORT_SEQUENCE type frames.
frameType = 'ESH';
return;
elseif strcmp(prevFrameType, 'OLS')
channelFrameType{channel} = 'LSS';
end
else
if strcmp(prevFrameType, 'ESH')
channelFrameType{channel} = 'LPS';
elseif strcmp(prevFrameType, 'OLS')
channelFrameType{channel} = 'OLS';
end
end
end
if strcmp(channelFrameType{1}, 'OLS')
frameType = channelFrameType{2};
elseif strcmp(channelFrameType{2}, 'OLS')
frameType = channelFrameType{1};
elseif strcmp(channelFrameType{1}, channelFrameType{2})
frameType = channelFrameType{1};
else
frameType = 'ESH';
end
end

19
Level_1/demoAAC1.m
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function SNR = demoAAC1(fNameIn, fNameOut)
%Implementation of WHAT?? //TODO!!
% Usage SNR = demoAAC1(fNameIn, fNameOut), where:
% Inputs
% - fNameIn is the filename and path of the file to encode
% - fNameOut is the filename and path of the file that will be
% written after decoding
%
% Output
% - SNR is the signal to noise ration computed after successively
% encoding and decoding the audio signal
AACSeq1 = AACoder1(fNameIn);
decodedAudio = iAACoder1(AACSeq1, fNameOut);
[audioData, ~] = audioread(fNameIn);
SNR = sum(10*log10((sum(audioData(1:length(decodedAudio), :)) .^ 2)./ ...
(sum(audioData(1:length(decodedAudio), :) - decodedAudio) .^ 2)));
end

103
Level_1/filterbank.m
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function frameF = filterbank(frameT, frameType, winType)
%Implementation of the Filter Bank step
% Usage frameF = filterbank(frameT, frameType, winType), where:
% Inputs
% - frameT is a frame in the time domain, containing both channels of
% the audio stored in an array of dimensions 2048X2
% - frameType is the type of the current frame in string
% representation, can be one of "OLS" (ONLY_LONG_SEQUENCE), "LSS"
% (LONG_START_SEQUENCE), "ESH" (EIGHT_SHORT_SEQUENCE), "LPS"
% (LONG_STOP_SEQUENCE)
% - winType is the type of the window selected, can be one of "KBD",
% "SIN"
%
% Output
% - frameF is the frame in the frequency domain, in MDCT coefficients
% representation containing both channels of the audio stored in an
% array of dimensions 1024X2
% Declares persistent windows variables and initializes if empty
persistent kaiserWindowLong kaiserWindowShort sinWindowLong sinWindowShort;
if isempty(kaiserWindowLong) || isempty(kaiserWindowShort) || ...
isempty(sinWindowLong) || isempty(sinWindowShort)
kaiserLong = kaiser(1024, 6*pi);
kaiserSumLong = sum(kaiserLong);
kaiserShort = kaiser(128, 4*pi);
kaiserSumShort = sum(kaiserShort);
for n = 1:1024
kaiserWindowLong(n) = sqrt(sum(kaiserLong(1:n))/kaiserSumLong);
kaiserWindowLong(1024 + n) = sqrt(sum(kaiserLong(1:end-n+1))/kaiserSumLong);
sinWindowLong(n) = sin(pi*(n + 0.5)/2048);
sinWindowLong(1024 + n) = sin(pi*(1024 + n + 0.5)/2048);
end
for n = 1:128
kaiserWindowShort(n) = sqrt(sum(kaiserShort(1:n))/kaiserSumShort);
kaiserWindowShort(128 + n) = sqrt(sum(kaiserShort(1:end-n+1))/kaiserSumShort);
sinWindowShort(n) = sin(pi*(n + 0.5)/256);
sinWindowShort(128 + n) = sin(pi*(128 + n + 0.5)/256);
end
end
frameF(1024, 2) = 0;
% Applies appropriate window to the frame
for channel=1:2
if strcmp(frameType, 'OLS')
if strcmp(winType, 'KBD')
frameT(:, channel) = frameT(:, channel) .* kaiserWindowLong(:);
elseif strcmp(winType, 'SIN')
frameT(:, channel) = frameT(:, channel) .* sinWindowLong(:);
else
error('filterbank, l[20]: Unsupported window type input!')
end
frameF = mdct4(frameT);
elseif strcmp(frameType, 'LSS')
if strcmp(winType, 'KBD')
frameT(1:1024, channel) = frameT(1:1024, channel) .* kaiserWindowLong(1:1024)';
frameT(1473:1600, channel) = frameT(1473:1600, channel) .* kaiserWindowShort(129:end)';
frameT(1601:end, channel) = 0;
elseif strcmp(winType, 'SIN')
frameT(1:1024, channel) = frameT(1:1024, channel) .* sinWindowLong(1:1024)';
frameT(1473:1600, channel) = frameT(1473:1600, channel) .* sinWindowShort(129:end)';
frameT(1601:end, channel) = 0;
else
error('filterbank, l[20]: Unsupported window type input!')
end
frameF = mdct4(frameT);
elseif strcmp(frameType, 'LPS')
if strcmp(winType, 'KBD')
frameT(1:448, channel) = 0;
frameT(449:576, channel) = frameT(449:576, channel) .* kaiserWindowShort(1:128)';
frameT(1025:end, channel) = frameT(1025:end, channel) .* kaiserWindowLong(1025:end)';
elseif strcmp(winType, 'SIN')
frameT(1:448, channel) = 0;
frameT(449:576, channel) = frameT(449:576, channel) .* sinWindowShort(1:128)';
frameT(1025:end, channel) = frameT(1025:end, channel) .* sinWindowLong(1025:end)';
else
error('filterbank, l[20]: Unsupported window type input!')
end
frameF = mdct4(frameT);
elseif strcmp(frameType, 'ESH')
% Splits the frame into sub-frames
[subFrames, ~] = buffer(frameT(449:end-448, channel), 256, 128, 'nodelay');
if strcmp(winType, 'KBD')
subFrames = subFrames .* repmat(kaiserWindowShort', [1 8]);
elseif strcmp(winType, 'SIN')
subFrames = subFrames .* repmat(sinWindowShort', [1 8]);
end
for subFrameIndex = 1:8
frameF((subFrameIndex - 1) * 128 + 1:subFrameIndex * 128, channel) = mdct4(subFrames(:, subFrameIndex));
end
end
end
end

30
Level_1/iAACoder1.m
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function x = iAACoder1(AACSeq1, fNameOut)
%Implementation of WHAT?? //TODO!!
% Usage x = iAACoder1(AACSeq1, fNameOut), where:
% Inputs
% - fNameOut is the filename and path of the file that will be
% written after decoding
% - AACSeq1 is an array of structs containing K structs, where K is
% the number of computed frames. Every struct of the array consists
% of a frameType, a winType, chl.frameF which are the MDCT
% coefficients of this frame's left channel, chr.frameF which are
% the MDCT coefficients of this frame's right channel
%
% Output
% - x is an array containing the decoded audio samples
decodedAudio(1024 * (length(AACSeq1) + 1), 2) = 0;
frameF(1024, 2) = 0;
for i = 0:length(AACSeq1)-1
currFrameStart = i * 1024 + 1;
currFrameStop = currFrameStart + 2047;
frameF(:, 1) = AACSeq1(i+1).chl.frameF;
frameF(:, 2) = AACSeq1(i+1).chr.frameF;
frameT = iFilterbank(frameF, AACSeq1(i+1).frameType, AACSeq1(i+1).winType);
decodedAudio(currFrameStart:currFrameStop, :) = decodedAudio(currFrameStart:currFrameStop, :) + frameT;
end
audiowrite(fNameOut, decodedAudio, 48000);
x = decodedAudio;
end

103
Level_1/iFilterbank.m
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function frameT = iFilterbank(frameF, frameType, winType)
%Implementation of the Inverse Filter Bank step
% Usage frameT = iFilterbank(frameF, frameType, winType), where:
% Inputs
% - frameF is the frame in the frequency domain, in MDCT coefficients
% representation containing both channels of the audio stored in an
% array of dimensions 1024X2
% - frameType is the type of the current frame in string
% representation, can be one of "OLS" (ONLY_LONG_SEQUENCE), "LSS"
% (LONG_START_SEQUENCE), "ESH" (EIGHT_SHORT_SEQUENCE), "LPS"
% (LONG_STOP_SEQUENCE)
% - winType is the type of the window selected, can be one of "KBD",
% "SIN"
%
% Output
% - frameT is a frame in the time domain, containing both channels of
% the audio stored in an array of dimensions 2048X2
% Declares persistent windows variables and initializes if empty
persistent kaiserWindowLong kaiserWindowShort sinWindowLong sinWindowShort;
if isempty(kaiserWindowLong) || isempty(kaiserWindowShort) || ...
isempty(sinWindowLong) || isempty(sinWindowShort)
kaiserLong = kaiser(1024, 6*pi);
kaiserSumLong = sum(kaiserLong);
kaiserShort = kaiser(128, 4*pi);
kaiserSumShort = sum(kaiserShort);
for n = 1:1024
kaiserWindowLong(n) = sqrt(sum(kaiserLong(1:n))/kaiserSumLong);
kaiserWindowLong(1024 + n) = sqrt(sum(kaiserLong(1:end-n+1))/kaiserSumLong);
sinWindowLong(n) = sin(pi*(n + 0.5)/2048);
sinWindowLong(1024 + n) = sin(pi*(1024 + n + 0.5)/2048);
end
for n = 1:128
kaiserWindowShort(n) = sqrt(sum(kaiserShort(1:n))/kaiserSumShort);
kaiserWindowShort(128 + n) = sqrt(sum(kaiserShort(1:end-n+1))/kaiserSumShort);
sinWindowShort(n) = sin(pi*(n + 0.5)/256);
sinWindowShort(128 + n) = sin(pi*(128 + n + 0.5)/256);
end
end
frameT(2048, 2) = 0;
% Applies appropriate window to the frame
for channel=1:2
if strcmp(frameType, 'OLS')
frameT = imdct4(frameF);
if strcmp(winType, 'KBD')
frameT(:, channel) = frameT(:, channel) .* kaiserWindowLong(:);
elseif strcmp(winType, 'SIN')
frameT(:, channel) = frameT(:, channel) .* sinWindowLong(:);
else
error('filterbank, l[20]: Unsupported window type input!')
end
elseif strcmp(frameType, 'LSS')
frameT = imdct4(frameF);
if strcmp(winType, 'KBD')
frameT(1:1024, channel) = frameT(1:1024, channel) .* kaiserWindowLong(1:1024)';
frameT(1473:1600, channel) = frameT(1473:1600, channel) .* kaiserWindowShort(129:end)';
frameT(1601:end, channel) = 0;
elseif strcmp(winType, 'SIN')
frameT(1:1024, channel) = frameT(1:1024, channel) .* sinWindowLong(1:1024)';
frameT(1473:1600, channel) = frameT(1473:1600, channel) .* sinWindowShort(129:end)';
frameT(1601:end, channel) = 0;
else
error('filterbank, l[20]: Unsupported window type input!')
end
elseif strcmp(frameType, 'LPS')
frameT = imdct4(frameF);
if strcmp(winType, 'KBD')
frameT(1:448, channel) = 0;
frameT(449:576, channel) = frameT(449:576, channel) .* kaiserWindowShort(1:128)';
frameT(1025:end, channel) = frameT(1025:end, channel) .* kaiserWindowLong(1025:end)';
elseif strcmp(winType, 'SIN')
frameT(1:448, channel) = 0;
frameT(449:576, channel) = frameT(449:576, channel) .* sinWindowShort(1:128)';
frameT(1025:end, channel) = frameT(1025:end, channel) .* sinWindowLong(1025:end)';
else
error('filterbank, l[20]: Unsupported window type input!')
end
elseif strcmp(frameType, 'ESH')
for subFrameIndex = 1:8
subFrame = imdct4(frameF((subFrameIndex - 1) * 128 + 1:subFrameIndex * 128, channel));
if strcmp(winType, 'KBD')
subFrame = subFrame .* kaiserWindowShort';
elseif strcmp(winType, 'SIN')
subFrame = subFrame .* sinWindowShort';
end
frameT(449 + (subFrameIndex - 1) * 128 + 1:449 + (subFrameIndex + 1) * 128) = ...
frameT(449 + (subFrameIndex - 1) * 128 + 1:449 + (subFrameIndex + 1) * 128) + subFrame';
end
end
end
end

61
Level_1/imdct4.m
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function y = imdct4(x)
% IMDCT4 Calculates the Modified Discrete Cosine Transform
% y = imdct4(x)
%
% x: input signal (can be either a column or frame per column)
% y: IMDCT of x
%
% Vectorize ! ! !
% ------- imdct4.m -----------------------------------------
% Marios Athineos, marios@ee.columbia.edu
% http://www.ee.columbia.edu/~marios/
% Copyright (c) 2002 by Columbia University.
% All rights reserved.
% ----------------------------------------------------------
[flen,fnum] = size(x);
% Make column if it's a single row
if (flen==1)
x = x(:);
flen = fnum;
fnum = 1;
end
% We need these for furmulas below
N = flen;
M = N/2;
twoN = 2*N;
sqrtN = sqrt(twoN);
% We need this twice so keep it around
t = (0:(M-1)).';
w = diag(sparse(exp(-j*2*pi*(t+1/8)/twoN)));
% Pre-twiddle
t = (0:(M-1)).';
c = x(2*t+1,:) + j*x(N-1-2*t+1,:);
c = (0.5*w)*c;
% FFT for N/2 points only !!!
c = fft(c,M);
% Post-twiddle
c = ((8/sqrtN)*w)*c;
% Preallocate rotation matrix
rot = zeros(twoN,fnum);
% Sort
t = (0:(M-1)).';
rot(2*t+1,:) = real(c(t+1,:));
rot(N+2*t+1,:) = imag(c(t+1,:));
t = (1:2:(twoN-1)).';
rot(t+1,:) = -rot(twoN-1-t+1,:);
% Shift
t = (0:(3*M-1)).';
y(t+1,:) = rot(t+M+1,:);
t = (3*M:(twoN-1)).';
y(t+1,:) = -rot(t-3*M+1,:);

75
Level_1/mdct4.m
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function y = mdct4(x)
% MDCT4 Calculates the Modified Discrete Cosine Transform
% y = mdct4(x)
%
% Use either a Sine or a Kaiser-Bessel Derived window (KBDWin)with
% 50% overlap for perfect TDAC reconstruction.
% Remember that MDCT coefs are symmetric: y(k)=-y(N-k-1) so the full
% matrix (N) of coefs is: yf = [y;-flipud(y)];
%
% x: input signal (can be either a column or frame per column)
% length of x must be a integer multiple of 4 (each frame)
% y: MDCT of x (coefs are divided by sqrt(N))
%
% Vectorize ! ! !
% ------- mdct4.m ------------------------------------------
% Marios Athineos, marios@ee.columbia.edu
% http://www.ee.columbia.edu/~marios/
% Copyright (c) 2002 by Columbia University.
% All rights reserved.
% ----------------------------------------------------------
[flen,fnum] = size(x);
% Make column if it's a single row
if (flen==1)
x = x(:);
flen = fnum;
fnum = 1;
end
% Make sure length is multiple of 4
if (rem(flen,4)~=0)
error('MDCT4 defined for lengths multiple of four.');
end
% We need these for furmulas below
N = flen; % Length of window
M = N/2; % Number of coefficients
N4 = N/4; % Simplify the way eqs look
sqrtN = sqrt(N);
% Preallocate rotation matrix
% It would be nice to be able to do it in-place but we cannot
% cause of the prerotation.
rot = zeros(flen,fnum);
% Shift
t = (0:(N4-1)).';
rot(t+1,:) = -x(t+3*N4+1,:);
t = (N4:(N-1)).';
rot(t+1,:) = x(t-N4+1,:);
clear x;
% We need this twice so keep it around
t = (0:(N4-1)).';
w = diag(sparse(exp(-j*2*pi*(t+1/8)/N)));
% Pre-twiddle
t = (0:(N4-1)).';
c = (rot(2*t+1,:)-rot(N-1-2*t+1,:))...
-j*(rot(M+2*t+1,:)-rot(M-1-2*t+1,:));
% This is a really cool Matlab trick ;)
c = 0.5*w*c;
clear rot;
% FFT for N/4 points only !!!
c = fft(c,N4);
% Post-twiddle
c = (2/sqrtN)*w*c;
% Sort
t = (0:(N4-1)).';
y(2*t+1,:) = real(c(t+1,:));
y(M-1-2*t+1,:) = -imag(c(t+1,:));
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