authMultimediaAssignment2018/Level_3/iAACoder3.m

function x = iAACoder3(AACSeq3, fNameOut)
%Implementation of AAC decoder
%   Usage x = iAACoder3(AACSeq3, fNameOut), where:
%       Inputs
%       - fNameOut is the filename and path of the file that will be
%       written after decoding
%        - AACSeq3 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.TNScoeffs which are the quantized TNS coefficients of
%               this frame's left channel,
%           * chr.TNScoeffs which are the quantized TNS coefficients of
%               this frame's right channel,
%           * chl.T which are the psychoacoustic thresholds of this frame's
%               left channel,
%           * chr.T which are the psychoacoustic thresholds of this frame's
%               right channel,
%           * chl.G which are the quantized global gains of this frame's
%               left channel,
%           * chr.G which are the quantized global gains of this frame's
%               right channel,
%           * chl.sfc which is the Huffman encoded sfc sequence of this
%               frame's left channel,
%           * chr.sfc which is the Huffman encoded sfc sequence of this
%               frame's right channel,
%           * chl.stream which is the Huffman encoded quantized MDCT
%               sequence of this frame's left channel,
%           * chr.stream which is the Huffman encoded quantized MDCT
%               sequence of this frame's right channel,
%           * chl.codebook which is the Huffman codebook used for this
%               frame's left channel
%           * chr.codebook which is the Huffman codebook used for this
%               frame's right channel
%
%       Output
%       - x is an array containing the decoded audio samples

    % Initializes an array to hold the decoded samples
    decodedAudio(1024 * (length(AACSeq3) + 1), 2) = 0;
    % Initializes an array to hold both audio channels
    frameF(1024, 2) = 0;

    % Decodes audio file
    huffLUT = loadLUT();
    for i = 0:length(AACSeq3) - 1
        currFrameStart = i * 1024 + 1;
        currFrameStop = currFrameStart + 2047;

        if i < 2
            continue;
            frameF(:, 1) = iTNS(AACSeq3(i + 1).chl.stream, ...
                AACSeq3(i+1).frameType, ...
                AACSeq3(i + 1).chl.TNScoeffs);
            frameF(:, 2) = iTNS(AACSeq3(i + 1).chr.stream, ...
                AACSeq3(i+1).frameType, ...
                AACSeq3(i + 1).chr.TNScoeffs);
            
            frameT = iFilterbank(frameF, AACSeq3(i+1).frameType, AACSeq3(i+1).winType);
        else
            SL = decodeHuff(AACSeq3(i + 1).chl.stream, ...
                AACSeq3(i + 1).chl.codebook, huffLUT);
            SR = decodeHuff(AACSeq3(i + 1).chr.stream, ...
                AACSeq3(i + 1).chr.codebook, huffLUT);
            
            sfcL = decodeHuff(AACSeq3(i + 1).chl.sfc, 12, huffLUT)';
            sfcR = decodeHuff(AACSeq3(i + 1).chr.sfc, 12, huffLUT)';
            if strcmp(AACSeq3(i+1).frameType, 'ESH')
                sfcDeHuffL(42, 8) = 0;
                sfcDeHuffR(42, 8) = 0;
                sfcDeHuffL(2:end, :) = reshape(sfcL, [41 8]);
                sfcDeHuffR(2:end, :) = reshape(sfcR, [41 8]);
                sfcDeHuffL(1, :) = AACSeq3(i+1).chl.G;
                sfcDeHuffR(1, :) = AACSeq3(i+1).chr.G;
            else
                sfcDeHuffL = [AACSeq3(i+1).chl.G; sfcL];
                sfcDeHuffR = [AACSeq3(i+1).chr.G; sfcR];
            end
            
            frameF(:, 1) = iAACquantizer(SL, sfcDeHuffL, ...
                AACSeq3(i + 1).chl.G, AACSeq3(i+1).frameType);
            frameF(:, 2) = iAACquantizer(SR, sfcDeHuffR, ...
                AACSeq3(i + 1).chr.G, AACSeq3(i+1).frameType);

            frameF(:, 1) = iTNS(frameF(:, 1), ...
                AACSeq3(i+1).frameType, ...
                AACSeq3(i + 1).chl.TNScoeffs);
            frameF(:, 2) = iTNS(frameF(:, 2), ...
                AACSeq3(i+1).frameType, ...
                AACSeq3(i + 1).chr.TNScoeffs);
            
            frameT = iFilterbank(frameF, AACSeq3(i+1).frameType, AACSeq3(i+1).winType);
        end

        decodedAudio(currFrameStart:currFrameStop, :) = decodedAudio(currFrameStart:currFrameStop, :) + frameT;
        
        clearvars sfcDeHuffL sfcDeHuffR
    end

    audiowrite(fNameOut, decodedAudio, 48000);
    x = decodedAudio;
end