function AACSeq3 = AACoder3(fNameIn, fnameAACoded)
%Implementation of AAC encoder
%   Usage AACSeq3 = AACoder3(fNameIn, fnameAACoded), where:
%       Inputs
%       - fNameIn is the filename and path of the file to encode
%       - frameAACoded is the filename and path of the mat file that will
%       be written after encoding
%
%       Output
%        - 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

    % Declares constant window type
    WINDOW_TYPE = 'KBD';
    % Declares constant numbers of bands for long and short windows
    LONG_WINDOW_NUMBER_OF_BANDS = 69;
    SHORT_WINDOW_NUMBER_OF_BANDS = 42;
    
    % Declares persistent variable holding the TNS tables and initializes if empty
    persistent TNSTables;
    if isempty(TNSTables)
        TNSTables = load('TableB219.mat');
    end

    % 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), 1} = '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

    % Assigns 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

    % Encodes audio file
    huffLUT = loadLUT();
    AACSeq3(length(frameTypes), 1) = struct;
    for i = 0:length(frameTypes) - 1
        currFrameStart = i * 1024 + 1;
        currFrameStop = currFrameStart + 2047;
        frameF = filterbank(originalAudioData(currFrameStart:currFrameStop, :), frameTypes{i+1}, WINDOW_TYPE);
        [frameF(:, 1), TNScoeffsL] = TNS(frameF(:, 1), frameTypes{i+1});
        [frameF(:, 2), TNScoeffsR] = TNS(frameF(:, 2), frameTypes{i+1});

        if i == 0
            SMRL = psycho(...
                originalAudioData(currFrameStart:currFrameStop, 1), ...
                frameTypes{i+1}, zeros(2048, 1), zeros(2048, 1));
            SMRR = psycho(...
                originalAudioData(currFrameStart:currFrameStop, 2), ...
                frameTypes{i+1}, zeros(2048, 1), zeros(2048, 1));
        elseif i == 1
            prev1FrameStart = (i - 1) * 1024 + 1;
            prev1FrameStop = prev1FrameStart + 2047;
            SMRL = psycho(...
                originalAudioData(currFrameStart:currFrameStop, 1), ...
                frameTypes{i+1}, ...
                originalAudioData(prev1FrameStart:prev1FrameStop, 1), ...
                zeros(2048, 1));
            SMRR = psycho(...
                originalAudioData(currFrameStart:currFrameStop, 2), ...
                frameTypes{i+1}, ...
                originalAudioData(prev1FrameStart:prev1FrameStop, 2), ...
                zeros(2048, 1));
        else
            prev1FrameStart = (i - 1) * 1024 + 1;
            prev1FrameStop = prev1FrameStart + 2047;
            prev2FrameStart = (i - 2) * 1024 + 1;
            prev2FrameStop = prev2FrameStart + 2047;
            SMRL = psycho(...
                originalAudioData(currFrameStart:currFrameStop, 1), ...
                frameTypes{i+1}, ...
                originalAudioData(prev1FrameStart:prev1FrameStop, 1), ...
                originalAudioData(prev2FrameStart:prev2FrameStop, 1));
            SMRR = psycho(...
                originalAudioData(currFrameStart:currFrameStop, 2), ...
                frameTypes{i+1}, ...
                originalAudioData(prev1FrameStart:prev1FrameStop, 2), ...
                originalAudioData(prev2FrameStart:prev2FrameStop, 2));
        end
        
        [SL, sfcL, GL] = AACquantizer(frameF(:, 1), frameTypes{i+1}, SMRL);
        [SR, sfcR, GR] = AACquantizer(frameF(:, 2), frameTypes{i+1}, SMRR);
        
        if ~strcmp(frameTypes{i+1}, 'ESH')
            TL(LONG_WINDOW_NUMBER_OF_BANDS, 1) = 0;
            TR(LONG_WINDOW_NUMBER_OF_BANDS, 1) = 0;
            for band = 1:LONG_WINDOW_NUMBER_OF_BANDS
                frameWlow = TNSTables.B219a(band, 2) + 1;
                frameWhigh = TNSTables.B219a(band, 3) + 1;
                subFrameF = frameF(frameWlow:frameWhigh);
                TL(band) = sumsqr(subFrameF) ./ SMRL(band);
                TR(band) = sumsqr(subFrameF) ./ SMRR(band);
            end
        else
            TL(SHORT_WINDOW_NUMBER_OF_BANDS, 1) = 0;
            TR(SHORT_WINDOW_NUMBER_OF_BANDS, 1) = 0;
            for subFrameIndex = 1:8
                currFrameStart = (subFrameIndex - 1) * 128 + 1;
                currFrameStop = currFrameStart + 127;
                subFrame = frameF(currFrameStart:currFrameStop);
                for band = 1:SHORT_WINDOW_NUMBER_OF_BANDS
                    frameWlow = TNSTables.B219b(band, 2);
                    frameWhigh = TNSTables.B219b(band, 3);
                    subFrameF = subFrame(frameWlow + 1:frameWhigh + 1);
                    
                    TL(band, subFrameIndex) = sumsqr(subFrameF) ./ SMRL(band);
                    TR(band, subFrameIndex) = sumsqr(subFrameF) ./ SMRR(band);
                end
            end
        end
        
        [streamL, huffcodebookL] = encodeHuff(SL, huffLUT);
        [streamR, huffcodebookR] = encodeHuff(SR, huffLUT);
        
        if strcmp(frameTypes(i+1), 'ESH')
            [sfcHuffL, ~] = encodeHuff(reshape(sfcL(2:end, :), 1, [])', ...
                huffLUT, 12);
            [sfcHuffR, ~] = encodeHuff(reshape(sfcR(2:end, :), 1, [])', ...
                huffLUT, 12);
        else
            [sfcHuffL, ~] = encodeHuff(sfcL(2:end), huffLUT, 12);
            [sfcHuffR, ~] = encodeHuff(sfcR(2:end), huffLUT, 12);
        end
        
        AACSeq3(i + 1).frameType = frameTypes(i + 1);
        AACSeq3(i + 1).winType = WINDOW_TYPE;
        AACSeq3(i + 1).chl.TNScoeffs = TNScoeffsL;
        AACSeq3(i + 1).chr.TNScoeffs = TNScoeffsR;
        AACSeq3(i + 1).chl.T = TL;
        AACSeq3(i + 1).chr.T = TR;
        AACSeq3(i + 1).chl.G = GL;
        AACSeq3(i + 1).chr.G = GR;
        AACSeq3(i + 1).chl.sfc = sfcHuffL;
        AACSeq3(i + 1).chr.sfc = sfcHuffR;
        AACSeq3(i + 1).chl.stream = streamL;
        AACSeq3(i + 1).chr.stream = streamR;
        AACSeq3(i + 1).chl.codebook = huffcodebookL;
        AACSeq3(i + 1).chr.codebook = huffcodebookR;
        
        clearvars TL TR
    end

    save(fnameAACoded, 'AACSeq3');
end