function [S, sfc, G] = AACquantizer(frameF, frameType, SMR)
%Implementation of Quantizer
%   Usage [S, sfc, G] = AACquantizer(frameF, frameType, SMR), where:
%       Inputs
%       - frameF is the frame in the frequency domain, in MDCT coefficients
%       representation containing only one of the audio channels stored in
%       a vector of length 1024
%       - 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)
%        - SMR is the signal to mask ratio array of dimensions 42X8 for
%       EIGHT_SHORT_SEQUENCE frames and 69X1 otherwise
%
%       Output
%        - S are the MDCT quantization symbols of one audio channel stored
%        in a vector of length 1024
%        - sfc are the scalefactors per band stored in an array of
%        dimensions NBX8 for EIGHT_SHORT_SEQUENCE frames and NBX1
%        otherwise, where NB is the number of bands
%        - G is the global gain stored in an array of dimensions 1X8 for
%        EIGHT_SHORT_SEQUENCE frames and a single value otherwise

    % 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

    if ~strcmp(frameType, 'ESH')
        T(LONG_WINDOW_NUMBER_OF_BANDS, 1) = 0;
        quantCoeff(LONG_WINDOW_NUMBER_OF_BANDS, 1) = 0;
        sfc(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);

            T(band) = sumsqr(subFrameF) ./ SMR(band);

            % Calculates an initial quantization coefficient and attempts
            % quantization
            quantCoeff(band) = 16 * log2(max(frameF) ^ (3 / 4) / 8191) / 3;
            S(frameWlow:frameWhigh, 1) = sign(subFrameF) .* floor(( ...
                abs(subFrameF) .* 2 ^ (-quantCoeff(band) / 4)) ...
                .^ (3 / 4) + 0.4054);

            % Calculates current quantization error
            quantErr = sumsqr(subFrameF - S(frameWlow:frameWhigh));

            % Gradually increases the quantization coefficient
            while quantErr < T(band) && (band > 1 || ...
                    (quantErr(band) - quantErr(band - 1) + 1) <= 60)
                quantCoeff(band) = quantCoeff(band) + 1;

                S(frameWlow:frameWhigh) = sign(subFrameF) .* round(( ...
                    abs(subFrameF) .* 2 ^ (-quantCoeff(band) / 4)) ...
                    .^ (3 / 4) + 0.4054);

                quantErr = sumsqr(subFrameF - S(frameWlow:frameWhigh));
            end

            if band == 1
                sfc(band) = quantCoeff(band);
            else
                sfc(band) = quantCoeff(band) - quantCoeff(band - 1);
            end
        end
        G = quantCoeff(1);
    else
        T(SHORT_WINDOW_NUMBER_OF_BANDS) = 0;
        for band = 1:SHORT_WINDOW_NUMBER_OF_BANDS
            T(band) = sumsqr(frameF((TNSTables.B219b(band, 2) + 1: ...
                TNSTables.B219b(band, 3) + 1), 1));
        end
        T = T ./ SMR;
    end
end