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172 lines
8.3 KiB
172 lines
8.3 KiB
function [frameFout, TNScoeffs] = TNS(frameFin, frameType)
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%Implementation of the TNS step
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% Usage [frameFout, TNScoeffs] = TNS(frameFin, frameType), where:
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% Inputs
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% - frameFin is the frame in the frequency domain, in MDCT coefficients
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% representation containing both channels of the audio stored in an
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% array of dimensions 1024X2
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% - frameType is the type of the current frame in string
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% representation, can be one of "OLS" (ONLY_LONG_SEQUENCE), "LSS"
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% (LONG_START_SEQUENCE), "ESH" (EIGHT_SHORT_SEQUENCE), "LPS"
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% (LONG_STOP_SEQUENCE)
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%
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% Output
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% - frameFout is the frame in the frequency domain after Temporal Noise
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% Shaping, in MDCT coefficients representation containing both channels
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% of the audio stored in an array of dimensions 1024X2
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% - TNScoeffs is the quantized TNS coefficients array of dimensions
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% 4X8 for EIGHT_SHORT_SEQUENCE frames and 4X1 otherwise
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% Declares constant numbers of bands for long and short windows
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LONG_WINDOW_NUMBER_OF_BANDS = 69;
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SHORT_WINDOW_NUMBER_OF_BANDS = 42;
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% Declares constant order of the linear prediction filter
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LPF_ORDER = 4;
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% Declares constant coefficients' resolution
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COEF_RES = 4;
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% Declares persistent variable holding the TNS tables and initializes if empty
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persistent TNSTables;
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if isempty(TNSTables)
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TNSTables = load('TableB219.mat');
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end
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if ~strcmp(frameType, 'ESH')
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% Calculates the energy per band
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bandEnergy(LONG_WINDOW_NUMBER_OF_BANDS) = 0;
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for band = 1:LONG_WINDOW_NUMBER_OF_BANDS - 1
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bandEnergy(band) = sumsqr(frameFin(TNSTables.B219a(band, 2) + 1:TNSTables.B219a(band + 1, 2)));
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end
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bandEnergy(LONG_WINDOW_NUMBER_OF_BANDS) = sumsqr( ...
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frameFin(TNSTables.B219a(LONG_WINDOW_NUMBER_OF_BANDS, 2) + 1:...
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TNSTables.B219a(LONG_WINDOW_NUMBER_OF_BANDS, 3) + 1));
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% Calculates the normalization factors
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% PROBABLY WRONG, THE ONE BELLOW SHOULD BE RIGHT AND BETTER
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% normalizationFactor(1024) = 0;
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% for normIndex = 1:1024
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% bandIndices = find(TNSTables.B219a(:, 2) >= (normIndex - 1), 1);
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% if ~isempty(bandIndices)
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% normalizationFactor(normIndex) = sqrt(bandEnergy(bandIndices));
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% else
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% normalizationFactor(normIndex) = sqrt(bandEnergy(find(TNSTables.B219a(:, 3) >= normIndex - 1, 1)));
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% end
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% end
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bandIndices = quantiz(0:1023, TNSTables.B219a(:, 2) - 1);
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normalizationFactor = sqrt(bandEnergy(bandIndices));
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% Smooths normalization factors
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for normIndex = 1023:-1:1
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normalizationFactor(normIndex) = (normalizationFactor(normIndex) + normalizationFactor(normIndex + 1)) / 2;
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end
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for normIndex = 2:1024
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normalizationFactor(normIndex) = (normalizationFactor(normIndex) + normalizationFactor(normIndex - 1)) / 2;
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end
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% Normalizes MDCT coefficients according to each band energy
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normalizedFrameFin = frameFin ./ normalizationFactor';
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% Calculates the linear prediction coefficients
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[linPredCoeff, ~] = lpc(normalizedFrameFin, LPF_ORDER);
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% Quantizes these coefficients
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quantizedLinPredCoeff(LPF_ORDER) = 0;
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for coeffIndex = 2:length(linPredCoeff)
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quantizedLinPredCoeff(coeffIndex - 1) = asin(linPredCoeff(coeffIndex));
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if linPredCoeff(coeffIndex) >= 0
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quantizedLinPredCoeff(coeffIndex - 1) = round(quantizedLinPredCoeff(coeffIndex - 1) * ...
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(bitshift(1, COEF_RES - 1) - 0.5) / (pi / 2));
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quantizedLinPredCoeff(coeffIndex - 1) = quantizedLinPredCoeff(coeffIndex - 1) / ...
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(bitshift(1, COEF_RES - 1) - 0.5) / (pi / 2);
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quantizedLinPredCoeff(coeffIndex - 1) = sin (quantizedLinPredCoeff(coeffIndex - 1));
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else
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quantizedLinPredCoeff(coeffIndex - 1) = round(quantizedLinPredCoeff(coeffIndex - 1) * ...
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(bitshift(1, COEF_RES - 1) + 0.5) / (pi / 2));
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quantizedLinPredCoeff(coeffIndex - 1) = quantizedLinPredCoeff(coeffIndex - 1) / ...
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(bitshift(1, COEF_RES - 1) + 0.5) / (pi / 2);
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quantizedLinPredCoeff(coeffIndex - 1) = sin (quantizedLinPredCoeff(coeffIndex - 1));
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end
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end
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% Filters MDCT coefficients
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if ~isstable(1, [1 (quantizedLinPredCoeff * (-1))])
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error('TNS, l[79]: Inverse filter not stable!');
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else
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TNScoeffs = quantizedLinPredCoeff;
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frameFout = filter([1 (quantizedLinPredCoeff * (-1))], 1, frameFin);
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end
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else
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% Initializes output vectors
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TNScoeffs(LPF_ORDER * 8) = 0;
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frameFout(1024) = 0;
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bandEnergy(SHORT_WINDOW_NUMBER_OF_BANDS) = 0;
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for subFrameIndex = 1:8
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subFrame = frameFin((subFrameIndex - 1) * 128 + 1:subFrameIndex * 128);
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% Calculates the energy per band
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for band = 1:SHORT_WINDOW_NUMBER_OF_BANDS - 1
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bandEnergy(band) = sumsqr(subFrame(TNSTables.B219b(band, 2) + 1:TNSTables.B219b(band + 1, 2)));
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end
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bandEnergy(SHORT_WINDOW_NUMBER_OF_BANDS) = sumsqr( ...
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subFrame(TNSTables.B219b(SHORT_WINDOW_NUMBER_OF_BANDS, 2) + 1:...
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TNSTables.B219b(SHORT_WINDOW_NUMBER_OF_BANDS, 3) + 1));
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% Calculates the normalization factors
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normalizationFactor(128) = 0;
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for normIndex = 1:128
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bandIndices = find(TNSTables.B219b(:, 2) >= normIndex - 1, 1);
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if ~isempty(bandIndices)
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normalizationFactor(normIndex) = sqrt(bandEnergy(bandIndices));
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else
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normalizationFactor(normIndex) = sqrt(bandEnergy(find(TNSTables.B219b(:, 3) <= normIndex - 1, 1)));
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end
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end
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% Smooths normalization factors
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for normIndex = 127:-1:1
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normalizationFactor(normIndex) = (normalizationFactor(normIndex) + normalizationFactor(normIndex + 1)) / 2;
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end
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for normIndex = 2:128
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normalizationFactor(normIndex) = (normalizationFactor(normIndex) + normalizationFactor(normIndex - 1)) / 2;
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end
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% Normalizes MDCT coefficients according to each band energy
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normalizedFrameFin = subFrame ./ normalizationFactor';
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% Calculates the linear prediction coefficients
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[linPredCoeff, ~] = lpc(normalizedFrameFin, LPF_ORDER);
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% Quantizes these coefficients
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quantizedLinPredCoeff(LPF_ORDER) = 0;
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for coeffIndex = 1:length(linPredCoeff)
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quantizedLinPredCoeff(coeffIndex - 1) = asin(linPredCoeff(coeffIndex));
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if linPredCoeff(coeffIndex) >= 0
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quantizedLinPredCoeff(coeffIndex - 1) = round(quantizedLinPredCoeff(coeffIndex - 1) * ...
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(bitshift(1, COEF_RES - 1) - 0.5) / (pi / 2));
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quantizedLinPredCoeff(coeffIndex - 1) = quantizedLinPredCoeff(coeffIndex - 1) / ...
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(bitshift(1, COEF_RES - 1) - 0.5) / (pi / 2);
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quantizedLinPredCoeff(coeffIndex - 1) = sin (quantizedLinPredCoeff(coeffIndex - 1));
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else
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quantizedLinPredCoeff(coeffIndex - 1) = round(quantizedLinPredCoeff(coeffIndex - 1) * ...
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(bitshift(1, COEF_RES - 1) + 0.5) / (pi / 2));
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quantizedLinPredCoeff(coeffIndex - 1) = quantizedLinPredCoeff(coeffIndex - 1) / ...
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(bitshift(1, COEF_RES - 1) + 0.5) / (pi / 2);
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quantizedLinPredCoeff(coeffIndex - 1) = sin (quantizedLinPredCoeff(coeffIndex - 1));
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end
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end
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% Filters MDCT coefficients
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if ~isstable(1, [1 (quantizedLinPredCoeff * (-1))])
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error('TNS, l[79]: Inverse filter not stable!');
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else
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TNScoeffs((subFrameIndex - 1) * 4 + 1:subFrameIndex * 4) = quantizedLinPredCoeff;
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frameFout((subFrameIndex - 1) * 128 + 1:subFrameIndex * 128) = ...
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filter([1 (quantizedLinPredCoeff * (-1))], 1, subFrame);
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end
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end
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end
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end
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