33 lines
1.2 KiB
Matlab
33 lines
1.2 KiB
Matlab
% Outputs a file for testing purposes.
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%
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% Adjust the following parameters to suit. Their purpose becomes more clear on
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% viewing the gain plots.
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% MaxGain: Max gain in dB
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% MinGain: Min gain at overload (0 dBov) in dB
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% CompRatio: Compression ratio, essentially determines the slope of the gain
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% function between the max and min gains
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% Knee: The smoothness of the transition to max gain (smaller is smoother)
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MaxGain = 5; MinGain = 0; CompRatio = 3; Knee = 1;
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% Compute gains
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zeros = 0:31; lvl = 2.^(1-zeros);
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A = -10*log10(lvl) * (CompRatio - 1) / CompRatio;
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B = MaxGain - MinGain;
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gains = round(2^16*10.^(0.05 * (MinGain + B * ( log(exp(-Knee*A)+exp(-Knee*B)) - log(1+exp(-Knee*B)) ) / log(1/(1+exp(Knee*B))))));
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fprintf(1, '\t%i, %i, %i, %i,\n', gains);
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% Save gains to file
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fid = fopen('gains', 'wb');
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if fid == -1
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error(sprintf('Unable to open file %s', filename));
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return
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end
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fwrite(fid, gains, 'int32');
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fclose(fid);
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% Plotting
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in = 10*log10(lvl); out = 20*log10(gains/65536);
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subplot(121); plot(in, out); axis([-60, 0, -5, 30]); grid on; xlabel('Input (dB)'); ylabel('Gain (dB)');
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subplot(122); plot(in, in+out); axis([-60, 0, -60, 10]); grid on; xlabel('Input (dB)'); ylabel('Output (dB)');
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zoom on;
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