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