mirror of
https://github.com/libretro/RetroArch
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49 lines
1.5 KiB
Matlab
49 lines
1.5 KiB
Matlab
% MATLAB test case for RetroArch SINC upsampler.
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close all;
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%%
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% Test RetroArch's kaiser function.
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real_kaiser = kaiser(1024, 10.0)';
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rarch_kaiser = kaiser_window(1024, 10.0);
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figure('name', 'Bessel function test');
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subplot(2, 1, 1), plot(rarch_kaiser), title('RetroArch kaiser');
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subplot(2, 1, 2), plot(rarch_kaiser - real_kaiser), title('Error');
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%%
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% 4-tap and 8-tap are Lanczos windowed, but include here for completeness.
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phases = 256;
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bw = 0.375;
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downsample = round(phases / bw);
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cutoffs = bw * [0.65 0.75 0.825 0.90 0.95];
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betas = [2.0 3.0 5.5 10.5 14.5];
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sidelobes = round([2 4 8 32 128] / bw);
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taps = sidelobes * 2;
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freqs = 0.05 : 0.02 : 0.99;
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filters = length(taps);
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for i = 1 : filters
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filter_length = taps(i) * phases;
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% Generate SINC.
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sinc_indices = 2 * ((0 : (filter_length - 1)) / (filter_length - 1)) - 1;
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s = cutoffs(i) * sinc(cutoffs(i) * sinc_indices * sidelobes(i));
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win = kaiser(filter_length, betas(i))';
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filter = s .* win;
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impulse_response_half = 0.5 * upfirdn(1, filter, phases, downsample);
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figure('name', sprintf('Response SINC: %d taps', taps(i)));
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freqz(impulse_response_half);
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ylim([-200 0]);
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signal = zeros(1, 8001);
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for freq = freqs
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signal = signal + sin(pi * freq * (0 : 8000));
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end
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resampled = upfirdn(signal, filter, phases, downsample);
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figure('name', sprintf('Kaiser SINC: %d taps, w = %.f', taps(i), freq));
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freqz(resampled .* kaiser(length(resampled), 40.0)');
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ylim([-80 70]);
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end |