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Bump SINC_HIGHEST BW to 0.962.

This commit is contained in:
Themaister 2013-03-09 13:28:40 +01:00
parent 4bca26097c
commit 1e44407bd8
2 changed files with 14 additions and 12 deletions
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2
audio/sinc.c
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@ -71,7 +71,7 @@
#elif defined(SINC_HIGHEST_QUALITY) #elif defined(SINC_HIGHEST_QUALITY)
#define SINC_WINDOW_KAISER #define SINC_WINDOW_KAISER
#define SINC_WINDOW_KAISER_BETA 14.5 #define SINC_WINDOW_KAISER_BETA 14.5
#define CUTOFF 0.95 #define CUTOFF 0.962
#define PHASE_BITS 10 #define PHASE_BITS 10
#define SUBPHASE_BITS 14 #define SUBPHASE_BITS 14
#define SINC_COEFF_LERP 1 #define SINC_COEFF_LERP 1

24
audio/test/sinc_test.m
View File

@ -12,9 +12,10 @@ subplot(2, 1, 2), plot(rarch_kaiser - real_kaiser), title('Error');
%% %%
% 4-tap and 8-tap are Lanczos windowed, but include here for completeness. % 4-tap and 8-tap are Lanczos windowed, but include here for completeness.
phases = 256; phases = 256;
bw = 0.375; ratio = 2.0;
downsample = round(phases / bw); bw = min(1.0, ratio);
cutoffs = bw * [0.65 0.75 0.825 0.90 0.95]; downsample = round(phases / ratio);
cutoffs = bw * [0.65 0.75 0.825 0.90 0.962];
betas = [2.0 3.0 5.5 10.5 14.5]; betas = [2.0 3.0 5.5 10.5 14.5];
sidelobes = round([2 4 8 32 128] / bw); sidelobes = round([2 4 8 32 128] / bw);
@ -22,28 +23,29 @@ taps = sidelobes * 2;
freqs = 0.05 : 0.02 : 0.99; freqs = 0.05 : 0.02 : 0.99;
filters = length(taps); %filters = length(taps);
for i = 1 : filters %for i = 1 : filters
for i = 5
filter_length = taps(i) * phases; filter_length = taps(i) * phases;
% Generate SINC. % Generate SINC.
sinc_indices = 2 * ((0 : (filter_length - 1)) / (filter_length - 1)) - 1; sinc_indices = 2 * ((0 : (filter_length - 1)) / filter_length) - 1;
s = cutoffs(i) * sinc(cutoffs(i) * sinc_indices * sidelobes(i)); s = cutoffs(i) * sinc(cutoffs(i) * sinc_indices * sidelobes(i));
win = kaiser(filter_length, betas(i))'; win = kaiser(filter_length, betas(i))';
filter = s .* win; filter = s .* win;
impulse_response_half = 0.5 * upfirdn(1, filter, phases, downsample); impulse_response_half = upfirdn(1, filter, phases, downsample) / bw;
figure('name', sprintf('Response SINC: %d taps', taps(i))); figure('name', sprintf('Response SINC: %d taps', taps(i)));
freqz(impulse_response_half); freqz(impulse_response_half);
ylim([-200 0]); ylim([-200 0]);
signal = zeros(1, 8001); signal = zeros(1, 80001);
for freq = freqs for freq = freqs
signal = signal + sin(pi * freq * (0 : 8000)); signal = signal + sin(pi * freq * (0 : 80000));
end end
resampled = upfirdn(signal, filter, phases, downsample); resampled = upfirdn(signal, filter, phases, downsample);
figure('name', sprintf('Kaiser SINC: %d taps, w = %.f', taps(i), freq)); figure('name', sprintf('Kaiser SINC: %d taps, w = %.f', taps(i), freq));
freqz(resampled .* kaiser(length(resampled), 40.0)'); freqz(resampled .* kaiser(length(resampled), 40.0)', 1, 16 * 1024);
ylim([-80 70]); ylim([-180 100]);
end end