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for resampling to 33 kHz another cutoff frequency is required otherwise we get aliasing

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This commit is contained in:
Volker Fischer 2009-07-08 17:37:20 +00:00
parent 391ef9f525
commit 85b7c09476
2 changed files with 69 additions and 69 deletions
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128
src/resamplefilter.h
View File

@ -31,70 +31,70 @@ static float fResTaps2[INTERP_I_2 * DECIM_D_2 * NUM_TAPS_PER_PHASE2] = {
// Filter for ratio 16 / 11
static float fResTaps16_11[INTERP_I_16_11 * DECIM_D_16_11 * NUM_TAPS_PER_PHASE16_11] = {
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0.00679052165107026960f,
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};
// Filter for ratios close to 1

10
src/resamplefilter.m
View File

@ -22,7 +22,7 @@ I2 = 2;
D2 = 1;
% filter design
h2 = DesignFilter(NoTapsP2, I2);
h2 = DesignFilter(NoTapsP2, I2, 0.97);
% Filter for ratio 16 / 11 -----------------------------------------------------
@ -31,7 +31,7 @@ I16_11 = 16;
D16_11 = 11;
% filter design
h16_11 = DesignFilter(NoTapsP16_11, I16_11);
h16_11 = DesignFilter(NoTapsP16_11, I16_11, 0.90);
% Filter for ratios close to 1 -------------------------------------------------
@ -39,7 +39,7 @@ h16_11 = DesignFilter(NoTapsP16_11, I16_11);
I1 = 10; % D = I in this mode
% MMSE filter-design and windowing
h1 = DesignFilter(NoTapsP1, I1);
h1 = DesignFilter(NoTapsP1, I1, 0.97);
% Export coefficiants to file ****************************************
@ -94,13 +94,13 @@ fclose(fid);
return;
function h = DesignFilter(NoTapsPIn, I)
function h = DesignFilter(NoTapsPIn, I, cutofffactor)
% number of taps, consider interpolation factor
NoTapsP = NoTapsPIn * I;
% Cut-off frequency (normlized)
fc = 0.97 / I;
fc = cutofffactor / I;
% MMSE filter design with Kaiser window, consider interpolation factor
h = I * firls(NoTapsP - 1, [0 fc fc 1], [1 1 0 0]) .* kaiser(NoTapsP, 5)';