You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
319 lines
9.9 KiB
319 lines
9.9 KiB
/*
|
|
* Copyright (C) 2007 The Android Open Source Project
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
#include <math.h>
|
|
#include <stdio.h>
|
|
#include <unistd.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
|
|
static inline double sinc(double x) {
|
|
if (fabs(x) == 0.0f) return 1.0f;
|
|
return sin(x) / x;
|
|
}
|
|
|
|
static inline double sqr(double x) {
|
|
return x*x;
|
|
}
|
|
|
|
static inline int64_t toint(double x, int64_t maxval) {
|
|
int64_t v;
|
|
|
|
v = static_cast<int64_t>(floor(x * maxval + 0.5));
|
|
if (v >= maxval) {
|
|
return maxval - 1; // error!
|
|
}
|
|
return v;
|
|
}
|
|
|
|
static double I0(double x) {
|
|
// from the Numerical Recipes in C p. 237
|
|
double ax,ans,y;
|
|
ax=fabs(x);
|
|
if (ax < 3.75) {
|
|
y=x/3.75;
|
|
y*=y;
|
|
ans=1.0+y*(3.5156229+y*(3.0899424+y*(1.2067492
|
|
+y*(0.2659732+y*(0.360768e-1+y*0.45813e-2)))));
|
|
} else {
|
|
y=3.75/ax;
|
|
ans=(exp(ax)/sqrt(ax))*(0.39894228+y*(0.1328592e-1
|
|
+y*(0.225319e-2+y*(-0.157565e-2+y*(0.916281e-2
|
|
+y*(-0.2057706e-1+y*(0.2635537e-1+y*(-0.1647633e-1
|
|
+y*0.392377e-2))))))));
|
|
}
|
|
return ans;
|
|
}
|
|
|
|
static double kaiser(int k, int N, double beta) {
|
|
if (k < 0 || k > N)
|
|
return 0;
|
|
return I0(beta * sqrt(1.0 - sqr((2.0*k)/N - 1.0))) / I0(beta);
|
|
}
|
|
|
|
static void usage(char* name) {
|
|
fprintf(stderr,
|
|
"usage: %s [-h] [-d] [-D] [-s sample_rate] [-c cut-off_frequency] [-n half_zero_crossings]"
|
|
" [-f {float|fixed|fixed16}] [-b beta] [-v dBFS] [-l lerp]\n"
|
|
" %s [-h] [-d] [-D] [-s sample_rate] [-c cut-off_frequency] [-n half_zero_crossings]"
|
|
" [-f {float|fixed|fixed16}] [-b beta] [-v dBFS] -p M/N\n"
|
|
" -h this help message\n"
|
|
" -d debug, print comma-separated coefficient table\n"
|
|
" -D generate extra declarations\n"
|
|
" -p generate poly-phase filter coefficients, with sample increment M/N\n"
|
|
" -s sample rate (48000)\n"
|
|
" -c cut-off frequency (20478)\n"
|
|
" -n number of zero-crossings on one side (8)\n"
|
|
" -l number of lerping bits (4)\n"
|
|
" -m number of polyphases (related to -l, default 16)\n"
|
|
" -f output format, can be fixed, fixed16, or float (fixed)\n"
|
|
" -b kaiser window parameter beta (7.865 [-80dB])\n"
|
|
" -v attenuation in dBFS (0)\n",
|
|
name, name
|
|
);
|
|
exit(0);
|
|
}
|
|
|
|
int main(int argc, char** argv)
|
|
{
|
|
// nc is the number of bits to store the coefficients
|
|
int nc = 32;
|
|
bool polyphase = false;
|
|
unsigned int polyM = 160;
|
|
unsigned int polyN = 147;
|
|
bool debug = false;
|
|
double Fs = 48000;
|
|
double Fc = 20478;
|
|
double atten = 1;
|
|
int format = 0; // 0=fixed, 1=float
|
|
bool declarations = false;
|
|
|
|
// in order to keep the errors associated with the linear
|
|
// interpolation of the coefficients below the quantization error
|
|
// we must satisfy:
|
|
// 2^nz >= 2^(nc/2)
|
|
//
|
|
// for 16 bit coefficients that would be 256
|
|
//
|
|
// note that increasing nz only increases memory requirements,
|
|
// but doesn't increase the amount of computation to do.
|
|
//
|
|
//
|
|
// see:
|
|
// Smith, J.O. Digital Audio Resampling Home Page
|
|
// https://ccrma.stanford.edu/~jos/resample/, 2011-03-29
|
|
//
|
|
|
|
// | 0.1102*(A - 8.7) A > 50
|
|
// beta = | 0.5842*(A - 21)^0.4 + 0.07886*(A - 21) 21 <= A <= 50
|
|
// | 0 A < 21
|
|
// with A is the desired stop-band attenuation in dBFS
|
|
//
|
|
// for eg:
|
|
//
|
|
// 30 dB 2.210
|
|
// 40 dB 3.384
|
|
// 50 dB 4.538
|
|
// 60 dB 5.658
|
|
// 70 dB 6.764
|
|
// 80 dB 7.865
|
|
// 90 dB 8.960
|
|
// 100 dB 10.056
|
|
double beta = 7.865;
|
|
|
|
// 2*nzc = (A - 8) / (2.285 * dw)
|
|
// with dw the transition width = 2*pi*dF/Fs
|
|
//
|
|
int nzc = 8;
|
|
|
|
/*
|
|
* Example:
|
|
* 44.1 KHz to 48 KHz resampling
|
|
* 100 dB rejection above 28 KHz
|
|
* (the spectrum will fold around 24 KHz and we want 100 dB rejection
|
|
* at the point where the folding reaches 20 KHz)
|
|
* ...___|_____
|
|
* | \|
|
|
* | ____/|\____
|
|
* |/alias| \
|
|
* ------/------+------\---------> KHz
|
|
* 20 24 28
|
|
*
|
|
* Transition band 8 KHz, or dw = 1.0472
|
|
*
|
|
* beta = 10.056
|
|
* nzc = 20
|
|
*/
|
|
|
|
int M = 1 << 4; // number of phases for interpolation
|
|
int ch;
|
|
while ((ch = getopt(argc, argv, ":hds:c:n:f:l:m:b:p:v:z:D")) != -1) {
|
|
switch (ch) {
|
|
case 'd':
|
|
debug = true;
|
|
break;
|
|
case 'D':
|
|
declarations = true;
|
|
break;
|
|
case 'p':
|
|
if (sscanf(optarg, "%u/%u", &polyM, &polyN) != 2) {
|
|
usage(argv[0]);
|
|
}
|
|
polyphase = true;
|
|
break;
|
|
case 's':
|
|
Fs = atof(optarg);
|
|
break;
|
|
case 'c':
|
|
Fc = atof(optarg);
|
|
break;
|
|
case 'n':
|
|
nzc = atoi(optarg);
|
|
break;
|
|
case 'm':
|
|
M = atoi(optarg);
|
|
break;
|
|
case 'l':
|
|
M = 1 << atoi(optarg);
|
|
break;
|
|
case 'f':
|
|
if (!strcmp(optarg, "fixed")) {
|
|
format = 0;
|
|
}
|
|
else if (!strcmp(optarg, "fixed16")) {
|
|
format = 0;
|
|
nc = 16;
|
|
}
|
|
else if (!strcmp(optarg, "float")) {
|
|
format = 1;
|
|
}
|
|
else {
|
|
usage(argv[0]);
|
|
}
|
|
break;
|
|
case 'b':
|
|
beta = atof(optarg);
|
|
break;
|
|
case 'v':
|
|
atten = pow(10, -fabs(atof(optarg))*0.05 );
|
|
break;
|
|
case 'h':
|
|
default:
|
|
usage(argv[0]);
|
|
break;
|
|
}
|
|
}
|
|
|
|
// cut off frequency ratio Fc/Fs
|
|
double Fcr = Fc / Fs;
|
|
|
|
// total number of coefficients (one side)
|
|
|
|
const int N = M * nzc;
|
|
|
|
// lerp (which is most useful if M is a power of 2)
|
|
|
|
int nz = 0; // recalculate nz as the bits needed to represent M
|
|
for (int i = M-1 ; i; i>>=1, nz++);
|
|
// generate the right half of the filter
|
|
if (!debug) {
|
|
printf("// cmd-line:");
|
|
for (int i=0 ; i<argc ; i++) {
|
|
printf(" %s", argv[i]);
|
|
}
|
|
printf("\n");
|
|
if (declarations) {
|
|
if (!polyphase) {
|
|
printf("const int32_t RESAMPLE_FIR_SIZE = %d;\n", N);
|
|
printf("const int32_t RESAMPLE_FIR_INT_PHASES = %d;\n", M);
|
|
printf("const int32_t RESAMPLE_FIR_NUM_COEF = %d;\n", nzc);
|
|
} else {
|
|
printf("const int32_t RESAMPLE_FIR_SIZE = %d;\n", 2*nzc*polyN);
|
|
printf("const int32_t RESAMPLE_FIR_NUM_COEF = %d;\n", 2*nzc);
|
|
}
|
|
if (!format) {
|
|
printf("const int32_t RESAMPLE_FIR_COEF_BITS = %d;\n", nc);
|
|
}
|
|
printf("\n");
|
|
printf("static %s resampleFIR[] = {", !format ? "int32_t" : "float");
|
|
}
|
|
}
|
|
|
|
if (!polyphase) {
|
|
for (int i=0 ; i<=M ; i++) { // an extra set of coefs for interpolation
|
|
for (int j=0 ; j<nzc ; j++) {
|
|
int ix = j*M + i;
|
|
double x = (2.0 * M_PI * ix * Fcr) / M;
|
|
double y = kaiser(ix+N, 2*N, beta) * sinc(x) * 2.0 * Fcr;
|
|
y *= atten;
|
|
|
|
if (!debug) {
|
|
if (j == 0)
|
|
printf("\n ");
|
|
}
|
|
if (!format) {
|
|
int64_t yi = toint(y, 1ULL<<(nc-1));
|
|
if (nc > 16) {
|
|
printf("0x%08x,", int32_t(yi));
|
|
} else {
|
|
printf("0x%04x,", int32_t(yi)&0xffff);
|
|
}
|
|
} else {
|
|
printf("%.9g%s", y, debug ? "," : "f,");
|
|
}
|
|
if (j != nzc-1) {
|
|
printf(" ");
|
|
}
|
|
}
|
|
}
|
|
} else {
|
|
for (unsigned int j=0 ; j<polyN ; j++) {
|
|
// calculate the phase
|
|
double p = ((polyM*j) % polyN) / double(polyN);
|
|
if (!debug) printf("\n ");
|
|
else printf("\n");
|
|
// generate a FIR per phase
|
|
for (int i=-nzc ; i<nzc ; i++) {
|
|
double x = 2.0 * M_PI * Fcr * (i + p);
|
|
double y = kaiser(i+N, 2*N, beta) * sinc(x) * 2.0 * Fcr;;
|
|
y *= atten;
|
|
if (!format) {
|
|
int64_t yi = toint(y, 1ULL<<(nc-1));
|
|
if (nc > 16) {
|
|
printf("0x%08x,", int32_t(yi));
|
|
} else {
|
|
printf("0x%04x,", int32_t(yi)&0xffff);
|
|
}
|
|
} else {
|
|
printf("%.9g%s", y, debug ? "," : "f,");
|
|
}
|
|
|
|
if (i != nzc-1) {
|
|
printf(" ");
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
if (!debug && declarations) {
|
|
printf("\n};");
|
|
}
|
|
printf("\n");
|
|
return 0;
|
|
}
|
|
|
|
// http://www.csee.umbc.edu/help/sound/AFsp-V2R1/html/audio/ResampAudio.html
|