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avfilter/af_aiir: simplify polynomial evaluation

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This commit is contained in:
Paul B Mahol 2020-05-30 17:55:32 +02:00
parent aac16abd92
commit 1329db8cfb
1 changed files with 18 additions and 31 deletions
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49
libavfilter/af_aiir.c
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@ -385,45 +385,32 @@ static int read_channels(AVFilterContext *ctx, int channels, uint8_t *item_str,
return 0;
}
static void multiply(double wre, double wim, int npz, double *coeffs)
static void cmul(double re, double im, double re2, double im2, double *RE, double *IM)
{
double nwre = -wre, nwim = -wim;
double cre, cim;
int i;
for (i = npz; i >= 1; i--) {
cre = coeffs[2 * i + 0];
cim = coeffs[2 * i + 1];
coeffs[2 * i + 0] = (nwre * cre - nwim * cim) + coeffs[2 * (i - 1) + 0];
coeffs[2 * i + 1] = (nwre * cim + nwim * cre) + coeffs[2 * (i - 1) + 1];
}
cre = coeffs[0];
cim = coeffs[1];
coeffs[0] = nwre * cre - nwim * cim;
coeffs[1] = nwre * cim + nwim * cre;
*RE = re * re2 - im * im2;
*IM = re * im2 + re2 * im;
}
static int expand(AVFilterContext *ctx, double *pz, int nb, double *coeffs)
static int expand(AVFilterContext *ctx, double *pz, int n, double *coefs)
{
int i;
coefs[2 * n] = 1.0;
coeffs[0] = 1.0;
coeffs[1] = 0.0;
for (int i = 1; i <= n; i++) {
for (int j = n - i; j < n; j++) {
double re, im;
for (i = 0; i < nb; i++) {
coeffs[2 * (i + 1) ] = 0.0;
coeffs[2 * (i + 1) + 1] = 0.0;
cmul(coefs[2 * (j + 1)], coefs[2 * (j + 1) + 1],
pz[2 * (i - 1)], pz[2 * (i - 1) + 1], &re, &im);
coefs[2 * j] -= re;
coefs[2 * j + 1] -= im;
}
}
for (i = 0; i < nb; i++)
multiply(pz[2 * i], pz[2 * i + 1], nb, coeffs);
for (i = 0; i < nb + 1; i++) {
if (fabs(coeffs[2 * i + 1]) > FLT_EPSILON) {
av_log(ctx, AV_LOG_ERROR, "coeff: %f of z^%d is not real; poles/zeros are not complex conjugates.\n",
coeffs[2 * i + 1], i);
for (int i = 0; i < n + 1; i++) {
if (fabs(coefs[2 * i + 1]) > FLT_EPSILON) {
av_log(ctx, AV_LOG_ERROR, "coefs: %f of z^%d is not real; poles/zeros are not complex conjugates.\n",
coefs[2 * i + 1], i);
return AVERROR(EINVAL);
}
}