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avfilter/af_asupercut: add order option

This commit is contained in:
Paul B Mahol 2020-11-29 14:06:44 +01:00
parent f194cedfe6
commit bebea78755
2 changed files with 34 additions and 12 deletions
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4
doc/filters.texi
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@ -2645,6 +2645,10 @@ The filter accepts the following options:
@item cutoff
Set cutoff frequency in Hertz. Allowed range is 20000 to 192000.
Default value is 20000.
@item order
Set filter order. Available values are from 3 to 20.
Default value is 10.
@end table
@subsection Commands

42
libavfilter/af_asupercut.c
View File

@ -32,10 +32,12 @@ typedef struct ASuperCutContext {
const AVClass *class;
double cutoff;
int order;
int filter_count;
int bypass;
BiquadCoeffs coeffs[5];
BiquadCoeffs coeffs[10];
AVFrame *w;
} ASuperCutContext;
@ -69,33 +71,48 @@ static int query_formats(AVFilterContext *ctx)
return ff_set_common_samplerates(ctx, formats);
}
static void calc_q_factors(int n, double *q)
{
for (int i = 0; i < n / 2; i++)
q[i] = 1. / (-2. * cos(M_PI * (2. * (i + 1) + n - 1.) / (2. * n)));
}
static int get_coeffs(AVFilterContext *ctx)
{
ASuperCutContext *s = ctx->priv;
AVFilterLink *inlink = ctx->inputs[0];
double w0 = s->cutoff / inlink->sample_rate;
double K = tan(M_PI * w0);
double q[5];
double q[10];
s->bypass = w0 >= 0.5;
if (s->bypass)
return 0;
q[0] = 0.50623256;
q[1] = 0.56116312;
q[2] = 0.70710678;
q[3] = 1.10134463;
q[4] = 3.19622661;
s->filter_count = s->order / 2 + (s->order & 1);
calc_q_factors(s->order, q);
for (int b = 0; b < 5; b++) {
if (s->order & 1) {
BiquadCoeffs *coeffs = &s->coeffs[0];
double omega = 2. * tan(M_PI * w0);
coeffs->b0 = omega / (2. + omega);
coeffs->b1 = coeffs->b0;
coeffs->b2 = 0.;
coeffs->a1 = -(omega - 2.) / (2. + omega);
coeffs->a2 = 0.;
}
for (int b = (s->order & 1); b < s->filter_count; b++) {
BiquadCoeffs *coeffs = &s->coeffs[b];
double norm = 1.0 / (1.0 + K / q[b] + K * K);
const int idx = b - (s->order & 1);
double norm = 1.0 / (1.0 + K / q[idx] + K * K);
coeffs->b0 = K * K * norm;
coeffs->b1 = 2.0 * coeffs->b0;
coeffs->b2 = coeffs->b0;
coeffs->a1 = -2.0 * (K * K - 1.0) * norm;
coeffs->a2 = -(1.0 - K / q[b] + K * K) * norm;
coeffs->a2 = -(1.0 - K / q[idx] + K * K) * norm;
}
return 0;
@ -106,7 +123,7 @@ static int config_input(AVFilterLink *inlink)
AVFilterContext *ctx = inlink->dst;
ASuperCutContext *s = ctx->priv;
s->w = ff_get_audio_buffer(inlink, 2 * 5);
s->w = ff_get_audio_buffer(inlink, 2 * 10);
if (!s->w)
return AVERROR(ENOMEM);
@ -130,7 +147,7 @@ static int filter_channels(AVFilterContext *ctx, void *arg, int jobnr, int nb_jo
const double *src = (const double *)in->extended_data[ch];
double *dst = (double *)out->extended_data[ch];
for (int b = 0; b < 5; b++) {
for (int b = 0; b < s->filter_count; b++) {
BiquadCoeffs *coeffs = &s->coeffs[b];
const double a1 = coeffs->a1;
const double a2 = coeffs->a2;
@ -209,6 +226,7 @@ static av_cold void uninit(AVFilterContext *ctx)
static const AVOption asupercut_options[] = {
{ "cutoff", "set cutoff frequency", OFFSET(cutoff), AV_OPT_TYPE_DOUBLE, {.dbl=20000}, 20000, 192000, FLAGS },
{ "order", "set filter order", OFFSET(order), AV_OPT_TYPE_INT, {.i64=10}, 3, 20, FLAGS },
{ NULL }
};