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avfilter/af_acrossover: improve filter output
Makes sum always flat. Also faster.
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616e9b5cff
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@ -47,7 +47,6 @@ typedef struct BiquadContext {
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typedef struct CrossoverChannel {
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BiquadContext lp[MAX_BANDS][4];
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BiquadContext hp[MAX_BANDS][4];
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} CrossoverChannel;
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typedef struct AudioCrossoverContext {
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@ -131,30 +130,16 @@ static av_cold int init(AVFilterContext *ctx)
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return ret;
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}
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static void set_lp(BiquadContext *b, float fc, float q, float sr)
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static void set_lp(BiquadContext *b, double fc, double q, double sr)
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{
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double omega = (2.0 * M_PI * fc / sr);
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double omega = 2.0 * M_PI * fc / sr;
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double sn = sin(omega);
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double cs = cos(omega);
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double alpha = (sn / (2 * q));
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double inv = (1.0 / (1.0 + alpha));
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b->a2 = b->a0 = (inv * (1.0 - cs) * 0.5);
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b->a1 = b->a0 + b->a0;
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b->b1 = -2. * cs * inv;
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b->b2 = (1. - alpha) * inv;
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}
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static void set_hp(BiquadContext *b, float fc, float q, float sr)
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{
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double omega = 2 * M_PI * fc / sr;
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double sn = sin(omega);
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double cs = cos(omega);
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double alpha = sn / (2 * q);
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double alpha = sn / (2. * q);
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double inv = 1.0 / (1.0 + alpha);
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b->a0 = inv * (1. + cs) / 2.;
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b->a1 = -2. * b->a0;
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b->a0 = (1. - cs) * 0.5 * inv;
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b->a1 = (1. - cs) * inv;
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b->a2 = b->a0;
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b->b1 = -2. * cs * inv;
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b->b2 = (1. - alpha) * inv;
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@ -189,18 +174,13 @@ static int config_input(AVFilterLink *inlink)
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for (ch = 0; ch < inlink->channels; ch++) {
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for (band = 0; band <= s->nb_splits; band++) {
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set_lp(&s->xover[ch].lp[band][0], s->splits[band], q, sample_rate);
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set_hp(&s->xover[ch].hp[band][0], s->splits[band], q, sample_rate);
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if (s->order > 1) {
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set_lp(&s->xover[ch].lp[band][1], s->splits[band], 1.34, sample_rate);
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set_hp(&s->xover[ch].hp[band][1], s->splits[band], 1.34, sample_rate);
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set_lp(&s->xover[ch].lp[band][2], s->splits[band], q, sample_rate);
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set_hp(&s->xover[ch].hp[band][2], s->splits[band], q, sample_rate);
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set_lp(&s->xover[ch].lp[band][3], s->splits[band], 1.34, sample_rate);
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set_hp(&s->xover[ch].hp[band][3], s->splits[band], 1.34, sample_rate);
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} else {
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set_lp(&s->xover[ch].lp[band][1], s->splits[band], q, sample_rate);
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set_hp(&s->xover[ch].hp[band][1], s->splits[band], q, sample_rate);
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}
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}
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}
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@ -275,23 +255,23 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
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const double *src = (const double *)in->extended_data[ch];
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CrossoverChannel *xover = &s->xover[ch];
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for (band = 0; band < ctx->nb_outputs; band++) {
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double *dst = (double *)frames[band]->extended_data[ch];
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for (i = 0; i < in->nb_samples; i++) {
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double sample = src[i], lo, hi;
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for (i = 0; i < in->nb_samples; i++) {
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dst[i] = src[i];
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for (band = 0; band < ctx->nb_outputs; band++) {
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double *dst = (double *)frames[band]->extended_data[ch];
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for (f = 0; f < s->filter_count; f++) {
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if (band + 1 < ctx->nb_outputs) {
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BiquadContext *lp = &xover->lp[band][f];
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dst[i] = biquad_process(lp, dst[i]);
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}
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if (band - 1 >= 0) {
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BiquadContext *hp = &xover->hp[band - 1][f];
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dst[i] = biquad_process(hp, dst[i]);
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}
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lo = sample;
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for (f = 0; band + 1 < ctx->nb_outputs && f < s->filter_count; f++) {
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BiquadContext *lp = &xover->lp[band][f];
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lo = biquad_process(lp, lo);
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}
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hi = sample - lo;
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dst[i] = lo;
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sample = hi;
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}
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}
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}
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