[FFmpeg-cvslog] avfilter/af_acrossover: improve filter output
Paul B Mahol
git at videolan.org
Thu Feb 6 16:45:30 EET 2020
ffmpeg | branch: master | Paul B Mahol <onemda at gmail.com> | Sun Apr 14 19:03:39 2019 +0200| [270068b5af281dae9280306b1621d1f2b7920adb] | committer: Paul B Mahol
avfilter/af_acrossover: improve filter output
Makes sum always flat. Also faster.
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=270068b5af281dae9280306b1621d1f2b7920adb
---
libavfilter/af_acrossover.c | 58 +++++++++++++++------------------------------
1 file changed, 19 insertions(+), 39 deletions(-)
diff --git a/libavfilter/af_acrossover.c b/libavfilter/af_acrossover.c
index b1a1155c29..31d7568abc 100644
--- a/libavfilter/af_acrossover.c
+++ b/libavfilter/af_acrossover.c
@@ -47,7 +47,6 @@ typedef struct BiquadContext {
typedef struct CrossoverChannel {
BiquadContext lp[MAX_BANDS][4];
- BiquadContext hp[MAX_BANDS][4];
} CrossoverChannel;
typedef struct AudioCrossoverContext {
@@ -131,30 +130,16 @@ static av_cold int init(AVFilterContext *ctx)
return ret;
}
-static void set_lp(BiquadContext *b, float fc, float q, float sr)
+static void set_lp(BiquadContext *b, double fc, double q, double sr)
{
- double omega = (2.0 * M_PI * fc / sr);
+ double omega = 2.0 * M_PI * fc / sr;
double sn = sin(omega);
double cs = cos(omega);
- double alpha = (sn / (2 * q));
- double inv = (1.0 / (1.0 + alpha));
-
- b->a2 = b->a0 = (inv * (1.0 - cs) * 0.5);
- b->a1 = b->a0 + b->a0;
- b->b1 = -2. * cs * inv;
- b->b2 = (1. - alpha) * inv;
-}
-
-static void set_hp(BiquadContext *b, float fc, float q, float sr)
-{
- double omega = 2 * M_PI * fc / sr;
- double sn = sin(omega);
- double cs = cos(omega);
- double alpha = sn / (2 * q);
+ double alpha = sn / (2. * q);
double inv = 1.0 / (1.0 + alpha);
- b->a0 = inv * (1. + cs) / 2.;
- b->a1 = -2. * b->a0;
+ b->a0 = (1. - cs) * 0.5 * inv;
+ b->a1 = (1. - cs) * inv;
b->a2 = b->a0;
b->b1 = -2. * cs * inv;
b->b2 = (1. - alpha) * inv;
@@ -189,18 +174,13 @@ static int config_input(AVFilterLink *inlink)
for (ch = 0; ch < inlink->channels; ch++) {
for (band = 0; band <= s->nb_splits; band++) {
set_lp(&s->xover[ch].lp[band][0], s->splits[band], q, sample_rate);
- set_hp(&s->xover[ch].hp[band][0], s->splits[band], q, sample_rate);
if (s->order > 1) {
set_lp(&s->xover[ch].lp[band][1], s->splits[band], 1.34, sample_rate);
- set_hp(&s->xover[ch].hp[band][1], s->splits[band], 1.34, sample_rate);
set_lp(&s->xover[ch].lp[band][2], s->splits[band], q, sample_rate);
- set_hp(&s->xover[ch].hp[band][2], s->splits[band], q, sample_rate);
set_lp(&s->xover[ch].lp[band][3], s->splits[band], 1.34, sample_rate);
- set_hp(&s->xover[ch].hp[band][3], s->splits[band], 1.34, sample_rate);
} else {
set_lp(&s->xover[ch].lp[band][1], s->splits[band], q, sample_rate);
- set_hp(&s->xover[ch].hp[band][1], s->splits[band], q, sample_rate);
}
}
}
@@ -275,23 +255,23 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
const double *src = (const double *)in->extended_data[ch];
CrossoverChannel *xover = &s->xover[ch];
- for (band = 0; band < ctx->nb_outputs; band++) {
- double *dst = (double *)frames[band]->extended_data[ch];
-
- for (i = 0; i < in->nb_samples; i++) {
- dst[i] = src[i];
+ for (i = 0; i < in->nb_samples; i++) {
+ double sample = src[i], lo, hi;
- for (f = 0; f < s->filter_count; f++) {
- if (band + 1 < ctx->nb_outputs) {
- BiquadContext *lp = &xover->lp[band][f];
- dst[i] = biquad_process(lp, dst[i]);
- }
+ for (band = 0; band < ctx->nb_outputs; band++) {
+ double *dst = (double *)frames[band]->extended_data[ch];
- if (band - 1 >= 0) {
- BiquadContext *hp = &xover->hp[band - 1][f];
- dst[i] = biquad_process(hp, dst[i]);
- }
+ lo = sample;
+ for (f = 0; band + 1 < ctx->nb_outputs && f < s->filter_count; f++) {
+ BiquadContext *lp = &xover->lp[band][f];
+ lo = biquad_process(lp, lo);
}
+
+ hi = sample - lo;
+
+ dst[i] = lo;
+
+ sample = hi;
}
}
}
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