avfilter: add multiband compand filter

Signed-off-by: Paul B Mahol <onemda@gmail.com>

1 files changed, 689 insertions, 0 deletions

diff --git a/libavfilter/af_mcompand.c b/libavfilter/af_mcompand.c
new file mode 100644
index 0000000000..02f987a6a8
--- /dev/null
+++ b/libavfilter/af_mcompand.c
@@ -0,0 +1,689 @@
+/*
+ * COpyright (c) 2002 Daniel Pouzzner
+ * Copyright (c) 1999 Chris Bagwell
+ * Copyright (c) 1999 Nick Bailey
+ * Copyright (c) 2007 Rob Sykes <robs@users.sourceforge.net>
+ * Copyright (c) 2013 Paul B Mahol
+ * Copyright (c) 2014 Andrew Kelley
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * audio multiband compand filter
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/avstring.h"
+#include "libavutil/ffmath.h"
+#include "libavutil/opt.h"
+#include "libavutil/samplefmt.h"
+#include "audio.h"
+#include "avfilter.h"
+#include "internal.h"
+
+typedef struct CompandSegment {
+    double x, y;
+    double a, b;
+} CompandSegment;
+
+typedef struct CompandT {
+    CompandSegment *segments;
+    int nb_segments;
+    double in_min_lin;
+    double out_min_lin;
+    double curve_dB;
+    double gain_dB;
+} CompandT;
+
+#define N 4
+
+typedef struct PrevCrossover {
+    double in;
+    double out_low;
+    double out_high;
+} PrevCrossover[N * 2];
+
+typedef struct Crossover {
+  PrevCrossover *previous;
+  size_t         pos;
+  double         coefs[3 *(N+1)];
+} Crossover;
+
+typedef struct CompBand {
+    CompandT transfer_fn;
+    double *attack_rate;
+    double *decay_rate;
+    double *volume;
+    double delay;
+    double topfreq;
+    Crossover filter;
+    AVFrame *delay_buf;
+    size_t delay_size;
+    ptrdiff_t delay_buf_ptr;
+    size_t delay_buf_cnt;
+} CompBand;
+
+typedef struct MCompandContext {
+    const AVClass *class;
+
+    char *args;
+
+    int nb_bands;
+    CompBand *bands;
+    AVFrame *band_buf1, *band_buf2, *band_buf3;
+    int band_samples;
+    size_t delay_buf_size;
+} MCompandContext;
+
+#define OFFSET(x) offsetof(MCompandContext, x)
+#define A AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+
+static const AVOption mcompand_options[] = {
+    { "args", "set parameters for each band", OFFSET(args), AV_OPT_TYPE_STRING, { .str = "0.005,0.1 6 -47/-40,-34/-34,-17/-33 100 | 0.003,0.05 6 -47/-40,-34/-34,-17/-33 400 | 0.000625,0.0125 6 -47/-40,-34/-34,-15/-33 1600 | 0.0001,0.025 6 -47/-40,-34/-34,-31/-31,-0/-30 6400 | 0,0.025 6 -38/-31,-28/-28,-0/-25 22000" }, 0, 0, A },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(mcompand);
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    MCompandContext *s = ctx->priv;
+    int i;
+
+    av_frame_free(&s->band_buf1);
+    av_frame_free(&s->band_buf2);
+    av_frame_free(&s->band_buf3);
+
+    if (s->bands) {
+        for (i = 0; i < s->nb_bands; i++) {
+            av_freep(&s->bands[i].attack_rate);
+            av_freep(&s->bands[i].decay_rate);
+            av_freep(&s->bands[i].volume);
+            av_freep(&s->bands[i].transfer_fn.segments);
+            av_freep(&s->bands[i].filter.previous);
+            av_frame_free(&s->bands[i].delay_buf);
+        }
+    }
+    av_freep(&s->bands);
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    AVFilterChannelLayouts *layouts;
+    AVFilterFormats *formats;
+    static const enum AVSampleFormat sample_fmts[] = {
+        AV_SAMPLE_FMT_DBLP,
+        AV_SAMPLE_FMT_NONE
+    };
+    int ret;
+
+    layouts = ff_all_channel_counts();
+    if (!layouts)
+        return AVERROR(ENOMEM);
+    ret = ff_set_common_channel_layouts(ctx, layouts);
+    if (ret < 0)
+        return ret;
+
+    formats = ff_make_format_list(sample_fmts);
+    if (!formats)
+        return AVERROR(ENOMEM);
+    ret = ff_set_common_formats(ctx, formats);
+    if (ret < 0)
+        return ret;
+
+    formats = ff_all_samplerates();
+    if (!formats)
+        return AVERROR(ENOMEM);
+    return ff_set_common_samplerates(ctx, formats);
+}
+
+static void count_items(char *item_str, int *nb_items, char delimiter)
+{
+    char *p;
+
+    *nb_items = 1;
+    for (p = item_str; *p; p++) {
+        if (*p == delimiter)
+            (*nb_items)++;
+    }
+}
+
+static void update_volume(CompBand *cb, double in, int ch)
+{
+    double delta = in - cb->volume[ch];
+
+    if (delta > 0.0)
+        cb->volume[ch] += delta * cb->attack_rate[ch];
+    else
+        cb->volume[ch] += delta * cb->decay_rate[ch];
+}
+
+static double get_volume(CompandT *s, double in_lin)
+{
+    CompandSegment *cs;
+    double in_log, out_log;
+    int i;
+
+    if (in_lin <= s->in_min_lin)
+        return s->out_min_lin;
+
+    in_log = log(in_lin);
+
+    for (i = 1; i < s->nb_segments; i++)
+        if (in_log <= s->segments[i].x)
+            break;
+    cs = &s->segments[i - 1];
+    in_log -= cs->x;
+    out_log = cs->y + in_log * (cs->a * in_log + cs->b);
+
+    return exp(out_log);
+}
+
+static int parse_points(char *points, int nb_points, double radius,
+                        CompandT *s, AVFilterContext *ctx)
+{
+    int new_nb_items, num;
+    char *saveptr = NULL;
+    char *p = points;
+    int i;
+
+#define S(x) s->segments[2 * ((x) + 1)]
+    for (i = 0, new_nb_items = 0; i < nb_points; i++) {
+        char *tstr = av_strtok(p, ",", &saveptr);
+        p = NULL;
+        if (!tstr || sscanf(tstr, "%lf/%lf", &S(i).x, &S(i).y) != 2) {
+            av_log(ctx, AV_LOG_ERROR,
+                    "Invalid and/or missing input/output value.\n");
+            return AVERROR(EINVAL);
+        }
+        if (i && S(i - 1).x > S(i).x) {
+            av_log(ctx, AV_LOG_ERROR,
+                    "Transfer function input values must be increasing.\n");
+            return AVERROR(EINVAL);
+        }
+        S(i).y -= S(i).x;
+        av_log(ctx, AV_LOG_DEBUG, "%d: x=%f y=%f\n", i, S(i).x, S(i).y);
+        new_nb_items++;
+    }
+    num = new_nb_items;
+
+    /* Add 0,0 if necessary */
+    if (num == 0 || S(num - 1).x)
+        num++;
+
+#undef S
+#define S(x) s->segments[2 * (x)]
+    /* Add a tail off segment at the start */
+    S(0).x = S(1).x - 2 * s->curve_dB;
+    S(0).y = S(1).y;
+    num++;
+
+    /* Join adjacent colinear segments */
+    for (i = 2; i < num; i++) {
+        double g1 = (S(i - 1).y - S(i - 2).y) * (S(i - 0).x - S(i - 1).x);
+        double g2 = (S(i - 0).y - S(i - 1).y) * (S(i - 1).x - S(i - 2).x);
+        int j;
+
+        if (fabs(g1 - g2))
+            continue;
+        num--;
+        for (j = --i; j < num; j++)
+            S(j) = S(j + 1);
+    }
+
+    for (i = 0; i < s->nb_segments; i += 2) {
+        s->segments[i].y += s->gain_dB;
+        s->segments[i].x *= M_LN10 / 20;
+        s->segments[i].y *= M_LN10 / 20;
+    }
+
+#define L(x) s->segments[i - (x)]
+    for (i = 4; i < s->nb_segments; i += 2) {
+        double x, y, cx, cy, in1, in2, out1, out2, theta, len, r;
+
+        L(4).a = 0;
+        L(4).b = (L(2).y - L(4).y) / (L(2).x - L(4).x);
+
+        L(2).a = 0;
+        L(2).b = (L(0).y - L(2).y) / (L(0).x - L(2).x);
+
+        theta = atan2(L(2).y - L(4).y, L(2).x - L(4).x);
+        len = hypot(L(2).x - L(4).x, L(2).y - L(4).y);
+        r = FFMIN(radius, len);
+        L(3).x = L(2).x - r * cos(theta);
+        L(3).y = L(2).y - r * sin(theta);
+
+        theta = atan2(L(0).y - L(2).y, L(0).x - L(2).x);
+        len = hypot(L(0).x - L(2).x, L(0).y - L(2).y);
+        r = FFMIN(radius, len / 2);
+        x = L(2).x + r * cos(theta);
+        y = L(2).y + r * sin(theta);
+
+        cx = (L(3).x + L(2).x + x) / 3;
+        cy = (L(3).y + L(2).y + y) / 3;
+
+        L(2).x = x;
+        L(2).y = y;
+
+        in1  = cx - L(3).x;
+        out1 = cy - L(3).y;
+        in2  = L(2).x - L(3).x;
+        out2 = L(2).y - L(3).y;
+        L(3).a = (out2 / in2 - out1 / in1) / (in2 - in1);
+        L(3).b = out1 / in1 - L(3).a * in1;
+    }
+    L(3).x = 0;
+    L(3).y = L(2).y;
+
+    s->in_min_lin  = exp(s->segments[1].x);
+    s->out_min_lin = exp(s->segments[1].y);
+
+    return 0;
+}
+
+static void square_quadratic(double const *x, double *y)
+{
+    y[0] = x[0] * x[0];
+    y[1] = 2 * x[0] * x[1];
+    y[2] = 2 * x[0] * x[2] + x[1] * x[1];
+    y[3] = 2 * x[1] * x[2];
+    y[4] = x[2] * x[2];
+}
+
+static int crossover_setup(AVFilterLink *outlink, Crossover *p, double frequency)
+{
+    double w0 = 2 * M_PI * frequency / outlink->sample_rate;
+    double Q = sqrt(.5), alpha = sin(w0) / (2*Q);
+    double x[9], norm;
+    int i;
+
+    if (w0 > M_PI)
+        return AVERROR(EINVAL);
+
+    x[0] =  (1 - cos(w0))/2;           /* Cf. filter_LPF in biquads.c */
+    x[1] =   1 - cos(w0);
+    x[2] =  (1 - cos(w0))/2;
+    x[3] =  (1 + cos(w0))/2;           /* Cf. filter_HPF in biquads.c */
+    x[4] = -(1 + cos(w0));
+    x[5] =  (1 + cos(w0))/2;
+    x[6] =   1 + alpha;
+    x[7] =  -2*cos(w0);
+    x[8] =   1 - alpha;
+
+    for (norm = x[6], i = 0; i < 9; ++i)
+        x[i] /= norm;
+
+    square_quadratic(x    , p->coefs);
+    square_quadratic(x + 3, p->coefs + 5);
+    square_quadratic(x + 6, p->coefs + 10);
+
+    p->previous = av_calloc(outlink->channels, sizeof(*p->previous));
+    if (!p->previous)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+static int config_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx  = outlink->src;
+    MCompandContext *s    = ctx->priv;
+    int ret, ch, i, k, new_nb_items, nb_bands;
+    char *p = s->args, *saveptr = NULL;
+    int max_delay_size = 0;
+
+    count_items(s->args, &nb_bands, '|');
+    s->nb_bands = FFMAX(1, nb_bands);
+
+    s->bands = av_calloc(nb_bands, sizeof(*s->bands));
+    if (!s->bands)
+        return AVERROR(ENOMEM);
+
+    for (i = 0, new_nb_items = 0; i < nb_bands; i++) {
+        int nb_points, nb_attacks, nb_items = 0;
+        char *tstr2, *tstr = av_strtok(p, "|", &saveptr);
+        char *p2, *p3, *saveptr2 = NULL, *saveptr3 = NULL;
+        double radius;
+
+        if (!tstr) {
+            uninit(ctx);
+            return AVERROR(EINVAL);
+        }
+        p = NULL;
+
+        p2 = tstr;
+        count_items(tstr, &nb_items, ' ');
+        tstr2 = av_strtok(p2, " ", &saveptr2);
+        if (!tstr2) {
+            av_log(ctx, AV_LOG_ERROR, "at least one attacks/decays rate is mandatory\n");
+            uninit(ctx);
+            return AVERROR(EINVAL);
+        }
+        p2 = NULL;
+        p3 = tstr2;
+
+        count_items(tstr2, &nb_attacks, ',');
+        if (!nb_attacks || nb_attacks & 1) {
+            av_log(ctx, AV_LOG_ERROR, "number of attacks rate plus decays rate must be even\n");
+            uninit(ctx);
+            return AVERROR(EINVAL);
+        }
+
+        s->bands[i].attack_rate = av_calloc(outlink->channels, sizeof(double));
+        s->bands[i].decay_rate = av_calloc(outlink->channels, sizeof(double));
+        s->bands[i].volume = av_calloc(outlink->channels, sizeof(double));
+        for (k = 0; k < FFMIN(nb_attacks / 2, outlink->channels); k++) {
+            char *tstr3 = av_strtok(p3, ",", &saveptr3);
+
+            p3 = NULL;
+            sscanf(tstr3, "%lf", &s->bands[i].attack_rate[k]);
+            tstr3 = av_strtok(p3, ",", &saveptr3);
+            sscanf(tstr3, "%lf", &s->bands[i].decay_rate[k]);
+
+            if (s->bands[i].attack_rate[k] > 1.0 / outlink->sample_rate) {
+                s->bands[i].attack_rate[k] = 1.0 - exp(-1.0 / (outlink->sample_rate * s->bands[i].attack_rate[k]));
+            } else {
+                s->bands[i].attack_rate[k] = 1.0;
+            }
+
+            if (s->bands[i].decay_rate[k] > 1.0 / outlink->sample_rate) {
+                s->bands[i].decay_rate[k] = 1.0 - exp(-1.0 / (outlink->sample_rate * s->bands[i].decay_rate[k]));
+            } else {
+                s->bands[i].decay_rate[k] = 1.0;
+            }
+        }
+
+        for (ch = k; ch < outlink->channels; ch++) {
+            s->bands[i].attack_rate[ch] = s->bands[i].attack_rate[k - 1];
+            s->bands[i].decay_rate[ch]  = s->bands[i].decay_rate[k - 1];
+        }
+
+        tstr2 = av_strtok(p2, " ", &saveptr2);
+        if (!tstr2) {
+            av_log(ctx, AV_LOG_ERROR, "transfer function curve in dB must be set\n");
+            uninit(ctx);
+            return AVERROR(EINVAL);
+        }
+        sscanf(tstr2, "%lf", &s->bands[i].transfer_fn.curve_dB);
+
+        radius = s->bands[i].transfer_fn.curve_dB * M_LN10 / 20.0;
+
+        tstr2 = av_strtok(p2, " ", &saveptr2);
+        if (!tstr2) {
+            av_log(ctx, AV_LOG_ERROR, "transfer points missing\n");
+            uninit(ctx);
+            return AVERROR(EINVAL);
+        }
+
+        count_items(tstr2, &nb_points, ',');
+        s->bands[i].transfer_fn.nb_segments = (nb_points + 4) * 2;
+        s->bands[i].transfer_fn.segments = av_calloc(s->bands[i].transfer_fn.nb_segments,
+                                                     sizeof(CompandSegment));
+        if (!s->bands[i].transfer_fn.segments) {
+            uninit(ctx);
+            return AVERROR(ENOMEM);
+        }
+
+        ret = parse_points(tstr2, nb_points, radius, &s->bands[i].transfer_fn, ctx);
+        if (ret < 0) {
+            av_log(ctx, AV_LOG_ERROR, "transfer points parsing failed\n");
+            uninit(ctx);
+            return ret;
+        }
+
+        tstr2 = av_strtok(p2, " ", &saveptr2);
+        if (!tstr2) {
+            av_log(ctx, AV_LOG_ERROR, "crossover_frequency is missing\n");
+            uninit(ctx);
+            return AVERROR(EINVAL);
+        }
+
+        new_nb_items += sscanf(tstr2, "%lf", &s->bands[i].topfreq) == 1;
+        if (s->bands[i].topfreq < 0 || s->bands[i].topfreq >= outlink->sample_rate / 2) {
+            av_log(ctx, AV_LOG_ERROR, "crossover_frequency should be >=0 and lower than half of sample rate\n");
+            uninit(ctx);
+            return AVERROR(EINVAL);
+        }
+
+        if (s->bands[i].topfreq != 0) {
+            ret = crossover_setup(outlink, &s->bands[i].filter, s->bands[i].topfreq);
+            if (ret < 0) {
+                uninit(ctx);
+                return ret;
+            }
+        }
+
+        tstr2 = av_strtok(p2, " ", &saveptr2);
+        if (tstr2) {
+            sscanf(tstr2, "%lf", &s->bands[i].delay);
+            max_delay_size = FFMAX(max_delay_size, s->bands[i].delay * outlink->sample_rate);
+
+            tstr2 = av_strtok(p2, " ", &saveptr2);
+            if (tstr2) {
+                double initial_volume;
+
+                sscanf(tstr2, "%lf", &initial_volume);
+                initial_volume = pow(10.0, initial_volume / 20);
+
+                for (k = 0; k < outlink->channels; k++) {
+                    s->bands[i].volume[k] = initial_volume;
+                }
+
+                tstr2 = av_strtok(p2, " ", &saveptr2);
+                if (tstr2) {
+                    sscanf(tstr2, "%lf", &s->bands[i].transfer_fn.gain_dB);
+                }
+            }
+        }
+    }
+    s->nb_bands = new_nb_items;
+
+    for (i = 0; max_delay_size > 0 && i < s->nb_bands; i++) {
+        s->bands[i].delay_buf = ff_get_audio_buffer(outlink, max_delay_size);
+        if (!s->bands[i].delay_buf)
+            return AVERROR(ENOMEM);
+    }
+    s->delay_buf_size = max_delay_size;
+
+    return 0;
+}
+
+#define CONVOLVE _ _ _ _
+
+static void crossover(int ch, Crossover *p,
+                      double *ibuf, double *obuf_low,
+                      double *obuf_high, size_t len)
+{
+    double out_low, out_high;
+
+    while (len--) {
+        p->pos = p->pos ? p->pos - 1 : N - 1;
+#define _ out_low += p->coefs[j] * p->previous[ch][p->pos + j].in \
+            - p->coefs[2*N+2 + j] * p->previous[ch][p->pos + j].out_low, j++;
+        {
+            int j = 1;
+            out_low = p->coefs[0] * *ibuf;
+            CONVOLVE
+            *obuf_low++ = out_low;
+        }
+#undef _
+#define _ out_high += p->coefs[j+N+1] * p->previous[ch][p->pos + j].in \
+            - p->coefs[2*N+2 + j] * p->previous[ch][p->pos + j].out_high, j++;
+        {
+            int j = 1;
+            out_high = p->coefs[N+1] * *ibuf;
+            CONVOLVE
+            *obuf_high++ = out_high;
+        }
+        p->previous[ch][p->pos + N].in = p->previous[ch][p->pos].in = *ibuf++;
+        p->previous[ch][p->pos + N].out_low = p->previous[ch][p->pos].out_low = out_low;
+        p->previous[ch][p->pos + N].out_high = p->previous[ch][p->pos].out_high = out_high;
+    }
+}
+
+static int mcompand_channel(MCompandContext *c, CompBand *l, double *ibuf, double *obuf, int len, int ch)
+{
+    int i;
+
+    for (i = 0; i < len; i++) {
+        double level_in_lin, level_out_lin, checkbuf;
+        /* Maintain the volume fields by simulating a leaky pump circuit */
+        update_volume(l, fabs(ibuf[i]), ch);
+
+        /* Volume memory is updated: perform compand */
+        level_in_lin = l->volume[ch];
+        level_out_lin = get_volume(&l->transfer_fn, level_in_lin);
+
+        if (c->delay_buf_size <= 0) {
+            checkbuf = ibuf[i] * level_out_lin;
+            obuf[i] = checkbuf;
+        } else {
+            double *delay_buf = (double *)l->delay_buf->extended_data[ch];
+
+            /* FIXME: note that this lookahead algorithm is really lame:
+               the response to a peak is released before the peak
+               arrives. */
+
+            /* because volume application delays differ band to band, but
+               total delay doesn't, the volume is applied in an iteration
+               preceding that in which the sample goes to obuf, except in
+               the band(s) with the longest vol app delay.
+
+               the offset between delay_buf_ptr and the sample to apply
+               vol to, is a constant equal to the difference between this
+               band's delay and the longest delay of all the bands. */
+
+            if (l->delay_buf_cnt >= l->delay_size) {
+                checkbuf =
+                    delay_buf[(l->delay_buf_ptr +
+                               c->delay_buf_size -
+                               l->delay_size) % c->delay_buf_size] * level_out_lin;
+                delay_buf[(l->delay_buf_ptr + c->delay_buf_size -
+                           l->delay_size) % c->delay_buf_size] = checkbuf;
+            }
+            if (l->delay_buf_cnt >= c->delay_buf_size) {
+                obuf[i] = delay_buf[l->delay_buf_ptr];
+            } else {
+                l->delay_buf_cnt++;
+            }
+            delay_buf[l->delay_buf_ptr++] = ibuf[i];
+            l->delay_buf_ptr %= c->delay_buf_size;
+        }
+    }
+
+    return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+    AVFilterContext  *ctx = inlink->dst;
+    AVFilterLink *outlink = ctx->outputs[0];
+    MCompandContext *s    = ctx->priv;
+    AVFrame *out, *abuf, *bbuf, *cbuf;
+    int ch, band, i;
+
+    out = ff_get_audio_buffer(outlink, in->nb_samples);
+    if (!out) {
+        av_frame_free(&in);
+        return AVERROR(ENOMEM);
+    }
+
+    if (s->band_samples < in->nb_samples) {
+        av_frame_free(&s->band_buf1);
+        av_frame_free(&s->band_buf2);
+        av_frame_free(&s->band_buf3);
+
+        s->band_buf1 = ff_get_audio_buffer(outlink, in->nb_samples);
+        s->band_buf2 = ff_get_audio_buffer(outlink, in->nb_samples);
+        s->band_buf3 = ff_get_audio_buffer(outlink, in->nb_samples);
+        s->band_samples = in->nb_samples;
+    }
+
+    for (ch = 0; ch < outlink->channels; ch++) {
+        double *a, *dst = (double *)out->extended_data[ch];
+
+        for (band = 0, abuf = in, bbuf = s->band_buf2, cbuf = s->band_buf1; band < s->nb_bands; band++) {
+            CompBand *b = &s->bands[band];
+
+            if (b->topfreq) {
+                crossover(ch, &b->filter, (double *)abuf->extended_data[ch],
+                          (double *)bbuf->extended_data[ch], (double *)cbuf->extended_data[ch], in->nb_samples);
+            } else {
+                bbuf = abuf;
+                abuf = cbuf;
+            }
+
+            if (abuf == in)
+                abuf = s->band_buf3;
+            mcompand_channel(s, b, (double *)bbuf->extended_data[ch], (double *)abuf->extended_data[ch], out->nb_samples, ch);
+            a = (double *)abuf->extended_data[ch];
+            for (i = 0; i < out->nb_samples; i++) {
+                dst[i] += a[i];
+            }
+
+            FFSWAP(AVFrame *, abuf, cbuf);
+        }
+    }
+
+    out->pts = in->pts;
+    av_frame_free(&in);
+    return ff_filter_frame(outlink, out);
+}
+
+static int request_frame(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    int ret;
+
+    ret = ff_request_frame(ctx->inputs[0]);
+
+    return ret;
+}
+
+static const AVFilterPad mcompand_inputs[] = {
+    {
+        .name           = "default",
+        .type           = AVMEDIA_TYPE_AUDIO,
+        .filter_frame   = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad mcompand_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_AUDIO,
+        .request_frame = request_frame,
+        .config_props  = config_output,
+    },
+    { NULL }
+};
+
+
+AVFilter ff_af_mcompand = {
+    .name           = "mcompand",
+    .description    = NULL_IF_CONFIG_SMALL(
+            "Multiband Compress or expand audio dynamic range."),
+    .query_formats  = query_formats,
+    .priv_size      = sizeof(MCompandContext),
+    .priv_class     = &mcompand_class,
+    .uninit         = uninit,
+    .inputs         = mcompand_inputs,
+    .outputs        = mcompand_outputs,
+};