avfilter: add sidechaingate filter

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

Changelog

@@ -38,6 +38,7 @@ version <next>:
 - acompressor filter
 - support encoding 16-bit RLE SGI images
 - apulsator filter
+- sidechaingate audio filter
 
 
 version 2.8:

doc/filters.texi

@@ -2597,6 +2597,67 @@ ffmpeg -i main.flac -i sidechain.flac -filter_complex "[1:a]asplit=2[sc][mix];[0
 @end example
 @end itemize
 
+@section sidechaingate
+
+A sidechain gate acts like a normal (wideband) gate but has the ability to
+filter the detected signal before sending it to the gain reduction stage.
+Normally a gate uses the full range signal to detect a level above the
+threshold.
+For example: If you cut all lower frequencies from your sidechain signal
+the gate will decrease the volume of your track only if not enough highs
+appear. With this technique you are able to reduce the resonation of a
+natural drum or remove "rumbling" of muted strokes from a heavily distorted
+guitar.
+It needs two input streams and returns one output stream.
+First input stream will be processed depending on second stream signal.
+
+The filter accepts the following options:
+
+@table @option
+@item level_in
+Set input level before filtering.
+Default is 1. Allowed range is from 0.015625 to 64.
+
+@item range
+Set the level of gain reduction when the signal is below the threshold.
+Default is 0.06125. Allowed range is from 0 to 1.
+
+@item threshold
+If a signal rises above this level the gain reduction is released.
+Default is 0.125. Allowed range is from 0 to 1.
+
+@item ratio
+Set a ratio about which the signal is reduced.
+Default is 2. Allowed range is from 1 to 9000.
+
+@item attack
+Amount of milliseconds the signal has to rise above the threshold before gain
+reduction stops.
+Default is 20 milliseconds. Allowed range is from 0.01 to 9000.
+
+@item release
+Amount of milliseconds the signal has to fall below the threshold before the
+reduction is increased again. Default is 250 milliseconds.
+Allowed range is from 0.01 to 9000.
+
+@item makeup
+Set amount of amplification of signal after processing.
+Default is 1. Allowed range is from 1 to 64.
+
+@item knee
+Curve the sharp knee around the threshold to enter gain reduction more softly.
+Default is 2.828427125. Allowed range is from 1 to 8.
+
+@item detection
+Choose if exact signal should be taken for detection or an RMS like one.
+Default is peak. Can be peak or rms.
+
+@item link
+Choose if the average level between all channels or the louder channel affects
+the reduction.
+Default is average. Can be average or maximum.
+@end table
+
 @section silencedetect
 
 Detect silence in an audio stream.

libavfilter/Makefile

@@ -83,6 +83,7 @@ OBJS-$(CONFIG_REPLAYGAIN_FILTER)             += af_replaygain.o
 OBJS-$(CONFIG_RESAMPLE_FILTER)               += af_resample.o
 OBJS-$(CONFIG_RUBBERBAND_FILTER)             += af_rubberband.o
 OBJS-$(CONFIG_SIDECHAINCOMPRESS_FILTER)      += af_sidechaincompress.o
+OBJS-$(CONFIG_SIDECHAINGATE_FILTER)          += af_agate.o
 OBJS-$(CONFIG_SILENCEDETECT_FILTER)          += af_silencedetect.o
 OBJS-$(CONFIG_SILENCEREMOVE_FILTER)          += af_silenceremove.o
 OBJS-$(CONFIG_STEREOTOOLS_FILTER)            += af_stereotools.o

libavfilter/af_agate.c

@@ -18,6 +18,12 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
+/**
+ * @file
+ * Audio (Sidechain) Gate filter
+ */
+
+#include "libavutil/avassert.h"
 #include "libavutil/channel_layout.h"
 #include "libavutil/opt.h"
 #include "avfilter.h"
@@ -46,12 +52,14 @@ typedef struct AudioGateContext {
     double lin_slope;
     double attack_coeff;
     double release_coeff;
+
+    AVFrame *input_frame[2];
 } AudioGateContext;
 
 #define OFFSET(x) offsetof(AudioGateContext, x)
 #define A AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
 
-static const AVOption agate_options[] = {
+static const AVOption options[] = {
     { "level_in",  "set input level",        OFFSET(level_in),  AV_OPT_TYPE_DOUBLE, {.dbl=1},           0.015625,   64, A },
     { "range",     "set max gain reduction", OFFSET(range),     AV_OPT_TYPE_DOUBLE, {.dbl=0.06125},     0, 1, A },
     { "threshold", "set threshold",          OFFSET(threshold), AV_OPT_TYPE_DOUBLE, {.dbl=0.125},       0, 1, A },
@@ -69,6 +77,7 @@ static const AVOption agate_options[] = {
     { NULL }
 };
 
+#define agate_options options
 AVFILTER_DEFINE_CLASS(agate);
 
 static int query_formats(AVFilterContext *ctx)
@@ -97,7 +106,7 @@ static int query_formats(AVFilterContext *ctx)
     return ff_set_common_samplerates(ctx, formats);
 }
 
-static int config_input(AVFilterLink *inlink)
+static int agate_config_input(AVFilterLink *inlink)
 {
     AVFilterContext *ctx = inlink->dst;
     AudioGateContext *s = ctx->priv;
@@ -221,7 +230,7 @@ static const AVFilterPad inputs[] = {
         .name         = "default",
         .type         = AVMEDIA_TYPE_AUDIO,
         .filter_frame = filter_frame,
-        .config_props = config_input,
+        .config_props = agate_config_input,
     },
     { NULL }
 };
@@ -243,3 +252,158 @@ AVFilter ff_af_agate = {
     .inputs         = inputs,
     .outputs        = outputs,
 };
+
+#if CONFIG_SIDECHAINGATE_FILTER
+
+#define sidechaingate_options options
+AVFILTER_DEFINE_CLASS(sidechaingate);
+
+static int scfilter_frame(AVFilterLink *link, AVFrame *in)
+{
+    AVFilterContext *ctx = link->dst;
+    AudioGateContext *s = ctx->priv;
+    AVFilterLink *outlink = ctx->outputs[0];
+    const double *scsrc;
+    double *sample;
+    int nb_samples;
+    int ret, i;
+
+    for (i = 0; i < 2; i++)
+        if (link == ctx->inputs[i])
+            break;
+    av_assert0(i < 2 && !s->input_frame[i]);
+    s->input_frame[i] = in;
+
+    if (!s->input_frame[0] || !s->input_frame[1])
+        return 0;
+
+    nb_samples = FFMIN(s->input_frame[0]->nb_samples,
+                       s->input_frame[1]->nb_samples);
+
+    sample = (double *)s->input_frame[0]->data[0];
+    scsrc = (const double *)s->input_frame[1]->data[0];
+
+    gate(s, sample, sample, scsrc, nb_samples,
+         ctx->inputs[0], ctx->inputs[1]);
+    ret = ff_filter_frame(outlink, s->input_frame[0]);
+
+    s->input_frame[0] = NULL;
+    av_frame_free(&s->input_frame[1]);
+
+    return ret;
+}
+
+static int screquest_frame(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    AudioGateContext *s = ctx->priv;
+    int i, ret;
+
+    /* get a frame on each input */
+    for (i = 0; i < 2; i++) {
+        AVFilterLink *inlink = ctx->inputs[i];
+        if (!s->input_frame[i] &&
+            (ret = ff_request_frame(inlink)) < 0)
+            return ret;
+
+        /* request the same number of samples on all inputs */
+        if (i == 0)
+            ctx->inputs[1]->request_samples = s->input_frame[0]->nb_samples;
+    }
+
+    return 0;
+}
+
+static int scquery_formats(AVFilterContext *ctx)
+{
+    AVFilterFormats *formats;
+    AVFilterChannelLayouts *layouts = NULL;
+    static const enum AVSampleFormat sample_fmts[] = {
+        AV_SAMPLE_FMT_DBL,
+        AV_SAMPLE_FMT_NONE
+    };
+    int ret, i;
+
+    if (!ctx->inputs[0]->in_channel_layouts ||
+        !ctx->inputs[0]->in_channel_layouts->nb_channel_layouts) {
+        av_log(ctx, AV_LOG_WARNING,
+               "No channel layout for input 1\n");
+            return AVERROR(EAGAIN);
+    }
+
+    if ((ret = ff_add_channel_layout(&layouts, ctx->inputs[0]->in_channel_layouts->channel_layouts[0])) < 0 ||
+        (ret = ff_channel_layouts_ref(layouts, &ctx->outputs[0]->in_channel_layouts)) < 0)
+        return ret;
+
+    for (i = 0; i < 2; i++) {
+        layouts = ff_all_channel_counts();
+        if ((ret = ff_channel_layouts_ref(layouts, &ctx->inputs[i]->out_channel_layouts)) < 0)
+            return ret;
+    }
+
+    formats = ff_make_format_list(sample_fmts);
+    if ((ret = ff_set_common_formats(ctx, formats)) < 0)
+        return ret;
+
+    formats = ff_all_samplerates();
+    return ff_set_common_samplerates(ctx, formats);
+}
+
+static int scconfig_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+
+    if (ctx->inputs[0]->sample_rate != ctx->inputs[1]->sample_rate) {
+        av_log(ctx, AV_LOG_ERROR,
+               "Inputs must have the same sample rate "
+               "%d for in0 vs %d for in1\n",
+               ctx->inputs[0]->sample_rate, ctx->inputs[1]->sample_rate);
+        return AVERROR(EINVAL);
+    }
+
+    outlink->sample_rate = ctx->inputs[0]->sample_rate;
+    outlink->time_base   = ctx->inputs[0]->time_base;
+    outlink->channel_layout = ctx->inputs[0]->channel_layout;
+    outlink->channels = ctx->inputs[0]->channels;
+
+    agate_config_input(ctx->inputs[0]);
+
+    return 0;
+}
+
+static const AVFilterPad sidechaingate_inputs[] = {
+    {
+        .name           = "main",
+        .type           = AVMEDIA_TYPE_AUDIO,
+        .filter_frame   = scfilter_frame,
+        .needs_writable = 1,
+        .needs_fifo     = 1,
+    },{
+        .name           = "sidechain",
+        .type           = AVMEDIA_TYPE_AUDIO,
+        .filter_frame   = scfilter_frame,
+        .needs_fifo     = 1,
+    },
+    { NULL }
+};
+
+static const AVFilterPad sidechaingate_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_AUDIO,
+        .config_props  = scconfig_output,
+        .request_frame = screquest_frame,
+    },
+    { NULL }
+};
+
+AVFilter ff_af_sidechaingate = {
+    .name           = "sidechaingate",
+    .description    = NULL_IF_CONFIG_SMALL("Audio sidechain gate."),
+    .priv_size      = sizeof(AudioGateContext),
+    .priv_class     = &sidechaingate_class,
+    .query_formats  = scquery_formats,
+    .inputs         = sidechaingate_inputs,
+    .outputs        = sidechaingate_outputs,
+};
+#endif  /* CONFIG_SIDECHAINGATE_FILTER */

libavfilter/allfilters.c

@@ -105,6 +105,7 @@ void avfilter_register_all(void)
     REGISTER_FILTER(RESAMPLE,       resample,       af);
     REGISTER_FILTER(RUBBERBAND,     rubberband,     af);
     REGISTER_FILTER(SIDECHAINCOMPRESS, sidechaincompress, af);
+    REGISTER_FILTER(SIDECHAINGATE,  sidechaingate,  af);
     REGISTER_FILTER(SILENCEDETECT,  silencedetect,  af);
     REGISTER_FILTER(SILENCEREMOVE,  silenceremove,  af);
     REGISTER_FILTER(STEREOTOOLS,    stereotools,    af);

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   6
-#define LIBAVFILTER_VERSION_MINOR  18
+#define LIBAVFILTER_VERSION_MINOR  19
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \