Signed-off-by: Kyle Swanson <k...@ylo.ph>
---
doc/filters.texi | 19 ++++++
libavfilter/Makefile | 1 +
libavfilter/af_tremolo.c | 173 +++++++++++++++++++++++++++++++++++++++++++++++
libavfilter/allfilters.c | 1 +
libavfilter/version.h | 2 +-
5 files changed, 195 insertions(+), 1 deletion(-)
create mode 100644 libavfilter/af_tremolo.c
diff --git a/doc/filters.texi b/doc/filters.texi
index 88cb3ce..5bbbaf0 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -2568,6 +2568,25 @@ slope
Determine how steep is the filter's shelf transition.
@end table
+@section tremolo
+
+Sinusoidal amplitude modulation.
+
+The filter accepts the following options:
+
+@table @option
+@item f
+Modulation frequency in Hertz. Modulation frequencies in the subharmonic range
+(20 Hz or lower) will result in a tremolo effect.
+This filter may also be used as a ring modulator by specifying
+a modulation frequency higher than 20 Hz.
+Range is 0.1 - 20000.0. Default value is 5.0 Hz.
+
+@item d
+Depth of modulation as a percentage. Range is 0.0 - 1.0.
+Default value is 0.5.
+@end table
+
@section volume
Adjust the input audio volume.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 05effd6..45fca3b 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -82,6 +82,7 @@ OBJS-$(CONFIG_SILENCEDETECT_FILTER) +=
af_silencedetect.o
OBJS-$(CONFIG_SILENCEREMOVE_FILTER) += af_silenceremove.o
OBJS-$(CONFIG_STEREOTOOLS_FILTER) += af_stereotools.o
OBJS-$(CONFIG_STEREOWIDEN_FILTER) += af_stereowiden.o
+OBJS-$(CONFIG_TREMOLO_FILTER) += af_tremolo.o
generate_wave_table.o
OBJS-$(CONFIG_TREBLE_FILTER) += af_biquads.o
OBJS-$(CONFIG_VOLUME_FILTER) += af_volume.o
OBJS-$(CONFIG_VOLUMEDETECT_FILTER) += af_volumedetect.o
diff --git a/libavfilter/af_tremolo.c b/libavfilter/af_tremolo.c
new file mode 100644
index 0000000..7896127
--- /dev/null
+++ b/libavfilter/af_tremolo.c
@@ -0,0 +1,173 @@
+/*
+ * Tremolo
+ * Copyright (c) 2015 Kyle Swanson <k...@ylo.ph>. Some rights reserved.
+ *
+ * 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
+ * Tremolo
+ */
+
+#include "libavutil/opt.h"
+#include "avfilter.h"
+#include "internal.h"
+#include "audio.h"
+#include "generate_wave_table.h"
+
+typedef struct TremoloContext {
+ const AVClass *class;
+ double freq;
+ double depth;
+ double *wave_table;
+ int wave_table_index;
+ int sample_rate;
+} TremoloContext;
+
+#define OFFSET(x) offsetof(TremoloContext, x)
+#define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+
+static const AVOption tremolo_options[] = {
+ { "f", "set frequency in hertz", OFFSET(freq), AV_OPT_TYPE_DOUBLE,
{.dbl = 5.0}, 0.1, 20000.0, FLAGS },
+ { "d", "set depth as percentage", OFFSET(depth), AV_OPT_TYPE_DOUBLE,
{.dbl = 0.5}, 0.0, 1.0, FLAGS },
+ { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(tremolo);
+
+static float trem_env(AVFilterContext *ctx)
+{
+ TremoloContext *s = ctx->priv;
+ float env = s->wave_table[s->wave_table_index];
+ s->wave_table_index++;
+ if (s->wave_table_index >= s->sample_rate / s->freq)
+ s->wave_table_index = 0;
+ return 1.0 - (s->depth * env);
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+ AVFilterContext *ctx = inlink->dst;
+ AVFilterLink *outlink = ctx->outputs[0];
+ AVFrame *out;
+
+ if (av_frame_is_writable(in)) {
+ out = in;
+ } else {
+ out = ff_get_audio_buffer(inlink, in->nb_samples);
+ if (!out) {
+ av_frame_free(&in);
+ return AVERROR(ENOMEM);
+ }
+ av_frame_copy_props(out, in);
+ }
+
+ int channels = inlink->channels;
+ int nb_samples = in->nb_samples;
+ double *dst = (double *)out->data[0];
+ int n, c;
+
+ for (n = 0; n < nb_samples; n++) {
+ float env = trem_env(ctx);
+ for (c = 0; c < channels; c++) {
+ dst[c] *= env;
+ }
+ dst += channels;
+ }
+
+ if (in != out)
+ av_frame_free(&in);
+
+ return ff_filter_frame(outlink, out);
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+ AVFilterFormats *formats;
+ AVFilterChannelLayouts *layouts;
+ static const enum AVSampleFormat sample_fmts[] = {
+ AV_SAMPLE_FMT_DBL,
+ 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 av_cold void uninit(AVFilterContext *ctx)
+{
+ TremoloContext *s = ctx->priv;
+ av_free(s->wave_table);
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+ AVFilterContext *ctx = inlink->dst;
+ TremoloContext *s = ctx->priv;
+ s->sample_rate = inlink->sample_rate;
+ s->wave_table = av_malloc_array(sizeof(double), s->sample_rate / s->freq);
+ ff_generate_wave_table(WAVE_SIN, AV_SAMPLE_FMT_DBL, s->wave_table,
s->sample_rate / s->freq, 0.0, 1.0, 0.0);
+ s->wave_table_index = 0;
+ return 0;
+}
+
+static const AVFilterPad avfilter_af_tremolo_inputs[] = {
+ {
+ .name = "default",
+ .type = AVMEDIA_TYPE_AUDIO,
+ .config_props = config_input,
+ .filter_frame = filter_frame,
+ },
+ { NULL }
+};
+
+static const AVFilterPad avfilter_af_tremolo_outputs[] = {
+ {
+ .name = "default",
+ .type = AVMEDIA_TYPE_AUDIO,
+ },
+ { NULL }
+};
+
+AVFilter ff_af_tremolo = {
+ .name = "tremolo",
+ .description = NULL_IF_CONFIG_SMALL("Audio Tremolo."),
+ .priv_size = sizeof(TremoloContext),
+ .priv_class = &tremolo_class,
+ .uninit = uninit,
+ .query_formats = query_formats,
+ .inputs = avfilter_af_tremolo_inputs,
+ .outputs = avfilter_af_tremolo_outputs,
+};
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index cab4564..59ba5f5 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -105,6 +105,7 @@ void avfilter_register_all(void)
REGISTER_FILTER(STEREOTOOLS, stereotools, af);
REGISTER_FILTER(STEREOWIDEN, stereowiden, af);
REGISTER_FILTER(TREBLE, treble, af);
+ REGISTER_FILTER(TREMOLO, tremolo, af);
REGISTER_FILTER(VOLUME, volume, af);
REGISTER_FILTER(VOLUMEDETECT, volumedetect, af);
diff --git a/libavfilter/version.h b/libavfilter/version.h
index e918184..9d44fd0 100644
--- a/libavfilter/version.h
+++ b/libavfilter/version.h
@@ -30,7 +30,7 @@
#include "libavutil/version.h"
#define LIBAVFILTER_VERSION_MAJOR 6
-#define LIBAVFILTER_VERSION_MINOR 5
+#define LIBAVFILTER_VERSION_MINOR 6
#define LIBAVFILTER_VERSION_MICRO 100
#define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \
--
1.8.4
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