[FFmpeg-devel] [PATCH] avfilter: add audio crossfeed filter
Paul B Mahol
onemda at gmail.com
Tue May 16 23:59:39 EEST 2017
Signed-off-by: Paul B Mahol <onemda at gmail.com>
---
doc/filters.texi | 16 +++++
libavfilter/Makefile | 1 +
libavfilter/af_crossfeed.c | 161 +++++++++++++++++++++++++++++++++++++++++++++
libavfilter/allfilters.c | 1 +
4 files changed, 179 insertions(+)
create mode 100644 libavfilter/af_crossfeed.c
diff --git a/doc/filters.texi b/doc/filters.texi
index 9611a41..2e7caf3 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -2248,6 +2248,22 @@ Set temperature degree in Celsius. This is the temperature of the environment.
Default is 20.
@end table
+ at section crossfeed
+Apply headphone crossfeed filter.
+
+The filter accepts the following options:
+
+ at table @option
+ at item strength
+Set strength of crossfeed. Default is 0.1. Allowed range is from 0 to 1.
+
+ at item level_in
+Set input gain. Default is 0.9.
+
+ at item level_out
+Set output gain. Default is 1.
+ at end table
+
@section crystalizer
Simple algorithm to expand audio dynamic range.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index f177fdb..434a989 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -81,6 +81,7 @@ OBJS-$(CONFIG_CHANNELSPLIT_FILTER) += af_channelsplit.o
OBJS-$(CONFIG_CHORUS_FILTER) += af_chorus.o generate_wave_table.o
OBJS-$(CONFIG_COMPAND_FILTER) += af_compand.o
OBJS-$(CONFIG_COMPENSATIONDELAY_FILTER) += af_compensationdelay.o
+OBJS-$(CONFIG_CROSSFEED_FILTER) += af_crossfeed.o
OBJS-$(CONFIG_CRYSTALIZER_FILTER) += af_crystalizer.o
OBJS-$(CONFIG_DCSHIFT_FILTER) += af_dcshift.o
OBJS-$(CONFIG_DYNAUDNORM_FILTER) += af_dynaudnorm.o
diff --git a/libavfilter/af_crossfeed.c b/libavfilter/af_crossfeed.c
new file mode 100644
index 0000000..8a9ecad
--- /dev/null
+++ b/libavfilter/af_crossfeed.c
@@ -0,0 +1,161 @@
+/*
+ * 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
+ */
+
+#include "libavutil/channel_layout.h"
+#include "libavutil/opt.h"
+#include "avfilter.h"
+#include "audio.h"
+#include "formats.h"
+
+typedef struct CrossfeedContext {
+ const AVClass *class;
+
+ double strength;
+ double level_in;
+ double level_out;
+
+ double a0, a1, a2;
+ double b0, b1, b2;
+
+ double i1, i2;
+ double o1, o2;
+} CrossfeedContext;
+
+static int query_formats(AVFilterContext *ctx)
+{
+ AVFilterFormats *formats = NULL;
+ AVFilterChannelLayouts *layout = NULL;
+ int ret;
+
+ if ((ret = ff_add_format (&formats, AV_SAMPLE_FMT_DBL )) < 0 ||
+ (ret = ff_set_common_formats (ctx , formats )) < 0 ||
+ (ret = ff_add_channel_layout (&layout , AV_CH_LAYOUT_STEREO)) < 0 ||
+ (ret = ff_set_common_channel_layouts (ctx , layout )) < 0 ||
+ (ret = ff_set_common_samplerates (ctx , ff_all_samplerates())) < 0)
+ return ret;
+
+ return 0;
+}
+
+static int config_input(AVFilterLink *inlink)
+{
+ AVFilterContext *ctx = inlink->dst;
+ CrossfeedContext *s = ctx->priv;
+ double w0 = 2 * M_PI * s->strength * 1000 / inlink->sample_rate;
+ double alpha;
+
+ alpha = sin(w0) / 2 * sqrt(2 * (1 / 0.707 - 1) + 2);
+
+ s->a0 = 1 + alpha;
+ s->a1 = -2 * cos(w0);
+ s->a2 = 1 - alpha;
+ s->b0 = (1 + cos(w0)) / 2;
+ s->b1 = -(1 + cos(w0));
+ s->b2 = (1 + cos(w0)) / 2;
+
+ s->a1 /= s->a0;
+ s->a2 /= s->a0;
+ s->b0 /= s->a0;
+ s->b1 /= s->a0;
+ s->b2 /= s->a0;
+
+ return 0;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+ AVFilterContext *ctx = inlink->dst;
+ AVFilterLink *outlink = ctx->outputs[0];
+ CrossfeedContext *s = ctx->priv;
+ const double *src = (const double *)in->data[0];
+ const double level_in = s->level_in;
+ const double level_out = s->level_out;
+ AVFrame *out;
+ double *dst;
+ int n;
+
+ 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);
+ }
+ dst = (double *)out->data[0];
+
+ for (n = 0; n < out->nb_samples; n++, src += 2, dst += 2) {
+ double mid = (src[0] + src[1]) * level_in * .5;
+ double side = (src[0] - src[1]) * level_in * .5;
+
+ double oside = side * s->b0 + s->i1 * s->b1 + s->i2 * s->b2 - s->o1 * s->a1 - s->o2 * s->a2;
+ s->i2 = s->i1;
+ s->i1 = side;
+ s->o2 = s->o1;
+ s->o1 = oside;
+
+ dst[0] = (mid + oside) * level_out;
+ dst[1] = (mid - oside) * level_out;
+ }
+
+ if (out != in)
+ av_frame_free(&in);
+ return ff_filter_frame(outlink, out);
+}
+
+#define OFFSET(x) offsetof(CrossfeedContext, x)
+#define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+
+static const AVOption crossfeed_options[] = {
+ { "strength", "set crossfeed strength", OFFSET(strength), AV_OPT_TYPE_DOUBLE, {.dbl=.1}, 0, 1, FLAGS },
+ { "level_in", "set level in", OFFSET(level_in), AV_OPT_TYPE_DOUBLE, {.dbl=.9}, 0, 1, FLAGS },
+ { "level_out", "set level out", OFFSET(level_out), AV_OPT_TYPE_DOUBLE, {.dbl=1.}, 0, 1, FLAGS },
+ { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(crossfeed);
+
+static const AVFilterPad inputs[] = {
+ {
+ .name = "default",
+ .type = AVMEDIA_TYPE_AUDIO,
+ .filter_frame = filter_frame,
+ .config_props = config_input,
+ },
+ { NULL }
+};
+
+static const AVFilterPad outputs[] = {
+ {
+ .name = "default",
+ .type = AVMEDIA_TYPE_AUDIO,
+ },
+ { NULL }
+};
+
+AVFilter ff_af_crossfeed = {
+ .name = "crossfeed",
+ .description = NULL_IF_CONFIG_SMALL("Apply headphone crossfeed filter."),
+ .query_formats = query_formats,
+ .priv_size = sizeof(CrossfeedContext),
+ .priv_class = &crossfeed_class,
+ .inputs = inputs,
+ .outputs = outputs,
+};
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index a8939b9..2bcfce7 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -94,6 +94,7 @@ static void register_all(void)
REGISTER_FILTER(CHORUS, chorus, af);
REGISTER_FILTER(COMPAND, compand, af);
REGISTER_FILTER(COMPENSATIONDELAY, compensationdelay, af);
+ REGISTER_FILTER(CROSSFEED, crossfeed, af);
REGISTER_FILTER(CRYSTALIZER, crystalizer, af);
REGISTER_FILTER(DCSHIFT, dcshift, af);
REGISTER_FILTER(DYNAUDNORM, dynaudnorm, af);
--
2.9.3
More information about the ffmpeg-devel
mailing list