[FFmpeg-devel] [PATCH] avfilter: add extrastereo filter
Paul B Mahol
onemda at gmail.com
Sat Sep 5 20:18:28 CEST 2015
Signed-off-by: Paul B Mahol <onemda at gmail.com>
---
doc/filters.texi | 15 ++++++
libavfilter/Makefile | 1 +
libavfilter/af_extrastereo.c | 122 +++++++++++++++++++++++++++++++++++++++++++
libavfilter/allfilters.c | 1 +
4 files changed, 139 insertions(+)
create mode 100644 libavfilter/af_extrastereo.c
diff --git a/doc/filters.texi b/doc/filters.texi
index d506d68..e430700 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -1817,6 +1817,21 @@ equalizer=f=1000:width_type=q:width=1:g=2,equalizer=f=100:width_type=q:width=2:g
@end example
@end itemize
+ at section extrastereo
+
+Linearly increases the difference between left and right channels which
+adds some sort of "live" effect to playback.
+
+The filter accepts the following option:
+
+ at table @option
+ at item m
+Sets the difference coefficient (default: 2.5). 0.0 means mono sound
+(average of both channels), with 1.0 sound will be unchanged, with
+-1.0 left and right channels will be swapped.
+ at end table
+
+
@section flanger
Apply a flanging effect to the audio.
diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index a2af794..e40b83d 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -73,6 +73,7 @@ OBJS-$(CONFIG_DYNAUDNORM_FILTER) += af_dynaudnorm.o
OBJS-$(CONFIG_EARWAX_FILTER) += af_earwax.o
OBJS-$(CONFIG_EBUR128_FILTER) += f_ebur128.o
OBJS-$(CONFIG_EQUALIZER_FILTER) += af_biquads.o
+OBJS-$(CONFIG_EXTRASTEREO_FILTER) += af_extrastereo.o
OBJS-$(CONFIG_FLANGER_FILTER) += af_flanger.o generate_wave_table.o
OBJS-$(CONFIG_HIGHPASS_FILTER) += af_biquads.o
OBJS-$(CONFIG_JOIN_FILTER) += af_join.o
diff --git a/libavfilter/af_extrastereo.c b/libavfilter/af_extrastereo.c
new file mode 100644
index 0000000..560f00e
--- /dev/null
+++ b/libavfilter/af_extrastereo.c
@@ -0,0 +1,122 @@
+/*
+ * 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 ExtraStereoContext {
+ const AVClass *class;
+ float mult;
+} ExtraStereoContext;
+
+#define OFFSET(x) offsetof(ExtraStereoContext, x)
+#define A AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+
+static const AVOption extrastereo_options[] = {
+ { "m", "set the difference coefficient", OFFSET(mult), AV_OPT_TYPE_FLOAT, {.dbl=2.5}, -10, 10, A },
+ { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(extrastereo);
+
+static int query_formats(AVFilterContext *ctx)
+{
+ AVFilterFormats *formats = NULL;
+ AVFilterChannelLayouts *layout = NULL;
+
+ ff_add_format(&formats, AV_SAMPLE_FMT_FLT);
+ ff_set_common_formats(ctx, formats);
+ ff_add_channel_layout(&layout, AV_CH_LAYOUT_STEREO);
+ ff_set_common_channel_layouts(ctx, layout);
+
+ formats = ff_all_samplerates();
+ if (!formats)
+ return AVERROR(ENOMEM);
+ return ff_set_common_samplerates(ctx, formats);
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *in)
+{
+ AVFilterContext *ctx = inlink->dst;
+ AVFilterLink *outlink = ctx->outputs[0];
+ ExtraStereoContext *s = ctx->priv;
+ const float *src = (const float *)in->data[0];
+ const float mult = s->mult;
+ AVFrame *out = NULL;
+ float *dst;
+ int n;
+
+ if (av_frame_is_writable(in)) {
+ out = in;
+ } else {
+ AVFrame *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 = (float *)out->data[0];
+
+ for (n = 0; n < in->nb_samples; n++) {
+ float average, left, right;
+
+ left = src[n * 2 ];
+ right = src[n * 2 + 1];
+ average = (left + right) / 2;
+ left = average + (mult * (left - average));
+ right = average + (mult * (right - average));
+
+ dst[n * 2 ] = av_clipf(left, -1, 1);
+ dst[n * 2 + 1] = av_clipf(right, -1, 1);
+ }
+
+ if (out != in)
+ av_frame_free(&in);
+ return ff_filter_frame(outlink, out);
+}
+
+static const AVFilterPad inputs[] = {
+ {
+ .name = "default",
+ .type = AVMEDIA_TYPE_AUDIO,
+ .filter_frame = filter_frame,
+ },
+ { NULL }
+};
+
+static const AVFilterPad outputs[] = {
+ {
+ .name = "default",
+ .type = AVMEDIA_TYPE_AUDIO,
+ },
+ { NULL }
+};
+
+AVFilter ff_af_extrastereo = {
+ .name = "extrastereo",
+ .description = NULL_IF_CONFIG_SMALL("Increase difference between stereo audio channels."),
+ .query_formats = query_formats,
+ .priv_size = sizeof(ExtraStereoContext),
+ .priv_class = &extrastereo_class,
+ .inputs = inputs,
+ .outputs = outputs,
+};
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index b7b3807..094b256 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -89,6 +89,7 @@ void avfilter_register_all(void)
REGISTER_FILTER(EARWAX, earwax, af);
REGISTER_FILTER(EBUR128, ebur128, af);
REGISTER_FILTER(EQUALIZER, equalizer, af);
+ REGISTER_FILTER(EXTRASTEREO, extrastereo, af);
REGISTER_FILTER(FLANGER, flanger, af);
REGISTER_FILTER(HIGHPASS, highpass, af);
REGISTER_FILTER(JOIN, join, af);
--
1.7.11.2
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