@@ -6,6 +6,7 @@ version <next>:

 - extrastereo filter

 - ocr filter

 - alimiter filter

+- stereowiden filter

 version 2.8:

@@ -2394,6 +2394,33 @@ silenceremove=1:5:0.02

 @end example

 @end itemize

+@section stereowiden

+

+This filter enhance the stereo effect by suppressing signal common to both

+channels and by delaying the signal of left into right and vice versa,

+thereby widening the stereo effect.

+

+The filter accepts the following options:

+

+@table @option

+@item delay

+Time in milliseconds of the delay of left signal into right and vice versa.

+Default is 20 milliseconds.

+

+@item feedback

+Amount of gain in delayed signal into right and vice versa. Gives a delay

+effect of left signal in right output and vice versa which gives widening

+effect. Default is 0.3.

+

+@item crossfeed

+Cross feed of left into right with inverted phase. This helps in suppressing

+the mono. If the value is 1 it will cancel all the signal common to both

+channels. Default is 0.3.

+

+@item drymix

+Set level of input signal of original channel. Default is 0.8.

+@end table

+

 @section treble

 Boost or cut treble (upper) frequencies of the audio using a two-pole

@@ -80,6 +80,7 @@ OBJS-$(CONFIG_RESAMPLE_FILTER)               += af_resample.o

 OBJS-$(CONFIG_SIDECHAINCOMPRESS_FILTER)      += af_sidechaincompress.o

 OBJS-$(CONFIG_SILENCEDETECT_FILTER)          += af_silencedetect.o

 OBJS-$(CONFIG_SILENCEREMOVE_FILTER)          += af_silenceremove.o

+OBJS-$(CONFIG_STEREOWIDEN_FILTER)            += af_stereowiden.o

 OBJS-$(CONFIG_TREBLE_FILTER)                 += af_biquads.o

 OBJS-$(CONFIG_VOLUME_FILTER)                 += af_volume.o

 OBJS-$(CONFIG_VOLUMEDETECT_FILTER)           += af_volumedetect.o

new file mode 100644

@@ -0,0 +1,167 @@

+/*

+ * Copyright (C) 2012 VLC authors and VideoLAN

+ * Author : Sukrit Sangwan < sukritsangwan at gmail dot com >

+ *

+ * 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 StereoWidenContext {

+    const AVClass *class;

+

+    float delay;

+    float feedback;

+    float crossfeed;

+    float drymix;

+

+    float *buffer;

+    float *write;

+    int length;

+} StereoWidenContext;

+

+#define OFFSET(x) offsetof(StereoWidenContext, x)

+#define A AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM

+

+static const AVOption stereowiden_options[] = {

+    { "delay",     "set delay time",    OFFSET(delay),     AV_OPT_TYPE_FLOAT, {.dbl=20}, 1, 100, A },

+    { "feedback",  "set feedback gain", OFFSET(feedback),  AV_OPT_TYPE_FLOAT, {.dbl=.3}, 0, 0.9, A },

+    { "crossfeed", "set cross feed",    OFFSET(crossfeed), AV_OPT_TYPE_FLOAT, {.dbl=.3}, 0, 0.8, A },

+    { "drymix",    "set dry-mix",       OFFSET(drymix),    AV_OPT_TYPE_FLOAT, {.dbl=.8}, 0, 1.0, A },

+    { NULL }

+};

+

+AVFILTER_DEFINE_CLASS(stereowiden);

+

+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 config_input(AVFilterLink *inlink)

+{

+    AVFilterContext *ctx = inlink->dst;

+    StereoWidenContext *s = ctx->priv;

+

+    s->length = 2 * s->delay * inlink->sample_rate / 1000;

+    s->buffer = av_calloc(s->length, sizeof(s->buffer));

+    if (!s->buffer)

+        return AVERROR(ENOMEM);

+    s->write = s->buffer;

+

+    return 0;

+}

+

+static int filter_frame(AVFilterLink *inlink, AVFrame *in)

+{

+    AVFilterContext *ctx = inlink->dst;

+    AVFilterLink *outlink = ctx->outputs[0];

+    StereoWidenContext *s = ctx->priv;

+    const float *src = (const float *)in->data[0];

+    const float drymix = s->drymix;

+    const float crossfeed = s->crossfeed;

+    const float feedback = s->feedback;

+    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++, src += 2, dst += 2) {

+        const float left = src[0], right = src[1];

+        float *read = s->write + 2;

+

+        if (read > s->buffer + s->length)

+            read = s->buffer;

+

+        dst[0] = drymix * left - crossfeed * right - feedback * read[1];

+        dst[1] = drymix * right - crossfeed * left - feedback * read[0];

+

+        s->write[0] = left;

+        s->write[1] = right;

+

+        if (s->write == s->buffer + s->length)

+            s->write = s->buffer;

+        else

+            s->write += 2;

+    }

+

+    if (out != in)

+        av_frame_free(&in);

+    return ff_filter_frame(outlink, out);

+}

+

+static av_cold void uninit(AVFilterContext *ctx)

+{

+    StereoWidenContext *s = ctx->priv;

+

+    av_freep(&s->buffer);

+}

+

+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_stereowiden = {

+    .name           = "stereowiden",

+    .description    = NULL_IF_CONFIG_SMALL("Apply stereo widening effect."),

+    .query_formats  = query_formats,

+    .priv_size      = sizeof(StereoWidenContext),

+    .priv_class     = &stereowiden_class,

+    .uninit         = uninit,

+    .inputs         = inputs,

+    .outputs        = outputs,

+};

@@ -102,6 +102,7 @@ void avfilter_register_all(void)

     REGISTER_FILTER(SIDECHAINCOMPRESS, sidechaincompress, af);

     REGISTER_FILTER(SILENCEDETECT,  silencedetect,  af);

     REGISTER_FILTER(SILENCEREMOVE,  silenceremove,  af);

+    REGISTER_FILTER(STEREOWIDEN,    stereowiden,    af);

     REGISTER_FILTER(TREBLE,         treble,         af);

     REGISTER_FILTER(VOLUME,         volume,         af);

     REGISTER_FILTER(VOLUMEDETECT,   volumedetect,   af);

@@ -30,7 +30,7 @@

 #include "libavutil/version.h"

 #define LIBAVFILTER_VERSION_MAJOR   6

-#define LIBAVFILTER_VERSION_MINOR   3

+#define LIBAVFILTER_VERSION_MINOR   4

 #define LIBAVFILTER_VERSION_MICRO 100

 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \