@@ -3,6 +3,7 @@ releases are sorted from youngest to oldest.

 version <next>:

 - DXV decoding

+- extrastereo filter

 version 2.8:

@@ -1817,6 +1817,23 @@ equalizer=f=1000:width_type=q:width=1:g=2,equalizer=f=100:width_type=q:width=2:g

 @end example

 @end itemize

+@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:

+

+@table @option

+@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.

+

+@item c

+Enable clipping. By default is enabled.

+@end table

+

 @section flanger

 Apply a flanging effect to the audio.

@@ -67,6 +67,7 @@ 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

new file mode 100644

@@ -0,0 +1,128 @@

+/*

+ * Copyright (c) 2015 The FFmpeg Project

+ *

+ * 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;

+    int clip;

+} 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 },

+    { "c", "enable clipping",                OFFSET(clip), AV_OPT_TYPE_INT,   {.i64=1},     0,  1, 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);

+

+        if (s->clip) {

+            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,

+};

@@ -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);

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

 #include "libavutil/version.h"

 #define LIBAVFILTER_VERSION_MAJOR   6

-#define LIBAVFILTER_VERSION_MINOR   0

+#define LIBAVFILTER_VERSION_MINOR   1

 #define LIBAVFILTER_VERSION_MICRO 100

 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \