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/*
* 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_BOOL, {.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,
};
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