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/*

 * 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

 */

/**

 * @file

 * Channel split filter

 *

 * Split an audio stream into per-channel streams.

 */

#include "libavutil/attributes.h"

#include "libavutil/channel_layout.h"

#include "libavutil/internal.h"

#include "libavutil/opt.h"

#include "audio.h"

#include "avfilter.h"

#include "formats.h"

#include "internal.h"

typedef struct ChannelSplitContext {

    const AVClass *class;

    uint64_t channel_layout;

    char    *channel_layout_str;

} ChannelSplitContext;

#define OFFSET(x) offsetof(ChannelSplitContext, x)

#define A AV_OPT_FLAG_AUDIO_PARAM

#define F AV_OPT_FLAG_FILTERING_PARAM

static const AVOption channelsplit_options[] = {

    { "channel_layout", "Input channel layout.", OFFSET(channel_layout_str), AV_OPT_TYPE_STRING, { .str = "stereo" }, .flags = A|F },

    { NULL }

};

AVFILTER_DEFINE_CLASS(channelsplit);

static av_cold int init(AVFilterContext *ctx)

{

    ChannelSplitContext *s = ctx->priv;

    int nb_channels;

    int ret = 0, i;

    if (!(s->channel_layout = av_get_channel_layout(s->channel_layout_str))) {

        av_log(ctx, AV_LOG_ERROR, "Error parsing channel layout '%s'.\n",

               s->channel_layout_str);

        ret = AVERROR(EINVAL);

        goto fail;

    }

    nb_channels = av_get_channel_layout_nb_channels(s->channel_layout);

    for (i = 0; i < nb_channels; i++) {

        uint64_t channel = av_channel_layout_extract_channel(s->channel_layout, i);

        AVFilterPad pad  = { 0 };

        pad.type = AVMEDIA_TYPE_AUDIO;

        pad.name = av_get_channel_name(channel);

        ff_insert_outpad(ctx, i, &pad);

    }

fail:

    return ret;

}

static int query_formats(AVFilterContext *ctx)

{

    ChannelSplitContext *s = ctx->priv;

    AVFilterChannelLayouts *in_layouts = NULL;

    int i;

    ff_set_common_formats    (ctx, ff_planar_sample_fmts());

    ff_set_common_samplerates(ctx, ff_all_samplerates());

    ff_add_channel_layout(&in_layouts, s->channel_layout);

    ff_channel_layouts_ref(in_layouts, &ctx->inputs[0]->out_channel_layouts);

    for (i = 0; i < ctx->nb_outputs; i++) {

        AVFilterChannelLayouts *out_layouts = NULL;

        uint64_t channel = av_channel_layout_extract_channel(s->channel_layout, i);

        ff_add_channel_layout(&out_layouts, channel);

        ff_channel_layouts_ref(out_layouts, &ctx->outputs[i]->in_channel_layouts);

    }

    return 0;

}

static int filter_frame(AVFilterLink *inlink, AVFrame *buf)

{

    AVFilterContext *ctx = inlink->dst;

    int i, ret = 0;

    for (i = 0; i < ctx->nb_outputs; i++) {

        AVFrame *buf_out = av_frame_clone(buf);

        if (!buf_out) {

            ret = AVERROR(ENOMEM);

            break;

        }

        buf_out->data[0] = buf_out->extended_data[0] = buf_out->extended_data[i];

        buf_out->channel_layout =

            av_channel_layout_extract_channel(buf->channel_layout, i);

        av_frame_set_channels(buf_out, 1);

        ret = ff_filter_frame(ctx->outputs[i], buf_out);

        if (ret < 0)

            break;

    }

    av_frame_free(&buf);

    return ret;

}

static const AVFilterPad avfilter_af_channelsplit_inputs[] = {

    {

        .name         = "default",

        .type         = AVMEDIA_TYPE_AUDIO,

        .filter_frame = filter_frame,

    },

    { NULL }

};

AVFilter avfilter_af_channelsplit = {

    .name           = "channelsplit",

    .description    = NULL_IF_CONFIG_SMALL("Split audio into per-channel streams."),

    .priv_size      = sizeof(ChannelSplitContext),

    .priv_class     = &channelsplit_class,

    .init           = init,

    .query_formats  = query_formats,

    .inputs         = avfilter_af_channelsplit_inputs,

    .outputs        = NULL,

    .flags          = AVFILTER_FLAG_DYNAMIC_OUTPUTS,

};