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/*

 * Copyright (c) 2010 Stefano Sabatini

 * Copyright (c) 2006 Ivo van Poorten

 * Copyright (c) 2006 Julian Hall

 * Copyright (c) 2002-2003 Brian J. Murrell

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 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 General Public License for more details.

 *

 * You should have received a copy of the GNU 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

 * Search for black frames to detect scene transitions.

 * Ported from MPlayer libmpcodecs/vf_blackframe.c.

 */

#include 

#include 

#include "libavutil/internal.h"

#include "libavutil/opt.h"

#include "avfilter.h"

#include "formats.h"

#include "internal.h"

#include "video.h"

typedef struct {

    const AVClass *class;

    int bamount;          ///< black amount

    int bthresh;          ///< black threshold

    unsigned int frame;   ///< frame number

    unsigned int nblack;  ///< number of black pixels counted so far

    unsigned int last_keyframe; ///< frame number of the last received key-frame

} BlackFrameContext;

static int query_formats(AVFilterContext *ctx)

{

    static const enum AVPixelFormat pix_fmts[] = {

        AV_PIX_FMT_YUV410P, AV_PIX_FMT_YUV420P, AV_PIX_FMT_GRAY8, AV_PIX_FMT_NV12,

        AV_PIX_FMT_NV21, AV_PIX_FMT_YUV444P, AV_PIX_FMT_YUV422P, AV_PIX_FMT_YUV411P,

        AV_PIX_FMT_NONE

    };

    ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));

    return 0;

}

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

{

    AVFilterContext *ctx = inlink->dst;

    BlackFrameContext *s = ctx->priv;

    int x, i;

    int pblack = 0;

    uint8_t *p = frame->data[0];

    for (i = 0; i < frame->height; i++) {

        for (x = 0; x < inlink->w; x++)

            s->nblack += p[x] < s->bthresh;

        p += frame->linesize[0];

    }

    if (frame->key_frame)

        s->last_keyframe = s->frame;

    pblack = s->nblack * 100 / (inlink->w * inlink->h);

    if (pblack >= s->bamount)

        av_log(ctx, AV_LOG_INFO, "frame:%u pblack:%u pts:%"PRId64" t:%f "

               "type:%c last_keyframe:%d\n",

               s->frame, pblack, frame->pts,

               frame->pts == AV_NOPTS_VALUE ? -1 : frame->pts * av_q2d(inlink->time_base),

               av_get_picture_type_char(frame->pict_type), s->last_keyframe);

    s->frame++;

    s->nblack = 0;

    return ff_filter_frame(inlink->dst->outputs[0], frame);

}

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

#define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM

static const AVOption blackframe_options[] = {

    { "amount", "Percentage of the pixels that have to be below the threshold "

        "for the frame to be considered black.", OFFSET(bamount), AV_OPT_TYPE_INT, { .i64 = 98 }, 0, 100,     FLAGS },

    { "threshold", "threshold below which a pixel value is considered black",

                                                 OFFSET(bthresh), AV_OPT_TYPE_INT, { .i64 = 32 }, 0, 255,     FLAGS },

    { "thresh", "threshold below which a pixel value is considered black",

                                                 OFFSET(bthresh), AV_OPT_TYPE_INT, { .i64 = 32 }, 0, 255,     FLAGS },

    { NULL }

};

AVFILTER_DEFINE_CLASS(blackframe);

static const AVFilterPad avfilter_vf_blackframe_inputs[] = {

    {

        .name         = "default",

        .type         = AVMEDIA_TYPE_VIDEO,

        .filter_frame = filter_frame,

    },

    { NULL }

};

static const AVFilterPad avfilter_vf_blackframe_outputs[] = {

    {

        .name = "default",

        .type = AVMEDIA_TYPE_VIDEO

    },

    { NULL }

};

AVFilter avfilter_vf_blackframe = {

    .name          = "blackframe",

    .description   = NULL_IF_CONFIG_SMALL("Detect frames that are (almost) black."),

    .priv_size     = sizeof(BlackFrameContext),

    .priv_class    = &blackframe_class,

    .query_formats = query_formats,

    .inputs        = avfilter_vf_blackframe_inputs,

    .outputs       = avfilter_vf_blackframe_outputs,

};