vf_blackframe.c 4.07 KB
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/*
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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
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 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or modify
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 * 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.
 *
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 * Libav is distributed in the hope that it will be useful,
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 * 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
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 * with Libav; if not, write to the Free Software Foundation, Inc.,
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 * 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.
 */

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#include <stdio.h>
#include <inttypes.h>

#include "libavutil/internal.h"
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#include "libavutil/opt.h"

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#include "avfilter.h"
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#include "formats.h"
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#include "internal.h"
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#include "video.h"
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typedef struct BlackFrameContext {
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    const AVClass *class;
    int bamount;          ///< black amount
    int bthresh;          ///< black threshold
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    unsigned int frame;   ///< frame number
    unsigned int nblack;  ///< number of black pixels counted so far
} BlackFrameContext;

static int query_formats(AVFilterContext *ctx)
{
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    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
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    };

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    ff_set_common_formats(ctx, ff_make_format_list(pix_fmts));
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    return 0;
}

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static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
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{
    AVFilterContext *ctx = inlink->dst;
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    BlackFrameContext *s = ctx->priv;
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    int x, i;
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    int pblack = 0;
    uint8_t *p = frame->data[0];
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    for (i = 0; i < frame->height; i++) {
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        for (x = 0; x < inlink->w; x++)
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            s->nblack += p[x] < s->bthresh;
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        p += frame->linesize[0];
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    }

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    pblack = s->nblack * 100 / (inlink->w * inlink->h);
    if (pblack >= s->bamount)
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        av_log(ctx, AV_LOG_INFO, "frame:%u pblack:%u pts:%"PRId64" t:%f\n",
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               s->frame, pblack, frame->pts,
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               frame->pts == AV_NOPTS_VALUE ? -1 : frame->pts * av_q2d(inlink->time_base));
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    s->frame++;
    s->nblack = 0;
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    return ff_filter_frame(inlink->dst->outputs[0], frame);
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}

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#define OFFSET(x) offsetof(BlackFrameContext, x)
#define FLAGS AV_OPT_FLAG_VIDEO_PARAM
static const AVOption 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, INT_MAX, FLAGS },
    { NULL },
};

static const AVClass blackframe_class = {
    .class_name = "blackframe",
    .item_name  = av_default_item_name,
    .option     = options,
    .version    = LIBAVUTIL_VERSION_INT,
};

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static const AVFilterPad avfilter_vf_blackframe_inputs[] = {
    {
        .name             = "default",
        .type             = AVMEDIA_TYPE_VIDEO,
        .get_video_buffer = ff_null_get_video_buffer,
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        .filter_frame     = filter_frame,
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    },
    { NULL }
};

static const AVFilterPad avfilter_vf_blackframe_outputs[] = {
    {
        .name = "default",
        .type = AVMEDIA_TYPE_VIDEO
    },
    { NULL }
};

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AVFilter ff_vf_blackframe = {
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    .name        = "blackframe",
    .description = NULL_IF_CONFIG_SMALL("Detect frames that are (almost) black."),

    .priv_size = sizeof(BlackFrameContext),
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    .priv_class = &blackframe_class,
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    .query_formats = query_formats,

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    .inputs    = avfilter_vf_blackframe_inputs,

    .outputs   = avfilter_vf_blackframe_outputs,
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};