/*

  * 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 <stdio.h>
 #include <inttypes.h>
 
 #include "libavutil/internal.h"

 #include "libavutil/opt.h"

 #include "avfilter.h"

 #include "formats.h"

 #include "internal.h"

 #include "video.h"

 typedef struct BlackFrameContext {

     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

     };
 

     AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts);
     if (!fmts_list)
         return AVERROR(ENOMEM);
     return ff_set_common_formats(ctx, fmts_list);

 }
 

 #define SET_META(key, format, value) \
     snprintf(buf, sizeof(buf), format, value);  \
     av_dict_set(metadata, key, buf, 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];

     AVDictionary **metadata;
     char buf[32];

     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) {

         metadata = &frame->metadata;

         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);

         SET_META("lavfi.blackframe.pblack", "%u", pblack);
     }
 

     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 ff_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,

 };