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  1. /*
  2.  * Copyright (c) 2015 Paul B Mahol
  3.  *
  4.  * This file is part of FFmpeg.
  5.  *
  6.  * FFmpeg is free software; you can redistribute it and/or
  7.  * modify it under the terms of the GNU Lesser General Public
  8.  * License as published by the Free Software Foundation; either
  9.  * version 2.1 of the License, or (at your option) any later version.
  10.  *
  11.  * FFmpeg is distributed in the hope that it will be useful,
  12.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14.  * Lesser General Public License for more details.
  15.  *
  16.  * You should have received a copy of the GNU Lesser General Public
  17.  * License along with FFmpeg; if not, write to the Free Software
  18.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19.  */
  20.  
  21. #include "libavutil/lfg.h"
  22. #include "libavutil/opt.h"
  23. #include "libavutil/random_seed.h"
  24. #include "avfilter.h"
  25. #include "formats.h"
  26. #include "internal.h"
  27. #include "video.h"
  28.  
  29. #define MAX_FRAMES 512
  30.  
  31. typedef struct RandomContext {
  32.     const AVClass *class;
  33.  
  34.     AVLFG lfg;
  35.     int nb_frames;
  36.     int64_t random_seed;
  37.     int nb_frames_filled;
  38.     AVFrame *frames[MAX_FRAMES];
  39.     int64_t pts[MAX_FRAMES];
  40.     int flush_idx;
  41. } RandomContext;
  42.  
  43. #define OFFSET(x) offsetof(RandomContext, x)
  44. #define FLAGS AV_OPT_FLAG_VIDEO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
  45.  
  46. static const AVOption random_options[] = {
  47.     { "frames", "set number of frames in cache", OFFSET(nb_frames),   AV_OPT_TYPE_INT,   {.i64=30},  2, MAX_FRAMES, FLAGS },
  48.     { "seed",   "set the seed",                  OFFSET(random_seed), AV_OPT_TYPE_INT64, {.i64=-1}, -1, UINT32_MAX, FLAGS },
  49.     { NULL }
  50. };
  51.  
  52. AVFILTER_DEFINE_CLASS(random);
  53.  
  54. static av_cold int init(AVFilterContext *ctx)
  55. {
  56.     RandomContext *s = ctx->priv;
  57.     uint32_t seed;
  58.  
  59.     if (s->random_seed < 0)
  60.         s->random_seed = av_get_random_seed();
  61.     seed = s->random_seed;
  62.     av_lfg_init(&s->lfg, seed);
  63.  
  64.     return 0;
  65. }
  66.  
  67. static int config_output(AVFilterLink *outlink)
  68. {
  69.     outlink->flags |= FF_LINK_FLAG_REQUEST_LOOP;
  70.     return 0;
  71. }
  72.  
  73. static int filter_frame(AVFilterLink *inlink, AVFrame *in)
  74. {
  75.     AVFilterContext *ctx = inlink->dst;
  76.     RandomContext *s = ctx->priv;
  77.     AVFilterLink *outlink = ctx->outputs[0];
  78.     AVFrame *out;
  79.     int idx;
  80.  
  81.     if (s->nb_frames_filled < s->nb_frames) {
  82.         s->frames[s->nb_frames_filled] = in;
  83.         s->pts[s->nb_frames_filled++] = in->pts;
  84.         return 0;
  85.     }
  86.  
  87.     idx = av_lfg_get(&s->lfg) % s->nb_frames;
  88.  
  89.     out = s->frames[idx];
  90.     out->pts = s->pts[0];
  91.     memmove(&s->pts[0], &s->pts[1], (s->nb_frames - 1) * sizeof(s->pts[0]));
  92.     s->frames[idx] = in;
  93.     s->pts[s->nb_frames - 1] = in->pts;
  94.  
  95.     return ff_filter_frame(outlink, out);
  96. }
  97.  
  98. static int request_frame(AVFilterLink *outlink)
  99. {
  100.     AVFilterContext *ctx = outlink->src;
  101.     RandomContext *s = ctx->priv;
  102.     int ret;
  103.  
  104.     ret = ff_request_frame(ctx->inputs[0]);
  105.  
  106.     if (ret == AVERROR_EOF && !ctx->is_disabled && s->nb_frames > 0) {
  107.         AVFrame *out = s->frames[s->nb_frames - 1];
  108.         out->pts = s->pts[s->flush_idx++];
  109.         ret = ff_filter_frame(outlink, out);
  110.         s->frames[s->nb_frames - 1] = NULL;
  111.         s->nb_frames--;
  112.     }
  113.  
  114.     return ret;
  115. }
  116.  
  117. static const AVFilterPad random_inputs[] = {
  118.     {
  119.         .name         = "default",
  120.         .type         = AVMEDIA_TYPE_VIDEO,
  121.         .filter_frame = filter_frame,
  122.     },
  123.     { NULL }
  124. };
  125.  
  126. static const AVFilterPad random_outputs[] = {
  127.     {
  128.         .name          = "default",
  129.         .type          = AVMEDIA_TYPE_VIDEO,
  130.         .request_frame = request_frame,
  131.         .config_props  = config_output,
  132.     },
  133.     { NULL }
  134. };
  135.  
  136. AVFilter ff_vf_random = {
  137.     .name        = "random",
  138.     .description = NULL_IF_CONFIG_SMALL("Return random frames."),
  139.     .priv_size   = sizeof(RandomContext),
  140.     .priv_class  = &random_class,
  141.     .init        = init,
  142.     .inputs      = random_inputs,
  143.     .outputs     = random_outputs,
  144. };
  145.