libavfilter/vf_framestep.c

   1 /*
   2  * Copyright (c) 2012 Stefano Sabatini
   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 /**
  22  * @file framestep filter, inspired on libmpcodecs/vf_framestep.c by
  23  * Daniele Fornighieri <guru AT digitalfantasy it>.
  24  */
  25
  26 #include "libavutil/opt.h"
  27 #include "avfilter.h"
  28 #include "filters.h"
  29 #include "video.h"
  30
  31 typedef struct NullContext {
  32     const AVClass *class;
  33     int frame_step;
  34 } FrameStepContext;
  35
  36 #define OFFSET(x) offsetof(FrameStepContext, x)
  37 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
  38
  39 static const AVOption framestep_options[] = {
  40     { "step", "set frame step",  OFFSET(frame_step), AV_OPT_TYPE_INT, {.i64=1}, 1, INT_MAX, FLAGS},
  41     { NULL },
  42 };
  43
  44 AVFILTER_DEFINE_CLASS(framestep);
  45
  46 static int config_output_props(AVFilterLink *outlink)
  47 {
  48     AVFilterContext *ctx = outlink->src;
  49     FrameStepContext *framestep = ctx->priv;
  50     AVFilterLink *inlink = ctx->inputs[0];
  51     FilterLink       *il = ff_filter_link(inlink);
  52     FilterLink       *ol = ff_filter_link(outlink);
  53
  54     ol->frame_rate =
  55         av_div_q(il->frame_rate, (AVRational){framestep->frame_step, 1});
  56
  57     av_log(ctx, AV_LOG_VERBOSE, "step:%d frame_rate:%d/%d(%f) -> frame_rate:%d/%d(%f)\n",
  58            framestep->frame_step,
  59            il->frame_rate.num, il->frame_rate.den, av_q2d(il->frame_rate),
  60            ol->frame_rate.num, ol->frame_rate.den, av_q2d(ol->frame_rate));
  61     return 0;
  62 }
  63
  64 static int filter_frame(AVFilterLink *inlink, AVFrame *ref)
  65 {
  66     FilterLink             *inl = ff_filter_link(inlink);
  67     FrameStepContext *framestep = inlink->dst->priv;
  68
  69     if (!(inl->frame_count_out % framestep->frame_step)) {
  70         return ff_filter_frame(inlink->dst->outputs[0], ref);
  71     } else {
  72         av_frame_free(&ref);
  73         return 0;
  74     }
  75 }
  76
  77 static const AVFilterPad framestep_inputs[] = {
  78     {
  79         .name         = "default",
  80         .type         = AVMEDIA_TYPE_VIDEO,
  81         .filter_frame = filter_frame,
  82     },
  83 };
  84
  85 static const AVFilterPad framestep_outputs[] = {
  86     {
  87         .name         = "default",
  88         .type         = AVMEDIA_TYPE_VIDEO,
  89         .config_props = config_output_props,
  90     },
  91 };
  92
  93 const FFFilter ff_vf_framestep = {
  94     .p.name        = "framestep",
  95     .p.description = NULL_IF_CONFIG_SMALL("Select one frame every N frames."),
  96     .p.priv_class  = &framestep_class,
  97     .p.flags       = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_METADATA_ONLY,
  98     .priv_size   = sizeof(FrameStepContext),
  99     FILTER_INPUTS(framestep_inputs),
 100     FILTER_OUTPUTS(framestep_outputs),
 101 };