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ffmpeg-4.2.2/libavfilter/vf_framestep.c 3.04 KB
aac5773f   hucm   功能基本完成,接口待打磨
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  /*
   * Copyright (c) 2012 Stefano Sabatini
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 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
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser 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 framestep filter, inspired on libmpcodecs/vf_framestep.c by
   * Daniele Fornighieri <guru AT digitalfantasy it>.
   */
  
  #include "libavutil/opt.h"
  #include "avfilter.h"
  #include "internal.h"
  #include "video.h"
  
  typedef struct NullContext {
      const AVClass *class;
      int frame_step;
  } FrameStepContext;
  
  #define OFFSET(x) offsetof(FrameStepContext, x)
  #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
  
  static const AVOption framestep_options[] = {
      { "step", "set frame step",  OFFSET(frame_step), AV_OPT_TYPE_INT, {.i64=1}, 1, INT_MAX, FLAGS},
      { NULL },
  };
  
  AVFILTER_DEFINE_CLASS(framestep);
  
  static int config_output_props(AVFilterLink *outlink)
  {
      AVFilterContext *ctx = outlink->src;
      FrameStepContext *framestep = ctx->priv;
      AVFilterLink *inlink = ctx->inputs[0];
  
      outlink->frame_rate =
          av_div_q(inlink->frame_rate, (AVRational){framestep->frame_step, 1});
  
      av_log(ctx, AV_LOG_VERBOSE, "step:%d frame_rate:%d/%d(%f) -> frame_rate:%d/%d(%f)\n",
             framestep->frame_step,
             inlink->frame_rate.num, inlink->frame_rate.den, av_q2d(inlink->frame_rate),
             outlink->frame_rate.num, outlink->frame_rate.den, av_q2d(outlink->frame_rate));
      return 0;
  }
  
  static int filter_frame(AVFilterLink *inlink, AVFrame *ref)
  {
      FrameStepContext *framestep = inlink->dst->priv;
  
      if (!(inlink->frame_count_out % framestep->frame_step)) {
          return ff_filter_frame(inlink->dst->outputs[0], ref);
      } else {
          av_frame_free(&ref);
          return 0;
      }
  }
  
  static const AVFilterPad framestep_inputs[] = {
      {
          .name         = "default",
          .type         = AVMEDIA_TYPE_VIDEO,
          .filter_frame = filter_frame,
      },
      { NULL }
  };
  
  static const AVFilterPad framestep_outputs[] = {
      {
          .name         = "default",
          .type         = AVMEDIA_TYPE_VIDEO,
          .config_props = config_output_props,
      },
      { NULL }
  };
  
  AVFilter ff_vf_framestep = {
      .name        = "framestep",
      .description = NULL_IF_CONFIG_SMALL("Select one frame every N frames."),
      .priv_size   = sizeof(FrameStepContext),
      .priv_class  = &framestep_class,
      .inputs      = framestep_inputs,
      .outputs     = framestep_outputs,
      .flags       = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
  };