text: /*
   * Copyright (c) 2010 Nicolas George
   * Copyright (c) 2011 Stefano Sabatini
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
   * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  
  /**
   * @file
   * API example for decoding and filtering
   * @example filtering_video.c
   */
  
  #define _XOPEN_SOURCE 600 /* for usleep */
  #include <unistd.h>
  
  #include <libavcodec/avcodec.h>
  #include <libavformat/avformat.h>
  #include <libavfilter/avfiltergraph.h>
  #include <libavfilter/avcodec.h>
  #include <libavfilter/buffersink.h>
  #include <libavfilter/buffersrc.h>
  #include <libavutil/opt.h>
  
  const char *filter_descr = "scale=78:24";
  
  static AVFormatContext *fmt_ctx;
  static AVCodecContext *dec_ctx;
  AVFilterContext *buffersink_ctx;
  AVFilterContext *buffersrc_ctx;
  AVFilterGraph *filter_graph;
  static int video_stream_index = -1;
  static int64_t last_pts = AV_NOPTS_VALUE;
  
  static int open_input_file(const char *filename)
  {
      int ret;
      AVCodec *dec;
  
      if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
          av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
          return ret;
      }
  
      if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
          av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
          return ret;
      }
  
      /* select the video stream */
      ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, &dec, 0);
      if (ret < 0) {
          av_log(NULL, AV_LOG_ERROR, "Cannot find a video stream in the input file\n");
          return ret;
      }
      video_stream_index = ret;
      dec_ctx = fmt_ctx->streams[video_stream_index]->codec;
      av_opt_set_int(dec_ctx, "refcounted_frames", 1, 0);
  
      /* init the video decoder */
      if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
          av_log(NULL, AV_LOG_ERROR, "Cannot open video decoder\n");
          return ret;
      }
  
      return 0;
  }
  
  static int init_filters(const char *filters_descr)
  {
      char args[512];
      int ret = 0;
      AVFilter *buffersrc  = avfilter_get_by_name("buffer");
      AVFilter *buffersink = avfilter_get_by_name("buffersink");
      AVFilterInOut *outputs = avfilter_inout_alloc();
      AVFilterInOut *inputs  = avfilter_inout_alloc();
      AVRational time_base = fmt_ctx->streams[video_stream_index]->time_base;
      enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };
  
      filter_graph = avfilter_graph_alloc();
      if (!outputs || !inputs || !filter_graph) {
          ret = AVERROR(ENOMEM);
          goto end;
      }
  
      /* buffer video source: the decoded frames from the decoder will be inserted here. */
      snprintf(args, sizeof(args),
              "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
              dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt,
              time_base.num, time_base.den,
              dec_ctx->sample_aspect_ratio.num, dec_ctx->sample_aspect_ratio.den);
  
      ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
                                         args, NULL, filter_graph);
      if (ret < 0) {
          av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
          goto end;
      }
  
      /* buffer video sink: to terminate the filter chain. */
      ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
                                         NULL, NULL, filter_graph);
      if (ret < 0) {
          av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
          goto end;
      }
  
      ret = av_opt_set_int_list(buffersink_ctx, "pix_fmts", pix_fmts,
                                AV_PIX_FMT_NONE, AV_OPT_SEARCH_CHILDREN);
      if (ret < 0) {
          av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
          goto end;
      }
  
      /*
       * Set the endpoints for the filter graph. The filter_graph will
       * be linked to the graph described by filters_descr.
       */
  
      /*
       * The buffer source output must be connected to the input pad of
       * the first filter described by filters_descr; since the first
       * filter input label is not specified, it is set to "in" by
       * default.
       */
      outputs->name       = av_strdup("in");
      outputs->filter_ctx = buffersrc_ctx;
      outputs->pad_idx    = 0;
      outputs->next       = NULL;
  
      /*
       * The buffer sink input must be connected to the output pad of
       * the last filter described by filters_descr; since the last
       * filter output label is not specified, it is set to "out" by
       * default.
       */
      inputs->name       = av_strdup("out");
      inputs->filter_ctx = buffersink_ctx;
      inputs->pad_idx    = 0;
      inputs->next       = NULL;
  
      if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
                                      &inputs, &outputs, NULL)) < 0)
          goto end;
  
      if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
          goto end;
  
  end:
      avfilter_inout_free(&inputs);
      avfilter_inout_free(&outputs);
  
      return ret;
  }
  
  static void display_frame(const AVFrame *frame, AVRational time_base)
  {
      int x, y;
      uint8_t *p0, *p;
      int64_t delay;
  
      if (frame->pts != AV_NOPTS_VALUE) {
          if (last_pts != AV_NOPTS_VALUE) {
              /* sleep roughly the right amount of time;
               * usleep is in microseconds, just like AV_TIME_BASE. */
              delay = av_rescale_q(frame->pts - last_pts,
                                   time_base, AV_TIME_BASE_Q);
              if (delay > 0 && delay < 1000000)
                  usleep(delay);
          }
          last_pts = frame->pts;
      }
  
      /* Trivial ASCII grayscale display. */
      p0 = frame->data[0];
      puts("\033c");
      for (y = 0; y < frame->height; y++) {
          p = p0;
          for (x = 0; x < frame->width; x++)
              putchar(" .-+#"[*(p++) / 52]);
          putchar('\n');
          p0 += frame->linesize[0];
      }
      fflush(stdout);
  }
  
  int main(int argc, char **argv)
  {
      int ret;
      AVPacket packet;
      AVFrame *frame = av_frame_alloc();
      AVFrame *filt_frame = av_frame_alloc();
      int got_frame;
  
      if (!frame || !filt_frame) {
          perror("Could not allocate frame");
          exit(1);
      }
      if (argc != 2) {
          fprintf(stderr, "Usage: %s file\n", argv[0]);
          exit(1);
      }
  
      av_register_all();
      avfilter_register_all();
  
      if ((ret = open_input_file(argv[1])) < 0)
          goto end;
      if ((ret = init_filters(filter_descr)) < 0)
          goto end;
  
      /* read all packets */
      while (1) {
          if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
              break;
  
          if (packet.stream_index == video_stream_index) {
              got_frame = 0;
              ret = avcodec_decode_video2(dec_ctx, frame, &got_frame, &packet);
              if (ret < 0) {
                  av_log(NULL, AV_LOG_ERROR, "Error decoding video\n");
                  break;
              }
  
              if (got_frame) {
                  frame->pts = av_frame_get_best_effort_timestamp(frame);
  
                  /* push the decoded frame into the filtergraph */
                  if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF) < 0) {
                      av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
                      break;
                  }
  
                  /* pull filtered frames from the filtergraph */
                  while (1) {
                      ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
                      if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
                          break;
                      if (ret < 0)
                          goto end;
                      display_frame(filt_frame, buffersink_ctx->inputs[0]->time_base);
                      av_frame_unref(filt_frame);
                  }
                  av_frame_unref(frame);
              }
          }
          av_free_packet(&packet);
      }
  end:
      avfilter_graph_free(&filter_graph);
      avcodec_close(dec_ctx);
      avformat_close_input(&fmt_ctx);
      av_frame_free(&frame);
      av_frame_free(&filt_frame);
  
      if (ret < 0 && ret != AVERROR_EOF) {
          fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
          exit(1);
      }
  
      exit(0);
  }
  