func: static int64_t read_ts(char **line, int *duration)
  
  {
  
      int64_t start, end;
  
  
  
      if (sscanf(*line, "%"SCNd64",%"SCNd64, &start, &end) == 2) {
  
          *line += strcspn(*line, "\"") + 1;
  
          *duration = end - start;
  
          return start;
  
      }
  
      return AV_NOPTS_VALUE;
  
  }
  