ros2+opencv抓取rtsp视频流

遇到的坑：

rtsp视频流和转ros2 topic放到一个线程里，频繁提示解码丢帧的情况。

解决这个问题需要将opencv获取rtsp视频流单独开一个线程，不能在里面处理任何多余的代码。

代码如下：

#include <chrono>
#include <cstdio>
#include <rclcpp/rclcpp.hpp>
#include <opencv2/opencv.hpp>
#include <cv_bridge/cv_bridge.h>
#include <sensor_msgs/msg/image.hpp>
#include <std_msgs/msg/string.hpp>

using namespace std::chrono_literals;

class VideoGrab : public rclcpp::Node
{
public:
  VideoGrab() : Node("video_grab")
  {
    // video_publisher_ = this->create_publisher<sensor_msgs::msg::Image>("video", 5);
    video_compressed_publisher_ = this->create_publisher<sensor_msgs::msg::CompressedImage>("video/compressed",5);
    cap.open("rtsp://admin:user@IP:999/Streaming/Channels/101");
    // timer_ = this->create_wall_timer(30ms,std::bind(&VideoGrab::timer_callback,this));

    rtsp_th_ = std::make_shared<std::thread>(std::bind(&VideoGrab::run, this));
    rtsp_th_->detach();
    pub_th_ = std::make_shared<std::thread>(std::bind(&VideoGrab::publish, this));
    pub_th_->join();
  }

private:
  void run()
  {
    while (rclcpp::ok())
    {
      cap.read(image);
      cv::waitKey(30);
    }
  }

  void publish()
  {
    while ((rclcpp::ok()))
    {
      // RCLCPP_INFO(this->get_logger(), "pub image");
      try
      {
        ros_img_ = cv_bridge::CvImage(std_msgs::msg::Header(), "bgr8", image).toImageMsg();
        if(!image.empty())
        {
          ros_img_compressed_ = cv_bridge::CvImage(std_msgs::msg::Header(), "bgr8", image).toCompressedImageMsg();
          video_compressed_publisher_->publish(*ros_img_compressed_);
        }
        else
          RCLCPP_WARN(this->get_logger(), "empty image");
        // video_publisher_->publish(*ros_img_);
      }
      catch (cv_bridge::Exception &e)
      {
        RCLCPP_ERROR(this->get_logger(),ros_img_->encoding.c_str());
      }

      cv::waitKey(30);
    }
  }

private:
  cv::VideoCapture cap;
  cv::Mat image;
  cv_bridge::CvImagePtr cv_ptr;
  sensor_msgs::msg::Image::SharedPtr ros_img_;
  sensor_msgs::msg::CompressedImage::SharedPtr ros_img_compressed_;
  rclcpp::TimerBase::SharedPtr timer_;
  rclcpp::Publisher<sensor_msgs::msg::Image>::SharedPtr video_publisher_;
  rclcpp::Publisher<sensor_msgs::msg::CompressedImage>::SharedPtr video_compressed_publisher_;
  std::shared_ptr<std::thread> rtsp_th_, pub_th_;

// private:
//   void timer_callback()
//   {
//     // cap.read(image);
//     RCLCPP_INFO(this->get_logger(), "pub image");
//     ros_img_ = cv_bridge::CvImage(std_msgs::msg::Header(), "bgr8", image).toImageMsg();
//     video_publisher_->publish(*ros_img_);
//   }
};

int main(int argc, char **argv)
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<VideoGrab>());
  rclcpp::shutdown();
  return 0;
}