Answer by CodeMade for I want to record video with a usb webcam to process it later. To do that, I found limited info. One is to use rosbag to save published topics. Another way is to use opencv to write video. Which method would provide a simple solution to save video ? (maybe another alternative method beyond what I said) I have a source code ofimage_pubpackage to publish images as following;#include <ros/ros.h> #include <camera_info_manager/camera_info_manager.h> #include <sensor_msgs/Image.h> #include <sensor_msgs/CameraInfo.h> #include <opencv2/opencv.hpp> int main(int argc, char **argv) { ROS_INFO("Starting image_pub ROS node...\n"); ros::init(argc, argv, "image_pub"); ros::NodeHandle nh("~"); std::string camera_topic; std::string camera_info_topic; std::string camera_info_url; std::string img_path; std::string frame_id; float pub_rate; int start_sec; bool repeat; nh.param<std::string>("camera_topic", camera_topic, "/camera/image_raw"); nh.param<std::string>("camera_info_topic", camera_info_topic, "/camera/camera_info"); nh.param<std::string>("camera_info_url", camera_info_url, ""); nh.param<std::string>("img_path", img_path, ""); nh.param<std::string>("frame_id", frame_id, ""); nh.param("pub_rate", pub_rate, 30.0f); nh.param("start_sec", start_sec, 0); nh.param("repeat", repeat, false); ROS_INFO("CTopic : %s", camera_topic.c_str()); ROS_INFO("ITopic : %s", camera_info_topic.c_str()); ROS_INFO("CI URL : %s", camera_info_url.c_str()); ROS_INFO("Source : %s", img_path.c_str()); ROS_INFO("Rate : %.1f", pub_rate); ROS_INFO("Start : %d", start_sec); ROS_INFO("Repeat : %s", repeat ? "yes" : "no"); ROS_INFO("FrameID: %s", frame_id.c_str()); camera_info_manager::CameraInfoManager camera_info_manager(nh); if (camera_info_manager.validateURL(camera_info_url)) camera_info_manager.loadCameraInfo(camera_info_url); ros::Publisher img_pub = nh.advertise<sensor_msgs::Image>(camera_topic, 1); ros::Publisher info_pub = nh.advertise<sensor_msgs::CameraInfo>(camera_info_topic, 1); cv::VideoCapture vid_cap(img_path.c_str()); if (start_sec > 0) vid_cap.set(CV_CAP_PROP_POS_MSEC, 1000.0 * start_sec); ros::Rate rate(pub_rate); while (ros::ok()) { cv::Mat img; if (!vid_cap.read(img)) { if (repeat) { vid_cap.open(img_path.c_str()); if (start_sec > 0) vid_cap.set(CV_CAP_PROP_POS_MSEC, 1000.0 * start_sec); continue; } ROS_ERROR("Failed to capture frame."); ros::shutdown(); } else { //ROS_DEBUG("Image: %dx%dx%d, %zu, %d", img.rows, img.cols, img.channels(), img.elemSize(), img.type() == CV_8UC3); if (img.type() != CV_8UC3) img.convertTo(img, CV_8UC3); // Convert image from BGR format used by OpenCV to RGB. cv::cvtColor(img, img, CV_BGR2RGB); auto img_msg = boost::make_shared<sensor_msgs::Image>(); img_msg->header.stamp = ros::Time::now(); img_msg->header.frame_id = frame_id; img_msg->encoding = "rgb8"; img_msg->width = img.cols; img_msg->height = img.rows; img_msg->step = img_msg->width * img.channels(); auto ptr = img.ptr<unsigned char>(0); img_msg->data = std::vector<unsigned char>(ptr, ptr + img_msg->step * img_msg->height); img_pub.publish(img_msg); if (camera_info_manager.isCalibrated()) { auto info = boost::make_shared<sensor_msgs::CameraInfo>(camera_info_manager.getCameraInfo()); info->header = img_msg->header; info_pub.publish(info); } } ros::spinOnce(); rate.sleep(); } return 0; }

I would use OpenCV to write video and then use the recording to run simulations later. But we probably need more info on what kind of processing you want to do before solid advice can be given.