如何在ROS上使用usb_cam節點？

Question

我使用ros-indigo和ubuntu 14.04。我用usb_cam從相機獲取幀，但現在我不能完成相同的任務。

如果我運行rosbuild_ws/package_dir$ roslaunch camera.launch命令，我得到以下的輸出：

Unable to open camera calibration file [/home/user/.ros/camera_info/head_camera.yaml] 
[ WARN] [1436602681.552893640]: Camera calibration file /home/user/.ros/camera_info/head_camera.yaml not found. 
[ INFO] [1436602681.552918876]: Starting 'head_camera' (/dev/video0) at 640x480 via mmap (yuyv) at 30 FPS 
[ WARN] [1436602681.584193482]: unknown control 'white_balance_temperature_auto' 

[ WARN] [1436602681.587047162]: unknown control 'focus_auto' 

處理這些錯誤&警告，我嘗試安裝usb_Cam。我跑rosdep install usb_cam，終端說#All required rosdeps installed successfully。我使用roscd usb_cam轉到usb_cam文件夾。

然後我運行下面的命令：

/opt/ros/indigo/share/usb_cam$ rosmake usb_cam 
No Makefile in package usb_cam 
[ rosmake ]   Results:                
[ rosmake ] Built 39 packages with 0 failures.         
[ rosmake ] Summary output to directory 

最後，我跑rosbuild_ws/package_dir$ roslaunch camera.launch，但我得到同樣的消息。我無法看到從usb相機拍攝的畫面。如何使用usb_cam從usb cam獲取幀？ camera.launch的

內容：

<!-- This will read a camera and show a streaming feed in a display window. --> 

<launch> 
    <node name="usb_cam" pkg="usb_cam" type="usb_cam_node" output="screen" > 
    <param name="video_device" value="/dev/video0" /> 
    <param name="image_width" value="640" /> 
    <param name="image_height" value="480" /> 
    <param name="pixel_format" value="yuyv" /> 
    <param name="camera_frame_id" value="usb_cam" /> 
    <param name="io_method" value="mmap"/> 
    </node> 
    <node name="image_view" pkg="image_view" type="image_view" respawn="false" output="screen"> 
    <remap from="image" to="/usb_cam/image_raw"/> 
    <param name="autosize" value="true" /> 
    </node> 
</launch> 

Answer 1

我不知道的警告，但我敢肯定，你已經可以訪問攝像機。 關於幀速率，你可以找到它usb_cam /節點/ usb_cam_node.cpp 內的默認幀速率應爲30 你可以找到你需要的所有參數：

node_.param("video_device", video_device_name_, std::string("/dev/video0")); 
    node_.param("brightness", brightness_, -1); //0-255, -1 "leave alone" 
    node_.param("contrast", contrast_, -1); //0-255, -1 "leave alone" 
    node_.param("saturation", saturation_, -1); //0-255, -1 "leave alone" 
    node_.param("sharpness", sharpness_, -1); //0-255, -1 "leave alone" 
    // possible values: mmap, read, userptr 
    node_.param("io_method", io_method_name_, std::string("mmap")); 
    node_.param("image_width", image_width_, 640); 
    node_.param("image_height", image_height_, 480); 
    node_.param("framerate", framerate_, 30); 
    // possible values: yuyv, uyvy, mjpeg, yuvmono10, rgb24 
    node_.param("pixel_format", pixel_format_name_, std::string("mjpeg")); 
    // enable/disable autofocus 
    node_.param("autofocus", autofocus_, false); 
    node_.param("focus", focus_, -1); //0-255, -1 "leave alone" 
    // enable/disable autoexposure 
    node_.param("autoexposure", autoexposure_, true); 
    node_.param("exposure", exposure_, 100); 
    node_.param("gain", gain_, -1); //0-100?, -1 "leave alone" 
    // enable/disable auto white balance temperature 
    node_.param("auto_white_balance", auto_white_balance_, true); 
    node_.param("white_balance", white_balance_, 4000); 

    // load the camera info 
    node_.param("camera_frame_id", img_.header.frame_id, std::string("head_camera")); 
    node_.param("camera_name", camera_name_, std::string("head_camera")); 
    node_.param("camera_info_url", camera_info_url_, std::string("")); 

，那麼你可能會改變他們在發射文件是這樣的：

<param name="autoexposure" value="false" /> 
    <param name="auto_whitebalance" value="false" /> 
    <param name="auto_focus" value="false" /> 
    <param name="auto_brigthness" value="false" /> 

我也是新的，希望可以給一些幫助。