title: How to use usb_cam node on ROS?
body: <p>I use ros-indigo and ubuntu 14.04. I used usb_cam to get frame from camera but I can't do same task now.</p>
  
  <p>If I run <code>rosbuild_ws/package_dir$ roslaunch camera.launch</code> command , I get below output : </p>
  
  <pre><code>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'
  </code></pre>
  
  <p>To handle these errors&amp;warnings, I try to install usb_Cam. I run <code>rosdep install usb_cam</code>, the terminal says that <code>#All required rosdeps installed successfully</code>. I go to usb_cam folder using <code>roscd usb_cam</code>. </p>
  
  <p>Then I run below command : </p>
  
  <pre><code>/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 
  </code></pre>
  
  <p>Finally, I run <code>rosbuild_ws/package_dir$ roslaunch camera.launch</code>, but I get same message. I can't see frame taken from usb camera. How can I get frame from usb cam using usb_cam?</p>
  
  <p>Content of camera.launch : </p>
  
  <pre><code>&lt;!-- This will read a camera and show a streaming feed in a display window. --&gt;
  
  &lt;launch&gt; 
    &lt;node name="usb_cam" pkg="usb_cam" type="usb_cam_node" output="screen" &gt; 
      &lt;param name="video_device" value="/dev/video0" /&gt; 
      &lt;param name="image_width" value="640" /&gt; 
      &lt;param name="image_height" value="480" /&gt; 
      &lt;param name="pixel_format" value="yuyv" /&gt; 
      &lt;param name="camera_frame_id" value="usb_cam" /&gt; 
      &lt;param name="io_method" value="mmap"/&gt; 
    &lt;/node&gt; 
    &lt;node name="image_view" pkg="image_view" type="image_view" respawn="false" output="screen"&gt; 
      &lt;remap from="image" to="/usb_cam/image_raw"/&gt; 
      &lt;param name="autosize" value="true" /&gt; 
    &lt;/node&gt; 
  &lt;/launch&gt;
  </code></pre>