Running warning and suggestions on grabing image

[hibetterheyj]

Dear authors:

Thanks in advance for your code!

I wrote a launch as follows:

<launch>
  <arg name="device_id" default="0" />
  <arg name="image_width" default="1280" />
  <arg name="image_height" default="720" />

  <node name="cv_camera" pkg="cv_camera" type="cv_camera_node" output="screen" >
    <param name="device_id" value="$(arg device_id)" />
    <param name="image_width" value="$(arg image_width)" />
    <param name="image_height" value="$(arg image_height)" />
  </node>
  <node name="image_view" pkg="image_view" type="image_view" respawn="false" output="screen">
    <remap from="image" to="/cv_camera/image_raw" />
    <param name="autosize" value="true" />
  </node>
</launch>

The running result is as follows:

SUMMARY
========

PARAMETERS
 * /cv_camera/device_id: 0
 * /cv_camera/image_height: 720
 * /cv_camera/image_width: 1280
 * /image_view/autosize: True
 * /rosdistro: melodic
 * /rosversion: 1.14.10

NODES
  /
    cv_camera (cv_camera/cv_camera_node)
    image_view (image_view/image_view)

auto-starting new master
process[master]: started with pid [11533]
ROS_MASTER_URI=http://localhost:11311

setting /run_id to 892cb1c4-7c51-11eb-b551-f0038c0ab1cd
process[rosout-1]: started with pid [11544]
started core service [/rosout]
process[cv_camera-2]: started with pid [11550]
process[image_view-3]: started with pid [11552]
[ INFO] [1614797520.944463821]: Initializing nodelet with 8 worker threads.
[ INFO] [1614797520.967735263]: Using transport "raw"
[ WARN:0] VIDEOIO(V4L2:/dev/video0): select() timeout.

and without image visualization. Any suggestions on the following code.

Best, Yujie