Error starting image_view video_recorder using launch file

Question

To record .avi video, I am using video_recorder for the image_view package. I want to do this through the launch file. Here is the how I put it in there

<node pkg="image_view" type="video_recorder" name="video_record_$(arg camera_name)" machine="$(arg machine)" if="$(eval record and enable_camera)">
             <arg name="fps" value="$(arg frame_rate)" />
             <arg name="codec" value="HFYU" />
             <arg name="encoding" value="$(arg image_encoding)" />

     </node>

I get error:

WARNING: WARN: unrecognized 'arg' child tag in the parent element:

Unfortunately I could not find a go-to syntax for this and I am new to ROS. Any help is appreciated. Feel free to ask for more details.

Answer 1

Here is the reference you are looking for: http://wiki.ros.org/roslaunch/XML

In this particular case, you probably want to use the args attribute inside the <node> node. From this page on the <node> node:

args="arg1 arg2 arg3"(optional)
Pass arguments to node.

Answer 2

Those values are parameters, not arguments. You can refer to http://wiki.ros.org/image_view#image_view.2BAC8-diamondback.video_recorder for documentation about video_recorder. In that case, your launch file should treat them as parameters with the <param> tag.

<node pkg="image_view" type="video_recorder" name="video_record_$(arg camera_name)" machine="$(arg machine)" if="$(eval record and enable_camera)">
     <param name="fps" value="$(arg frame_rate)" />
     <param name="codec" value="HFYU" />
     <param name="encoding" value="$(arg image_encoding)" />    
</node>

Notice the distinction between param and arg. 'arg' is an argument you're receiving from the commandline, which you're encoding as a parameter and sending to the node.