I am currently using 2 logicool BRIO web camera. The program launched perfectly when it was just 1 camera using below code

<?xml version="1.0"?> <!-- lentimark node --> <node name="lentimark" pkg="lentimark" type="lentimark" output="screen" > <!-- marker param file -->

<!-- camera param -->

<!-- type  0:file 1:topic (CameraInfo) -->
<param name="campara_type" value="0"/>

<!-- camera param file -->
<param name="cam_param_file" value="$(find lenti_mark)/Data/CameraParams/20.txt"/>

<!-- debug (RViz) -->
<!--TF frame_id world -->
<param name="world_flg" value="true" />
<!-- camera position -->_AL
<param name="cam_pos_x" value="0.0" />
<param name="cam_pos_y" value="0.0" />
<param name="cam_pos_z" value="0.3" />

<node name="uvc_camera" pkg="uvc_camera" type="uvc_camera_node" output="screen">
  <param name="device" type="string" value="/dev/video6"/>
  <param name="width" value="1920"/>
  <param name="height" value="1080"/>
  <param name="pixel_format" value="MJPG"/>
  <param name="fps" value="30"/>
  <param name="focus_auto" value="0" />
  <param name="frame_id" value="camera_right"/>

But when I modified those code with below code to launched 2 camera at the same time, the code went error.

<group ns="camera_right">
      <node name="uvc_camera" pkg="uvc_camera" type="uvc_camera_node" output="screen">
        <param name="device" type="string" value="/dev/video6"/>
        <param name="width" value="1920"/>
        <param name="height" value="1080"/>
        <param name="pixel_format" value="MJPG"/>
        <param name="fps" value="30"/>
        <param name="focus_auto" value="0" />
        <param name="frame_id" value="camera_right"/>
        <remap from="image_raw" to="image_rawR">
        </remap>
      </node>


      <node name="rviz" pkg="rviz" type="rviz" args="-d $(find lenti_mark)/launch/leag.rviz"/>

</group>

<group ns="camera_left">
      <node name="uvc_camera" pkg="uvc_camera" type="uvc_camera_node" output="screen">
        <param name="device" type="string" value="/dev/video2"/>
        <param name="width" value="1920"/>
        <param name="height" value="1080"/>
        <param name="pixel_format" value="MJPG"/>
        <param name="fps" value="30"/>
        <param name="focus_auto" value="0" />
        <param name="frame_id" value="camera_left"/>
        <remap from="image_raw" to="image_rawL">
        </remap>
      </node>


      <node name="rviz" pkg="rviz" type="rviz" args="-d $(find lenti_mark)/launch/leag.rviz"/>



</group>

This is the error messages

terminate called after throwing an instance of 'std::runtimeerror' what(): couldn't dequeue buffer select timeout in grab [cameraleft/uvccamera-5] process has died [pid 5795, exit code -6, cmd /opt/ros/melodic/lib/uvccamera/uvccameranode imageraw:=imagerawL _name:=uvccamera _log:=/home/member/.ros/log/6372719c-069e-11ee-8ece-e4a7a0e56889/cameraleft-uvccamera-5.log]. log file: /home/member/.ros/log/6372719c-069e-11ee-8ece-e4a7a0e56889/cameraleft-uvc_camera-5*.log

I already make sure the dev/video number, so I think the problem is not there. I really appreciate if anyone has a clue regarding to this problem.