openni_tracker crashes upon launching [closed]

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Hi everybody.. When I run openni_tracker, often (not always) it may not launch. Sometimes it simply says segmentation fault, or InitFromXml failed: Can't create any node of the requested type!. It happens more often when I run it from roslaunch: it says openni_tracker process has died . What makes things harder is that nothing is recorded in the log. I know this is a similar discussion to this. But I have checked that the openni_tracker.xml do exist in the package root. I'm completely clueless and frustrated with this.

1. How could this problem be solved?
2. How do we check if a process has died from within one of ROS's nodes, and reactivate that node that has died?

Thank you, everyone.