How to find the frame id of a bag file

edit

Hi, I recorded a bag file to fetch the /camera/rgb/points topic published by a kinect with

rosbag record /camera/rgb/points

I am able to play the file back and see the pointclouds in rviz When i try to convert this bag to pcd using

rosrun pcl_ros bag_to_pcd source.bag /camera/rgb/points .

I get the following error

Saving recorded sensor_msgs::PointCloud2 messages on topic /camera/rgb/points to .
[ERROR] [1321569889.237783893]: Frame id /base_link does not exist! Frames (1): 
Segmentation fault

I tried changing the /base_link in the bag_to_pcd.cpp to /openni_camera but its not working even then. I guess the frame id has to appropriate and I am missing something here. So help me figure out the frame id of the recorded pointcloud in my bag file.

Thanks, Karthik

After recording the bag file with /tf included and then doing the bag_to_pcd gives me the following error

[ERROR] [1321638863.658386805]: Frame id /base_link does not exist! Frames (6): Frame /openni_depth_frame exists with parent /openni_camera.
Frame /openni_camera exists with parent NO_PARENT.
Frame /openni_depth_optical_frame exists with parent /openni_depth_frame.
Frame /openni_rgb_optical_frame exists with parent /openni_rgb_frame.
Frame /openni_rgb_frame exists with parent /openni_camera.

Segmentation fault

So the Frame id is still a problem here?.

Thanks, Karthik

After running the static transform publisher while recording i get the following error while converting

[ERROR] [1321643793.300622410]: Unable to lookup transform, cache is empty, when looking up transform from frame [/openni_rgb_optical_frame] to frame [/base_link]
Segmentation fault

I am not sure what we are doing here. Can you give me the links where significance of this can be learnt?

Thanks Karthik