Only depth info from kinect

edit

You can just record the depth image directly. It is published.

Is that what you are looking for?

To get raw XYZ data from the pointcloud2 rosmsg, I used the pcl library to convert the complicated pointcloud2 format to something easier. Below a code snippet to read the xyz data, you can then write it to whatever file you want using your favorite filewriting commands.

pcl::PointCloud< pcl::PointXYZ > PointCloudXYZ;
pcl::fromROSMsg(cloud_t,PointCloudXYZ);
std::cout << "width is " << PointCloudXYZ.width << std::endl;
std::cout << "height is " << PointCloudXYZ.height << std::endl;
int cloudsize = (PointCloudXYZ.width) * (PointCloudXYZ.height);
for (int i=0; i< cloudsize; i++){
std::cout << "(x,y,z) = " << PointCloudXYZ.points[i] << std::endl;
}

cloud_t here points to the rosmsg you want to read the pointcloud from. You can find more information about this in the pcl conversions files (which also uses cloud_t) or I can look into my code for you next week.