how to make openni_camera package to output 320x240 rgb and depth images directly

edit

hi, in openni_camera, i got to know that it's ROS API has parameters like:

~image_mode (int, default: 2)

Image output mode for the color/grayscale image Possible values are: SXGA_15Hz (1): 1280x1024@15Hz, VGA_30Hz (2): 640x480@30Hz, VGA_25Hz (3): 640x480@25Hz, QVGA_25Hz (4): 320x240@25Hz, QVGA_30Hz (5): 320x240@30Hz, QVGA_60Hz (6): 320x240@60Hz, QQVGA_25Hz (7): 160x120@25Hz, QQVGA_30Hz (8): 160x120@30Hz, QQVGA_60Hz (9): 160x120@60Hz ~image_mode (int, default: 2)

~depth_mode (int, default: 2)

depth output mode Possible values are: SXGA_15Hz (1): 1280x1024@15Hz, VGA_30Hz (2): 640x480@30Hz, VGA_25Hz (3): 640x480@25Hz, QVGA_25Hz (4): 320x240@25Hz, QVGA_30Hz (5): 320x240@30Hz, QVGA_60Hz (6): 320x240@60Hz, QQVGA_25Hz (7): 160x120@25Hz, QQVGA_30Hz (8): 160x120@30Hz, QQVGA_60Hz (9): 160x120@60Hz

Now I want the kinect to output 320x240 rgb and depth images directly, i tried to set this para in launch file but failed , How to set this parameters?

Thank you vary much~~