CachingCamera

The visca_over_ip.CachingCamera class is a subclass of the Camera class (see Camera Reference). CachingCamera is designed to reduce superfluous network traffic in real-time applications. CachingCamera has exactly the same API as Camera. There are some important drawbacks to using this class however, and it only improves the performance of a few Camera methods.

An example application

Let’s say you want to bind the zoom speed of a camera to the position of a joystick. To accomplish that, you might write code something like this:

from visca_over_ip import Camera

cam = Camera('192.168.0.123')

def main_loop():
    zoom_speed = get_joystick_zoom_axis()  # imaginary method to read the value of a joystick axis
    cam.zoom(zoom_speed)

Whenever your user is not moving the joystick (which will be most of the time), the camera is going to be bombarded with instructions to not zoom which is kind of a waste. If we substitute CachingCamera for Camera in the above example, the class will be smart enough to tell the camera to stop zooming just once. Subsequent cam.zoom(0) calls will not send a message to the camera. As soon as the user moves the joystick, communications to the camera will resume.

Methods with caching behavior

CachingCamera.get_focus_mode()

CachingCamera.set_focus_mode()

CachingCamera.pantilt()

CachingCamera.zoom()

Drawbacks

This class depends on having exclusive control over a camera. That means that if you have some other software or two instances of the same software interfacing with a camera, CachingCamera may cause unexpected behavior.

CachingCamera also only has benefits if methods are called multiple times with the same parameters. In many applications, this doesn’t happen.