Blackmagic USB Control - Python

Controlling Blackmagic cameras via USB provides a number of advantages over Bluetooth control:

• No need to authenticate control systems: if the control system is connected to a camera via a USB connection, it has full control of the camera automatically without the need for authentication. Bluetooth pairing, by contrast, may be inadvertently reset - which then requires a new pairing to be established
• Better granularity of control: in testing it was possible to set focus to specific absolute values when Bluetooth only allowed incremental focus changes
• Better event reporting: for example USB control provides notification of when precise focus setting has completed

The Blackmagic Cameras Code Samples provided by Blackmagic Design include a sample Swift / Mac OS application for controlling Blackmagic cameras via a USB connection. In order to provide USB control of Blackmagic cameras for non-Mac-OS platforms, this project was created. It consists of a file-by-file and line-by-line code conversion of the USB control elements of Blackmagic's original Swift sample application into Python.

The code has been successfully tested on a Raspberry Pi Zero W running Python 3.10 connected via USB to a Blackmagic Pocket Cinema Camera 6K with Sigma 18-35AF lens.

Using the code

Instantiate an instance of CameraControlInterface from within a USB context:

from CameraControlInterface import *

with usb1.USBContext() as usbcontext:
    with CameraControlInterface(usbcontext) as cameracontrol:

Then call a particular function of CameraControlInterface from within the CameraControlInterface context:

from CameraControlInterface import *

with usb1.USBContext() as usbcontext:
    with CameraControlInterface(usbcontext) as cameracontrol:
        cameracontrol.onFocusPullSetInt(30000)

To see a list of available functions for CameraControlInterface, view CameraControlInterface.py

Client Server

Within the clientserver folder, the two files client.html and server.py provide a simple demonstration of a client-server camera control system for controlling a Blackmagic camera via USB.

• server.py should be run on a device with a USB connection to a Blackmagic camera
• client.html should be run on any web browser with an internet connection to the device running server.py.

The demo client-server application uses a constant websocket connection to send client requests to the server, eg Change focus, and to receive camera notifications from the server, eg ISO has changed. To view the camera notifications from the browser, open a Javascript console.

Python Version

The library uses the new match case available in Python 3.10 so Python >= 3.10 should be used. Alternatively, replace all match case instances with the appropriate if elif construction for Python < 3.10

Installation

Create a Python 3.10 virtual environment from within Blackmagic-USB:

cd Blackmagic-USB
which python3.10
virtualenv -p [path-to-python3.10] venv
source venv/bin/activate

Install relevant Python libraries:

pip install -r requirements.txt

Disclaimer

This is a first pass code conversion to demonstrate the principle of making a USB connection to Blackmagic cameras using Python. It has not been rigorously tested and is provided as-is for other developers to use and/or improve.

To contact the author, email [email protected]

Please note: This project is in no way affiliated with Blackmagic Design. All trademarks are property of their respective owners