Manually setting gain of raspberry pi camera from within python

set_picamera_gain.py

from __future__ import print_function

import picamera
from picamera import mmal, mmalobj, exc
from picamera.mmalobj import to_rational
import time


MMAL_PARAMETER_ANALOG_GAIN = mmal.MMAL_PARAMETER_GROUP_CAMERA + 0x59
MMAL_PARAMETER_DIGITAL_GAIN = mmal.MMAL_PARAMETER_GROUP_CAMERA + 0x5A

def set_gain(camera, gain, value):
    """Set the analog gain of a PiCamera.
    
    camera: the picamera.PiCamera() instance you are configuring
    gain: either MMAL_PARAMETER_ANALOG_GAIN or MMAL_PARAMETER_DIGITAL_GAIN
    value: a numeric value that can be converted to a rational number.
    """
    if gain not in [MMAL_PARAMETER_ANALOG_GAIN, MMAL_PARAMETER_DIGITAL_GAIN]:
        raise ValueError("The gain parameter was not valid")
    ret = mmal.mmal_port_parameter_set_rational(cam._camera.control._port, 
                                                    gain,
                                                    to_rational(value))
    if ret == 4:
        raise exc.PiCameraMMALError(ret, "Are you running the latest version of the userland libraries? Gain setting was introduced in late 2017.")
    elif ret != 0:
        raise exc.PiCameraMMALError(ret)

def set_analog_gain(camera, value):
    """Set the gain of a PiCamera object to a given value."""
    set_gain(camera, MMAL_PARAMETER_ANALOG_GAIN, value)

def set_digital_gain(camera, value):
    """Set the digital gain of a PiCamera object to a given value."""
    set_gain(camera, MMAL_PARAMETER_DIGITAL_GAIN, value)


if __name__ == "__main__":
    with picamera.PiCamera() as cam:
        cam.start_preview(fullscreen=False, window=(0,50,640,480))
        time.sleep(2)

        # fix the auto white balance gains at their current values
        g = cam.awb_gains
        cam.awb_mode = "off"
        cam.awb_gains = g

        # fix the shutter speed
        cam.shutter_speed = cam.exposure_speed

        print("Current a/d gains: {}, {}".format(cam.analog_gain, cam.digital_gain))

        print("Attempting to set analogue gain to 1")
        set_analog_gain(cam, 1)
        print("Attempting to set digital gain to 1")
        set_digital_gain(cam, 1)
        # The old code is left in here in case it is a useful example...
        #ret = mmal.mmal_port_parameter_set_rational(cam._camera.control._port, 
        #                                            MMAL_PARAMETER_DIGITAL_GAIN,
        #                                            to_rational(1))
        #print("Return code: {}".format(ret))

        try:
            while True:
                print("Current a/d gains: {}, {}".format(cam.analog_gain, cam.digital_gain))
                time.sleep(1)
        except KeyboardInterrupt:
            print("Stopping...")

setting picamera gain.md

Setting Pi camera analogue/digital gain from Python

This gist contains a very minimal Python script that shows how to set the analogue and digital gains of the Raspberry Pi camera module from within Python. It is a trivial thing, all the actual work was done by the developers of userland in particular 6by9, and of course the developers of picamera. It does require the latest version of the userland libraries in order to be able to send the gain-setting commands. These are not yet (as of January 2018) in the main Raspbian distribution, but it is not scary to build this yourself:

sudo apt-get install cmake
git clone https://github.com/raspberrypi/userland.git
cd userland
./buildme
sudo shutdown -r now

After you've got the latest version of the userland libraries, you should be able to run

python set_gain.py

This will open a preview window and then freeze the analogue and digital gains at 1. Look at the code to see how it's done - it is not complicated. To use this in your own code, just do:

import picamera
from set_picamera_gain import set_analog_gain, set_digital_gain

with picamera.PiCamera() as cam:
    set_analog_gain(cam, 2)
    set_digital_gain(cam, 1)

Hopefully I will get round to making a pull request to picamera - but of course that's only really useful once the userland code is updated in the distribution.

@oferbentovim I've never found a definitive answer, but raw RGB captures don't often work at full resolution. I've had better success with JPEG captures at full resolution, or JPEG plus Bayer data (if you want the full uncompressed pixel data). The latter requires a bit more work to process the image and is slow, but seems way more reliable.

@jhihn that line sets the shutter speed to the last value used by the auto exposure - it means the exposure doesn't change when we switch from auto to manual. If you already have a sensible value for shutter speed, you can safely ignore it.

Did anyone get this to work without getting errors or find another way of setting the analog gain high consitently? @dogadogan @vijayashri91 did you manage to find a solution to this problem around the error wit userland download?