[Bug]: Python default camera controls cannot be passed directly

[JulianKnodt]

When trying to initiate a camera as

cam.start(cam.controls)

This will fail, as currently cam.controls has values of type ControlInfo, which should be directly passable, but as is this call currently fails.
I would expect this to succeed.

[siddharth-diwakar]

I can take this issue

[naushir]

Can you provide the full script that you are running please?

[JulianKnodt]

import libcamera as lc
import selectors
import cv2 as cv
import mmap
import numpy as np

cm = lc.CameraManager.singleton()
cam = cm.cameras[0]
cam.acquire()

config = cam.generate_configuration([ lc.StreamRole.Viewfinder ])

stream_config = config.at(0)
W = 5120
H = 3840
stream_config.size.width = W
stream_config.size.height = H
stream_config.pixel_format = lc.formats.R8

stream_config.buffer_count = 1

config.validate()
cam.configure(config)

allocator = lc.FrameBufferAllocator(cam)
stream_config = config.at(0)
stream = stream_config.stream
allocator.allocate(stream)
buffers = allocator.buffers(stream)

req = cam.create_request()
#
req.add_buffer(stream, buffers[0])
sub_objects = {}
for k, v in cam.controls.items():
  print(k.name)
  sub_objects[k] = v.default

# not sure why trying to put cam.controls here does not work?
cam.start(sub_objects)
exit()
#cam.start(cam.controls)
cam.queue_request(req)

[naushir]

cam.controls is a mapping of ControlId : ControlInfo, where ControlInfo gives the min/max/default values and not a scalar value. start() on the other hand expects ControlId : value, which is why cam.start(cam.controls) fails.

Your workaround is exactly the right approach, it pulls an actual value (the default) out of each ControlInfo:

sub_objects = {k: v.default for k, v in cam.controls.items()}
cam.start(sub_objects)

[JulianKnodt]

What I'm saying is that this is unintuitive, I would expect the camera controls to automatically take the config provided by the camera, and use the default values.

[kbingham]

Are you saying the camera is not set to it's default values at start already?

[kbingham]

Well now I think about it at start() indeed there's no guarantee the camera is at default values if it's already run, so perhaps something that makes it easier to say "set all controls to default" easily makes sense?

[naushir]

What I'm saying is that this is unintuitive, I would expect the camera controls to automatically take the config provided by the camera, and use the default values.

The controls should all take their default values on startup without needing an explicit set call. Are you seeing something different?

[JulianKnodt]

What I'm saying is that I would expect this call to succeed, like I should be able to directly pass these parameters in this format (while possibly tweaking a few), and the rest should be kept as the default.

[naushir]

Perhaps this is an issue that's better discussed on the official libcamera-devel mailing list?

[kbingham]

Or open an issue here : https://gitlab.freedesktop.org/camera/libcamera/-/work_items which is the tracker for the libcamera project.