[HOW-TO] Know USB camera resolution

[RobertFlatt]

Please only ask one question per issue!
I want to get the best possible usb resolution, for still image capture. How do I know what I can specify?

Describe what it is that you want to accomplish
By default usb camera resolution appears to be 640x480 for both YUYV and MJPEG
This seems good for a 4:3 preview.
I want higher resolution for a still capture, I expect the resolution to depend on the usb camera used.

Describe alternatives you've considered
I tried setting a plausible, and higher resolution:
If in a still_configuration I set main = {'size' : (1440, 1080)}
I get a capture that is 1600 x 896 , so it seems there is more resolution to be had.
But this is not the size I asked for, and is not 4:3 it is 16:9
Configuring higher resolutions, showed similar behavior.

Additional context
Add any other context or screenshots about the request here.

[RolandasRazma]

can you use .sensor_modes and sort them?

https://github.com/raspberrypi/picamera2/blob/af75efd3b76479a2f6401dda120a67f3ee417eea/examples/pick_mode.py

[RobertFlatt]

For a usb cameras I tried picam2.sensor_modes only contains 'format' , tried two Logitech (very common) usb cameras, for each all that is returned by sensor_modes is two formats:

{'format': 'MJPEG'}
{'format': 'YUYV'}

Experiment shows that picamera2 generates a stream from a usb camera that can have discrete values of "size".
How to enumerate these discrete values?
Is it possible to query libcamera directly?

[RolandasRazma]

what about
v4l2-ctl --list-formats-ext -d /dev/video0 ?

[davidplowman]

Hi, I'm afraid USB camera support is limited with Picamera2, and we have no plans to extend it at the moment. You could try whether picam2.sensor_resolution will give you the maximum output resolution . You can of course use the regular V4L2 style interface, such as v4l2-ctl, too.