Questions about camera resolutions and how to get the old "modes" of the old picamera-lib?

[cpixip]

While having fun in understanding the new picamera2-lib and trying to adapt the new lib to my existing software suite (based on the old picamera-lib) I stumbled upon a few things I could not figure out by reading/searching the examples and documentation.

(System: RP4 with HQ sensor, socket-based client-server structure, MJPEG-encoded 2016x1520 frames (q=90) send from the RP4 to a WIN10 machine at 23 fps. Bandwidth used about 130 MBit/s)

First, requesting an image resolution like this,

video_config = picam2.video_configuration(main={"size": (2028,1520)})

it seems I only get 2016 x 1520 px in the end. Libcamera reports:

Selected sensor format: 2028x1520-SGRBG12_1X12 - Selected unicam format: 2028x1520-pgCC

So I think the camera is using the 2x2 binned mode here, but is cropping the image somewhat.

The same thing kind of happens if I request the full sensor resolution:

still_config = picam2.still_configuration(main={"size": picam2.sensor_resolution})

and libcamera again reports

Selected sensor format: 4056x3040-SGRBG12_1X12 - Selected unicam format: 4056x3040-pgCC

as requested.

But: I only get 4032 x 3040 px images. (I needed here to use the still_configuration because the video_configuration ran out of buffer space). So again, the delivered image size is slightly smaller in x-dimension than the requested one.

Has this behaviour something to do with buffer alignments or so? Is it caused by libcamera or the encoder used (simplejpeg)?

A further question: the old picamera-lib (based on the Broadcom-stack) allowed to run the sensor at full resolution (mode=3) and half the output image size to 2028 x 1520 by rescaling. This yielded a noticably better image quality than running the HQ sensor in mode=2 with it's 2x2 binning. Here's an example of the difference (obtained with the old picamera/Broadcom stuff):

How can I request from libcamera the use of the non-binned 4056 x 3040 sensor mode while working with an output image size of 2028 x 1520 or so?

[sandyol55]

Think the recommended method is to specify an additional raw configuration at the full sensor resolution along with the main 1/2 resolution required image size.

Not tested on an HQ camera, but with a V2.1 the following configuration drives the sensor into its max resolution mode but outputs a rescaled 'full format but 1/2 pixel density per axis' image.

still_config = picam2.still_configuration(main={"size" : (1640,1232}), raw={"size" : (3280,2464)})

Interestingly the achieved image size is also reduced horizontally, by 8 pixels in this case, for a 1632 x 1232 image

[cpixip]

thank you! That does the trick. Seems that the horizontal size of a delivered image is always quantized to 16 in our case. There is the align_stream(self, stream_config: dict)-fct in the code which does such a thing with certain image formats, but I am explicitly requesting "RGB888" which is not in this list. Anyway, thanks for resolving my "mode"-question!

[sandyol55]

Glad it worked, the tip came from an answer I'm sure DP has given elsewhere but I couldn't remember where, to link to it.
Seeing your USAF three bar charts brought back some early memories of QA testing 35mm projection systems for a moving map system!

[cpixip]

👍

[davidplowman]

A couple of points that might interest folks here:

• You can find out what raw camera modes are available using libcamera-hello --list-cameras. To have that available in Picamera2 is a feature on the list. I'd like to provide a bit more information about the modes, but whether that's possible is still TBD.
• When you ask for a camera configuration, it gives you a suggested configuration, but you can still change it. For example, it forces widths to be aligned to how the hardware works so that you get less copying of multi-megapixel buffers. The assumption is that the optimal alignment rules are a bit tricky, so it's best if it gets done for you. But you can ask for other sizes if you want: just do config['main']['size'] = (4056, 3040) once the suggested configuration has been returned to you.

I hope a lot of this will become clearer once there's official documentation (which I'm just starting on).

[davidplowman]

Just to add to this that the latest versions of Picamera2 have a sensor_modes property, which you can use like this:

from picamera2 import Picamera2
from pprint import *
picam2 = Picamera2()
pprint(picam2.sensor_modes)

It's best to query the sensor_modes property immediately after creating the Picamera2 object because it will try to reconfigure the camera multiple times, but after that it is cached. You can even write things like

config = picam2.create_preview_configuration(raw=picam2.sensor_modes[0])
picam2.configure(config)