Depth 16bit vs 8bit

Since the subpixel is a quite huge operation which costs a lot of resources. Can we somehow do it in chosen ROI? I can imagine, that it would lower the demand if we say, that subpixeling iterests us in 50x50 window?

Thanks for the info :-)

Hopefully last question We use the Pro Wide camera so in order to align the RGB and Depth, we had to use at first the manual undistortion via OpenCV: https://docs.luxonis.com/software/perception/rgb-d. We came across problematic behaviour. There is some discrepancy between measured depth values between this setting and setting when Alpha scaling is not set.

If I understand it correctly, we ought to use the Alpha scaling, since we want 100% align with undistorted RGB and its Depth. However, if we just undistort and not scale via Alpha, the measured distances jump around our needed 4-5cm and not 7-10cm like with the set scaling. Is the scaling set by some default value?

Below is the code we used, plus without scaling, we just commented out the setAlphaScaling().

alpha = 0
stereo.setAlphaScaling(alpha)

rgb_w = camRgb.getResolutionWidth()
rgb_h = camRgb.getResolutionHeight()
rgbIntrinsics = np.array(calibData.getCameraIntrinsics(rgbCamSocket, rgb_w, rgb_h))
rgb_d = np.array(calibData.getDistortionCoefficients(rgbCamSocket))
rgb_new_cam_matrix, _ = cv2.getOptimalNewCameraMatrix(rgbIntrinsics, rgb_d, (rgb_w, rgb_h), alpha)
map_x, map_y = cv2.initUndistortRectifyMap(rgbIntrinsics, rgb_d, None, rgb_new_cam_matrix, (rgb_w, rgb_h), cv2.CV_32FC1)

frameRgb = cv2.remap(frameRgb, map_x, map_y, cv2.INTER_LINEAR)

Thanks.
I understand, but once I set the Alpha scaling to zero, the depth values jumps by average more than 10 cm. If I wont use Alpha scaling, meaning I commented that line out, the depth values are more precise. However, as you also mentioned, without the alpha scaling, the depth is not perfectly aligned to RGB.

That is what I worry most about, because we must use undistortion upon our RGB, since we use the Pro Wide camera. We are doing that by your tutorial with OpenCV and its manual undistortion. We set its matrix Alpha the same way we set the Alpha for stereo alphascaling. This is done for the perfect alignment. However, the depth values after that jumps more. We dont know why.

Yes, we measured as an experiment single depth value at the center of an image. The camera was pointed towards a rectangular object. We captured the object at the start around 1m and moved step by step (around 1cm) further.

Since I cannot upload our measured text files here, you can look at them here. There are two text files with and without alpha scaling.

If I take only the unique captured values, then:

• With alpha scaling: 103, 107, 112, 117, 123, 130, 137, 145, 154, 164, 176 cm
• No alpha scaling: 113, 116, 119, 123, 126, 130, 134, 139, 143, 148, 154, 159, 165 cm

The object, environment and lightning was the same.

As you can see, the steps with alpha scaling are larger than without alpha scaling. I mean without, like as I described, the setAlphaScaling is commented out, meaning no alpha is set.

The camera settings is as follows:

• Pro Wide
• 12MP with isp scaling 4x13
• Depth res 800p
• LR check on
• 30 FPS
• Without any filters

Another question please. We are thinking of manual subpixeling. I would like to ask, is there a possibility how to obtain the disparity (98MB) without turning ON the subpixel? I mean, is there a way, how to do the subpixeling manually with some computation later on? I imagine to calculate it just for specific pixels. Because I read here, that the disparity output is supposed to be dumped into memory, then the software interpolation is done.

jakaskerl
I tried the main.py script from the experiments repo you provided and it seems it does the rectification but not undistortion. I guess, it needs to be done manually? However, if I look into the depthai_demo script, the rectified left/right camera are already undistorted as well.

jakaskerl

Another question please regarding the outputing of disparity map. Is there a way how to debugDispCostDump without turning on the subpixel? Because right now, we can only access the 96 values per pixel if the subpixel is ON.

Thanks a lot for your support.

jakaskerl Can you elaborate on what you wish to achieve?

Yes, we are thinking of "subpixeling" in specific ROI on host PC. Because we need to boost the accuracy and the subpixeling look good, but it cost a lot of resources. We still need to proceed in 30 FPS, therefore, we are thinking of subpixeling just important ROI.