IMX8MP ISP calibration - AWB

[jp4]

Hello @joanxie ,

We are performing ISP calibration for our own Camera(IMX662 sensor).

We have completed all the steps of the calibration using ISP Calibration Tool Suite User Guide document. But AWB is not performing as expected. 

We need to clarify below points in AWB calibration (Chapter 8).

1. One of the steps says "Chapter 8.1 : The pixel value should be in the range [80~150] (8-bit)". Actually our output is 12bit pixel, So what should be the pixel value range for 12-bit and How I can ensure those pixel value range using tuning-client tool.

2. As per the Chapter 8.5, we need to define illumination spectral distribution files and we need to mention indoor or outdoor. On what basis and how we need to calculate those illumination spectral distribution if I am using real light source. Since I am doing calibration in indoor lab, how I can go outdoor profile. Please give some lights on this points.

3. As per the Chapter 8.9 Gain Region Modifier Tool, we need to upload  new illumination white-points in .png format but chapter 8.1 say, need to capture grey chart in raw format. Please clarify this. Also using Tuning-client tool, we could not capture image in .png format. Please let us know how to capture grey chart in .png using tuning-client tool, FYI I have captured grey chat using below gstreamer for various colour temperature. I have attached those images(A and D65). please correct me if I am wrong.

gst-launch-1.0 -v v4l2src device=/dev/video2 num-buffers=1 ! "video/x-raw,format=YUY2,width=1920,height=1080" ! queue ! imxvideoconvert_g2d ! pngenc ! filesink location=captured_image.png

Thanks in advance.

[joanxie]

got information from internal team:

"1）the required pixel value is using 8-bit value as an example. For 12-bit images, the value should be between 1280 to 2400. The tuning tool does not have the function of checking pixel values. Customer needs to use 3rd party software to check the pixel values.

2）normally indoor light has lower color temperature. For example, if customer is using A, CWF, TL84, D50 and D65 to do the calibration as we suggested, the indoor light sources will be A, CWF, TL84 and the outdoor light sources will be D50 and D65. However, if customer decides that the light source with 5000K should be indoor light source, they can customize their setting. Calibration should be done in the lab of course, but the light box should have the option to change color temperature.

3） after capturing the raw image of a grey card, the LSC parameters should be applied on the image. Therefore, customer can use the LSC calibration module in calibration tool to correct the image and the LSC module also has the function to output .png images.

"

[jp4]

Thanks for the response, I need some more clarity
Do we need to calculate spectral illumination distribution for each colour source that I am using, or I can use existing CIE_ILLUMINATS files that was provided along with samples folder.

[joanxie · Accepted solution]

"There are two files needed for the AWB calibration: Sensor_sensitivity.txt and CIE_ILLUMINATS file.

Sensor Spectral Sensitivity can be shown as the graph attached. Customers need to convert it into a txt file. The spectral sensitivity data is normally provided by the sensor manufacturer.

CIE illuminants file should be same for all sensors, customers can use the file in our example directly. Therefore, there is no need to calculate illuminance data for each color temperature."