ISP IQTune 2.0.0 AWB R/B Ratios Wrong

[chornbeck]

When using the ISP IQTune application to generate ISP parameters for the STM32N6 DCMIPP, the Auto White Balance expresses an error that I believe is incorrect. The error claims that AWB cannot start becase the R/B ratios for white balance must decrease, as the color temperature increases. The ratio IS decreasing, as shown in the image below.

When the temperature is 5100K, the R/B ratio is 2.1/1.9 = 1.105

When the temperature is 3800K, the R/B ratio is 2.3/1.9 = 1.210

Thus, as the temperature increases, the R/B ratio decreases. Either this is wrong, or I’m missing a key component of this calibration process.

 

[Saket_Om]

Hello ​@chornbeck 

The R/B ratio mentioned in the warning message is the ratio of the RGB components statistics before demosaicing that identify the color temperature of the current scene.

For CT = 3800K, we expect the ratio of the statistics Average_R/AverageB to be higher than the one for CT= 5100K.

You can read the statistics collected for each profile using the menu “Open RGB stats”. If there are not consistent, then collect new statistics for each profile:

https://wiki.st.com/stm32mcu/wiki/ISP:How_to_tune_ISP_using_the_STM32_ISP_IQTune#Collect_the_RAW_RGB_statistics_of_the_profile

In any case, it is probably better to use the autocalibration for the tuning. It will collect the statistics automatically.

 

FYI, a newer version 2.1.0 of the STM32 ISP IQTune  will be released soon. It is probably best to update your version when it will be available, since this version is more stable. This will require a minor update of the X-CUBE-ISP version to v2.0.2.