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AM62A1-Q1: question about TI_AWB_stab of white balance

guangyi wu
Prodigy 20 points
Part Number: AM62A1-Q1

Tool/software:

Hi TI Expert,

During the deployment of our self-developed AWB (Auto White Balance) algorithm, we noticed that the TI_AWB_stab() function performs post-processing on the output results of our algorithm. We would like to understand the function and internal logic of this function. Through experiments, we found that both our self-developed AWB algorithm and TI's AWB algorithm exhibit the following identical phenomena when capturing test charts with fixed color temperature and scene in a light box:
  1. When the TI_AWB_stab() function is enabled and sensor_awb_pre_gain is enabled, the AWB output results can remain stable.
  2. When the TI_AWB_stab() function is disabled but sensor_awb_pre_gain is enabled, the AWB output results cannot stay stable.
  3. When both the TI_AWB_stab() function and sensor_awb_pre_gain are disabled, the AWB output results can be stable.
We understand that the TI_AWB_stab() function is designed to filter and stabilize AWB results. However, if sensor_awb_pre_gain is enabled and there are no changes in parameters such as color temperature or brightness of the image, why can the AWB results not converge when TI_AWB_stab() is disabled? What specific post-processing operations does TI_AWB_stab() perform on the AWB output results?
We hope to get your answer，thank you!

  • 0
    TI__Guru 59600 points

    Hi guangyi,

    guangyi wu said:
    When the TI_AWB_stab() function is disabled but sensor_awb_pre_gain is enabled, the AWB output results cannot stay stable.

    In a static scene, I would not expect this to happen in general.

    What actually happened to cause the stability issue?

  • 0 in reply to Gang Hua
    Prodigy 20 points

       Shoot the 24-color chart in the light box. The test environment is a stable state with an illuminance of 1500 lux and a color temperature of 5000 K. When pre_awb is turned on, the AWB (Auto White Balance) will keep flickering after TI_AWB_stab() is turned off. Which parameters does this function affect? 

  • 0 in reply to guangyi wu
    TI__Guru 59600 points
    guangyi wu said:
    The test environment is a stable state with an illuminance of 1500 lux and a color temperature of 5000 K. When pre_awb is turned on, the AWB (Auto White Balance) will keep flickering after TI_AWB_stab() is turned off. Which parameters does this function affect? 

    It seems AWB fails frequently in that lighting condition, what is the cause of the failure?

    Is it due to invalid H3A data (after cancelling pre-awb-gain) are feeding into AWB algo?
    You shall be able to see that in your own AWB.

  • 0 in reply to Gang Hua
    TI__Guru 59600 points

    BTW, which sensor (vendor, color format, etc.) is this?

  • 0 in reply to Gang Hua
    Prodigy 20 points

    Sony623, color format is bayer RGGB

  • 0 in reply to Gang Hua
    Prodigy 20 points

    The lighting environment may not be the main cause. When both the preAWB and stab functions are enabled or disabled, TI's AWB algorithm does not appear flicker at any color temperatures above 3000K. However, when preAWB is enabled and the stab function is disabled, flicker occurs at all color temperatures. Besides processing the gain output by AWB, does the stab function also handle other parameters?

  • 0 in reply to guangyi wu
    TI__Guru 59600 points
    guangyi wu said:
    However, when preAWB is enabled and the stab function is disabled, flicker occurs at all color temperatures.

    What is the cause and behavior of the flicker?

    There must be some serious failure in this case.
    I suppose you would need to identify and resolve that first.

    guangyi wu said:
    Besides processing the gain output by AWB, does the stab function also handle other parameters?

    No, it does not do anything special.

  • 0 in reply to Gang Hua
    Prodigy 20 points

    Could I understand it this way: if the shooting scene is static, the exposure parameters are fixed, pre_awb is enabled, and regardless of whether the stab function is turned on or off, there will be no flicker if there are no other errors?

  • 0 in reply to guangyi wu
    TI__Guru 59600 points
    guangyi wu said:
    pre_awb is enabled, and regardless of whether the stab function is turned on or off, there will be no flicker if there are no other errors?

    "there is no error" meaning AWB is working properly and stably.