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TDA4VH-Q1: About H3A parameter causes image abnormal under bright scenes

wang zhili
Intellectual 885 points
Part Number: TDA4VH-Q1
Other Parts Discussed in Thread: TDA4VH

Hi TI experts,

I found that there is a strange phenomenon that the image of camera will become abnormal after I changed the H3A parameter "Output 10 out of 20 linear bits from LSB #" in DCC from 4 to 1,as shown below:

 fig1. Abnormal image (Output 10 out of 20 linear bits from LSB # 1)

 fig2. Normal image (Output 10 out of 20 linear bits from LSB # 4)

This happened when the camera was lightened up under bright scenes, if the scene is not bright enough the image will ok. Please help me check, thanks.

The SDK version is 8.5,and the DCC version is 3.1, the board is TDA4VH. The RAW and YUV files are attched here:

H3A problem files.zip

  • 0
    TI__Guru 59600 points

    Hi Zhili,

    Using lower bits for H3A may results in very high sensor exposure for the bright scene as AE only adjusts for average H3A output brightness.

    You can clearly see the difference in your captured raw images.
    You may also check your sensor exposure in the 2 cases.

  • 0 in reply to Gang Hua
    Intellectual 885 points

    Hi Gang,

    I found the reason of abnormal image is the value of sensor exposure register didn't change with the bright scene but still keep the original value in sensor setting, while the value of exposure time in "Algorithm View" tap of DCC is normal.  After I changed the sensor exposure register in sensor setting to a small value that match the bright scene, the abnormal image disappeared.

    But I have some questions on H3A:

    In this case, the value of "Output 10 out of 20 linear bits from LSB #" in H3A plugin was set to 1 and lightened up camera under a bright scene, why the sensor exposure register value didn't change?

    Gang Hua said:
    Using lower bits for H3A may results in very high sensor exposure for the bright scene as AE only adjusts for average H3A output brightness.

    Can you explain this in more detail? Is it because the average H3A output brightness has not changed so that the sensor exposure register value has not changed?

    Thanks.

  • 0 in reply to wang zhili
    TI__Guru 59600 points

    AE only sees input from H3A.
    When H3A's 10 input bits are changed, AE will have its input values changed.

    As AE has a target for its input from H3A, AE will increase or decrease the sensor exposure accordingly.

  • 0 in reply to Gang Hua
    Intellectual 885 points

    So the reason why the sensor exposure register does not change with AE is that H3A's 10 input bits in bright scene do not change when "Output 10 out of 20 linear bits from LSB #" is selected as 1?

  • 0 in reply to wang zhili
    TI__Guru 59600 points

    Yes, AE input from H3A's output could be all saturated in that case.