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TDA4VM: Tone Mapping error when use DCC tool generate PWL table

?? ?
Prodigy 10 points
Part Number: TDA4VM

When we use DCC tool(v2.5) to tune IQ, we change the PWL knee point with the table provided by sensor vendor , then the IQ will show tone mapping error : the whole image is dark but over-exposure in the bright part of image.

We have feedback this issue to FAE, we were told that mabe something wrong with the DCC tool，so we are looking forward to get the tool which can generate the PWL table rightly.

Pls see the attachment

PWL knee point.jpg: the knee point provided by sensor vendor, which corresponding to sensor setting

OX08B40_lut_wdr_overall_pwl_global.txt: generate by DCC tool, which performs tone mapping error.

OX08B40_lut_wdr_overall_pwl_global.txt
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0,
0,
0,
0,
0,
0,
0,
0,
0,
1,
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1,
1,
1,
1,
1,
1,
2,
2,
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

  • 0
    TI__Guru 52965 points

    You will need to choose a proper Gamma value and tune the pipeline and sensor exposure very carefully for 24-bit WDR sensors.

    Please follow the plugin guides in the help menu of V2.5 (esp. for CFA-WDR, H3A, GLBCE).

    The gamma is typically around 0.5 (50 on GUI) for 24-bit WDR sensors (you seem to have 100 on the GUI).

  • 0 in reply to Gang Hua
    Prodigy 10 points

    When we use default knee point（12bit->24bit->16bit，gamma 100），it shows better tone perfermance,but too much noise caused by using too high digital gain. if use gamma 70 or 50,it will be over-exposure  in most scenes.

    When we change the knee point provided by Omnivision, the image will be very dark, after using gamma 50, it would be brighter ,but shows tone mapping error and lose saturation, and we can also see over-exposure in raw file.

    so our concern is how to switch the knee point to the 16bit PWL table.

  • 0 in reply to ?? ?
    TI__Guru 52965 points

    Most customers and sensor vendors I know about use gamma value around 0.5 with 24-bit WDR sensor in tuning tool and they don't seem to have the issues you mentioned above. 
    Please follow the plugin guides in the help menu of V2.5 for CFA-WDR and H3A to get the proper PWL LUTs for RFE/H3A/CFAI.

    Then, you may need to tune sensor exposure (AE) and GLBCE carefully to get good output image brightness in all conditions.

    A minor issue with sensor companding knee points is that the left column in your picture above should be all multiples of 32 in order to have perfect decompanding (otherwise small color shift may happen in certain conditions).