hi_isp_wdr_exposure_attr

Description

Defines the exposure attribute in WDR mode.

Definition

typedef struct { 
    hi_op_mode  exp_ratio_type; 
    hi_u32 exp_ratio[HI_ISP_EXP_RATIO_NUM]; 
    hi_u32 exp_ratio_max; 
    hi_u32 exp_ratio_min; 
    hi_u16 tolerance; 
    hi_u16 speed;  
    hi_u16 ratio_bias;  
    hi_u16 high_light_target; 
    hi_u16 exp_coef_min;
} hi_isp_wdr_exposure_attr;

Members

Member	Description
exp_ratio_type	This parameter is valid only in multi-frame combination WDR mode.
exp_ratio[HI_ISP_EXP_RATIO_NUM]	This parameter is valid only in multi-frame combination WDR mode. When exp_ratio_type is set to HI_OP_MODE_AUTO, exp_ratio is invalid. When exp_ratio_type is set to HI_OP_MODE_MANUAL, exp_ratio indicates the expected exposure ratio of two adjacent frames in multi-frame combination WDR mode, and can be read and written. exp_ratio[0] indicates the S/VS exposure ratio, exp_ratio[1] indicates the M/S exposure ratio, and exp_ratio[2] indicates the L/M exposure ratio. VS, S, M, and L represent the exposure time of the extremely short frame, the short frame, the middle frame, and the long frame, respectively. Only VS and S are valid in 2-frame combination mode. Only VS, S, and M are valid in 3-frame combination mode. VS, S, M, and L are all valid in 4-frame combination mode. The precision is 6-bit decimal precision. The value 0x40 indicates 1x exposure time ratio. Value range: [0x40, 0xFFF] #define HI_ISP_EXP_RATIO_NUM 3
exp_ratio_max	This parameter is valid only in multi-frame combination WDR mode. When exp_ratio_type is set to HI_OP_MODE_AUTO, exp_ratio_max indicates the maximum ratio of the exposure time of the longest frame to that of the shortest frame. That is, the maximum S/VS exposure time ratio in 2-frame combination mode, the maximum S/VS exposure time ratio in 3-frame combination mode, or the maximum L/VS exposure time ratio in 4-frame combination mode. If exp_ratio_type is set to HI_OP_MODE_MANUAL, exp_ratio_max is invalid. The precision is 6-bit decimal precision. The value 0x40 indicates 1x exposure time ratio. Value range: [0x40, 0x4000]
exp_ratio_min	This parameter is valid only in multi-frame combination WDR mode. When exp_ratio_type is set to HI_OP_MODE_AUTO, exp_ratio_min indicates the minimum ratio of the long frame exposure time to the short frame exposure time. If exp_ratio_type is set to HI_OP_MODE_MANUAL, exp_ratio_min is invalid. The format is unsigned 6.6-bit fixed point. The default value 0x40 indicates 1x exposure time ratio. Value range: [0x40, exp_ratio_max]
tolerance	Tolerance of the exposure ratio, valid only in 2-frame combination WDR mode. When exp_ratio_type is HI_OP_MODE_AUTO, a larger value indicates that the exposure ratio remains unchanged when the change of the scenario dynamic range falls within a certain range. The default value is 0xC. Value range: [0x0, 0xFF]
speed	Adjustment speed of the automatic exposure ratio, valid only in 2-frame combination WDR mode. When exp_ratio_type is HI_OP_MODE_AUTO, a larger value indicates faster adjustment of the automatic exposure ratio. The default value is 0x20. Value range: [0x0, 0xFF]
ratio_bias	Deviation of the exposure ratio, valid only in multi-frame combination WDR mode When exp_ratio_type is HI_OP_MODE_AUTO, a larger value indicates a larger automatic exposure ratio. The default value 0x400, indicating that the calculation result of the automatic exposure ratio algorithm is not adjusted. The exposure ratio adjusted by ratio_bias will be restricted by the maximum/minimum value of the exposure ratio. Value range: [0x0, 0xFFFF]
high_light_target	Target value of image overexposure. This member is valid only when advance_ae is enabled. A larger value indicates greater image overexposure. The default value is 0x30. Value range: [0x0, 0x400]
exp_coef_min	Minimum exposure coefficient. This member is valid only when advance_ae is enabled. It has a 10-bit decimal precision. The default value 0x400 indicates that the minimum exposure coefficient is 1x. Value range: [0x0, 0x400]

Restrictions

It is recommended that tolerance not be too large. This avoids the case that the exposure ratio cannot correctly reflect the change of the scenario dynamic range.
For the sensors with limited short-frame exposure time, when the exposure value is small, the maximum exposure time for long frames is short, and the dynamic range and noise performance are poor, resulting in inaccurate automatic exposure ratio calculation. In this case, you are advised to limit the minimum exposure ratio to ensure that the maximum exposure time for long frames reaches at least 3 ms. For example, for Sony IMX274@30 fps, the maximum exposure time of short frames is 680 μs. In this case, you are advised to limit the minimum exposure ratio to 1:5, that is, set exp_ratio_min to 0x140 to ensure the image quality.
It is recommended that speed be greater than or equal to 0x8. This avoids the case that the adjustment of the exposure ratio is too slow or the exposure ratio is not adjusted due to insufficient calculation precision in some scenarios. If speed is too large, the exposure ratio may change too fast and the image luminance may be unstable.

It is recommended that exp_ratio in manual mode not be greater than 0x400. If the exposure ratio is greater than 0x400, properly increasing the exposure ratio in super WDR scenarios with high luminance will optimize the noise performance of long-frame images. However, in dark or low WDR scenarios, if the exposure ratio is too large, the maximum exposure time of short frames is compressed. As a result, the image noise performance deteriorates, causing obvious noise discontinuity and poor motion performance.
If advance_ae is enabled, when the exposure ratio reaches the configured maximum value but the image overexposure does not reach the target value, the target AE luminance is decreased to reduce the overall overexposure of the image. You can set exp_coef_min to a proper value so that the target AE luminance can be reduced to the value of compensation x exp_coef_min/1024 at most.

Parent topic: Data Types