About HiSilicon hi3518+ov9712 ISP image debugging-night vision effect, exposure, image stability response effect

Night Vision Effect Debugging

Commissioning Requirements:

Because of the use of the light is white LED lights, design requirements are in the night can also see the color of the picture, the reality of the scheme to achieve the picture is not ideal, the light is not bright enough, the image noise is large, because can not modify the hardware can only optimize the image as far as possible.

hiisp_ae_attr_ex_s parameter Description:

Enaemode the priority mode of auto exposure, such as frame rate first, noise priority.

U8expcompensation The amount of exposure compensation when auto exposure is adjusted.

The larger the value, the higher the target brightness value of the AE, the brighter the image

U32gainthreshold the system gain threshold when the frame is automatically dropped.

Range of values: [0x400, 0xFFFFFFFF]

Automatic drop-frame gain threshold u32gainthreshold means that in lownoise mode, the system will automatically enter Lownoise mode when the gain reaches the threshold value set

Because we use white led to fill the light, so in the light of the environment prone to noise is too large problem, the following parameters can be adjusted in the night environment, the lens to achieve optimal noise and exposure;

isp_ae_attr_ex_s Aeattrex;

Aeattrex.enaemode = ae_mode_low_noise; Noise reduction mode, reduced frame rate to ensure image quality when light is low

Aeattrex.u8expcompensation = 64;//AE Adjusts the amount of exposure compensation, because the machine uses a white LED light, so this side needs to be set to 64 if set too general exposure.

Aeattrex.u32gainthreshold = 45000; Here is still set as the default good, the smaller the clearer, but the premise is to reduce the frame in exchange for effects, screen card.

Here the minimum value is 4096, the value of the screen is the most clear also the most stuttering, if set 65536, the image will be poor, but the smoothness is also the best;

Image Stabilization Response effect debugging

Commissioning Requirements:

Due to product requirements, when the machine starts the lens, sensor needs to be in the first time out of the image, and the image must be stable and clear.

hiisp_ae_attr_ex_s parameter Description:

U8expstep The initial step of the auto-exposure adjustment.

S16exptolerance tolerance for exposure when auto exposure is adjusted.

Value range: [0x0, 0xFFFF].

Aeattrex.u8expstep = 255; Exposure adjustment step, setting too small will make the exposure slow, the image from dark to bright change time long

Aeattrex.s16exptolerance = tolerance deviation of exposure amount when 50;//auto exposure adjustment

The larger the value, the smaller the sensitivity to the ambient brightness changes.

Note: U8expstep is the "initial step in auto exposure adjustment", meaning that the brightness of the image automatically adjusts the length of time, if the setting is small, the response time is long, if the setting is large, the response time is short, if you need to start the lens when the image stability response time is short, you need to set a large point , but there is a drawback, that is, when the light is not stable (test effect: There is a small part of the light source, but the light is not stable), then the screen will continue a dark and bright flashing.

After we have tested, I do this: when the machine is started, will u8expstep = 255, s16exptolerance = 50, this is because the image appears faster, if the setting is small, the image will be from dark to light about 5 seconds (here to see personal needs). When the machine executes to about 5 seconds, we then set the value to U8expstep = 16, S16exptolerance =10,u8expstep is set to 16 because preventing changes in the light source will cause the image to quickly effect (flash flash). The s16exptolerance set to 10 is set for daytime exposure, which allows the change of the light source to be a more sensitive response from the ISP.

Exposure Commissioning-wide dynamic

Commissioning Requirements:

3518 of common problems, the camera is facing the "human face" (Human face near the IPC) and "Ambient backlight" (IPC is the outdoor sunny environment) caused the IPC to "face" black or "backlight environment" exposure.

For the anti-flicker frequency properties (antiflicker) and AE attribute (setaeattr) parameter settings:

When the anti-flicker non-enable, the sun can be seen clear picture, but with the automatic exposure time setting has a direct relationship, when the minimum exposure time increases, the screen obviously exposed.

isp_inner_state_info_s parameter Description:

U8avelum image average brightness. Range of values: [0x0,0xff]

hiisp_ae_attr_ex_s parameter Description:

U32exptimemin the minimum exposure time for automatic exposure.

Range of values: [0x2, 0xFFFF], the specific range of sensor-related.

Maximum minimum time and gain for auto exposure

The exposure time and gain can be limited according to different scenes, such as high-speed moving object scene can limit the most

The large exposure time value is a small value, which reduces the phenomenon of motion object drag shadow. setting of the minimum digital gain value

Currently not supported.

About the camera is facing the "human face" (Human face near IPC) and "Ambient backlight" (IPC is on the outdoor sunny environment) caused IPC to "face" black or "backlight environment" exposure problem.

AE automatic exposure of the minimum exposure time increase or decrease to the above phenomenon has a direct impact, u16exptimemin small, backlight environment clear, when the face of a black, u16exptimemin large, human face clear, environmental exposure;

Here we solve this problem by turning off the flicker-resistant function, the automatic wide dynamic, the step setting exposure time value method.

About the wide dynamic AE exposure study, you can read the isp_inner_state_info_s structure parameters by the function Hi_mpi_isp_queryinnerstateinfo:

There are three main parameters of backlight and exposure brightness change:

U8avelum image average brightness, range of values: [0x0,0xff]

U32exposure Sensor exposure, value range [0X0,0XFFFFFFFF].

U32exposuretime Sensor exposure time, value range [0X0,0XFFFFFFFF].

The higher the backlight brightness, the greater the U8avelum and u32exposuretime values, the brighter the backlight

When the face of the basic coverage of the lens, the image of the light immediately darkened, U8avelum also become smaller, then need to raise the U16exptimemin value to 5000 to 9000 (according to the Effect of darkness);

Under normal circumstances, the U8avelum value is 45 to 56, when the U8avelum is less than 45 o'clock, the lens is obviously dark (human face or local non-light back), the darker the lower the value is close to one hundred or two hundred, the background is obviously exposed, Our solution is to step-adjust the value of the u16exptimemin;

It is not necessary to set the exposure value because the sensor is not stable at the beginning of the IPs and the image luminosity is constantly changing.

According to the actual situation on our side, when the light is dark enough, the u8avelum is less than 20, so we have divided the five zone limits:

U8avelum >= 20;

U8avelum >= && U8avelum < 20;

U8avelum >= && U8avelum < 15;

U8avelum >= 5 && u8avelum < 10;

U8avelum >= 0 && U8avelum < 5;

For the set u32exptimemin value:

U32exptimemin = 2;

U32exptimemin = 4000;

U32exptimemin = 5000;

U32exptimemin = 7000;

U32exptimemin = 9000;

The larger the U8avelum value (more than the exposure time), the smaller the u32exptimemin needs to be set (equal to 2), if the U8avelum value is close to 0 o'clock, the local light is suddenly dimmed (the face is near), which is the need to set the exposure value u32exptimemin greater.

Optimize the outdoor environment (under the sun), environmental exposure and human face can not be seen, optimize the wide dynamic exposure, the effect is: when the lens to the environment, the display of the focus environment color (not exposure), when the lens on the face, the focus of the face so that clearly see the face but behind the environment for exposure, when the face removed, Lens re-focus the ambient color (no exposure).