ISP feature

 Pixel readout

Four readout per pixe

HCG and LCG of first exposure on LPD

VS of second exposure on LPD

SPD, usually with exposure time of 11ms or longer to capture flickering LED.

HDR combination

On-chip align buffer, flicker detection, and HDR combination.

HDR 4 means combination of all four captures, HDR 3 means combination of 3 captures (no SPD) with the option to have SPD for flickering pixels.

Option to output detected flickering map (1 bit/pixel) or the SPD pixel itself in a separated VC. 

SNR curve

In bright condition, HCG and LCG covers the dark portion, and VS covers the very bright object, and SPD is in between.

In dark condition, VS can move between LCG and SPD to improve SNR.

HDR combination cont

The figure below shows a typical blending weight map for mering two linear captures. 

Based on the signal level in the image with short exposure (upper) and long exposure (lower) a weight is calculated from the programmable weight map which is then used to blend the images together.