Updates***
Today i send the video to dahua, here is the answers from dahua egineer:
The picture is no problem, because focus need time and can't be focus shortly when the camera move, esp in the dark area, the focus will be much slower. And the device motorized continually so it shows can't foucs. The IR for the PTZ has many levels. 150meters IR can't be the top power shortly.
So the device will auto-adjust the IR power based on the using enviroment. The suddenly bright like a
flashlight, this because the camera make a lens motorized. The principle for the PTZ is the longer distance need more powerful IR to make the light supply. So when you see too bright then it turn off the IR light.
For the picture blurry, better to increase the stream, and not use VBR. This can ease the picture change frequency which make
code efficiency too low.
As i checked the other model some members talked here, you can see his using area has very good light, for the guys who use at a very dark area,so when the auto tracking will make the picture change fast.
They also suggest can install a IR illumination to work with the PTZ.
@nayr how do you think for this issue? I remember you talked with us Auto-tracking is not a good function, maybe the reason is like dahua engineer talked?