How to do window region capture in C++/NodeJs like in OBS?

Question

C++ / C#

How can you capture a window in real time, just like it works in the OBS program on the preview, there is no delay at all. I tried to do it through ffmpeg running NodeJs

ffmpeg -re -f gdigrab -framerate 30 -probesize 32 -offset_x 1000 -offset_y 300 -draw_mouse 0 -video_size 600x240 -i title=TestStopwatch -preset ultrafast -tune zerolatency -f flv rtmp://localhost:1935/live

But I have a delay of 1 second, and it didn’t work out to make it smaller, maybe there is another way to implement this in C ++ for example, or how can I do it through the same ffmpeg? I am writing a simple program to determine by a small area of ​​the screen, an action that needs to be performed with a minimum delay.