Drawing on output frames of sample yolo app

Hi,
I’ve only started using the DeepStream SDK on the Jetson Nano and have been looking through the sample Yolo app. I’m having trouble identifying where the code for drawing the output frames and bounding boxes is located.

A webinar mentioned that the nvosd plugin handled the drawing, and there are some details on its parameters in the plugin manual, but there is no mention on how to use it to draw custom text and polygons.

Would someone be able to point me to some resources on understanding the code responsible for displaying the outputs of the DeepStream sample apps? I’d like to modify the code to display a simple counter.

Can you check check sample Test1 app and check how we display person and vehicle count ?