Gstreamer with Python is highly flexible for data visualization. Any video streaming pipeline could be extended with custom Python plugins that allows you to draw any information (bounding boxes, confidences, class names, etc.). Next information is simple comparison of two most popular approaches to draw on gstreamer buffer: PyCairo, OpenCV.
Gstreamer is flexible plugin based data streaming framework. One of the main advantange of plugins is that developer can pass not only data buffer, but custom metadata which can describe buffer and store any information about buffer. Next information is a simple guide with code templates on how to pass any data from