Hi,
You could add a tee or GstInterpipe to the pipeline and use an appsink in the second branch, like this:
Another option is to implement an element based on GstVideoFilter and add it to the DeepStream pipeline. You can perform the custom algorithm in the _transform_ip virtual method. For a reference you can check our perf plugin that is quite simple, based on VideoFilter and implements transform_ip: gst-perf/plugins at master · RidgeRun/gst-perf · GitHub