Where does nvtracker get its metadata from?

Hello! I am new to GStreamer, and am attempting to write a pipeline that includes nvinfer and nvtracker.

I also wrote a plugin that prints out the bounding box metadata in the stream for each buffer, placing one after nvinfer and another after nvtracker, as follows:
nvinfer -> printmeta -> nvtracker -> printmeta

However, for a particular frame, it seems that nvtracker detects more boxes than nvinfer. Simple example below:

<PrintMeta After Infer, Frame Num 12>
10 boxes found.
<PrintMeta After Tracker, Frame Num 12>
13 boxes found.

Furthermore, since I set nvinfer at interval 10, in frames where nvinfer does not run, the following scenario occurs:
<PrintMeta After Infer, Frame Num 11>
0 boxes found.
<PrintMeta After Tracker, Frame Num 11>
10 boxes found.

Thus, my question is why is this so? Does nvtracker also obtain bounding box information from other sources?

Thank you for your time!

Best Regards,


Tracker is applied across different frames.
It may contain the bounding boxes detected in the previous frames.