I already use active tracking for my P3. Probably be similar to the results expected from the P4. Does have it's flaws but still get good results.
Screen grab
Final version
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Processing on P4 would need powerful processor on P4.Basically the same thing as the P4.
Only potential difference is that the P4 *might* be doing the processing on the bird rather than the controller, but that's unknown as of yet.