update filter, flow ema 0.5 + med 3

src/orisys/tracker.py

@@ -94,13 +94,30 @@ class Tracker:
         return mask.astype(bool)
 
     def apply_valid_mask(self, flow, valid_mask, erode_iters=1):
-        """Zero flow outside the valid UV domain."""
+        """Zero flow outside the valid UV domain (in place when safe).
+
+        Multiplying by a 0/1 mask is a single streaming pass, whereas
+        ``flow.copy()`` followed by a boolean fancy-index assignment costs a
+        full copy plus a gather/scatter over the masked-out pixels.
+
+        Note: a masked-out *negative* component becomes ``-0.0`` rather than
+        ``+0.0``. The two compare, sum and magnitude identically; only the raw
+        bit pattern of those zeros differs from the previous implementation.
+        """
         if flow is None or valid_mask is None:
             return flow
         mask = self._prepare_valid_mask(valid_mask, flow.shape[:2], erode_iters=erode_iters)
-        flow_out = flow.copy()
-        flow_out[~mask] = 0
-        return flow_out
+        if not getattr(self, "_Tracker__adaptive", False):
+            # The non-adaptive path hands back the DIS state buffer, which feeds
+            # the next frame as its initial guess; never mutate it.
+            flow_out = flow.copy()
+            flow_out[~mask] = 0
+            return flow_out
+        if not flow.flags.writeable:
+            flow = flow.copy()
+        mask_f = mask.astype(np.float32, copy=False)[:, :, None]
+        np.multiply(flow, mask_f, out=flow)
+        return flow
 
     def track(self, frame, valid_mask=None):
         """Main tracking function that dispatches to CUDA or CPU implementation"""