fix(mps): allow bisection_timestamp_search to match the first or last timestamp exactly

The border guards used <= and >=, so querying the exact first or last
timestamp returned None instead of index 0 or len - 1, violating the
"closest or equal" wording in every get_nearest_* wrapper docstring.
Tightened to < and >.

Separable from the issue #100 fix; can be dropped if you'd rather see
it as its own PR.

Author: Ace3Z

core/python/test/mpsUtilsTest.py

@@ -36,6 +36,12 @@ def test_equidistant_prefers_lower_index(self) -> None:
         # Tie-break is deterministic toward the lower index.
         self.assertEqual(bisection_timestamp_search(self.ts, 6000), 2)
 
+    def test_exact_match_on_first_or_last_returns_its_index(self) -> None:
+        # The border guards used <= / >=, so an exact match on the first or
+        # last timestamp returned None instead of its index.
+        self.assertEqual(bisection_timestamp_search(self.ts, 1000), 0)
+        self.assertEqual(bisection_timestamp_search(self.ts, 19000), 9)
+
 
 if __name__ == "__main__":
     unittest.main()

projectaria_tools/core/mps/utils.py

@@ -36,9 +36,9 @@ def bisection_timestamp_search(timed_data, query_timestamp_ns: int) -> int:
     if timed_data and len(timed_data) > 1:
         first_timestamp = timed_data[0].tracking_timestamp.total_seconds() * 1e9
         last_timestamp = timed_data[-1].tracking_timestamp.total_seconds() * 1e9
-        if query_timestamp_ns <= first_timestamp:
+        if query_timestamp_ns < first_timestamp:
             return None
-        elif query_timestamp_ns >= last_timestamp:
+        elif query_timestamp_ns > last_timestamp:
             return None
     # If this is safe we perform the Bisection search
     start = 0