[detectors] Add downscale performance hit #401

Author: Breakthrough

scenedetect/detectors/hash_detector.py

@@ -179,3 +179,7 @@ def hash_frame(frame_img, hash_size, factor) -> numpy.ndarray:
         hash_img = dct_low_freq > med
 
         return hash_img
+
+    @property
+    def downscale_performance_hint(self) -> bool:
+        return False

scenedetect/scene_detector.py

@@ -131,6 +131,11 @@ def event_buffer_length(self) -> int:
         """
         return 0
 
+    @property
+    def downscale_performance_hint(self) -> bool:
+        """Indicates if the detector's performance is improved by downscaling."""
+        return True
+
 
 # TODO(v0.7): Remove this early, no point in keeping it around.
 class SparseSceneDetector(SceneDetector):

scenedetect/scene_manager.py

@@ -1283,7 +1283,9 @@ def detect_scenes(
                 1 + min(max_y, frame_height) - min_y,
             )
         # Calculate downscale factor and log effective resolution.
-        if self.auto_downscale:
+        if self.auto_downscale and all(
+            detector.downscale_performance_hint for detector in self._detector_list
+        ):
             downscale_factor = compute_downscale_factor(max(effective_frame_size))
         else:
             downscale_factor = self.downscale