From dda9f7bfed65a4c371d0fd53c1defe6213a5d37a Mon Sep 17 00:00:00 2001
From: Josh Hawkins <32435876+hawkeye217@users.noreply.github.com>
Date: Sat, 7 Mar 2026 07:42:27 -0600
Subject: [PATCH] apply filters after clustering (#22308)

apply length and format filters to the clustered representative plate rather than individual OCR readings, so noisy variants still contribute to clustering even when they don't pass on their own
---
 .../common/license_plate/mixin.py             | 50 +++++++++----------
 1 file changed, 23 insertions(+), 27 deletions(-)

diff --git a/frigate/data_processing/common/license_plate/mixin.py b/frigate/data_processing/common/license_plate/mixin.py
index ae06c0d0a..c184b8b75 100644
--- a/frigate/data_processing/common/license_plate/mixin.py
+++ b/frigate/data_processing/common/license_plate/mixin.py
@@ -401,35 +401,10 @@ class LicensePlateProcessingMixin:
             all_confidences.append(flat_confidences)
             all_areas.append(combined_area)
 
-        # Step 3: Filter and sort the combined plates
+        # Step 3: Sort the combined plates
         if all_license_plates:
-            filtered_data = []
-            for plate, conf_list, area in zip(
-                all_license_plates, all_confidences, all_areas
-            ):
-                if len(plate) < self.lpr_config.min_plate_length:
-                    logger.debug(
-                        f"{camera}: Filtered out '{plate}' due to length ({len(plate)} < {self.lpr_config.min_plate_length})"
-                    )
-                    continue
-
-                if self.lpr_config.format:
-                    try:
-                        if not re.fullmatch(self.lpr_config.format, plate):
-                            logger.debug(
-                                f"{camera}: Filtered out '{plate}' due to format mismatch"
-                            )
-                            continue
-                    except re.error:
-                        # Skip format filtering if regex is invalid
-                        logger.error(
-                            f"{camera}: Invalid regex in LPR format configuration: {self.lpr_config.format}"
-                        )
-
-                filtered_data.append((plate, conf_list, area))
-
             sorted_data = sorted(
-                filtered_data,
+                zip(all_license_plates, all_confidences, all_areas),
                 key=lambda x: (x[2], len(x[0]), sum(x[1]) / len(x[1]) if x[1] else 0),
                 reverse=True,
             )
@@ -1557,6 +1532,27 @@ class LicensePlateProcessingMixin:
                 f"{camera}: Clustering changed top plate '{top_plate}' (conf: {avg_confidence:.3f}) to rep '{rep_plate}' (conf: {rep_conf:.3f})"
             )
 
+        # Apply length and format filters to the clustered representative
+        # rather than individual OCR readings, so noisy variants still
+        # contribute to clustering even when they don't pass on their own.
+        if len(rep_plate) < self.lpr_config.min_plate_length:
+            logger.debug(
+                f"{camera}: Filtered out clustered plate '{rep_plate}' due to length ({len(rep_plate)} < {self.lpr_config.min_plate_length})"
+            )
+            return
+
+        if self.lpr_config.format:
+            try:
+                if not re.fullmatch(self.lpr_config.format, rep_plate):
+                    logger.debug(
+                        f"{camera}: Filtered out clustered plate '{rep_plate}' due to format mismatch"
+                    )
+                    return
+            except re.error:
+                logger.error(
+                    f"{camera}: Invalid regex in LPR format configuration: {self.lpr_config.format}"
+                )
+
         # Update stored rep
         self.detected_license_plates[id].update(
             {