From bc06b8c753844a92b76a0615d0f4c195d3e6f59b Mon Sep 17 00:00:00 2001
From: Josh Hawkins <32435876+hawkeye217@users.noreply.github.com>
Date: Sun, 11 Oct 2026 22:01:58 -0500
Subject: [PATCH] run opencv single threaded in camera tracking processes
 (#24640)

OpenCV's default thread pool is sized to every core, and its idle threads spin while it works on the small motion frames and detection regions in each camera tracking process. On a 16 thread machine replaying 720p clips at 5 fps, tracking CPU dropped from 27-50 ms to 5-8 ms per frame with identical output and no change in wall time. Frames from ffmpeg are now also read directly into shared memory with readinto(), which skips one copy per frame.
---
 frigate/video/detect.py | 5 +++++
 frigate/video/ffmpeg.py | 3 ++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/frigate/video/detect.py b/frigate/video/detect.py
index d1048e4270..f55c1c9635 100644
--- a/frigate/video/detect.py
+++ b/frigate/video/detect.py
@@ -144,6 +144,11 @@ class CameraTracker(FrigateProcess):
 
     def run(self) -> None:
         self.pre_run_setup(self.log_config)
+
+        # OpenCV only sees small images here, and its default per-core thread
+        # pool burns ~5x the CPU of running them inline
+        cv2.setNumThreads(1)
+
         frame_queue = self.camera_metrics.frame_queue
         frame_shape = self.config.frame_shape
 
diff --git a/frigate/video/ffmpeg.py b/frigate/video/ffmpeg.py
index c4364f8d71..16e3afcdb5 100644
--- a/frigate/video/ffmpeg.py
+++ b/frigate/video/ffmpeg.py
@@ -79,7 +79,8 @@ def capture_frames(
         frame_name = f"{config.name}_frame{frame_index}"
         frame_buffer = frame_manager.write(frame_name)
         try:
-            frame_buffer[:] = ffmpeg_process.stdout.read(frame_size)
+            if ffmpeg_process.stdout.readinto(frame_buffer) != frame_size:
+                raise EOFError("incomplete frame")
         except Exception:
             # shutdown has been initiated
             if stop_event.is_set():