refactor: only publish if frame changed + allow path to change show_stats

app.py

@@ -10,9 +10,10 @@ class Session:
     def __init__(self, id: str):
         self.id = id
         self.latest_frame: MatLike = None
+        self.published_frame: MatLike = None
         self.measured_fps = 0
         self.cpu_usage = 0
-        self.show_stats = os.environ.get("SHOW_STATS", "0") == "1"
+        self.show_stats = True
 
 app = Flask(__name__)
 PORT = int(os.environ.get("PORT", 5000))
@@ -83,25 +84,30 @@ def stream_mjpeg(session_id: str):
 
     if session is not None:
         while True:
-            if session.latest_frame is None:
-                continue
-            encode_param = [int(cv2.IMWRITE_JPEG_QUALITY), 50]
-            ret, jpeg = cv2.imencode(".jpg", session.latest_frame, encode_param)
-            frame_bytes = jpeg.tobytes() if ret else None
-            # print(f"frame filesize: {len(frame_bytes) / (1024 * 1024):.4f} MB")
-            if frame_bytes is not None:
-                yield (b"--frame\r\n"b"Content-Type: image/jpeg\r\n\r\n" + frame_bytes + b"\r\n")
+            if session.published_frame is not session.latest_frame:
+                if session.latest_frame is None:
+                    continue
+                encode_param = [int(cv2.IMWRITE_JPEG_QUALITY), 50]
+                ret, jpeg = cv2.imencode(".jpg", session.latest_frame, encode_param)
+                frame_bytes = jpeg.tobytes() if ret else None
+                if frame_bytes is not None:
+                    session.published_frame = session.latest_frame
+                    yield (b"--frame\r\n"b"Content-Type: image/jpeg\r\n\r\n" + frame_bytes + b"\r\n")
             
 @app.route("/")
 def video_feed():
     global sessions
 
     session_id = request.args.get("id", "default")
+    show_stats = request.args.get("show_stats", "0") == "1"
 
     if session_id not in [s.id for s in sessions]:
         session = Session(session_id)
         sessions.add(session)
         threading.Thread(target=frame_processor, args=[session_id], daemon=True).start()
+    else:
+        session = next(s for s in sessions if s.id == session_id)
+        session.show_stats = show_stats
         
     return Response(stream_with_context(stream_mjpeg(session_id)), mimetype="multipart/x-mixed-replace; boundary=frame")