Support 3 parallel stream clients via CameraBroadcaster

Vorher: pro Client ein eigener rpicam-vid-Prozess → 2. und 3. Client schlagen fehl.
Jetzt: CameraBroadcaster startet rpicam-vid einmal in einem Hintergrund-Thread,
alle Clients lesen denselben aktuellen Frame. Flask läuft mit threaded=True.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/main.py

@@ -7,10 +7,10 @@ Babycam Flask Webinterface
 """
 
 import subprocess
-import json
 import re
 import time
 import os
+import threading
 from flask import Flask, Response, render_template, request, jsonify
 
 app = Flask(__name__)
@@ -21,47 +21,85 @@ STREAM_FPS = 20
 
 
 # ---------------------------------------------------------------------------
-# Kamera-Stream
+# Kamera-Broadcaster – ein Prozess, N Clients
 # ---------------------------------------------------------------------------
 
-def generate_frames():
-    cmd = [
-        "rpicam-vid",
-        "-t", "0",
-        "--width", str(STREAM_WIDTH),
-        "--height", str(STREAM_HEIGHT),
-        "--framerate", str(STREAM_FPS),
-        "--codec", "mjpeg",
-        "-o", "-",
-        "--nopreview",
-    ]
-    process = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.DEVNULL)
+class CameraBroadcaster:
+    """
+    Startet rpicam-vid einmal in einem Hintergrund-Thread.
+    Alle Clients lesen denselben aktuellen Frame – keine parallelen Kameraprozesse.
+    """
 
-    boundary = b"--frame\r\nContent-Type: image/jpeg\r\n\r\n"
-    buf = b""
+    def __init__(self):
+        self._frame: bytes | None = None
+        self._lock = threading.Lock()
+        self._thread: threading.Thread | None = None
+        self._running = False
 
-    try:
+    def start(self):
+        if self._thread and self._thread.is_alive():
+            return
+        self._running = True
+        self._thread = threading.Thread(target=self._capture, daemon=True)
+        self._thread.start()
+
+    def _capture(self):
+        cmd = [
+            "rpicam-vid",
+            "-t", "0",
+            "--width", str(STREAM_WIDTH),
+            "--height", str(STREAM_HEIGHT),
+            "--framerate", str(STREAM_FPS),
+            "--codec", "mjpeg",
+            "-o", "-",
+            "--nopreview",
+        ]
+        process = subprocess.Popen(
+            cmd, stdout=subprocess.PIPE, stderr=subprocess.DEVNULL
+        )
+        buf = b""
+        try:
+            while self._running:
+                chunk = process.stdout.read(4096)
+                if not chunk:
+                    break
+                buf += chunk
+                start = buf.find(b"\xff\xd8")
+                end   = buf.find(b"\xff\xd9")
+                if start != -1 and end != -1 and end > start:
+                    frame = buf[start:end + 2]
+                    buf   = buf[end + 2:]
+                    with self._lock:
+                        self._frame = frame
+        finally:
+            process.kill()
+            self._running = False
+
+    def get_frame(self) -> bytes | None:
+        with self._lock:
+            return self._frame
+
+    def generate(self):
+        """Generator für einen MJPEG-Client."""
+        boundary = b"--frame\r\nContent-Type: image/jpeg\r\n\r\n"
+        last_frame = None
         while True:
-            chunk = process.stdout.read(4096)
-            if not chunk:
-                break
-            buf += chunk
-
-            start = buf.find(b"\xff\xd8")
-            end = buf.find(b"\xff\xd9")
-
-            if start != -1 and end != -1 and end > start:
-                frame = buf[start:end + 2]
-                buf = buf[end + 2:]
+            frame = self.get_frame()
+            if frame and frame is not last_frame:
+                last_frame = frame
                 yield boundary + frame + b"\r\n"
-    finally:
-        process.kill()
+            else:
+                time.sleep(1 / STREAM_FPS)
+
+
+camera = CameraBroadcaster()
+camera.start()
 
 
 @app.route("/stream")
 def stream():
     return Response(
-        generate_frames(),
+        camera.generate(),
         mimetype="multipart/x-mixed-replace; boundary=frame",
     )
 
@@ -216,4 +254,4 @@ def wifi_connect():
 # ---------------------------------------------------------------------------
 
 if __name__ == "__main__":
-    app.run(host="0.0.0.0", port=80, debug=False)
+    app.run(host="0.0.0.0", port=80, debug=False, threaded=True)