Fix #191

waveform80 · Sep 30, 2016 · c92f65e · c92f65e
1 parent 0384a44
commit c92f65e
Showing 1 changed file with 134 additions and 0 deletions.
diff --git a/docs/recipes2.rst b/docs/recipes2.rst
@@ -697,6 +697,140 @@ on firmware #685. However, utilizing the MJPEG splitting demonstrated in
 The above script achieves 30fps with ease.
 
 
+.. _web_streaming:
+
+Web streaming
+=============
+
+Streaming video over the web is surprisingly complicated. At the time of
+writing, there are still no video standards that are universally supported by
+all web browsers on all platforms. Furthermore, HTTP was originally designed as
+a one-shot protocol for serving web-pages. Since its invention, various
+additions have bolted on to cater for its ever increasing use cases (file
+downloads, resumption, streaming, etc.) but the fact remains there's no
+"simple" solution for video streaming at the moment.
+
+If you want to have a play with streaming a "real" video format (specifically,
+MPEG1) you may want to have a look at the `pistreaming`_ demo. However, for the
+purposes of this recipe we'll be using a much simpler format: MJPEG. The
+following script uses Python's built-in :mod:`http.server` module to make a
+simple video streaming server::
+
+    import io
+    import picamera
+    import socketserver
+    from threading import Lock
+    from http import server
+
+    PAGE="""\
+    <html>
+    <head>
+    <title>picamera MJPEG streaming demo</title>
+    </head>
+    <body>
+    <h1>PiCamera MJPEG Streaming Demo</h1>
+    <img src="stream.mjpg" width="640" height="480" />
+    </body>
+    </html>
+    """
+
+    class StreamingOutput(object):
+        def __init__(self):
+            self.lock = Lock()
+            self.frame = io.BytesIO()
+            self.clients = []
+
+        def write(self, buf):
+            died = []
+            if buf.startswith(b'\xff\xd8'):
+                # New frame, send old frame to all connected clients
+                size = self.frame.tell()
+                if size > 0:
+                    self.frame.seek(0)
+                    data = self.frame.read(size)
+                    self.frame.seek(0)
+                    with self.lock:
+                        for client in self.clients:
+                            try:
+                                client.wfile.write(b'--FRAME\r\n')
+                                client.send_header('Content-Type', 'image/jpeg')
+                                client.send_header('Content-Length', size)
+                                client.end_headers()
+                                client.wfile.write(data)
+                                client.wfile.write(b'\r\n')
+                            except Exception as e:
+                                died.append(client)
+            self.frame.write(buf)
+            if died:
+                self.remove_clients(died)
+
+        def flush(self):
+            with self.lock:
+                for client in self.clients:
+                    client.wfile.close()
+
+        def add_client(self, client):
+            print('Adding streaming client %s:%d' % client.client_address)
+            with self.lock:
+                self.clients.append(client)
+
+        def remove_clients(self, clients):
+            with self.lock:
+                for client in clients:
+                    try:
+                        print('Removing streaming client %s:%d' % client.client_address)
+                        self.clients.remove(client)
+                    except ValueError:
+                        pass # already removed
+
+    class StreamingHandler(server.BaseHTTPRequestHandler):
+        def do_GET(self):
+            if self.path == '/':
+                self.send_response(301)
+                self.send_header('Location', '/index.html')
+                self.end_headers()
+            elif self.path == '/index.html':
+                content = PAGE.encode('utf-8')
+                self.send_response(200)
+                self.send_header('Content-Type', 'text/html')
+                self.send_header('Content-Length', len(content))
+                self.end_headers()
+                self.wfile.write(content)
+            elif self.path == '/stream.mjpg':
+                self.close_connection = False
+                self.send_response(200)
+                self.send_header('Age', 0)
+                self.send_header('Cache-Control', 'no-cache, private')
+                self.send_header('Pragma', 'no-cache')
+                self.send_header('Content-Type', 'multipart/x-mixed-replace; boundary=--FRAME')
+                self.end_headers()
+                output.add_client(self)
+            else:
+                self.send_error(404)
+                self.end_headers()
+
+    class StreamingServer(socketserver.ThreadingMixIn, server.HTTPServer):
+        pass
+
+    with picamera.PiCamera(resolution='640x480', framerate=24) as camera:
+        output = StreamingOutput()
+        camera.start_recording(output, format='mjpeg')
+        try:
+            address = ('', 8000)
+            server = StreamingServer(address, StreamingHandler)
+            server.serve_forever()
+        finally:
+            camera.stop_recording()
+
+Once the script is running, visit ``http://your-pi-address:8000/`` with your
+web-browser to view the video stream.
+
+.. note::
+
+    This recipe assumes Python 3.x (the ``http.server`` module was named
+    ``SimpleHTTPServer`` in Python 2.x)
+
+
 .. _record_and_capture:
 
 Capturing images whilst recording