Add remote stream relay feature: relay remote DJ streams to listeners

- Server-side: Added remote URL support in ffmpeg transcoder
- UI: Added relay controls in streaming panel with URL input
- Client: Added start/stop relay functions with socket communication
- Listener: Shows remote relay status in stream indicator

server.py

@@ -53,6 +53,7 @@ _transcode_threads_started = False
 _transcoder_bytes_out = 0
 _transcoder_last_error = None
 _last_audio_chunk_ts = 0.0
+_remote_stream_url = None  # For relaying remote streams
 
 
 def _start_transcoder_if_needed():
@@ -61,32 +62,55 @@ def _start_transcoder_if_needed():
     if _ffmpeg_proc is not None and _ffmpeg_proc.poll() is None:
         return
 
-    cmd = [
-        'ffmpeg',
-        '-hide_banner',
-        '-loglevel', 'error',
-        '-i', 'pipe:0',
-        '-vn',
-        '-acodec', 'libmp3lame',
-        '-b:a', '192k',
-        '-f', 'mp3',
-        'pipe:1',
-    ]
+    if _remote_stream_url:
+        # Remote relay mode: input from URL
+        cmd = [
+            'ffmpeg',
+            '-hide_banner',
+            '-loglevel', 'error',
+            '-i', _remote_stream_url,
+            '-vn',
+            '-acodec', 'libmp3lame',
+            '-b:a', '192k',
+            '-f', 'mp3',
+            'pipe:1',
+        ]
+    else:
+        # Local broadcast mode: input from pipe
+        cmd = [
+            'ffmpeg',
+            '-hide_banner',
+            '-loglevel', 'error',
+            '-i', 'pipe:0',
+            '-vn',
+            '-acodec', 'libmp3lame',
+            '-b:a', '192k',
+            '-f', 'mp3',
+            'pipe:1',
+        ]
 
     try:
-        _ffmpeg_proc = subprocess.Popen(
-            cmd,
-            stdin=subprocess.PIPE,
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
-            bufsize=0,
-        )
+        if _remote_stream_url:
+            _ffmpeg_proc = subprocess.Popen(
+                cmd,
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+                bufsize=0,
+            )
+        else:
+            _ffmpeg_proc = subprocess.Popen(
+                cmd,
+                stdin=subprocess.PIPE,
+                stdout=subprocess.PIPE,
+                stderr=subprocess.PIPE,
+                bufsize=0,
+            )
     except FileNotFoundError:
         _ffmpeg_proc = None
         print('⚠️ ffmpeg not found; /stream.mp3 fallback disabled')
         return
 
-    print('🎛️ ffmpeg transcoder started for /stream.mp3')
+    print(f'🎛️ ffmpeg transcoder started for /stream.mp3 ({ "remote relay" if _remote_stream_url else "local broadcast" })')
 
     def _writer():
         global _transcoder_last_error
@@ -152,7 +176,7 @@ def _stop_transcoder():
 
 def _feed_transcoder(data: bytes):
     global _last_audio_chunk_ts
-    if _ffmpeg_proc is None or _ffmpeg_proc.poll() is not None:
+    if _ffmpeg_proc is None or _ffmpeg_proc.poll() is not None or _remote_stream_url:
         return
     _last_audio_chunk_ts = time.time()
     try:
@@ -480,6 +504,43 @@ def dj_stop():
     listener_socketio.emit('broadcast_stopped', namespace='/')
     listener_socketio.emit('stream_status', {'active': False}, namespace='/')
 
+@dj_socketio.on('start_remote_relay')
+def dj_start_remote_relay(data):
+    global _remote_stream_url
+    url = data.get('url', '').strip()
+    if not url:
+        dj_socketio.emit('error', {'message': 'No URL provided for remote relay'})
+        return
+    
+    # Stop any existing broadcast/relay
+    if broadcast_state['active']:
+        dj_stop()
+    
+    _remote_stream_url = url
+    broadcast_state['active'] = True
+    broadcast_state['remote_relay'] = True
+    session['is_dj'] = True
+    print(f"🔗 Starting remote relay from: {url}")
+    
+    _start_transcoder_if_needed()
+    
+    listener_socketio.emit('broadcast_started', namespace='/')
+    listener_socketio.emit('stream_status', {'active': True, 'remote_relay': True}, namespace='/')
+
+@dj_socketio.on('stop_remote_relay')
+def dj_stop_remote_relay():
+    global _remote_stream_url
+    _remote_stream_url = None
+    broadcast_state['active'] = False
+    broadcast_state['remote_relay'] = False
+    session['is_dj'] = False
+    print("🛑 Remote relay stopped")
+
+    _stop_transcoder()
+    
+    listener_socketio.emit('broadcast_stopped', namespace='/')
+    listener_socketio.emit('stream_status', {'active': False}, namespace='/')
+
 @dj_socketio.on('audio_chunk')
 def dj_audio(data):
     # MP3-only mode: do not relay raw chunks to listeners; feed transcoder only.