diff --git a/src/overlay/__main__.py b/src/overlay/__main__.py
index 6edb372..a50a380 100644
--- a/src/overlay/__main__.py
+++ b/src/overlay/__main__.py
@@ -12,7 +12,8 @@ parser.add_argument('infile', type=argparse.FileType('r'), help='scene descripti
 parser.add_argument('--nick-font', default='/Users/partynorge/down/Montserrat/Montserrat-Bold.ttf')
 parser.add_argument('--chat-font', default='/Users/partynorge/down/Montserrat/Montserrat-Light.ttf')
 parser.add_argument('-n', '--nickname', help='Twitch chat nickname', default='shizacular')
-parser.add_argument('-t', '--token', help='Twitch OAuth token', required=True)
+parser.add_argument('-t', '--token', help='Twitch OAuth token')
+parser.add_argument('-p', '--preview', help='preview using mpv', default=False, action='store_true')
 parser.add_argument('channel', help='Twitch channel')
 
 args = parser.parse_args()
@@ -23,22 +24,14 @@ scene = OBSScene()
 scene.load(args.infile)
 
 # Convert scene graph
-runners, graph = scene.to_ffmpeg()
-chat_runner, chat_chains = make_twitch_chat('test', args.nickname, args.token, args.channel,
-    nick_args={'fontfile': args.nick_font},
-    chat_args={'fontfile': args.chat_font}
-)
-runners.extend(chat_runner)
-graph.extend(chat_chains, link=True)
+graph = scene.to_ffmpeg()
 graph.fixup()
+ffmpeg_args = graph.format()
 
-# Launch background runners
-threads = {}
-for r in runners:
-    t = threading.Thread(target=r, daemon=True)
-    t.start()
-    threads[r] = t
-
-# Launch main process
-chain = str(graph)
-subprocess.run('ffmpeg -re -f lavfi -i ' + shlex.quote(chain) + ' -f nut -c:v libx264 -preset veryfast pipe:1 | ffplay -', shell=True)
+if args.preview:
+    # Launch background runners
+    graph.run()
+    # Launch main process
+    subprocess.run('ffmpeg ' + ' '.join(shlex.quote(a) for a in ffmpeg_args) + ' -f nut -c:v libx264 -preset veryfast pipe:1 | mpv -', shell=True)
+else:
+    raise ValueError('TODO')