-    url = info_dict['url']
-    protocol = info_dict.get('protocol')
-
-    if url.startswith('rtmp'):
-        return RtmpFD
-    if (protocol == 'm3u8') or (protocol is None and determine_ext(url) == 'm3u8'):
-        return HlsFD
-    if url.startswith('mms') or url.startswith('rtsp'):
-        return MplayerFD
-    if determine_ext(url) == 'f4m':
-        return F4mFD
-    else:
-        return HttpFD
+    protocol = determine_protocol(info_dict)
+    info_dict['protocol'] = protocol
+
+    external_downloader = params.get('external_downloader')
+    if external_downloader is not None:
+        ed = get_external_downloader(external_downloader)
+        if ed.supports(info_dict):
+            return ed
+
+    if protocol == 'm3u8' and params.get('hls_prefer_native'):
+        return NativeHlsFD
+
+    return PROTOCOL_MAP.get(protocol, HttpFD)
+
+
+__all__ = [
+    'get_suitable_downloader',
+    'FileDownloader',
+]