Make audio description the lowest priority

Co-Authored-By: pukkandan <pukkandan.ytdlp@gmail.com>

yt_dlp/extractor/rts.py

@@ -11,7 +11,7 @@ from ..utils import (
 from ..utils.traversal import traverse_obj
 
 
-class RTSIE(SRGSSRIE):
+class RTSIE(SRGSSRIE):  # XXX: Do not subclass from concrete IE
     _GEO_COUNTRIES = ['CH']
     IE_DESC = 'RTS.ch'
     _VALID_URL = [

yt_dlp/extractor/srgssr.py

@@ -128,6 +128,10 @@ class SRGSSRIE(InfoExtractor):
                     'quality': q(quality),
                 })
 
+        for idx, fmt in enumerate(formats):
+            if fmt['format_id'].endswith('(AD)'):
+                formats[idx]['language_preference'] = -10
+
         if media_type == 'video':
             for sub in (media_data.get('subtitleList') or []):
                 sub_url = sub.get('url')