diff --git a/yt_dlp/YoutubeDL.py b/yt_dlp/YoutubeDL.py
index 48185b769..f08a31afa 100644
--- a/yt_dlp/YoutubeDL.py
+++ b/yt_dlp/YoutubeDL.py
@@ -2849,13 +2849,10 @@ def is_wellformed(f):
             sanitize_string_field(fmt, 'format_id')
             sanitize_numeric_fields(fmt)
             fmt['url'] = sanitize_url(fmt['url'])
-            if fmt.get('ext') is None:
-                fmt['ext'] = determine_ext(fmt['url']).lower()
+            FormatSorter._fill_sorting_fields(fmt)
             if fmt['ext'] in ('aac', 'opus', 'mp3', 'flac', 'vorbis'):
                 if fmt.get('acodec') is None:
                     fmt['acodec'] = fmt['ext']
-            if fmt.get('protocol') is None:
-                fmt['protocol'] = determine_protocol(fmt)
             if fmt.get('resolution') is None:
                 fmt['resolution'] = self.format_resolution(fmt, default=None)
             if fmt.get('dynamic_range') is None and fmt.get('vcodec') != 'none':
diff --git a/yt_dlp/utils/_utils.py b/yt_dlp/utils/_utils.py
index 7aff67ddf..b7de04e63 100644
--- a/yt_dlp/utils/_utils.py
+++ b/yt_dlp/utils/_utils.py
@@ -5578,14 +5578,15 @@ def _calculate_field_preference(self, format_, field):
             value = get_value(field)
         return self._calculate_field_preference_from_value(format_, field, type_, value)
 
-    def calculate_preference(self, format):
+    @staticmethod
+    def _fill_sorting_fields(format):
         # Determine missing protocol
         if not format.get('protocol'):
             format['protocol'] = determine_protocol(format)
 
         # Determine missing ext
         if not format.get('ext') and 'url' in format:
-            format['ext'] = determine_ext(format['url'])
+            format['ext'] = determine_ext(format['url']).lower()
         if format.get('vcodec') == 'none':
             format['audio_ext'] = format['ext'] if format.get('acodec') != 'none' else 'none'
             format['video_ext'] = 'none'
@@ -5613,6 +5614,8 @@ def calculate_preference(self, format):
         if not format.get('tbr'):
             format['tbr'] = try_call(lambda: format['vbr'] + format['abr']) or None
 
+    def calculate_preference(self, format):
+        self._fill_sorting_fields(format)
         return tuple(self._calculate_field_preference(format, field) for field in self._order)