diff --git a/yt_dlp/YoutubeDL.py b/yt_dlp/YoutubeDL.py
index 9f730d038..39d17be5c 100644
--- a/yt_dlp/YoutubeDL.py
+++ b/yt_dlp/YoutubeDL.py
@@ -2136,6 +2136,8 @@ class YoutubeDL:
 
     def _check_formats(self, formats):
         for f in formats:
+            if f.get('__working'):
+                yield f
             self.to_screen('[info] Testing format %s' % f['format_id'])
             path = self.get_output_path('temp')
             if not self._ensure_dir_exists(f'{path}/'):
@@ -2153,16 +2155,32 @@ class YoutubeDL:
                     except OSError:
                         self.report_warning('Unable to delete temporary file "%s"' % temp_file.name)
             if success:
+                f['__working'] = True
                 yield f
             else:
                 self.to_screen('[info] Unable to download format %s. Skipping...' % f['format_id'])
 
+    def _select_formats(self, formats, selector):
+        return list(selector({
+            'formats': formats,
+            'has_merged_format': any('none' not in (f.get('acodec'), f.get('vcodec')) for f in formats),
+            'incomplete_formats': (all(f.get('vcodec') == 'none' for f in formats)  # No formats with video
+                                   or all(f.get('acodec') == 'none' for f in formats)),  # OR, No formats with audio
+        }))
+
     def _default_format_spec(self, info_dict, download=True):
 
         def can_merge():
             merger = FFmpegMergerPP(self)
             return merger.available and merger.can_merge()
 
+        def evaluate_formats(format_spec):
+            formats = self._get_formats(info_dict)
+            return self._select_formats(formats, self.build_format_selector(format_spec))
+        if not can_merge() and evaluate_formats('best/bestvideo+bestaudio') != evaluate_formats('bestvideo*+bestaudio/best'):
+            self.report_warning('ffmpeg not found. The downloaded format is not the highest available quality. '
+                                'Installing ffmpeg is strongly recommended: https://github.com/yt-dlp/yt-dlp#dependencies')
+
         prefer_best = (
             not self.params.get('simulate')
             and download
@@ -2928,12 +2946,7 @@ class YoutubeDL:
                 self.write_debug(f'Default format spec: {req_format}')
                 format_selector = self.build_format_selector(req_format)
 
-            formats_to_download = list(format_selector({
-                'formats': formats,
-                'has_merged_format': any('none' not in (f.get('acodec'), f.get('vcodec')) for f in formats),
-                'incomplete_formats': (all(f.get('vcodec') == 'none' for f in formats)  # No formats with video
-                                       or all(f.get('acodec') == 'none' for f in formats)),  # OR, No formats with audio
-            }))
+            formats_to_download = self._select_formats(formats, format_selector)
             if interactive_format_selection and not formats_to_download:
                 self.report_error('Requested format is not available', tb=False, is_error=False)
                 continue