[utils] `parse_codecs`: Fix parsing of mixed case codec strings

Authored by: bashonly

test/test_utils.py

@@ -929,6 +929,11 @@ class TestUtil(unittest.TestCase):
             'acodec': 'none',
             'dynamic_range': 'DV',
         })
+        self.assertEqual(parse_codecs('fLaC'), {
+            'vcodec': 'none',
+            'acodec': 'flac',
+            'dynamic_range': None,
+        })
         self.assertEqual(parse_codecs('theora, vorbis'), {
             'vcodec': 'theora',
             'acodec': 'vorbis',

yt_dlp/utils/_utils.py

@@ -2984,6 +2984,7 @@ def parse_codecs(codecs_str):
         str.strip, codecs_str.strip().strip(',').split(','))))
     vcodec, acodec, scodec, hdr = None, None, None, None
     for full_codec in split_codecs:
+        full_codec = re.sub(r'^([^.]+)', lambda m: m.group(1).lower(), full_codec)
         parts = re.sub(r'0+(?=\d)', '', full_codec).split('.')
         if parts[0] in ('avc1', 'avc2', 'avc3', 'avc4', 'vp9', 'vp8', 'hev1', 'hev2',
                         'h263', 'h264', 'mp4v', 'hvc1', 'av1', 'theora', 'dvh1', 'dvhe'):