diff --git a/yt_dlp/extractor/youtube/_video.py b/yt_dlp/extractor/youtube/_video.py
index 081ed6ac8..492ad9b3b 100644
--- a/yt_dlp/extractor/youtube/_video.py
+++ b/yt_dlp/extractor/youtube/_video.py
@@ -3488,8 +3488,8 @@ def build_fragments(f):
                 'width': int_or_none(fmt.get('width')),
                 'language': join_nonempty(language_code, 'desc' if is_descriptive else '') or None,
                 'language_preference': PREFERRED_LANG_VALUE if is_original else 5 if is_default else -10 if is_descriptive else -1,
-                # Strictly de-prioritize damaged and 3gp formats
-                'preference': -10 if is_damaged else -2 if itag == '17' else None,
+                # Strictly de-prioritize damaged, 3gp and iamf formats
+                'preference': -10 if is_damaged else -2 if itag in ('17', '773') else None,
             }
             mime_mobj = re.match(
                 r'((?:[^/]+)/(?:[^;]+))(?:;\s*codecs="([^"]+)")?', fmt.get('mimeType') or '')
diff --git a/yt_dlp/utils/_utils.py b/yt_dlp/utils/_utils.py
index 20aa341ca..c89f50a51 100644
--- a/yt_dlp/utils/_utils.py
+++ b/yt_dlp/utils/_utils.py
@@ -3040,7 +3040,7 @@ def parse_codecs(codecs_str):
             elif parts[:2] == ['vp9', '2']:
                 hdr = 'HDR10'
         elif parts[0] in ('flac', 'mp4a', 'opus', 'vorbis', 'mp3', 'aac', 'ac-4',
-                          'ac-3', 'ec-3', 'eac3', 'dtsc', 'dtse', 'dtsh', 'dtsl'):
+                          'ac-3', 'ec-3', 'eac3', 'dtsc', 'dtse', 'dtsh', 'dtsl', 'iamf'):
             acodec = acodec or full_codec
         elif parts[0] in ('stpp', 'wvtt'):
             scodec = scodec or full_codec