3 files changed, 18 insertions, 12 deletions
diff --git a/yt_dlp/compat/_legacy.py b/yt_dlp/compat/_legacy.py
index 7ea5d08..dfc792e 100644
--- a/yt_dlp/compat/_legacy.py
+++ b/yt_dlp/compat/_legacy.py
@@ -35,7 +35,7 @@ from .compat_utils import passthrough_module
 from ..dependencies import brotli as compat_brotli  # noqa: F401
 from ..dependencies import websockets as compat_websockets  # noqa: F401
 from ..dependencies.Cryptodome import AES as compat_pycrypto_AES  # noqa: F401
-from ..networking.exceptions import HTTPError as compat_HTTPError  # noqa: F401
+from ..networking.exceptions import HTTPError as compat_HTTPError
 
 passthrough_module(__name__, '...utils', ('WINDOWS_VT_MODE', 'windows_enable_vt_mode'))
 
diff --git a/yt_dlp/compat/functools.py b/yt_dlp/compat/functools.py
index 36c9836..9668957 100644
--- a/yt_dlp/compat/functools.py
+++ b/yt_dlp/compat/functools.py
@@ -7,6 +7,6 @@ passthrough_module(__name__, 'functools')
 del passthrough_module
 
 try:
-    cache  # >= 3.9
+    _ = cache  # >= 3.9
 except NameError:
     cache = lru_cache(maxsize=None)
diff --git a/yt_dlp/compat/imghdr.py b/yt_dlp/compat/imghdr.py
index 5d64ab0..4ae173f 100644
--- a/yt_dlp/compat/imghdr.py
+++ b/yt_dlp/compat/imghdr.py
@@ -1,16 +1,22 @@
-tests = {
-    'webp': lambda h: h[0:4] == b'RIFF' and h[8:] == b'WEBP',
-    'png': lambda h: h[:8] == b'\211PNG\r\n\032\n',
-    'jpeg': lambda h: h[6:10] in (b'JFIF', b'Exif'),
-    'gif': lambda h: h[:6] in (b'GIF87a', b'GIF89a'),
-}
-
-
 def what(file=None, h=None):
     """Detect format of image (Currently supports jpeg, png, webp, gif only)
-    Ref: https://github.com/python/cpython/blob/3.10/Lib/imghdr.py
+    Ref: https://github.com/python/cpython/blob/3.11/Lib/imghdr.py
+    Ref: https://www.w3.org/Graphics/JPEG/itu-t81.pdf
     """
     if h is None:
         with open(file, 'rb') as f:
             h = f.read(12)
-    return next((type_ for type_, test in tests.items() if test(h)), None)
+
+    if h.startswith(b'RIFF') and h.startswith(b'WEBP', 8):
+        return 'webp'
+
+    if h.startswith(b'\x89PNG'):
+        return 'png'
+
+    if h.startswith(b'\xFF\xD8\xFF'):
+        return 'jpeg'
+
+    if h.startswith(b'GIF'):
+        return 'gif'
+
+    return None