diff --git a/moviepy/__init__.py b/moviepy/__init__.py
index 2b9baa8d7..2d4d60c74 100644
--- a/moviepy/__init__.py
+++ b/moviepy/__init__.py
@@ -1,6 +1,7 @@
 """Imports everything that you need from the MoviePy submodules so that every thing
 can be directly imported with ``from moviepy import *``.
 """
+
 from moviepy.audio import fx as afx
 from moviepy.audio.AudioClip import (
     AudioArrayClip,
diff --git a/moviepy/decorators.py b/moviepy/decorators.py
index 9c7b9a211..3bdd13db3 100644
--- a/moviepy/decorators.py
+++ b/moviepy/decorators.py
@@ -78,22 +78,32 @@ def audio_video_effect(func, effect, clip, *args, **kwargs):
         return func(effect, clip, *args, **kwargs)
 
 
-def preprocess_args(fun, varnames):
-    """Applies fun to variables in varnames before launching the function."""
+def preprocess_args(preprocess_func, varnames):
+    """Applies preprocess_func to variables in varnames before launching
+    the function.
+    """
 
-    def wrapper(func, *args, **kwargs):
-        names = inspect.getfullargspec(func).args
-        new_args = [
-            fun(arg) if (name in varnames) and (arg is not None) else arg
-            for (arg, name) in zip(args, names)
-        ]
-        new_kwargs = {
-            kwarg: fun(value) if kwarg in varnames else value
-            for (kwarg, value) in kwargs.items()
-        }
-        return func(*new_args, **new_kwargs)
+    def decor(func):
+        argnames = inspect.getfullargspec(func).args
+
+        def wrapper(func, *args, **kwargs):
+            new_args = [
+                (
+                    preprocess_func(arg)
+                    if (name in varnames) and (arg is not None)
+                    else arg
+                )
+                for (arg, name) in zip(args, argnames)
+            ]
+            new_kwargs = {
+                kwarg: preprocess_func(value) if kwarg in varnames else value
+                for (kwarg, value) in kwargs.items()
+            }
+            return func(*new_args, **new_kwargs)
 
-    return decorator.decorator(wrapper)
+        return decorator.decorate(func, wrapper)
+
+    return decor
 
 
 def convert_parameter_to_seconds(varnames):
@@ -114,11 +124,11 @@ def add_mask_if_none(func, clip, *args, **kwargs):
     return func(clip, *args, **kwargs)
 
 
-@decorator.decorator
-def use_clip_fps_by_default(func, clip, *args, **kwargs):
+def use_clip_fps_by_default(func):
     """Will use ``clip.fps`` if no ``fps=...`` is provided in **kwargs**."""
+    argnames = inspect.getfullargspec(func).args[1:]
 
-    def find_fps(fps):
+    def find_fps(clip, fps):
         if fps is not None:
             return fps
         elif getattr(clip, "fps", None):
@@ -130,14 +140,16 @@ def find_fps(fps):
             " the clip's fps with `clip.fps=24`" % func.__name__
         )
 
-    names = inspect.getfullargspec(func).args[1:]
+    def wrapper(func, clip, *args, **kwargs):
+        new_args = [
+            find_fps(clip, arg) if name == "fps" else arg
+            for (arg, name) in zip(args, argnames)
+        ]
+        new_kwargs = {
+            kwarg: find_fps(clip, kwarg) if kwarg == "fps" else value
+            for (kwarg, value) in kwargs.items()
+        }
 
-    new_args = [
-        find_fps(arg) if (name == "fps") else arg for (arg, name) in zip(args, names)
-    ]
-    new_kwargs = {
-        kwarg: find_fps(value) if kwarg == "fps" else value
-        for (kwarg, value) in kwargs.items()
-    }
+        return func(clip, *new_args, **new_kwargs)
 
-    return func(clip, *new_args, **new_kwargs)
+    return decorator.decorate(func, wrapper)
diff --git a/moviepy/video/io/ffmpeg_reader.py b/moviepy/video/io/ffmpeg_reader.py
index ea552f200..640263fcf 100644
--- a/moviepy/video/io/ffmpeg_reader.py
+++ b/moviepy/video/io/ffmpeg_reader.py
@@ -480,12 +480,12 @@ def parse(self):
                 # for default streams, set their numbers globally, so it's
                 # easy to get without iterating all
                 if self._current_stream["default"]:
-                    self.result[
-                        f"default_{stream_type_lower}_input_number"
-                    ] = input_number
-                    self.result[
-                        f"default_{stream_type_lower}_stream_number"
-                    ] = stream_number
+                    self.result[f"default_{stream_type_lower}_input_number"] = (
+                        input_number
+                    )
+                    self.result[f"default_{stream_type_lower}_stream_number"] = (
+                        stream_number
+                    )
 
                 # exit chapter
                 if self._current_chapter: