Add fps argument to RecordVideoV0 (#503)

gymnasium/experimental/wrappers/rendering.py

@@ -100,8 +100,6 @@ class RecordVideoV0(
     then every 1000 episodes.
     By default, the recording will be stopped once reset is called. However, you can also create recordings of fixed
     length (possibly spanning several episodes) by passing a strictly positive value for ``video_length``.
-    This wrapper uses the value `fps` from metadata as the number of frames per second;
-    if `fps` is not defined in metadata, the default value 30 is used.
     """
 
     def __init__(
@@ -112,6 +110,7 @@ def __init__(
         step_trigger: Callable[[int], bool] | None = None,
         video_length: int = 0,
         name_prefix: str = "rl-video",
+        fps: int | None = None,
         disable_logger: bool = False,
     ):
         """Wrapper records videos of rollouts.
@@ -124,6 +123,8 @@ def __init__(
             video_length (int): The length of recorded episodes. If 0, entire episodes are recorded.
                 Otherwise, snippets of the specified length are captured
             name_prefix (str): Will be prepended to the filename of the recordings
+            fps (int): The frame per second in the video. The default value is the one specified in the environment metadata.
+                If the environment metadata doesn't specify `render_fps`, the value 30 is used.
             disable_logger (bool): Whether to disable moviepy logger or not
         """
         gym.utils.RecordConstructorArgs.__init__(
@@ -172,9 +173,11 @@ def capped_cubic_video_schedule(episode_id: int) -> bool:
             )
         os.makedirs(self.video_folder, exist_ok=True)
 
+        if fps is None:
+            fps = self.metadata.get("render_fps", 30)
+        self.frames_per_sec: int = fps
         self.name_prefix: str = name_prefix
         self._video_name: str | None = None
-        self.frames_per_sec: int = self.metadata.get("render_fps", 30)
         self.video_length: int = video_length if video_length != 0 else float("inf")
         self.recording: bool = False
         self.recorded_frames: list[RenderFrame] = []