fix(envs): set LiberoEnvConfig.fps default to 20 to match robosuite (#4124)

* fix(envs): set LiberoEnvConfig.fps default to 20 to match robosuite

LiberoEnvConfig.fps was set to 30, but the underlying robosuite
OffScreenRenderEnv always runs at its default control_freq of 20 Hz
since fps is never passed through. This mismatch silently decouples
the dataset/eval loop rate from the actual simulation step rate.

Set the default to 20 to match the real sim rate and avoid the
footgun.

Fixes #3368

* fix(libero): apply configured control frequency

---------

Co-authored-by: xinmotlanthua <275663218+xinmotlanthua@users.noreply.github.com>

src/lerobot/envs/configs.py

@@ -322,7 +322,7 @@ class HILSerlRobotEnvConfig(EnvConfig):
 class LiberoEnv(EnvConfig):
     task: str = "libero_10"  # can also choose libero_spatial, libero_object, etc.
     task_ids: list[int] | None = None
-    fps: int = 30
+    fps: int = 20  # Must match robosuite's default control_freq (20 Hz)
     episode_length: int | None = None
     obs_type: str = "pixels_agent_pos"
     render_mode: str = "rgb_array"
@@ -354,6 +354,9 @@ class LiberoEnv(EnvConfig):
     control_mode: str = "relative"  # or "absolute"
 
     def __post_init__(self):
+        if self.fps <= 0:
+            raise ValueError(f"fps must be positive, got {self.fps}")
+
         if self.obs_type == "pixels":
             self.features[LIBERO_KEY_PIXELS_AGENTVIEW] = PolicyFeature(
                 type=FeatureType.VISUAL, shape=(self.observation_height, self.observation_width, 3)
@@ -412,6 +415,7 @@ class LiberoEnv(EnvConfig):
             "render_mode": self.render_mode,
             "observation_height": self.observation_height,
             "observation_width": self.observation_width,
+            "control_freq": self.fps,
         }
         if self.task_ids is not None:
             kwargs["task_ids"] = self.task_ids

src/lerobot/envs/libero.py

@@ -125,10 +125,13 @@ class LiberoEnv(gym.Env):
         n_envs: int = 1,
         camera_name_mapping: dict[str, str] | None = None,
         num_steps_wait: int = 10,
+        control_freq: int = 20,
         control_mode: str = "relative",
         is_libero_plus: bool = False,
     ):
         super().__init__()
+        if control_freq <= 0:
+            raise ValueError(f"control_freq must be positive, got {control_freq}")
         self.task_id = task_id
         self.is_libero_plus = is_libero_plus
         self.obs_type = obs_type
@@ -154,6 +157,7 @@ class LiberoEnv(gym.Env):
             }
         self.camera_name_mapping = camera_name_mapping
         self.num_steps_wait = num_steps_wait
+        self.control_freq = control_freq
         self.episode_index = episode_index
         self.episode_length = episode_length
         # Load once and keep
@@ -260,6 +264,7 @@ class LiberoEnv(gym.Env):
             bddl_file_name=self._task_bddl_file,
             camera_heights=self.observation_height,
             camera_widths=self.observation_width,
+            control_freq=self.control_freq,
         )
         env.reset()
         self._env = env

tests/envs/test_dispatch.py

@@ -35,6 +35,17 @@ def test_unknown_type():
         make_env_config("nonexistent")
 
 
+def test_libero_fps_controls_simulator_frequency():
+    cfg = LiberoEnv(fps=17)
+
+    assert cfg.gym_kwargs["control_freq"] == 17
+
+
+def test_libero_rejects_nonpositive_fps():
+    with pytest.raises(ValueError, match="fps must be positive"):
+        LiberoEnv(fps=0)
+
+
 def test_identity_processors():
     """Base class get_env_processors() returns identity pipelines."""
     cfg = make_env_config("aloha")