feat(stats units): rescaling stats when loading a dataset so that the stats are given in the requested unit

src/lerobot/datasets/dataset_metadata.py

@@ -26,12 +26,13 @@ import pyarrow as pa
 import pyarrow.parquet as pq
 from huggingface_hub import snapshot_download
 
-from lerobot.configs import VideoEncoderConfig
+from lerobot.configs import DEPTH_METER_UNIT, VideoEncoderConfig
 from lerobot.utils.constants import DEFAULT_FEATURES, HF_LEROBOT_HOME, HF_LEROBOT_HUB_CACHE
 from lerobot.utils.feature_utils import _validate_feature_names
 from lerobot.utils.utils import flatten_dict
 
 from .compute_stats import aggregate_stats
+from .depth_utils import MM_PER_METRE
 from .feature_utils import create_empty_dataset_info
 from .io_utils import (
     get_file_size_in_mb,
@@ -358,6 +359,26 @@ class LeRobotDatasetMetadata:
 
         return [key for key, ft in self.features.items() if _is_depth(ft)]
 
+    def rescale_depth_stats(self, output_unit: str) -> None:
+        """Rescale depth feature stats in place from their recorded unit to ``output_unit``.
+
+        Depth stats are stored in the unit the frames were recorded in
+        (``features[key]["info"]["depth_unit"]``), while frames are returned in
+        ``output_unit`` on read. This converts the unit-bearing stat entries so 
+        stats match the frames consumers see.
+        """
+        if self.stats is None:
+            return
+        for key in self.depth_keys:
+            stored_unit = (self.features[key].get("info") or {}).get("depth_unit")
+            if stored_unit is None or stored_unit == output_unit or key not in self.stats:
+                continue
+            factor = MM_PER_METRE if stored_unit == DEPTH_METER_UNIT else 1.0 / MM_PER_METRE
+            self.stats[key] = {
+                stat: value if stat == "count" else value * factor
+                for stat, value in self.stats[key].items()
+            }
+
     @property
     def camera_keys(self) -> list[str]:
         """Keys to access visual modalities (regardless of their storage method)."""

src/lerobot/datasets/lerobot_dataset.py

@@ -224,6 +224,7 @@ class LeRobotDataset(torch.utils.data.Dataset):
         )
         self.root = self.meta.root
         self.revision = self.meta.revision
+        self.meta.rescale_depth_stats(self._depth_output_unit)
 
         if episodes is not None and any(
             episode >= self.meta.total_episodes or episode < 0 for episode in episodes

src/lerobot/datasets/streaming_dataset.py

@@ -310,6 +310,7 @@ class StreamingLeRobotDataset(torch.utils.data.IterableDataset):
         )
         self.root = self.meta.root
         self.revision = self.meta.revision
+        self.meta.rescale_depth_stats(self._depth_output_unit)
         # Check version
         check_version_compatibility(self.repo_id, self.meta._version, CODEBASE_VERSION)