fix(datasets): remap absolute indices in __getitem__ for filtered datasets

src/lerobot/datasets/lerobot_dataset.py

@@ -474,6 +474,8 @@ class LeRobotDataset(torch.utils.data.Dataset):
         if reader.hf_dataset is None:
             # One-shot load after finalize()
             reader.load_and_activate()
+        if reader._absolute_to_relative_idx is not None and idx in reader._absolute_to_relative_idx:
+            idx = reader._absolute_to_relative_idx[idx]
         return reader.get_item(idx)
 
     def select_columns(self, column_names: str | list[str]):

src/lerobot/scripts/lerobot_train.py

@@ -435,8 +435,6 @@ def train(cfg: TrainPipelineConfig, accelerator: "Accelerator | None" = None):
                     f"Resuming data order at epoch {sampler_state['epoch']}, "
                     f"sample {sampler_state['start_index']}"
                 )
-        if dataset.reader._absolute_to_relative_idx is not None:
-            sampler.indices = [dataset.reader._absolute_to_relative_idx[i] for i in sampler.indices]
     else:
         shuffle = True
         sampler = None