Move ImageWriter creation inside the dataset

lerobot/common/datasets/lerobot_dataset.py

@@ -177,11 +177,13 @@ class LeRobotDataset(torch.utils.data.Dataset):
         self.episodes = episodes
         self.tolerance_s = tolerance_s
         self.video_backend = video_backend if video_backend is not None else "pyav"
-        self.image_writer = image_writer
         self.delta_indices = None
-        self.consolidated = True
-        self.episode_buffer = {}
         self.local_files_only = local_files_only
+        self.consolidated = True
+
+        # Unused attributes
+        self.image_writer = None
+        self.episode_buffer = {}
 
         # Load metadata
         self.root.mkdir(exist_ok=True, parents=True)
@@ -626,8 +628,7 @@ class LeRobotDataset(torch.utils.data.Dataset):
         self.consolidated = False
 
     def _save_episode_table(self, episode_index: int) -> None:
-        features = self.features
+        ep_dataset = datasets.Dataset.from_dict(self.episode_buffer, features=self.features, split="train")
-        ep_dataset = datasets.Dataset.from_dict(self.episode_buffer, features=features, split="train")
         ep_table = ep_dataset._data.table
         ep_data_path = self.root / self.get_data_file_path(ep_index=episode_index)
         ep_data_path.parent.mkdir(parents=True, exist_ok=True)
@@ -675,10 +676,25 @@ class LeRobotDataset(torch.utils.data.Dataset):
         # Reset the buffer
         self.episode_buffer = self._create_episode_buffer()
 
-    def read_mode(self) -> None:
+    def start_image_writter(self, num_processes: int = 0, num_threads: int = 1) -> None:
-        """Whenever wrapping this dataset inside a parallelized DataLoader, this needs to be called first."""
+        if isinstance(self.image_writer, ImageWriter):
-        # TODO(aliberts, rcadene): find better api/interface for this.
+            logging.warning(
+                "You are starting a new ImageWriter that is replacing an already exising one in the dataset."
+            )
+
+        self.image_writer = ImageWriter(
+            write_dir=self.root,
+            num_processes=num_processes,
+            num_threads=num_threads,
+        )
+
+    def stop_image_writter(self) -> None:
+        """
+        Whenever wrapping this dataset inside a parallelized DataLoader, this needs to be called first to
+        remove the image_write in order for the LeRobotDataset object to be pickleable and parallelized.
+        """
         if self.image_writer is not None:
+            self.image_writer.stop()
             self.image_writer = None
 
     def encode_videos(self) -> None:
@@ -708,20 +724,20 @@ class LeRobotDataset(torch.utils.data.Dataset):
             shutil.rmtree(self.image_writer.dir)
 
         if run_compute_stats:
-            self.read_mode()
+            self.stop_image_writter()
             self.stats = compute_stats(self)
             write_stats(self.stats, self.root / STATS_PATH)
             self.consolidated = True
         else:
-            logging.warning("Skipping computation of the dataset statistics.")
+            logging.warning(
+                "Skipping computation of the dataset statistics, dataset is not fully consolidated."
+            )
 
         # TODO(aliberts)
         # Sanity checks:
         # - [ ] shapes
         # - [ ] ep_lenghts
         # - [ ] number of files
-        # - [ ] names of files (e.g. parquet 00000-of-00001 and 00001-of-00002)
-        # - [ ] no remaining self.image_writer.dir
 
     @classmethod
     def create(
@@ -731,7 +747,8 @@ class LeRobotDataset(torch.utils.data.Dataset):
         robot: Robot,
         root: Path | None = None,
         tolerance_s: float = 1e-4,
-        image_writer: ImageWriter | None = None,
+        image_writer_processes: int = 0,
+        image_writer_threads_per_camera: int = 0,
         use_videos: bool = True,
         video_backend: str | None = None,
     ) -> "LeRobotDataset":
@@ -740,7 +757,6 @@ class LeRobotDataset(torch.utils.data.Dataset):
         obj.repo_id = repo_id
         obj.root = root if root is not None else LEROBOT_HOME / repo_id
         obj.tolerance_s = tolerance_s
-        obj.image_writer = image_writer
 
         if not all(cam.fps == fps for cam in robot.cameras.values()):
             logging.warning(
@@ -755,20 +771,24 @@ class LeRobotDataset(torch.utils.data.Dataset):
         # TODO(aliberts, rcadene, alexander-soare): Merge this with OnlineBuffer/DataBuffer
         obj.episode_buffer = obj._create_episode_buffer()
 
+        obj.image_writer = None
+        if len(robot.cameras) > 0 and (image_writer_processes or image_writer_threads_per_camera):
+            obj.start_image_writter(
+                image_writer_processes, image_writer_threads_per_camera * robot.num_cameras
+            )
+
         # This bool indicates that the current LeRobotDataset instance is in sync with the files on disk. It
         # is used to know when certain operations are need (for instance, computing dataset statistics). In
         # order to be able to push the dataset to the hub, it needs to be consolidated first by calling
         # self.consolidate().
         obj.consolidated = True
 
-        obj.local_files_only = True
-        obj.download_videos = False
-
         obj.episodes = None
         obj.hf_dataset = None
         obj.image_transforms = None
         obj.delta_timestamps = None
         obj.delta_indices = None
+        obj.local_files_only = True
         obj.episode_data_index = None
         obj.video_backend = video_backend if video_backend is not None else "pyav"
         return obj

lerobot/scripts/control_robot.py

@@ -105,7 +105,6 @@ from pathlib import Path
 from typing import List
 
 # from safetensors.torch import load_file, save_file
-from lerobot.common.datasets.image_writer import ImageWriter
 from lerobot.common.datasets.lerobot_dataset import LeRobotDataset
 from lerobot.common.robot_devices.control_utils import (
     control_loop,
@@ -232,17 +231,14 @@ def record(
 
     # Create empty dataset or load existing saved episodes
     sanity_check_dataset_name(repo_id, policy)
-    if len(robot.cameras) > 0:
-        image_writer = ImageWriter(
-            write_dir=root,
-            num_processes=num_image_writer_processes,
-            num_threads=num_image_writer_threads_per_camera * robot.num_cameras,
-        )
-    else:
-        image_writer = None
-
     dataset = LeRobotDataset.create(
-        repo_id, fps, robot, root=root, image_writer=image_writer, use_videos=video
+        repo_id,
+        fps,
+        robot,
+        root=root,
+        image_writer_processes=num_image_writer_processes,
+        image_writer_threads_per_camera=num_image_writer_threads_per_camera,
+        use_videos=video,
     )
 
     if not robot.is_connected: