From f9fd0fb841d318b16635fbd1fb70171e04852861 Mon Sep 17 00:00:00 2001
From: CarolinePascal <caroline8.pascal@gmail.com>
Date: Mon, 24 Nov 2025 21:51:33 +0100
Subject: [PATCH] feat(multi-processes): adding support for multiprocess
 encoding

---
 src/lerobot/datasets/lerobot_dataset.py | 29 +++++++++++++++++++++----
 src/lerobot/datasets/video_utils.py     |  2 +-
 2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/src/lerobot/datasets/lerobot_dataset.py b/src/lerobot/datasets/lerobot_dataset.py
index a6840891f..381c91b70 100644
--- a/src/lerobot/datasets/lerobot_dataset.py
+++ b/src/lerobot/datasets/lerobot_dataset.py
@@ -27,6 +27,7 @@ import pandas as pd
 import PIL.Image
 import pyarrow as pa
 import pyarrow.parquet as pq
+from concurrent.futures import ProcessPoolExecutor
 import torch
 import torch.utils
 from huggingface_hub import HfApi, snapshot_download
@@ -1149,8 +1150,9 @@ class LeRobotDataset(torch.utils.data.Dataset):
         use_batched_encoding = self.batch_encoding_size > 1
 
         if has_video_keys and not use_batched_encoding:
-            for video_key in self.meta.video_keys:
-                ep_metadata.update(self._save_episode_video(video_key, episode_index))
+            video_paths = self._encode_multiple_temporary_episode_videos(self.meta.video_keys, episode_index)
+            for (video_key, video_path) in zip(self.meta.video_keys, video_paths):
+                ep_metadata.update(self._save_episode_video(video_key, episode_index, video_path))
 
         # `meta.save_episode` need to be executed after encoding the videos
         self.meta.save_episode(episode_index, episode_length, episode_tasks, ep_stats, ep_metadata)
@@ -1315,9 +1317,12 @@ class LeRobotDataset(torch.utils.data.Dataset):
 
         return metadata
 
-    def _save_episode_video(self, video_key: str, episode_index: int) -> dict:
+    def _save_episode_video(self, video_key: str, episode_index: int, video_path: str | Path | None = None) -> dict:
         # Encode episode frames into a temporary video
-        ep_path = self._encode_temporary_episode_video(video_key, episode_index)
+        if video_path is None:
+            ep_path = self._encode_temporary_episode_video(video_key, episode_index)
+        else:
+            ep_path = video_path
         ep_size_in_mb = get_file_size_in_mb(ep_path)
         ep_duration_in_s = get_video_duration_in_s(ep_path)
 
@@ -1441,6 +1446,22 @@ class LeRobotDataset(torch.utils.data.Dataset):
         shutil.rmtree(img_dir)
         return temp_path
 
+    def _encode_multiple_temporary_episode_videos(self, video_keys, episode_index):
+        temp_paths = []
+        img_dirs = []
+        for video_key in video_keys:
+            temp_paths.append(Path(tempfile.mkdtemp(dir=self.root)) / f"{video_key}_{episode_index:03d}.mp4")
+            img_dirs.append(self._get_image_file_dir(episode_index, video_key))
+        fps = [self.fps]*len(video_keys)
+
+        with ProcessPoolExecutor() as executor:
+            executor.map(encode_video_frames,img_dirs,temp_paths,fps)
+
+        for img_dir in img_dirs:
+            shutil.rmtree(img_dir)
+
+        return temp_paths
+
     @classmethod
     def create(
         cls,
diff --git a/src/lerobot/datasets/video_utils.py b/src/lerobot/datasets/video_utils.py
index 04deb2bc1..f9e521c44 100644
--- a/src/lerobot/datasets/video_utils.py
+++ b/src/lerobot/datasets/video_utils.py
@@ -310,7 +310,7 @@ def encode_video_frames(
     crf: int | None = 30,
     fast_decode: int = 0,
     log_level: int | None = av.logging.ERROR,
-    overwrite: bool = False,
+    overwrite: bool = True,
 ) -> None:
     """More info on ffmpeg arguments tuning on `benchmark/video/README.md`"""
     # Check encoder availability