Rerun LeRobot ingestion

There are two ways in, and which one you want depends on whether you are viewing or converting.

• Just viewing? Rerun has a built-in LeRobot importer: point log_file_from_path (or the viewer, or rerun <dir> on the CLI) at the dataset directory and it ingests episodes, camera videos, and state/action tables with no conversion code.
• Converting? rr.experimental.LeRobotReader reads the dataset one episode at a time as a lazy chunk stream, which is what you want for per-episode RRDs and for lenses.

The download step needs huggingface_hub.

Step 0: pick a dataset and check the HF token

Both scripts below live in scripts/ next to this file, and run standalone through uv — they declare huggingface_hub inline, so there is no environment to set up.

Two facts decide what a dataset costs to fetch, and the Hub search results show neither. Get both, for every candidate, in one call:

uv run scripts/find_lerobot_dataset.py <query> --robot-type <robot> --want 5

codebase_version decides whether a partial download is possible at all.

• v2.1 and earlier store one parquet and one mp4 per episode (video_path ends in episode_{episode_index:06d}.mp4), so "just the first N episodes" downloads only those episodes.
• v3.0 concatenates every episode into a few large files (video_path ends in file-{file_index:03d}.mp4), so any subset costs the whole download. If the user asked for a few episodes, prefer a v2.1 dataset — for the download only. LeRobotReader reads a single episode out of either version once the files are local.

How camera frames are stored decides the size, and it varies by two orders of magnitude. The frames and MB/ep columns report it:

• mp4: a video-dtype feature, one file per episode beside the parquet.
• inline: an image-dtype feature, raw frames inside the episode parquet, which is far larger for the same footage.

Both scripts report the actual size for the dataset in hand, so use that number rather than guessing. Tell the user the size before you start the download, and prefer mp4 unless they asked for something only the other set has.

HF_TOKEN is not required for public datasets, but without it the Hub rate-limits and throttles downloads. If it is unset, say so and point the user at https://huggingface.co/settings/tokens to create a read token, then export HF_TOKEN=hf_… (or hf auth login). Do not block on it — carry on unauthenticated and let the user decide.

[ -n "$HF_TOKEN" ] || echo "HF_TOKEN unset — downloads will be throttled"

Step 1: dataset -> one combined RRD

Only needed if you want every episode in one file — to hand someone a single RRD, or to reprocess data you cannot re-read from the dataset directory. For per-episode segments, skip to Step 2 and let LeRobotReader read the dataset directly.

from huggingface_hub import snapshot_download
import rerun as rr

dataset_dir = snapshot_download(repo_id=repo_id, repo_type="dataset", local_dir=dest)

with rr.RecordingStream("rerun_example_lerobot") as rec:
    rec.save(str(combined_rrd))
    rec.log_file_from_path(str(dataset_dir))  # the built-in importer

The importer emits one recording per episode (recording ids like episode_1), plus a metadata-only root recording, all into the single RRD.

rr.RecordingStream + log_file_from_path here is the importer bootstrap — the one place RecordingStream is correct in an ingestion pipeline (it drives the built-in importer, not per-message logging). Do not generalize it to rr.log-per-message loops; for everything after import, reprocess with a reader + lenses (see rerun-chunk-processing: Chunk API vs logging API).

Downloading only the first few episodes

uv run scripts/fetch_lerobot_episodes.py <repo_id> --episodes 5   # prints the dataset directory

It reports the download size before starting, downloads meta/* plus the wanted episode_%06d files, trims meta/ to match, verifies that exactly the requested episodes landed, and prints what it got. Its last line is the dataset directory; do not follow it with find or du. Do the equivalent by hand and three things bite:

• The importer iterates the episode list in meta/, so an untrimmed meta/ warns once per absent episode.
• snapshot_download writes into an existing directory, so episodes left by an earlier run with a different N survive and inflate the result.
• Both failures are invisible until you count the recordings in the viewer, which is why the script asserts instead of leaving you to look.

Just looking at it in the viewer?

Skip the RRD entirely — the viewer imports the dataset directory itself. Pass the plain path (rerun /path/to/dataset, or open_url over MCP). Each episode arrives as its own recording, with recording_id episode_0, episode_1, ….

Step 2: one RRD per episode

Catalog segments are one-recording-per-file, and recording_id becomes the segment id on registration.

LeRobotReader goes straight there, without building the combined RRD of Step 1 first:

reader = rr.experimental.LeRobotReader(dataset_dir)  # v2 or v3
for episode in reader.episodes():
    episode_id = f"episode_{episode:05d}"  # zero-padded; see below
    reader.stream(episode).write_rrd(
        rrd_dir / f"{episode_id}.rrd",
        application_id="my_dataset",
        recording_id=episode_id,
    )

Streaming is lazy end to end, so memory is bounded by chunk size rather than by episode or dataset size, and video is cut to the episode's time window. B-frame-free video (AV1, LeRobot's default codec) streams directly; a stream that must be re-encoded — H.264 with B-frames, or a window starting mid-GOP — needs ffmpeg on the PATH. stream() also takes entity_path_prefix, timeline, and video_mode="skip" to drop video entirely.

To add lenses, drop topics, or fix data, put them between the stream and the write — see rerun-chunk-processing.

Splitting an RRD you already have

If the combined RRD of Step 1 already exists — or the data came from somewhere other than the dataset directory — split it with RrdReader instead:

reader = rr.chunk.RrdReader(str(combined_rrd))
for entry in reader.recordings():
    store = reader.store(store=entry)
    if not store.schema().entity_paths():  # skip the metadata-only root recording
        continue
    episode_id = zero_pad(entry.recording_id)  # episode_1 -> episode_00001
    with rr.RecordingStream("rerun_example_lerobot", recording_id=episode_id, send_properties=False) as rec:
        rec.save(str(rrd_dir / f"{episode_id}.rrd"))
        rec.send_chunks(store)

Two non-obvious moves:

• Zero-pad the episode id. episode_10 sorts before episode_2 lexicographically; segment tables and viewers sort lexicographically. Pad to a fixed width when re-assigning recording_id.
• send_properties=False on the new stream, so the copy doesn't inject fresh recording properties on top of the copied chunks.

send_chunks does not preserve the source store's identity; the new stream's recording_id wins, which is exactly what makes the rename work.

If episodes need cleanup (drop topics, fix data, add derived components), run the store through lenses between read and write: reader.stream(store=entry).drop(...).lenses(...) then collect().write_rrd(..., recording_id=episode_id) (see rerun-chunk-processing).

Computed layers and per-episode properties then follow the standard patterns in rerun-data-model (layer recording_id must equal the episode segment id).

Step 3: add the robot model (URDF)

A LeRobot dataset ships joint values, never a robot. Without a URDF you get camera views and joint plots but no 3D arm, which is usually not what the user pictured when they asked to look at the data. Adding one is a forward-kinematics layer — rerun-urdf owns that; this section is only the LeRobot-specific wiring.

• The URDF. meta/info.json robot_type names it (so100, so101, aloha, …); rerun-urdf has the source table.
• The joint names. meta/info.json features.observation.state.names lists them in column order. Map each source name explicitly to the corresponding URDF joint name; do not assume that removing a prefix produces a valid URDF name.
• The values. observation.state is the measured pose and the one to run FK on; action is the commanded pose and belongs on the plots, not the robot.
• The units and calibration. Confirm the units, sign, and offset against the dataset and robot documentation. Run rerun-urdf's check_joint_mapping.py against the episode parquets before trusting a pose.

The FK source is the per-episode parquet, read directly rather than out of the imported RRD:

ParquetReader(str(episode_parquet)).stream(
    column_grouping="individual",
    index_columns=[IndexColumn.sequence("frame_index")],
).drop(content="/__properties/**")

frame_index is the index the importer uses too, so the FK transforms line up with the video and plots. Merge the URDF model stream plus the FK stream into each episode's RRD, keeping the episode's recording_id (see rerun-urdf's "Minimal shape"). For a whole dataset, the model belongs in a shared asset rather than in every segment — also rerun-urdf.

Gotchas

1. log_file_from_path must target the dataset root directory, not a file inside it. So does LeRobotReader.
2. Unpadded episode ids sort incorrectly downstream; pad before registering.
3. The combined RRD contains a metadata-only root recording; skip stores with no entity paths or you register an empty segment.
4. A partially-downloaded dataset imports fine, but warns once per episode listed in meta/ and missing on disk.
5. Downloading a subset into a directory an earlier run already populated leaves the older episodes in place; start from an empty directory.
6. image-dtype (inline) datasets can be ~100x larger per episode than mp4 ones; check before downloading, not after.
7. Check signs and units - e.g. an observation.state in degrees could produce wrong FK when fed into a robot model that expects radians.

References

• rerun-chunk-processing (LazyChunkStream, lenses, RrdReader)
• rerun-urdf (adding the robot model and the joint-value mapping)
• https://github.com/rerun-io/rerun/tree/main/examples/python/dataloader prepare_dataset.py (download → import → split → register, complete and runnable) and train.py (training-side consumption via rerun.experimental.dataloader)