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fix(streaming): decode video at episode-local timestamp + from_timestamp offset

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make_frame used `item["index"] / fps` (a dataset-global value) as the in-file
video timestamp. That only matches the file timeline when the whole dataset is a
single video (as in the test fixtures); on multi-file v3 datasets it decodes
out-of-range frames and crashes (e.g. RoboCasa: "Invalid frame index=23314614 ...
must be less than 41021").

Mirror the map-style reader: use the episode-local `timestamp` column as the base,
clamp delta query timestamps to per-camera episode-local bounds [0, duration], and
shift by the episode's `from_timestamp` per camera at decode time. For single-file
datasets `from_timestamp + timestamp == index / fps`, so existing parity tests are
unaffected; multi-file streaming is now correct.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Pepijn
2026-06-09 14:54:10 +02:00
parent 68fa5d80b0
commit 77af66a29c
1 changed files with 15 additions and 5 deletions
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src/lerobot/datasets/streaming_dataset.py
+15 -5
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@@ -590,13 +590,20 @@ class StreamingLeRobotDataset(torch.utils.data.IterableDataset):
# Get episode index from the item
ep_idx = item["episode_index"]
# "timestamp" restarts from 0 for each episode, whereas we need a global timestep within the single .mp4 file (given by index/fps)
current_ts = item["index"] / self.fps
# `timestamp` is episode-local (restarts at 0 each episode). The absolute in-file timestamp is
# `from_timestamp + timestamp`, applied per camera at decode time (see `_query_videos`), mirroring
# the map-style reader. Using `index / fps` here is a dataset-global value that only matches the
# file timeline when the whole dataset is a single video (e.g. small test fixtures), and otherwise
# decodes out-of-range frames on multi-file v3 datasets.
current_ts = float(item["timestamp"])
# Per-camera episode-local bounds [0, duration]. Query timestamps are clamped into this range so
# out-of-episode deltas pad rather than decode against a neighbouring episode in the same file.
episode_boundaries_ts = {
key: (
self.meta.episodes[ep_idx][f"videos/{key}/from_timestamp"],
self.meta.episodes[ep_idx][f"videos/{key}/to_timestamp"],
0.0,
self.meta.episodes[ep_idx][f"videos/{key}/to_timestamp"]
- self.meta.episodes[ep_idx][f"videos/{key}/from_timestamp"],
)
for key in self.meta.video_keys
}
@@ -669,11 +676,14 @@ class StreamingLeRobotDataset(torch.utils.data.IterableDataset):
item = {}
for video_key, query_ts in query_timestamps.items():
# query_ts is episode-local; shift to the absolute in-file timeline by the episode's offset.
from_timestamp = self.meta.episodes[ep_idx][f"videos/{video_key}/from_timestamp"]
shifted_query_ts = [from_timestamp + ts for ts in query_ts]
root = self.meta.url_root if self.streaming and not self.streaming_from_local else self.root
video_path = f"{root}/{self.meta.get_video_file_path(ep_idx, video_key)}"
frames = decode_video_frames_torchcodec(
video_path,
query_ts,
shifted_query_ts,
self.tolerance_s,
decoder_cache=self.video_decoder_cache,
return_uint8=self._return_uint8,