Usage

1. Conversion for Visualization

Generate visualization-ready MCAP files from raw egosuite MCAP data.

1.1 Single File Conversion

cd LW-Egosuite-DevKit
lw-egosuite convert --mcap $input_mcap_path --mcap_vis $mcap_for_vis_path

Parameter	Description
--mcap	Path to the source MCAP file (not a directory)
--mcap_vis	(Optional) Output path. Default: {input_dir}/{input_stem}_vis.mcap

Output path is printed at the start of conversion.

1.2 Batch Conversion

cd LW-Egosuite-DevKit

data_path="/path/to/your/data"

for input_mcap_path in "$data_path"/*.mcap; do
    [ -e "$input_mcap_path" ] || continue

    echo "Processing: $input_mcap_path ..."

    # output goes to same directory as input
    lw-egosuite convert --mcap "$input_mcap_path"
done

• $data_path: The directory containing the source MCAP files. Each file will be converted and saved with a _vis.mcap suffix in the same directory as the source file.

2. Data Visualization

Follow these steps to visualize the processed data in LW-VIZ or Foxglove Studio:

LW-VIZ:

1. Open browser: Open the LW-VIZ visualization platform.
2. Select Layout: Select default mode in the Layouts option.
3. Load Data Streams: Simultaneously load the source file mcap_filename.mcap and the generated visualization file {mcap_filename}_vis.mcap (in the same directory as the source by default).

Foxglove:

1. Launch Foxglove: Open the Foxglove Studio desktop application or web version.
2. Import Layout: Load the recommended configuration file: assets/default_layout.json.
3. Load Data Streams: Simultaneously load the source file mcap_filename.mcap and the generated visualization file {mcap_filename}_vis.mcap (in the same directory as the source by default).

Once loaded, the visualization will appear in the Foxglove Studio dashboard as shown below:

3. Reading from MCAP

3.1 Export Video (CLI)

Export video requires ffmpeg on PATH. If not installed:

sudo apt install ffmpeg

Export a foxglove.CompressedVideo topic from an MCAP file to MP4. Uses stream copy (no re-encode). Output is a valid MP4 with moov atom at the start for compatibility.

lw-egosuite export-video --mcap path/to/file.mcap --output output.mp4

Parameter	Description
--mcap	Input MCAP file path
--output	Output MP4 file path
--topic	(Optional) CompressedVideo topic to export. Default: /sensor/camera/head_left/video

3.2 Iterate decoded messages (Python API)

Iterate decoded proto messages with the built-in reader:

from lw_egosuite_backend.mcap_reader import iter_messages

for m in iter_messages("out.mcap"):
    print(m.topic, m.log_time_ns, m.message)

# Filter by topics
for m in iter_messages("out.mcap", topics=["/pose/body"]):
    print(m.topic, m.message)

3.3 Decoding camera video frames (Python API)

Camera streams are stored as foxglove.CompressedVideo messages on topics such as:

• /sensor/camera/head_left/video
• /sensor/camera/head_right/video

You can decode these into numpy.ndarray or torch.Tensor using EgosuiteMcapReader.iter_video_frames:

from lw_egosuite_backend.mcap_reader import EgosuiteMcapReader, iter_video_frames

# Using the context-managed reader:
with EgosuiteMcapReader("episode.mcap") as r:
    for frame in r.iter_video_frames("/sensor/camera/head_left/video", output="numpy"):
        # frame is a numpy.ndarray with shape (H, W, 3), dtype=uint8
        print(frame.shape, frame.dtype)

# Using the convenience helper for a single topic:
for frame in iter_video_frames(
    "episode.mcap",
    topic="/sensor/camera/head_left/video",
    output="numpy",  # or "torch"
):
    print(frame.shape)

Notes:

• Video decoding requires ffmpeg and ffprobe on PATH.
• numpy is required; torch is only required when output="torch".