velodyne_decoder

Python package and C++ library for Velodyne packet decoding. Point cloud extraction from PCAP and ROS bag files is supported out of the box.

The decoded point clouds are provided either as a structured NumPy array:

array([(8.327308, -2.161341, 0.3599853, 85., 17, -0.04960084),
       (8.323784, -2.9578836, 0.27016047, 102., 15, -0.04959854),
       (8.184404, -2.845847, -0.8741639, 39., 2, -0.04959623), ...,
       (8.369528, -2.8161895, 2.307987, 17., 31, 0.00064051),
       (8.377898, -3.2570598, 1.7714221, 104., 30, 0.00064282),
       (8.358282, -2.8030438, 0.31229734, 104., 16, 0.00064282)],
      dtype={'names': ['x', 'y', 'z', 'intensity', 'ring', 'time'],
             'formats': ['<f4', '<f4', '<f4', '<f4', '<u2', '<f4'], 'offsets': [0, 4, 8, 16, 20, 24], 'itemsize': 32})

or as a contiguous array of floats (default):

array([[8.327308, -2.161341, 0.3599853, 85., 17., -0.04960084],
       [8.323784, -2.9578836, 0.27016047, 102., 15., -0.04959854],
       [8.184404, -2.845847, -0.8741639, 39., 2., -0.04959623],
       ...,
       [8.369528, -2.8161895, 2.307987, 17., 31., 0.00064051],
       [8.377898, -3.2570598, 1.7714221, 104., 30., 0.00064282],
       [8.358282, -2.8030438, 0.31229734, 104., 16., 0.00064282]], dtype=float32)

The layout of the structs matches the layout of PointXYZIRT point cloud points output by the ROS driver.

Installation

Wheels are available from PyPI for Linux, MacOS and Windows. Python versions 2.7 and 3.6+ are supported.

pip install velodyne-decoder

Alternatively, you can build and install the development version from source.

sudo apt-get install cmake build-essential python3-dev
pip install git+https://github.com/valgur/velodyne_decoder.git

Usage

Decoding Velodyne data from a ROS bag

import velodyne_decoder as vd

config = vd.Config(model='VLP-32C')
bagfile = 'xyz.bag'
lidar_topics = ['/velodyne_packets']
cloud_arrays = []
for stamp, points, topic in vd.read_bag(bagfile, config, lidar_topics):
    cloud_arrays.append(points)

The rosbag library must be installed. If needed, you can install it without setting up the entire ROS stack with

pip install rosbag --extra-index-url https://rospypi.github.io/simple/

To extract all VelodyneScan messages in the bag you can leave the list of topics unspecified.

The header timestamp from the scan messages will be returned by default. To use the message arrival time instead set use_header_time=False.

To return arrays of structs instead of the default contiguous arrays, set as_pcl_structs=True.

Decoding Velodyne data from a PCAP file

import velodyne_decoder as vd

config = vd.Config(model='VLP-16', rpm=600)
pcap_file = 'vlp16.pcap'
cloud_arrays = []
for stamp, points in vd.read_pcap(pcap_file, config):
    cloud_arrays.append(points)

config.model and config.rpm must be set.

To return arrays of structs instead of the default contiguous arrays, set as_pcl_structs=True.

Configuration

The main parameter config.model must always be set. For a list of supported model IDs see

>> > velodyne_decoder.Config.SUPPORTED_MODELS
['HDL-32E', 'HDL-64E', 'HDL-64E_S2', 'HDL-64E_S3', 'VLP-16', 'VLP-32C', 'Alpha Prime']

Note that timing info is available for only a subset of the models:

>> > velodyne_decoder.Config.TIMINGS_AVAILABLE
['HDL-32E', 'VLP-16', 'VLP-32C', 'Alpha Prime']

Other available options are:

• calibration_file – the beam calibration details from Velodyne are used by default based on the model ID. If you however wish to use a more specific calibration, you can specify one in the YAML format used by the ROS driver.
• min_range and max_range – only return points between these range values.
• min_angle and max_angle – only return points between these azimuth angles.

Options only applicable to PCAP decoding:

• rpm – the device rotation speed in revolutions per minute.
• gps_time – use the timestamp from the packet's data if true, packet's arrival time otherwise (default).
• timestamp_first_packet – whether the timestamps are set based on the first or last packet in the scan

Authors

• Martin Valgur (@valgur)

The core functionality has been adapted from the ROS velodyne driver.

License

BSD 3-Clause License