event_array_py

This repository holds ROS/ROS2 tools for processing event_array_msgs under ROS and ROS2 with python. These messages are produced by the metavision_ros_driver.

Supported platforms

Currently tested on Ubuntu 20.04 under ROS Noetic and ROS2 Galactic.

How to build

Create a workspace (event_array_py_ws), clone this repo, and use wstool to pull in the remaining dependencies:

pkg=event_array_py
mkdir -p ~/${pkg}_ws/src
cd ~/${pkg}_ws
git clone https://github.com/berndpfrommer/${pkg}.git src/${pkg}
wstool init src src/${pkg}/${pkg}.rosinstall
# to update an existing space:
# wstool merge -t src src/${pkg}/${pkg}.rosinstall
# wstool update -t src

configure and build on ROS1:

catkin config -DCMAKE_BUILD_TYPE=RelWithDebInfo  # (optionally add -DCMAKE_EXPORT_COMPILE_COMMANDS=1)
catkin build

configure and build on ROS2:

cd ~/${pkg}_ws
colcon build --symlink-install --cmake-args -DCMAKE_BUILD_TYPE=RelWithDebInfo  # (optionally add -DCMAKE_EXPORT_COMPILE_COMMANDS=1)

Decoding event array messages

The following sample code shows how to decode event array messages under ROS1.

import rosbag
from event_array_py import Decoder

topic = '/event_camera/events'
bag = rosbag.Bag('foo.bag')
decoder = Decoder()

for topic, msg, t in bag.read_messages(topics=topic):
    decoder.decode_bytes(msg.encoding, msg.width, msg.height,
	                     msg.time_base, msg.events)
    cd_events = decoder.get_cd_events()
    print(cd_events)
    trig_events = decoder.get_ext_trig_events()
    print(trig_events)

Here is a sample code for ROS2. It uses a helper class "BagReader" that you can find in the src folder. Note the conversion to numpy array:

import numpy as np
from bag_reader_ros2 import BagReader
from event_array_py import Decoder

topic = '/event_camera/events'
bag = BagReader('foo', topic)
decoder = Decoder()

while bag.has_next():
        topic, msg, t_rec = bag.read_next()
        decoder.decode_array(msg.encoding, msg.width, msg.height,
                             msg.time_base,
                             np.frombuffer(msg.events, dtype=np.uint8))
        cd_events = decoder.get_cd_events()
        print(cd_events)
        trig_events = decoder.get_ext_trig_events()
        print(trig_events)

The returned event arrays are structured numpy ndarrays that are compatible with Prophesee's Metavision SDK.

License

This software is issued under the Apache License Version 2.0.