ROS package with messages for event based cameras

This package has definitions for ROS / ROS2 messages created by event based vision sensors. The events are kept in a compact binary format to avoid slow serialization and deserialization during recording.

Event camera messages can be visualized with the event_camera_renderer and converted to other message formats using event_camera_tools.

For encoding and decoding of messages in C++ look at event_camera_codecs. The event_camera_py package provides a module for fast and convenient loading of events in python.

Messages

EventPacket

The EventPacket message contains a packet (array) of events in binary format.

Description of the encodings:

• evt3: raw Metavision evt3 data as it comes from the SDK. For the details of the encoding scheme refer to the Prophesee Metavision documents.

  The time_base field is not used and its content is undefined. Recovery of sensor time requires decoding the data packets. For more about time stamps see documentation in event_camera_codecs.

• mono: messages from monochrome cameras using the libcaer driver (Davis, dvXplorer etc). Encodes on 64 bit boundaries as follows:

  bits	interpretation
  63	polarity: ON event = 1, OFF event = 0
  48-62	y (15 bits)
  32-48	x (16 bits)
  0-32	dt (32 bits)

  To recover the original sensor time, add the delta dt to the message time_base field. Both dt and time_base are in nanoseconds. To recover the best estimate ROS sensor time stamp add dt to the ROS header stamp.

• trigger (deprecated): external trigger messages from e.g. the Prophesee Metavision cameras.

  bits	interpretation
  63	polarity: ON event = 1, OFF event = 0
  33-62	unused (31 bits)
  0-32	dt (32 bits)

  To recover the original sensor time add the delta dt to the message time_base field (in nanoseconds). To recover the best estimate ROS sensor time stamp add dt to the header stamp.

License

This package is released under the Apache-2 license.