ROS 2 - ZED Mono Node

The easiest way to start a ZED ROS 2 node for a monocular camera is by using the command line:

$ ros2 launch zed_wrapper zed_camera.launch.py camera_model:=<camera model>

where <camera model> must be replaced with one in the list zedxonegs, and zedxone4k

Published Topics

The ZED node publishes data to the following topics:

Image streams

The image topic names are created using the following naming convention: ~/<sensor_type>/<color_model>/<rect_type>/image

Starting from version 5.1.0 of the ROS 2 Wrapper the new convention replaces the previous formats such as ~/<sensor_type>/image_<rect_type>_<color_model> and ~/<sensor_type>_<rect_type>/image_<rect_type>_<color_model> (e.g., ~/left/image_rect_color, ~/rgb_raw/image_raw_gray). Please update your launch files and scripts to use the new topic names.
- RGB channel
  - ~/rgb/color/rect/image: Color rectified image.
  - ~/rgb/color/rect/camera_info: Color camera calibration data.
  - ~/rgb/gray/rect/image: Grayscale rectified image.
  - ~/rgb/gray/rect/camera_info: Grayscale camera calibration data.
  - ~/rgb/color/raw/image: Color unrectified image.
  - ~/rgb/color/raw/camera_info: Color raw calibration data.
  - ~/rgb/gray/raw/image: Grayscale unrectified image.
  - ~/rgb/gray/raw/camera_info: Grayscale raw calibration data.
Sensors data
- ~/imu/data
- ~/imu/data_raw
- ~/temperature
- ~/left_cam_imu_transform

Image Transport

The ROS 2 wrapper supports the stack image_transport introduced with ROS 2 Crystal Clemmys.

All the image topics are published using the image_transport::Publisher object, correctly associating the sensor_msgs::msg::CameraInfo message to the relative sensor_msg::msg::Image message and creates the relative compressed image streams.

We recommend using the standard available image transports:

raw: uncompressed image
compressed: JPEG or PNG compressed image
theora: Ogg Theora compressed image
compressedDepth: depth image compressed with a lossless algorithm

For proper association between images and their corresponding camera information, the ZED ROS 2 Wrapper also publishes camera_info topics for all compressed image streams:

~/rgb/color/rect/image/camera_info
~/rgb/gray/rect/image/camera_info
~/rgb/color/raw/image/camera_info
~/rgb/gray/raw/image/camera_info

The image transport topics are not advertised if NITROS is enabled. Please refer to the dedicated section about NVIDIA® Isaac ROS Nitros for more details.

NVIDIA® Isaac ROS Nitros

The ZED ROS 2 Wrapper supports the NVIDIA® Isaac™ ROS Nitros package for zero-copy transport of ROS messages using NVIDIA® GPUDirect® RDMA.

NVIDIA® Isaac ROS Nitros integration is enabled and used only if the required packages are manually installed. They are not added as a dependency because this is an optional feature.

For more information about the installation and usage of the NVIDIA® Isaac™ ROS packages, please refer to the dedicated section of the documentation: ZED Isaac™ ROS Integration Overview.

QoS profiles

All the topics are configured by default to use the following ROS 2 QoS profile:

Reliability: RELIABLE
History (Depth): KEEP_LAST (10)
Durability: VOLATILE
Lifespan: Infinite
Deadline: Infinite
Liveliness: AUTOMATIC
Liveliness lease duration: Infinite

Read the official ROS 2 documentation about the QoS and the relatived settings for details.

The QoS settings can be modified by changing the relative parameters in the YAML files, as described in this official ROS 2 design document.

When creating a subscriber, be sure to use a compatible QOS profile according to the following tables:

Compatibility of QoS durability profiles:

Publisher	Subscriber	Connection	Result
Volatile	Volatile	Yes	Volatile
Volatile	Transient local	No	-
Transient local	Volatile	Yes	Volatile
Transient local	Transient local	Yes	Transient local

Compatibility of QoS reliability profiles:

Publisher	Subscriber	Connection	Result
Best effort	Best effort	Yes	Best effort
Best effort	Reliable	No	-
Reliable	Best effort	Yes	Best effort
Reliable	Reliable	Yes	Reliable

In order for a connection to be made, all of the policies that affect compatibility must be compatible. For instance, if a publisher-subscriber pair has compatible reliability QoS profiles, but incompatible durability QoS profiles, the connection will not be made.

for a detailed list of all the compatibility settings, please refer to the official ROS 2 documentation.

Configuration parameters

Specify your launch parameters in the common_mono.yaml, zedxonegs.yaml, and zedxone4k.yaml files available in the folder zed_wrapper/config.

General parameters

Namespace: general

common_mono.yaml

Parameter	Description	Value
serial_number	Select a ZED camera by its Serial Number	int
pub_resolution	The resolution used for output. ‘NATIVE’ to use the same `general.grab_resolution` - `CUSTOM` to apply the `general.pub_downscale_factor` downscale factory to reduce bandwidth in transmission	string,‘NATIVE”SVGA’, ‘VGA’, ‘LOW’
pub_downscale_factor	Rescale factor used to rescale image before publishing when ‘pub_resolution’ is ‘CUSTOM’	double
gpu_id	Select a GPU device for depth computation	int
optional_opencv_calibration_file	Optional path where the ZED SDK can find a file containing the calibration information of the camera computed with OpenCV.	string

^* Dynamic parameter

zedxonegs.yaml, and zedxone4k.yaml

Parameter	Description	Value
camera_model	Type of StereoLabs camera	string, `zedxonegs`, `zedxone4k`
camera_name	User name for the camera, can be different from camera model	string
grab_resolution	The native camera grab resolution.	string, ‘HD1200’, ‘QHDPLUS’, ‘HD1080’, ‘SVGA’, ‘AUTO’
grab_frame_rate	ZED SDK internal grabbing rate	int, ‘15’,‘30’,‘60’,‘90’,‘100’,‘120’

Streaming server parameters

Namespace: stream_server

common_mono.yaml

Parameter	Description	Value
stream_enabled	enable the streaming server when the camera is open	`true`, `false`
codec	ifferent encoding types for image streaming: ‘H264’, ‘H265’	string
port	Port used for streaming. Port must be an even number. Any odd number will be rejected.	int
bitrate	Streaming bitrate (in Kbits/s) used for streaming. See doc	int, [1000 - 60000]
gop_size	The GOP size determines the maximum distance between IDR/I-frames. Very high GOP size will result in slightly more efficient compression, especially on static scenes. But latency will increase.	int, [max 256]
adaptative_bitrate	Bitrate will be adjusted depending the number of packet dropped during streaming. If activated, the bitrate can vary between [bitrate/4, bitrate].	`true`, `false`
chunk_size	Stream buffers are divided into X number of chunks where each chunk is chunk_size bytes long. You can lower chunk_size value if network generates a lot of packet lost: this will generates more chunk for a single image, but each chunk sent will be lighter to avoid inside-chunk corruption. Increasing this value can decrease latency.	int, [1024 - 65000]
target_framerate	Framerate for the streaming output. This framerate must be below or equal to the camera framerate. Allowed framerates are 15, 30, 60 or 100 if possible. Any other values will be discarded and camera FPS will be taken.	int

Video parameters

Namespace: video

common_mono.yaml

Parameter	Description	Value
saturation^*	Image saturation	int, [0,8]
sharpness^*	Image sharpness	int, [0,8]
gamma^*	Image gamma	int, [0,8]
auto_whitebalance^*	Enable the auto white balance	`true`, `false`
whitebalance_temperature^*	White balance temperature	int [28,65]
exposure_time^*	Defines the real exposure time in microseconds. Recommended to control manual exposure (instead of `video.exposure` setting)	int, [28,30000]
auto_exposure_time_range_min^*	Defines the minimum range of exposure auto control in micro seconds	int
auto_exposure_time_range_max^*	Defines the maximum range of exposure auto control in micro seconds	int
exposure_compensation^*	Defines the Exposure-target compensation made after auto exposure. Reduces the overall illumination target by factor of F-stops.	int, [0 - 100]
analog_gain^*	Defines the real analog gain (sensor) in mDB. Recommended to control manual sensor gain (instead of `video.gain` setting)	int, [1000-16000].
auto_analog_gain_range_min^*	Defines the minimum range of sensor gain in automatic control	int
auto_analog_gain_range_max^*	Defines the maximum range of sensor gain in automatic control	int
digital_gain^*	Defines the real digital gain (ISP) as a factor. Recommended to control manual ISP gain (instead of `video.gain` setting)	int, [1-256]
auto_digital_gain_range_min^*	Defines the minimum range of digital ISP gain in automatic control	int
auto_digital_gain_range_max^*	Defines the maximum range of digital ISP gain in automatic control	int
denoising^*	Defines the level of denoising applied on both left and right images	int, [0-100]
enable_24bit_output	Enable BGR 24-bit output for images (instead of 32-bit)	`true`, `false`
publish_rgb	Enable publishing of RGB image streams	`true`, `false`
publish_raw	Enable publishing of raw (unrectified) image streams	`true`, `false`
publish_gray	Enable publishing of grayscale image streams	`true`, `false`

^* Dynamic parameter

zedxone4k.yaml

Parameter	Description	Value
enable_hdr	When set to true, the camera will be set in HDR mode if the camera model and resolution allows it	`true`, `false`

Sensors parameters

Namespace: sensors

common_mono.yaml

Parameter	Description	Value
publish_imu_tf	Enable/disable the IMU TF broadcasting	`true`, `false`
sensors_pub_rate^*	Frequency of publishing of sensors data	double
publish_imu	Advertise the IMU topic that is published only if a node subscribes to it	`true`, `false`
publish_imu_raw	Advertise the raw IMU topic that is published only if a node subscribes to it	`true`, `false`
publish_cam_imu_transf	Advertise the CAMERA-IMU transformation topic that is published only if a node subscribes to it	`true`, `false`
publish_temp	Advertise the temperature topics that are published only if a node subscribes to them	`true`, `false`

^* Dynamic parameter

Debug parameters

Namespace: debug

common_mono.yaml

Parameter	Description	Value
sdk_verbose	Set the verbose level of the ZED SDK	int, `0` -> disable
sdk_verbose_log_file	Path to the file where the ZED SDK will log its messages. If empty, no file will be created. The log level can be set using the `sdk_verbose` parameter.	string
use_pub_timestamps	Use the current ROS time for the message timestamp instead of the camera timestamp. This is useful to test data communication latency.	`true`, `false`
debug_common	Enable general debug log outputs	`true`, `false`
debug_video_depth	Enable videodebug log outputs	`true`, `false`
debug_camera_controls	Enable camera controls debug log outputs	`true`, `false`
debug_sensors	Enable sensors debug log outputs	`true`, `false`
debug_streaming	Enable streaming debug log outputs	`true`, `false`
debug_advanced	Enable advanced debug log outputs	`true`, `false`
debug_nitros	Enable Nitros debug log outputs	`true`, `false`
disable_nitros	If available, disable NITROS usage for debugging and testing purposes	`true`, `false`

Dynamic parameters

The ZED node lets you reconfigure many parameters dynamically during the execution of the node. All the dynamic parameters are indicated with a ^* in the list above and with the tag [DYNAMIC] in the comments of the YAML files.

You can set the parameters using the CLI command ros2 param set, e.g.:

$ ros2 param set /zed/zed_node video.exposure_time 5000

if the parameter is set successfully, you will get a confirmation message:

$ Set parameter successful

In the case you tried to set a parameter that’s not dynamically reconfigurable, or you specified an invalid value, you will get this type of error:

$ ros2 param set /zed/zed_node video.exposure_time 0
$ Setting parameter failed: Parameter {video.exposure_time} doesn't comply with integer range.

and the ZED node will report a warning message explaining the error type:

You can also use the Configuration -> Dynamic Reconfigure plugin of the rqt tool to dynamically set parameters by using a graphic interface.

Transform frames

The ZED ROS 2 wrapper broadcasts multiple coordinate frames that each provides information about the camera’s position and orientation. If needed, the reference frames can be changed in the launch file.

<camera_name>_camera_link is the current position and orientation of the ZED base center. It corresponds to the bottom central fixing hole.
<camera_name>_camera_center is the current position and orientation of ZED middle baseline, determined by visual odometry and the tracking module.
<camera_name>_camera_frame is the position and orientation of the ZED’s CMOS sensor.
<camera_name>_camera_optical is the position and orientation of the ZED’s camera optical frame.
<camera_name>_imu_link is the origin of the inertial data frame (not available with ZED).

Frames

Services

The ZED node provides the following services:

~/enable_streaming: enable/disable a local streaming server.

Services can be called using the rqt graphical tool by enabling the plugin Plugins -> Services -> Service caller.

It is possible to call a service also by using the CLI command ros2 service call.

For example to start Object Detection for the ZED2 camera:

$ ros2 service call /zed/zed_node/enable_streaming std_srvs/srv/SetBool "{data: True}"

and the service server will reply:

$ requester: making request: std_srvs.srv.SetBool_Request(data=True)
$ 
$ response:
$ std_srvs.srv.SetBool_Response(success=True, message='Streaming Server started')

Assigning a GPU to a camera

To improve performance, you can specify the gpu_id of the graphic card that will be used for the depth computation in the common_mono.yaml configuration file. The default value (-1) will select the GPU with the highest number of CUDA cores. When using multiple ZEDs, you can assign each camera to a GPU to increase performance.