ZED topic rate drops

[kushal2507]

I am running 2 PCs with two zed2 cameras on each. The computers are connected to each other through a high speed gigabit network. So essentially, one pc is the master and the other one is the slave.

The ZED camera on the host pc publishes topics at the specified rate but the same topic when viewed on the other pc gives me half the rate. At this moment I have not even started subscribing to these topics.

I use rostopic hz to view the publishing rate.

PC specs (identical for both pcs) - intel i7 11th gen 64gb ram nvidia rtx 2060 6GB ROS Melodic Ubuntu 18.04

[Myzhar]

Hi @kushal2507 can you provide more information about the topic that you are subscribing to? This seems a bandwidth problem not strictly related to the ZED Wrapper...

[kushal2507]

I'm subscribing to the pointcloud topic. I set it to 15Hz in the common.yaml file but I am receiving onl 7.5-8Hz when viewing the rate on the other PC. We have a gigabit switch and a gigabit router for our networking.

[Myzhar]

What resolution? You can also try $ rostopic bw <topic> to monitor the bandwidth

[kushal2507]

RGB - 720 p Depth - Performance I am trying to publish images and pointcloud at 15Hz.

I tried rostopic bw /zed2/zed_node/point_cloud/cloud_registered

Host PC - average: 221.42MB/s mean: 14.75MB min: 14.75MB max: 14.75MB window: 12 Other PC - 118.52MB/s mean: 14.75MB min: 14.75MB max: 14.75MB window: 54

[Myzhar]

@kushal2507 221.42 MB/s is more than 1 Gbit/s, it's ~1.73 Gbit/s On the remote PC indeed you get 118.52 MB/s that's ~1Gbit/s (a bit lower, but there is other traffic on the network)

[kushal2507]

Remote PC : average: 58.98MB/s mean: 3.69MB min: 3.69MB max: 3.69MB window: 14

Host PC : average: 57.13MB/s mean: 3.69MB min: 3.69MB max: 3.69MB window: 30

I get the above results if I check the left/image_rect_color image topic. The rate of publishing is also constant at 15 Hz.

The descripancy is happening only with the point cloud topic from what I can see.

What would you suggest I do? Look into a new network switch? Or are there any settings I can change within ZED or ROS for that matter?

[Myzhar]

Can you copy and paste here your common.yaml file?

[kushal2507]

params/common.yaml

Common parameters to Stereolabs ZED and ZED mini cameras

---

Dynamic parameters cannot have a namespace

brightness: 4 # Dynamic contrast: 4 # Dynamic hue: 0 # Dynamic saturation: 4 # Dynamic sharpness: 4 # Dynamic gamma: 8 # Dynamic - Requires SDK >=v3.1 auto_exposure_gain: true # Dynamic gain: 100 # Dynamic - works only if auto_exposure_gain is false exposure: 100 # Dynamic - works only if auto_exposure_gain is false auto_whitebalance: true # Dynamic whitebalance_temperature: 42 # Dynamic - works only if auto_whitebalance is false depth_confidence: 50 # Dynamic depth_texture_conf: 100 # Dynamic pub_frame_rate: 15.0 # Dynamic - frequency of publishing of video and depth data point_cloud_freq: 15.0 # Dynamic - frequency of the pointcloud publishing (equal or less to grab_frame_rate value)

general: camera_name: zed # A name for the camera (can be different from camera model and node name and can be overwritten by the launch file) zed_id: 0 serial_number: 0 resolution: 2 # '0': HD2K, '1': HD1080, '2': HD720, '3': VGA grab_frame_rate: 30 # Frequency of frame grabbing for internal SDK operations gpu_id: -1 base_frame: 'base_link' # must be equal to the frame_id used in the URDF file verbose: false # Enable info message by the ZED SDK svo_compression: 2 # 0: LOSSLESS, 1: AVCHD, 2: HEVC self_calib: true # enable/disable self calibration at starting camera_flip: false

video: img_downsample_factor: 1.0 # Resample factor for images [0.01,1.0] The SDK works with native image sizes, but publishes rescaled image. extrinsic_in_camera_frame: true # if false extrinsic parameter in camera_info will use ROS native frame (X FORWARD, Z UP) instead of the camera frame (Z FORWARD, Y DOWN) [true use old behavior as for version < v3.1]

depth: quality: 2 # '0': NONE, '1': PERFORMANCE, '2': QUALITY, '3': ULTRA sensing_mode: 0 # '0': STANDARD, '1': FILL (not use FILL for robotic applications) depth_stabilization: 1 # 0: disabled, 1: enabled openni_depth_mode: false # 'false': 32bit float meters, 'true': 16bit uchar millimeters depth_downsample_factor: 1.0 # Resample factor for depth data matrices [0.01,1.0] The SDK works with native data sizes, but publishes rescaled matrices (depth map, point cloud, ...)

pos_tracking: pos_tracking_enabled: true # True to enable positional tracking from start publish_tf: true # publish odom -> base_link TF publish_map_tf: true # publish map -> odom TF map_frame: 'map' # main frame odometry_frame: 'odom' # odometry frame area_memory_db_path: 'zed_area_memory.area' # file loaded when the node starts to restore the "known visual features" map. save_area_memory_db_on_exit: false # save the "known visual features" map when the node is correctly closed to the path indicated by area_memory_db_path area_memory: true # Enable to detect loop closure floor_alignment: false # Enable to automatically calculate camera/floor offset initial_base_pose: [0.0,0.0,0.0, 0.0,0.0,0.0] # Initial position of the base_frame -> [X, Y, Z, R, P, Y] init_odom_with_first_valid_pose: true # Enable to initialize the odometry with the first valid pose path_pub_rate: 2.0 # Camera trajectory publishing frequency path_max_count: -1 # use '-1' for unlimited path size two_d_mode: false # Force navigation on a plane. If true the Z value will be fixed to "fixed_z_value", roll and pitch to zero fixed_z_value: 0.00 # Value to be used for Z coordinate if two_d_mode is true

mapping: mapping_enabled: false # True to enable mapping and fused point cloud pubblication resolution: 0.05 # maps resolution in meters [0.01f, 0.2f] max_mapping_range: -1 # maximum depth range while mapping in meters (-1 for automatic calculation) [2.0, 20.0] fused_pointcloud_freq: 1.0 # frequency of the publishing of the fused colored point cloud

[Myzhar]

OK, like I supposed you are using the default parameters, so it's correct that the topic rate is ~15Hz. There is more than a parameter to set the topic rate:

• grab_frame_rate: it's the grabbing rate of the ZED SDK. This can be higher than the publishing rate
• pub_frame_rate: publishing rate of the RGB and depth topics. This can be equal/lower than grab_frame_rate. This is a dynamic parameter
• point_cloud_freq: publishing rate of the point cloud topic. This can be equal/lower than grab_frame_rate. This is a dynamic parameter

You can get the full description of all the parameters on the online documentation: https://www.stereolabs.com/docs/ros/zed-node/#zed-parameters

Regarding the point cloud, if the bandwidth is not enough you can switch to openni mode setting the openni_depth_mode to true. In this way, 16-bit unsigned int values will be used for the points coordinates instead of 32-bit floating-point values. Be aware that openni mode will provide points coordinate in millimeters and not in meters. You can read more in the official ROS REP108 document

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