Elaboration takes longer, lower the 'frame_rate'

flabrosse · September 12, 2022, 4:04pm

All,

I’m running a ZED2i on a Jetson nano through ROS1 with a recent version of the ZED software as well as ROS. I get lots of

Elaboration takes longer (0.139038 sec) than the requested FPS rate (0.066666667 sec). Please consider to lower the 'frame_rate' setting or to reduce the power requirements reducing the resolutions

There is no “frame_rate” setting that I can see. There are quite a few rate and freq settings, but none have a value of 15. I have also inspected all the dynamic ones using the parameter server and none have a value of 15. Which am I supposed to change?

Cheers,
Fred

Myzhar · September 13, 2022, 2:03pm

The parameter is grab_frame_rate:

github.com

stereolabs/zed-ros-wrapper/blob/master/zed_wrapper/params/common.yaml#L27

    
      
          depth_confidence:           30                                  # Dynamic
          depth_texture_conf:         100                                 # Dynamic
          pub_frame_rate:             15.0                                # Dynamic - frequency of publishing of video and depth data
          point_cloud_freq:           10.0                                # 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:            15                              # 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:      0.5                             # 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]

The real problem is that your main loop is running at ~7 Hz, which is less than the minimum available ZED frame rate (15 FPS).

What is the resolution that you are using? What modules are you using?
Did you start the jetson_clocks script?

flabrosse · September 13, 2022, 2:25pm

Thank you for confirming which parameter it is. Before answering your questions however, this parameter is set to 10 in my config file (confirmed by rosparam get). Why is it asking for 15?

I use VGA resolution, I have position tracking. I have experimented with mapping or not and that makes no difference.

jetson_clocks shows the power mode is MAXN. Current freqs are all at the max allowed. This is on a Jetson nano.

Myzhar · September 14, 2022, 8:43am

For grab_frame_rate you must use one of the values allowed by the ZED SDK: 15, 30, 60, 100.

You can instead change the rate of the message publishing: pub_frame_rate

flabrosse · September 14, 2022, 8:54am

So I can’t specify slower than 15Hz. That explains it. I’m pretty sure my pub_frame_rate is also lower, but I can’t check right now.

But why is it I can’t process faster than 7Hz?

flabrosse · September 14, 2022, 2:20pm

I confirm, pub_frame_rate is set to 10 and point_cloud_freq is set to 8. So I still don’t understand the message.

Myzhar · September 14, 2022, 2:44pm

The message is related to the “grab time”. It says that your configuration is too hard for your hardware because it cannot reach the 15 FPS required for “grabbing”.