Large Latency in Images about zethus

[seadeep42]

Hi,
Zethus visualizes the topic messages received through rosbridge websocket but web_video_server serves raw video packets to the client over http. The delay might be at roslibjs.

We'll look into it and come up with a solution by tomorrow. Would it be possible to provide more information - the dimensions of image and the frequency it's published at.

Thank you

[WesleyYue]

We're publishing 720p images using cv_camera at 30hz

[tocttou]

@WesleyYue I tried to use cv_camera with my webcam:

rosparam set cv_camera/device_id 0
rosrun cv_camera cv_camera_node]

This seems to be working fine without any latency! (although I did not try publishing from the docker env).

Demo: https://i.imgur.com/qrNG1XG.mp4

Couple of questions:

1. is there a latency only or some lag as well (also what is the FPS shown in Zethus)?
2. would it be possible to reproduce the environment somehow?

[tocttou]

@WesleyYue we are adding an option to display the image stream directly from web_video_server as an option. Should be available tomorrow.

[tocttou]

@WesleyYue you can use ImageStream visualization type instead of Image in latest Zethus.
ImageStream takes a stream URL from the web_video_server.

I did find some lag when the video is kept running using the Image viz, and it seems that it can be attributed to the slow link between Zethus and the rosbridge server.