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WebRTC H.264

This is the default mode. It'is using the efficient H.264 encoding to save traffic. The video is streamed over WebRTC protocol which you may have encountered when you used video calls in Discord or Google Chat.

It is available on PiKVM V3, V4 Plus/Mini and all DIYdevices based on HDMI-CSI bridge.

The video mode can be switched in the System menu in the Web UI. If you don't see the switch, probably your browser does not support H.264 video.

How it's working

The Direct H.264 or MJPEG video is streaming video using the similar HTTP connection like to get the Web UI. This means that for remote access, you just need to forward only ports 80 and 443 on your router it has public external IP address.

In contrast, WebRTC is a completely different way of transmitting video. It uses a P2P connection and UDP. This reduces network load, but makes it difficult to connect - the PiKVM needs to know your network configuration in order to use it correctly: public IP, NAT type and so on.

To achieve this, the PiKVM checks which of the network interfaces is used for the default gateway, and tries to find out your external IP address using the Google STUN server.

Tip

Google STUN servers was choosen for reliability reasons.

If you don't want to use it, you can choose any other public STUN server you like, or set up your own.

To change the STUN server, edit /etc/kvmd/override.yaml (an example):

janus:
    stun:
        host: stun.stunprotocol.org
        port: 3478

... and restart kvmd-janus service using systemctl restart kvmd-janus.

Custom Janus config

Janus is a WebRTC gateway that is used to transmit the video from PiKVM uStreamer. PiKVM has a special service named kvmd-janus which is a wrapper for Janus that monitors the network configuration and applies changes.

However, if your PiKVM is not connected to the Internet and/or you want to use a custom Janus configuration, you should run the kvmd-janus-static service instead.

The configuration is located in /etc/kvmd/janus/janus.jcfg. You can change all you need according to the Janus Documentation, stop the kvmd-janus and start the kvmd-janus-static service:

[root@pikvm ~]# systemctl disable --now kvmd-janus
[root@pikvm ~]# systemctl enable --now kvmd-janus-static

Troubleshooting

In some cases, WebRTC may not work. Here some common tips:

  • Clear the browser cache.

  • Try any other browser, incognito or private window without any extensions.

  • Tricky IPv6 configuration on the network can be a problem. IPv6 support for WebRTC in PiKVM is still in its infancy, so if your network has IPv4, it will be easiest to disable IPv6 on PiKVM. To do this, switch the file system to write mode using rw command, add option ipv6.disable_ipv6=1 to /boot/cmdline.txt and perform reboot. Also see here.

  • A paranoid firewall can interfere too when you try to connect to the PiKVM by forwarding port 443 to the Internet from the internal network. WebRTC is not enough of this, it uses UDP on ports 20000-40000 for a P2P connection. Make sure that the Firewall does not block them.

  • If nothing helps, open the browser's JavaScript console, look at the log and contact our community via Discord. Developers and/or experienced users will definitely help you.