Can't find /dev/video12 after running script on YOLO output

[cayleb247]

I have my camera feed streaming to the YOLO script with RSTP protocol. Everything seems like it was working smoothly until I try to connect to the device through the website. I am getting this error now.

terminate called after throwing an instance of 'std::runtime_error' what(): Failed to open v4l2 device: /dev/video12 Aborted

[TzuHuanTai]

Are you using pi 5? If so, please remove the flag --hw-accel. /dev/video12 is a hardware video scaler only available on pi 4 or zero 2w.

[cayleb247]

Thank you. That worked. I also had another question about how to best convert a rstp stream to a virtual camera or directly to the ./pi-webrtc script. All my methods are not working well. Thanks again!

[TzuHuanTai]

FFmpeg combined with v4l2loopback can turn an RTSP stream into a local virtual camera. But if you just want to bridge RTSP to WebRTC, MediaMTX might be the better choice.

[cayleb247]

Sounds good. Apologies for all the questions, but I am working on a research project, and this is my first time working with webRTC and streaming in general. I have a couple problems that I am facing, however. Please let me know if you can answer any of them.

1. How can I best run AI inference in a two pi system (4b and 5 with Hailo)?

What I've tried -- I've attempted to use mediaMTX to forward the stream via RTSP and that works fine. Have you used Hailo's software for hardware accelaration yet? They output a UDP stream, and I am not sure how to best use that stream in the webRTC MQTT system.

2. Why can't I access my stream from public internet?

A simple setup of the configuration and files on one Pi, as well as two, works fine on my network and on hotspots but things seem to be blocked once on a public network. How can I work around this? I've looked briefly at tailscale VPN but am stuck. Would Nginx help?

Apologies again for all the questions. I am a bit inexperienced. Thank you! This is great work.

[TzuHuanTai]

I didn't buy the AI HAT, so I'm not familiar with how Hailo works.
You might need to set up port forwarding for your pi on the router. If you just want to watch live streams, webrtc already has NAT hole punching for most cases. The turn server is required only if you're behind a symmetric NAT.

[cayleb247]

Do turn servers necessarily require a VPS? I am trying to set one up using coturn but am hitting deadends with the config. Do you have any examples of turn servers and piwebrtc? Thanks again for all the help.

[TzuHuanTai]

VPS is not a requirement. But if you don't have a public ip, it can save you time. Or sign up for a free managed services, such as cloudflare's turn service.
Here is the doc to set up a basic coturn. Then add turn-url turn-username, and turn-passwordflags when you run pi-webrtc. So does the client side.