Use a SRT server to stream video from different networks

[jean-michel-gonet]

Why?

After #4, we're able to stream video from the phone to a computer that is listening. But this setup won't work if the two devices have private IP in different networks.

The solution is using a SRT server:

• The SRT server has a public IP address.
• Both the mobile and the target computer connect to the SRT server.
• The SRT server relays the video stream from one to the other.

Condition of satisfaction

Write a procedure describing how to:

• Install a SRT server application on a cloud computer (for example Linode)
• Connect the mobile and the target computer to it.
• Stream video.
• Display video on the target computer with some ready made application.

Hints:

Ubuntu + Nimble

According to their creators, Nimble is:

• Nimble Streamer provides wide feature set for live streaming via various protocols including SRT, RTMP, WebRTC with WHIP ingest and WHEP ABR playback, subtitles, Dante® audio support, Zixi, NDI® and Apple Low Latency HLS with codecs like H.264, HEVC, AV1 and more.
• https://softvelum.com/nimble/

This is a tutorial on how to install a SRT server on Ubuntu using Nimble.

• It shows some criteria to choose the right server (tldr; choose the smallest one)
• It shows a step-by-step installation
• https://youtu.be/tGLNsWTPkwQ?si=LVzEejHEumnLLV5H

Ubuntu + srt-live-server

There is another library that can act as a SRT server:

• srt-live-server(SLS) is an open source live streaming server for low latency based on Secure Reliable Tranport(SRT). Normally, the latency of transport by SLS is less than 1 second in internet.
• https://gitlab.com/mattwb65/srt-live-server

This is a tutorial to install SLS on an Ubuntu server:

• https://www.ionos.com/digitalguide/server/know-how/srt-server-creation/
• It also shows how to test it.

[jean-michel-gonet]

It turns out that:

• There are no free SRT servers that are robust:
  • I was never able to use SLS. I don't even believe it works.
  • Nimble probably works, but you need a subscription. As of today, it's 30$/month. That's too expensive for a toy project.

But, there is an alternative solution:

• Most home routers allow WireGuard or IPSec VPN.
• Setting up a VPN connection allows to connect the mobile phone to the home network.
• In this case, no need of SRT servers: the IP addresses of the devices in home network become addressable from the phone, just as if it were connected to the WiFi.