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Streaming to Twitch using OpenBSD

Written by Solène, on 06 July 2019.
Tags: #openbsd66 #gaming

Comments on Mastodon


If you ever wanted to make a twitch stream from your OpenBSD system, this is now possible, thanks to OpenBSD developer thfr@ who made a wrapper named fauxstream using ffmpeg with relevant parameters.

The setup is quite easy, it only requires a few steps and searching on Twitch website two informations, hopefully, to ease the process, I found the links for you.

You will need to make an account on twitch, get your api key (a long string of characters) which should stay secret because it allow anyone having it to stream on your account.

Preparation steps

  1. Register / connect on twitch
  2. Get your Stream API key at https://www.twitch.tv/YOUR_USERNAME/dashboard/settings (from this page you can also choose if twitch should automatically saves streams as videos for 14 days)
  3. Choose your nearest server from this page
  4. Add in your shell environnement a variable TWITCH=rtmp://SERVER_FROM_STEP_3/YOUR_API_KEY
  5. Get fauxstream with cvs -d anoncvs@anoncvs.thfr.info:/cvs checkout -P projects/fauxstream/
  6. chmod u+x fauxstream/fauxstream
  7. Allow recording of the microphone
  8. Allow recording of the output sound

Once you have all the pieces, start a new shell and check the $TWITCH variable is correctly set, it should looks like rtmp://live-ams.twitch.tv/app/live_2738723987238_jiozjeoizaeiazheizahezah (this is not a real api key).

Using fauxstream

fauxstream script comes with a README.md file containing some useful informations, you can also check the usage

View usage:

$ ./fauxstream

Starting a stream

When you start a stream, take care your API key isn’t displayed on the stream! I redirect stderr to /dev/null so all the output containing the key is not displayed.

Here is the settings I use to stream:

$ ./fauxstream -m -vmic 5.0 -vmon 0.2 -r 1920x1080 -f 20 -b 4000 $TWITCH 2> /dev/null

If you choose a smaller resolution than your screen, imagine a square of that resolution starting at the top left corner of your screen, the content of this square will be streamed.

I recommend bwm-ng package (I wrote a ports of the week article about it) to view your realtime bandwidth usage, if you see the bandwidth reach a fixed number this mean you reached your bandwidth limit and the stream is certainly not working correctly, you should lower resolution, fps or bitrate.

I recommend doing a few tries before you want to stream, to be sure it’s ok. Note that the flag -a may be be required in case of audio/video desynchronization, there is no magic value so you should guess and try.

Adding webcam

I found an easy trick to add webcam on top of a video game.

$ mpv --no-config --video-sync=display-vdrop --framedrop=vo --ontop av://v4l2:/dev/video1

The trick is to use mpv to display your webcam video on your screen and use the flag to make it stay on top of any other window (this won’t work with cwm(1) window manager). Then you can resize it and place it where you want. What you see is what get streamed.

The others mpv flags are to reduce lag between the webcam video stream and the display, mpv slowly get a delay and after 10 minutes, your webcam will be lagging by like 10 seconds and will be totally out of sync between the action and your face.

Don’t forget to use chown to change the ownership of your video device to your user, by default only root has access to video devices. This is reset upon reboot.

Viewing a stream

For less overhead, people can watch a stream using mpv software, I think this will require youtube-dl package too.

Example to view me streaming:

$ mpv https://www.twitch.tv/seriphyde

This would also work with a recorded video:

$ mpv https://www.twitch.tv/videos/447271018