Title: Stream your OpenBSD desktop audio to other devices

	Title: Stream your OpenBSD desktop audio to other devices
	Author: Solène
	Date: 05 May 2023
	Tags: openbsd streaming icecast hacking
	Description: In this article, you will learn how to set up icecast or
	pulseaudio to broadcast your OpenBSD system audio to a remote system
	(and make use of bluetooth)

	# Introduction

	Hi, back on OpenBSD desktop, I miss being able to use my bluetooth
	headphones (especially the Shokz ones that allow me to listen to music
	without anything on my ears).

	Unfortunately, OpenBSD doesn't have a bluetooth stack, but I have a
	smartphone (and a few other computers), so why not stream my desktop
	sound to another device with bluetooh? Let's see what we can do!

	I'll often refer to the "monitor" input source, which is the name of an
	input that provides "what you hear" from your computer.

	While it would be easy to just allow a remote device to play music
	files, I want to stream the computer's monitor input, so it could be
	litteraly anything, and not just music files.

	This method can be used on any Linux distribution, and certainly on
	other BSDs, but I will only cover OpenBSD.

	# The different solutions

	## Icecast

	One simple setup is to use icecast, the program used by most web
	radios, and ices, a companion program to icecast, in order to stream
	your monitor input to the network.

	The pros:

	* it works with anything that can read OGG from the network (any
	serious audio client or web browser can do this)
	* it's easy to set up
	* you can have multiple clients at once
	* secure (icecast is in a chroot, and other components are sending data
	or playing music)

	The cons:

	* there is a ~10s delay, which prevents you from watching a video on
	your computer and listening the audio from another device (you could
	still set 10s offset, but it's not constant)
	* reencoding happens, which can slightly reduce the sound quality (if
	you are able to tell the difference)

	## Sndiod

	The default sound server in OpenBSD, namely sndiod, supports network
	streaming!

	Too bad, if you want to use Bluetooth as an output, you would have to
	run sndiod on Linux (which is perfectly fine), but you can't use
	Bluetooth with sndiod, even on Linux.

	So, no sndiod. Between two OpenBSD, or OpenBSD and Linux, it works
	perfectly well without latency, and it's a super simple setup, but as
	Bluetooth can't be used, I won't cover this setup.

	The pros:

	* easy to setup
	* works fine

	The cons:

	* no android support

	## Pulseaudio

	This sound server is available as a port on OpenBSD, and has two
	streaming modes: native-protocol-tcp and RTP, the former is exchanging
	pulseaudio internal protocol from one server to another which isn't
	ideal and prone to problems over a bad network, the latter being more
	efficient and resilient.

	However, the RTP sender doesn't work on OpenBSD, and I have no interest
	in finding out why (the bug doesn't seem to be straightforward), but
	the native protocol works just fine.

	The pros:

	* almost no latency (may depend of the network and remote hardware)
	* easy to setup

	## Snapcast

	Snapcast is an amazing piece of software that you can use to broadcast
	your audio toward multiple other client (using snapcast or a web page)
	with the twist that the audio will be synchronized on each client,
	allowing a multi room setup at no cost.

	Unfortunately, I've not been able to build it on OpenBSD :(

	The pros:

	* multi room setup with synchronized clients
	* compatible with almost any client able to display an HTML5 page

	The cons:

	* playback latency
	* not so easy to setup

	# Setup

	Here are the instructions to setup different solutions.

	## Pulseaudio

	### Client setup (OpenBSD)

	On the local OpenBSD, you need to install `pulseaudio` and `ffmpeg`
	packages.

	You also need to set sndiod flags, using `rcctl set sndiod flags -s
	default -m play,mon -s mon`, this will allow you to use the monitor
	input through the device `snd/0.mon`.

	Now, when you want to stream your monitor to a remote pulseaudio, run
	this command in your terminal:

	```
	ffmpeg -f sndio -i snd/0.mon -ar 44100 -f s16le - \| pacat -s 10.42.42.199 --raw…
	```

	The command is composed of two parts:

	* ffmpeg reading the monitor input and sending it to the pipe
	* pacat (pulseaudio cat) relaying the pipe input to the pulseaudio
	server 10.42.42.199, with some tweaks to reduce the latency

	## Server setup (the device with bluetooth)

	The setup is easy, but note that this doesn't involve any
	authentication or encryption, so please use this on trusted network, or
	through a VPN.

	On a system with pulseaudio, type:

	```
	pacmd load-module module-native-protocol-tcp auth-anonymous=1 auth-ip-acl=192.1…
	```

	This will load the module accepting network connections, the
	`auth-anonymous` option is there to simplify connection to the server,
	otherwise you would have to share the pulseaudio cookie between
	computers, which I recommend doing but on a smartphone this can be
	really cumbersome to do, and out of scope here.

	The other option is pretty obvious, just give a list of IPs you want to
	allow to connect to the server.

	If you want the changes to be persistent, edit `/etc/pulse/default.pa`
	to add the line `load-module module-native-protocol-tcp
	auth-anonymous=1 auth-ip-acl=192.168.1.0/24`.

	On Android, you can install pulseaudio using Termux (available on
	f-droid), using the commands:

	```
	pkg install pulseaudio
	pulseaudio --start --exit-idle-time=3600
	pacmd load-module module-native-protocol-tcp auth-anonymous=1 auth-ip-acl=192.1…
	```

	There is a project named PulseDroid, the original project has been
	unmaintained for 13 years, but someone took it back quite recently,
	unfortunately no APK are provided, and I'm still trying to build it to
	try, it should provide an easier user experience to run pulseaudio on
	Android.

	PulseDroid gitlab repository

	## Icecast

	Using icecast, you will have to setup an icecast server, and locally
	use ices2 client to broadcast your monitor input. Then, any client can
	play the stream URL.

	Install the component using:

	```
	pkg_add icecast ices--%ices2
	```

	### Server part

	As suggested by the file `/usr/local/share/doc/pkg-readmes/icecast`,
	run the following commands to populate icecast's chroot:

	```
	cp -p /etc/{hosts,localtime,resolv.conf} /var/icecast/etc
	cp -p /usr/share/misc/mime.types /var/icecast/etc
	```

	Edit `/var/icecast/icecast.xml`:

	* in the `<authentication>` node, change all the passwords. The only
	one you will need is the `source` password used to send the audio to
	icecast, but set all other passwords to something random.
	* in the `<hostname>` node, set the IP or hostname of the computer with
	icecast.
	* add a `<bind-address>` node to `<listen-socket>` using the example
	for 127.0.0.1, but use the IP of the icecast server, this will allow
	other to connect.

	Keep in mind this is the bare minimum for a working setup, if you want
	to open it to the wide Internet, I'd strongly recommend reading icecast
	documentation before. Using a VPN may be wiser if it's only for private
	use.

	We can start icecast and set it to start at boot:

	```shell
	rcctl enable icecast
	rcctl start icecast
	```

	### Broadcast part

	Then, to configure ices2, copy the file
	`/usr/local/share/examples/ices2/ices-sndio.xml` somewhere you feel
	comfortable for storing user configuration files. The example file is
	an almost working template to send sndio sources to icecast.

	Edit the file, under the `<instance>` node:

	* modify `<hostname>` with the hostname used in icecast.
	* modify `<password>` with the source password defined earlier.
	* modify `<mount>` to something ending in `.ogg` of your liking, this
	will be the filename in the URL (can be `/stream.ogg` if you are out of
	ideas).
	* set `<yp>` to 0, otherwise the stream will appear on the icecast
	status page (you may want to have it displayed though).

	Now, search for `<channels>` and set it to 2 because we want to
	broadcast stereo sound, and set `<downmix>` to 0 because we don't need
	to merge both channels into a mono output. (If those values aren't in
	sync, you will have funny results =D)

	When you want to broadcast, run the command:

	```shell
	env AUDIORECDEVICE=snd/0.mon ices2 ices-sndio.xml
	```

	With any device, open the url `http://<hostname>:8000/file.ogg` with
	`file.ogg` being what you've put in `<mount>` earlier. And voilà, you
	have a working local audio streaming!

	# Limitations

	Of course, the setup isn't ideal, you can't use your headset microphone
	or buttons (using MPRIS protocol).

	# Conclusion

	With these two setup, you have a choice for occasionnaly streaming your
	audio to another device, which may have bluetooth support or something
	making it interesting enough to go through the setup.

	I'm personally happy to be able to use bluetooth headphones through my
	smartphone to listen to my OpenBSD desktop sound.

	# Going further

	If you want to directly attach bluetooth headphones to your OpenBSD,
	you can buy an USB dongle that will pair to the headphones and appear
	as a sound card to OpenBSD.

	jcs@ article about Bluetooth audio on OpenBSD