Shairport-Sync (Airplay2) on OpenWRT - How To

Installing and Using OpenWrt
1

I just found out that OpenWRT can be used as Apple Airplay2 Receiver via shairport-sync.

Audio is a bit finicky to setup, if you are unfamiliar with Linux audio (like me :grinning_face_with_smiling_eyes: ). I also could not find useful step-by-step instructions.

Here is what I found, after some hours of experiments, to get it up and running (for me it worked on OpenWRT 24 and 25, on a Raspberry and a x86 device). Maybe it is helpful for someone else.

Restrictions:

  • you need ~40MB (!) of free space on the OpenWRT device, as it needs FFMPEG to be installed. So you may need to configure extroot-on-USB on plastic routers first.
  • there is no LuCi GUI

You need to connect Linux-ALSA-supported audio hardware:

  • any USB-Audio-adapter or USB-soundcard will do, as this is a generic standard (a simple adapter might have come as headphone-jack-to-USB adapter with your mobile phone)
  • or a X86 device with on-mainboard HD-Audio-Audio-chip
  • or a Raspberry (like the 4) with built-in audio output jack
    (I have not tested, whether HDMI output would work)

Install ALSA audio driver:

  • RaspberryPi4: BMC audio packages are already contained in default OpenWRT image
  • x86 with Realtek audio chip: packages kmod-snd-hda-scodec-component kmod-sound-core kmod-sound-hda-core kmod-sound-hda-codec-realtek
  • USB sound card: package kmod-usb-audio kmod-usb2 kmod-usb3
  • other audio hardware: check if the packageskmod-sound-* have anything matching your audio hardware

Install ALSA utils:

  • Install package alsa-utils: one of the contained tools is alsamixer, you will likely need this, to configure your sound card audio mixer, before you are able to hear any audio output.

Install the service:

  • Install the package shairport-sync-mbedtls (or one of its other two variants, depending on which SSL library you are using on your OpenWRT device)

Configure the audio mixer channels of the sound card:

  • Make sure to have rebooted once after installing the modules, then run alsamixer.
  • Use F6 to select the audio adapter.
  • Iterate through all mixers and set each to the max volume using the cursor keys.
  • Pay attention to the line xOOx or xMMxunder each mixer channel. If any of it says xMMx, this means, the channel is muted, if so, you need to use the m-key to unmute the channel.
  • The config gets autosaved, when you exit via ESC-key.

Understand that there are 3 shairport-sync usage variants on OpenWRT:

  1. /etc/init.d/shairport-sync + config file /etc/config/shairport-sync
  2. /etc/init.d/shairport-sync + config file /etc/config/shairport-sync + config file /etc/shairport-sync.conf
  3. /usr/bin/shairport-sync + config file /etc/shairport-sync.conf

I will refer to variant 1 for the following steps.

Check if shairport-sync can successfully detect the audio hardware:
Run /usr/bin/shairport-sync -h.
On x86 hardware with onboard sound chip, the end of the output will look like:

hardware output devices:
"hdmi:PCH"

on a Raspberry 4 with an additional USB-analogue dongle, the output will look like:

hardware output devices:
"hw:Audio" (<- this was an USB audio dongle in my case)
"hw:Headphones" (<- this was the RPI4 integrated headphone jack)

Configure and run shairport-sync:
Step 1: If you only have a single audio device, you can safely skip step 1. If you have multiple audio devices, you need to tell Shairport-sync which of the audio devices it is supposed to use:
To do so, edit /etc/config/shairport-sync and
in section config shairport-sync 'shairport_sync', set the output device to one of the previously detected audio device:
option alsa_output_device 'hw:Audio'

Step 2: In /etc/config/shairport-sync
in the default sectionconfig shairport-sync 'shairport_sync'
enable the config via:
option enabled '1'

Step 3: Start the OpenWRT shairport-sync daemon:
/etc/init.d/shairport-sync enable
/etc/init.d/shairport-sync start

Done. You should now find a new working Airplay2 receiver target in your Apple device music app.

Troubleshooting:

  • x86: make sure the sound chip is in enabled in BIOS
  • any: if no audio hardware was found, verify, if all required modules are installed.
  • any: check the config of alsamixer again.
  • any: take a look, if the output of the additional diagnostic tools amixer, aplay -l, aplay -L are of any help (the utils are also part of the package alsa-utils).
  • USB soundcards and USB audio dongles: lsusb (Package usbutils) must list the device.
  • USB soundcards and USB audio dongles: You can use Windows 11, to verify, if the adapter is working properly. Without having to install any Windows drivers, the device manager devmgmt.msc should list a new USB audio device in the “Sound, video and game controllers” section. The Sound Manager mmsys.cpl should list an additional output device in the “Playback” tab. Under its context menu->Configure, you can test play a test sample and under its context menu->Properties-> Advanced, you can check the supported hardware specs.