PulseAudio on OpenWRT with MPD and other Stuff

First of all, good to be back. Issues with MediaWiki, along with time constraints on fixing it, have prevented new articles from being created.

Anyway, working on several different Routers running OpenWRT 23.05.03 using PulseAudio, MPD (MPC), Bluetooth (BlueZ), and a bunch of other stuff including PulseMixer (works great on OpenWRT, even though the 'required' version is above the version of Python3 available in OpenWRT).

Starting Thoughts

The PulseAudio people are brilliant. But their documentation is a bit questionable. Case in point is the https://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/User/Network/ page. It starts off on a big tangent, then seems to go off on other tangents before addressing the main concepts. That's cool and not a complaint against the PulseAudio people. It's just a little note to let people know who are reading it and just want to get RTP to work that they shouldn't get frustrated. Just keep reading, ignore most of the stuff at the beginning and you'll get there.

A Deep, Deep Hole with PulseAudio at the Very Beginning (on OpenWRT)

The nice people with the OpenWRT project and all their hard work is very much appreciated. But there are also the head scratching (and head exploding) moments too. For instance: How can so much effort be put into something, yet one little item is allowed to (or isn't configured correctly) remain in place that prevents the PulseAudio service from operating properly?

Short Answer: Configure and / or compile the PulseAudio Service in such way that it requires whatever user (including the ROOT User!) be a member of the audio Group. And then don't put that User in the Audio Group as part of the installation. There you go, problem created! And all the work done to include PulseAudio in OpenWRT? Pointless (until the issue is corrected).

The issue? As noted, the root User is not included in the audio Group. Add it in there using groupadd (which in and of itself is interesting to install) or just edit the /etc/group File.

Ready? Let's Install PulseAudio (and dependencies, plus other tools, and see what happens)

Installation of Software

opkg update

opkg install pulseaudio-daemon-avahi pulseaudio-profiles pulseaudio-tools

Do NOT install pulseaudio-daemon (plain), if you want to use Bluetooth to connect to Speakers. The pulseaudio-daemon-avahi contains the necessary bluetooth modules, pulseaudio-daemon (plain) does NOT. One can always disable the avahi service too, without affecting PulseAudio.

Dependencies include some basic ALSA (Advanced Linux Sound Architecture) stuff, but a couple of more items are nice to have for several reason, including testing, so;

opkg install alsa-utils alsa-ucm-conf mpd-full mpd-avahi-service mpc libmpdclient

...and maybe opkg install madplay mpg123 (they don't install any services, so they're just there if you need them)

And some other tools related to hardware: opkg install usbutils pciutils

A nice graphical way to control some aspects of PulseAudio is PulseMixer: https://github.com/GeorgeFilipkin/pulsemixer?tab=readme-ov-file

...but first: opkg install python3 (don't worry that the OpenWRT version of Python 3 is lower than the required version of PulseMixer, as it seems to work fine)

The Errors

Are these the errors referred to earlier as the "show stopper" for PulseAudio. Nope. Just an annoyance that can be fixed.

chown: /dev/mixer: No such file or directory
chown: /dev/dsp: No such file or directory
chmod: /dev/mixer: No such file or directory
chmod: /dev/dsp: No such file or directory

Will this fix it (spoiler alert, NO, so like Frankie said "don't do it")?: opkg install gst1-mod-dvdspu gst1-mod-audiomixer (a bunch of dependencies would be installed too). We'll get to the fix later, let's focus on the "Show Stopper"

The "Show Stopper" for PulseAudio

Issue this command (it is for 'talking' to the PulseAudio Service): pactl list short sinks

The result: Connection failure: Access denied

Why (as noted earlier, but more details and a solution later): The root User (that's right, the ROOT user) doesn't have the privileges to execute the command. WTF!?

How long did it take to figure out and what was the anger level: 10 Page Diatribe DELETED

Solution: Add the root user to the Audio Group: nano /etc/group;

Before: audio:x:29:
After: audio:x:29:root,mpd

Result: It forking works now: pactl list short sinks

There's a bunch of stuff about Cookies (one of PulseAudio's security methods), anonymous authentication, etc., but this is the simplest and works without changing PulseAudio's default configuration.

Bluetooth (AKA Bluez)

Installation

opkg install bluez-daemon bluez-libs bluez-tools bluez-utils bluez-utils-btmon bluez-utils-extra kmod-input-uinput (other dependencies will install too)

...and that's just the basic Bluetooth stuff. It doesn't include the firmware and driver for any specific hardware

Hardware

Bluetooth hardware is fairly inexpensive these days. To 'future-proof' things as much as possible, order hardware with the latest and greatest version of Bluetooth. As of this writing, summer 2024, Bluetooth 5.3 is the contemporary version.

A nice feature to have is a removable antenna. There are more compact devices that don't have removable antennas. And if you want super cheap device, step down to Bluetooth 4.x (still works great with speakers).

Bluetooth Controller - A nice feature to have is a removable Antenna.

Oh, one obnoxious note with Bluez and PulseAudio on OpenWRT is that as of this writing, even though Bluetooth 5.x supports two sets of speakers, just can't make a single controller connect to more than one speaker. Woof!

Example of installing firmware and drivers for Bluetooth Hardware: opkg install rtl8761bu-firmware (bu is the version of the rtl8761 that was designed to work with USB 2.0, so if you're hooking up to a USB 3.0 port, this will work, but according to documentation, won't be optimized. PS: Bluetooth to Speaker will not exceed USB 2.0 speeds).

Example to install Firmware and Drivers: opkg install rtl8761bu-firmware kmod-bluetooth kmod-usb-core kmod-usb2 kmod-usb3 kmod-usb-ohci kmod-usb-uhci kmod-usb-hid  kmod-hid kmod-cfg80211

FIRST! (or rather the next thing to do)

Because OpenWRT doesn't include of the Bluez Tools (nope, not Blues Clues), make sure PulseAudio has the Bluetooth Modules loaded up and ready to go!

Crap that Does NOT work

btmgmt "connect" (doesn't exist)

hcitool cc WhatEverMACaddress (doesn't work)

ALSA Related Commands

alsamixer: shows a text GUI of controls

aplay -l : shows list of sound devices

aplay -L : Shows a list of the various output ports

arecord -l : Shows a list of input / source devices (note, if PulseAudio is running and / or using a device it will show the device as 0, IE, 'unavailable')

arecord -L : Shows a 'limited' list of the input / source devices

amixer scontrols : Shows a 'brief' list of devices

amixer scontents : Shows a detailed list of devices

Example below;

amixer scontrols

Simple mixer control 'Speaker',0
Simple mixer control 'PCM',0
Simple mixer control 'PCM Capture Source',0
Simple mixer control 'Line',0
Simple mixer control 'Mic',0
Simple mixer control 'IEC958 In',0


amixer sdevices

Simple mixer control 'Speaker',0
  Capabilities: pvolume pswitch pswitch-joined
  Playback channels: Front Left - Front Right - Rear Left - Rear Right - Front Center - Woofer - Side Left - Side Right
  Limits: Playback 0 - 197
  Mono:
  Front Left: Playback 184 [93%] [-2.44dB] [on]
  Front Right: Playback 184 [93%] [-2.44dB] [on]
  Rear Left: Playback 196 [99%] [-0.19dB] [on]
  Rear Right: Playback 196 [99%] [-0.19dB] [on]
  Front Center: Playback 196 [99%] [-0.19dB] [on]
  Woofer: Playback 196 [99%] [-0.19dB] [on]
  Side Left: Playback 196 [99%] [-0.19dB] [on]
  Side Right: Playback 196 [99%] [-0.19dB] [on]
Simple mixer control 'PCM',0
  Capabilities: cvolume cswitch cswitch-joined
  Capture channels: Front Left - Front Right
  Limits: Capture 0 - 6928
  Front Left: Capture 4096 [59%] [-0.01dB] [on]
  Front Right: Capture 4096 [59%] [-0.01dB] [on]
Simple mixer control 'PCM Capture Source',0
  Capabilities: enum
  Items: 'Mic' 'Line' 'IEC958 In' 'Mixer'
  Item0: 'Line'
Simple mixer control 'Line',0
  Capabilities: pvolume cvolume pswitch pswitch-joined cswitch cswitch-joined
  Playback channels: Front Left - Front Right
  Capture channels: Front Left - Front Right
  Limits: Playback 0 - 8065 Capture 0 - 6928
  Front Left: Playback 4781 [59%] [-5.33dB] [off] Capture 4507 [65%] [1.60dB] [on]
  Front Right: Playback 4781 [59%] [-5.33dB] [off] Capture 4507 [65%] [1.60dB] [on]
Simple mixer control 'Mic',0
  Capabilities: pvolume cvolume pswitch pswitch-joined cswitch cswitch-joined
  Playback channels: Front Left - Front Right
  Capture channels: Front Left - Front Right
  Limits: Playback 0 - 8065 Capture 0 - 6928
  Front Left: Playback 5046 [63%] [-4.30dB] [off] Capture 2451 [35%] [-6.43dB] [on]
  Front Right: Playback 5046 [63%] [-4.30dB] [off] Capture 2451 [35%] [-6.43dB] [on]
Simple mixer control 'IEC958 In',0
  Capabilities: cswitch cswitch-joined
  Capture channels: Mono
  Mono: Capture [on]

The above output from the amixer scontrols and amixer sdevices command shows the following;

The 'Speaker' is actually a 7.1 Surround Sound USB Audio Device with several physical AUX / 1/8" / 3.5mm Output Jacks

The 'PCM' is a "CAPTURE" Device that does absolutely nothing on this device
The 'PCM Capture Source' is the currently selected input / source (mic, line, or SPDIF)
The 'Line' is represented physically by an AUX / 1/8" / 3.5mm Input Jack ("traditionally" blue)
The 'Mic' is represented physically by an AUX / 1/8" / 3.5mm Input Jack ("traditionally" pink), and on this device, there are actually two physical Jacks, but the software doesn't know this because the Jacks are simply wired in parallel.
The 'IEC958' is represented physically by the SPDIF Jack for a Fiber Optic Cable
...and for this device, the SPDIF output isn't represented to software and apparently is just 'wired' up like a "monitor", where it gets constant full output and cannot be controlled in software (oh, well)