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Automatically update an ALSA configuration as BlueALSA devices connect and disconnect

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BlueALSA ALSA Configuration Service and PCM Event Handler Service

Introduction

This project maintains two utilities (bluealsa-autoconfig and bluealsa-agent) which are designed to help simplify the management of the Bluetooth audio user experience when using BlueALSA. See The bluez-alsa project for more information on BlueALSA.

Important

This version supports only BlueALSA latest development sources, it is not compatible with BlueALSA 4.3.1 or earlier

bluealsa-autoconfig

bluealsa-autoconfig is a simple program to add and remove ALSA configuration nodes for BlueALSA Bluetooth PCM and CTL devices. It can also optionally simulate udev events on Bluetooth audio device connect and disconnect.

ALSA has built-in functions to add and remove PCM configuration nodes when sound cards are added or removed. However, it provides no equivalent functionality for software PCM types such as BlueALSA. This is unfortunate because Bluetooth audio devices are more likely to be disconnected during a session, so dynamic management of the ALSA configuration is even more important for Bluetooth than it is for sound cards.

bluealsa-autoconfig aims to rectify that situation by updating the ALSA configuration dynamically whenever a Bluetooth audio device connects or disconnects. So, for example, when no Bluetooth audio devices are connected, aplay -L may show:

$ aplay -L
default
    Default Audio Device
sysdefault:CARD=PCH
    HDA Intel PCH, ALC236 Analog
    Default Audio Device
surround21:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    2.1 Surround output to Front and Subwoofer speakers
surround40:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    4.0 Surround output to Front and Rear speakers
surround41:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers

And then when a Bluetooth device is connected:

$ aplay -L
default
    Default Audio Device
sysdefault:CARD=PCH
    HDA Intel PCH, ALC236 Analog
    Default Audio Device
surround21:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    2.1 Surround output to Front and Subwoofer speakers
surround40:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    4.0 Surround output to Front and Rear speakers
surround41:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
surround71:CARD=PCH,DEV=0
    HDA Intel PCH, ALC236 Analog
    7.1 Surround output to Front, Center, Side, Rear and Woofer speakers
bluealsa:DEV=C4:67:B5:37:26:12,PROFILE=sco
    Libratone Zipp Mini HFP (CVSD)
    Bluetooth Audio Input/Output
bluealsa:DEV=C4:67:B5:37:26:12,PROFILE=a2dp
    Libratone Zipp Mini A2DP (aptX)
    Bluetooth Audio Output

The last two entries in the above listing have been created by bluealsa-autoconfig.

As an example GUI application, here's a screenshot of the kodi audio device selection dialog with the same Bluetooth speaker connected:

kodi

bluealsa-autoconfig can also optionally create a new default device definition that uses a connected BlueALSA device; and it can also optionally trigger a udev audio device change event to notify ALSA applications when the configuration has changed. The udev option is particularly important when using applications such as kodi because otherwise they will not see the changes to the ALSA configuration and therefore will not display devices connected after the application started.

In the above kodi example, bluealsa-autoconfig is running as

bluealsa-autoconfig --udev

and /etc/asound.conf contains:

defaults.bluealsa.namehint "%n %p (%c) Bluetooth %s"

bluealsa-autoconfig must be run as root to gain the necessary privileges for modifying the global ALSA configuration and triggering udev events. See the manual page for full details.

A systemd system service unit file is included for bluealsa-autoconfig

bluealsa-agent

bluealsa-agent is a simple program to invoke arbitrary user commands in response to BlueALSA PCM D-Bus signals. It does not require root privileges and is intended to be used as a user service.

See the manual page for full details.

Some practical example scripts are included in the examples directory

Installation

meson setup builddir
cd builddir
meson compile
sudo meson install

To include the manual pages, the application rst2man from the docutils project is required. Many distributions provide this in the package python3-docutils. To enable building and installing the manual page, setup the build directory with

meson setup -Ddoc=true builddir

or, if the build directory has already been set up, change its configuration with

meson configure -Ddoc=true builddir

Usage

The two services are documented in their respective manual pages:

systemd configuration is documented in:

License

This project is licensed under the terms of the MIT license.

It includes copies of source code files from the bluez-alsa project, which are also licensed under the MIT license and all rights to those files remain with their original author.

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Automatically update an ALSA configuration as BlueALSA devices connect and disconnect

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