This project is a rebirth of a direct integration between BlueZ and ALSA. Since BlueZ >= 5, the built-in integration has been removed in favor of 3rd party audio applications. From now on, BlueZ acts as a middleware between an audio application, which implements Bluetooth audio profile, and a Bluetooth audio device.
The current status quo is, that in order to stream audio from/to a Bluetooth device, one has to install a general-purpose audio server such as PipeWire or PulseAudio, or use BlueZ version 4 which is deprecated and unmaintained.
This project created and maintains a product called BlueALSA, with which one can achieve the same Bluetooth audio profile support as with PulseAudio, but with fewer dependencies and at a lower level in the software stack. BlueALSA registers all known Bluetooth audio profiles in BlueZ, so in theory every Bluetooth device (with audio capabilities) can be connected.
BlueALSA is designed specifically for use on small, low-powered, dedicated audio or audio/visual systems where the high-level audio management features of PulseAudio or PipeWire are not required. The target system must be able to function correctly with all its audio applications interfacing directly with ALSA. In such systems BlueALSA adds Bluetooth audio support to the existing ALSA sound card support.
BlueALSA consists of the daemon bluealsa, ALSA plug-ins, and a number of
utilities. The basic context is shown in this diagram:
flowchart TD
classDef external fill:#eee,stroke:#333,stroke-width:4px,color:black;
classDef bluealsa fill:#bbf,stroke:#333,stroke-width:4px,color:black;
A[Bluetooth Adapter] <--> B((bluetoothd\ndaemon))
A <--> C((bluealsa daemon))
B <--> C
C <--> D((bluealsa-aplay))
C <--> E(("ALSA clients\n(via plugin)"))
C <--> F((other\nD-Bus clients))
class A,B external;
class C,D,E,F bluealsa;
The heart of BlueALSA is the daemon bluealsa which interfaces with the BlueZ
Bluetooth daemon bluetoothd and the local Bluetooth adapter. It handles the
profile connection and configuration logic for A2DP, HFP and HSP and presents
the resulting audio streams to applications via D-Bus.
BlueALSA includes ALSA plug-ins which hide all the D-Bus specifics and permit applications to use the ALSA PCM and mixer interfaces, so that existing ALSA applications can access Bluetooth audio devices in the same way as they use sound card PCMs and mixers.
BlueALSA also includes a number of utility applications. Of particular note are:
-
bluealsa-aplay
an application to simplify the task of building a Bluetooth speaker using BlueALSA. -
bluealsa-cli
an application to allow command-line management of the BlueALSA system. -
bluealsa-rfcomm
a command-line application which provides access to the RFCOMM terminal for HFP/HSP devices.
Build and install instructions are included in the file INSTALL.md and more detailed guidance is available in the wiki.
The main component of BlueALSA is a program called bluealsa. By default, this
program shall be run as a root during system startup. It will register
org.bluealsa service in the D-Bus system bus, which can be used for accessing
configured audio devices. In general, BlueALSA acts as a proxy between BlueZ
and ALSA.
For details of command-line options to bluealsa, consult the bluealsa manual
page.
In order to stream audio to e.g. a Bluetooth headset, firstly one has to
connect the device. The most straightforward method is to use BlueZ CLI utility
called bluetoothctl. When the device is connected one can use the bluealsa
virtual PCM device with ALSA applications just like any other PCM device:
aplay -D bluealsa Bourree_in_E_minor.wavIf there is more than one Bluetooth device connected, the target one can be specified as a parameter to the PCM:
aplay -D bluealsa:XX:XX:XX:XX:XX:XX, Bourree_in_E_minor.wavPlease note that this PCM device is based on the ALSA software PCM I/O plug-in - it will not be available in the ALSA Kernel proc interface.
Setup parameters of the bluealsa PCM device can be set in the local .asoundrc
configuration file like this:
cat ~/.asoundrc
defaults.bluealsa.service "org.bluealsa"
defaults.bluealsa.device "XX:XX:XX:XX:XX:XX"
defaults.bluealsa.profile "a2dp"
defaults.bluealsa.delay 10000BlueALSA also allows to capture audio from the connected Bluetooth device. To do so, one has to use the capture PCM device, e.g.:
arecord -D bluealsa -f s16_le -c 2 -r 48000 capture.wavIn addition to A2DP profile, used for high quality audio, BlueALSA also allows
to use phone audio connection via SCO link. One can use either built-in HSP/HFP
support, which implements only audio related part of the specification, or use
oFono service as a back-end. In order to open SCO audio connection one
shall switch to sco profile like follows:
aplay -D bluealsa:DEV=XX:XX:XX:XX:XX:XX,PROFILE=sco Bourree_in_E_minor.wavIn order to control input or output audio level, one can use provided
bluealsa control plug-in. This plug-in allows adjusting the volume of the
audio stream or simply mute/unmute it, e.g.:
amixer -D bluealsa sset '<control name>' 70%where the control name is the name of a connected Bluetooth device with a control element suffix, e.g.:
amixer -D bluealsa sset 'Jabra MOVE v2.3.0 A2DP' 50%For full details of the BlueALSA ALSA PCM device and mixer device consult the BlueALSA plug-ins manual page.
There are also a number of articles on the bluez-alsa project wiki giving more examples of using these plug-ins.
For more advanced ALSA configuration, consult the asoundrc on-line documentation provided by the AlsaProject wiki page.
It is possible to create Bluetooth-powered speaker using BlueALSA. For this it
is required to forward the audio signal from the BlueALSA capture PCM to some
other playback PCM (e.g. built-in audio card). In order to simplify this task,
BlueALSA includes a program called bluealsa-aplay, which acts as a simple
BlueALSA player. Connect your Bluetooth device (e.g. smartphone) and do as
follows:
bluealsa-aplay XX:XX:XX:XX:XX:XXFor details of command-line options to bluealsa-aplay, consult the
bluealsa-aplay manual page. There are also some
articles on the bluez-alsa project wiki giving examples of its use.
The list of available BlueALSA PCMs (provided by connected Bluetooth devices
with audio capabilities) can be obtained directly from BlueALSA D-Bus
API or using bluealsa-aplay as a convenient wrapper as
follows:
bluealsa-aplay -L-
Using BlueALSA alongside PulseAudio or PipeWire.
Due to BlueZ limitations, only one program can register as provider of Bluetooth audio profile implementation. So it is not possible to use BlueALSA if either PulseAudio or PipeWire are also running with their own Bluetooth modules enabled; it is first necessary to disable Bluetooth in those applications.
-
ALSA thread-safe API (alsa-lib >= 1.1.2, <= 1.1.3).
ALSA library versions 1.1.2 and 1.1.3 had a bug in their thread-safe API functions. This bug does not affect hardware audio devices, but it affects many software plug-ins. Random deadlocks are inevitable. The best advice is to use a more recent alsa-lib release, or if that is not possible then disable the thread locking code via an environment variable, as follows:
export LIBASOUND_THREAD_SAFE=0. -
Couldn't acquire D-Bus name: org.bluealsa
It is not possible to run more than one instance of the BlueALSA server per D-Bus interface. If one tries to run second instance, it will fail with the
"Couldn't acquire D-Bus name: org.bluealsa"error message. This message might also appear when D-Bus policy does not allow acquiring "org.bluealsa" name for a particular user - by default only root is allowed to start BlueALSA server. -
Couldn't get BlueALSA PCM: PCM not found
In contrast to standard ALSA sound cards, BlueALSA does not expose all PCMs right away. In the first place it is required to connect remote Bluetooth device with desired Bluetooth profile - run
bluealsa --helpfor the list of available profiles. For querying currently connected audio profiles (and connected devices), runbluealsa-aplay --list-devices. The common misconception is an attempt to use A2DP playback device as a capture one in case where A2DP is not listed in the "List of CAPTURE Bluetooth Devices" section.Additionally, the cause of the "PCM not found" error might be an incorrect ALSA PCM name. Run
bluealsa-aplay --list-pcmsfor the list of currently available ALSA PCM names - it might give you a hint what is wrong with your.asoundrcentry. Also, take a look at the bluealsa-plugins manual page.
This project welcomes contributions of code, documentation and testing. For code and manual page contributions, please use GitHub Pull Requests. There is no strict policy for PRs, each contribution will be evaluated individually. If you wish to help by testing PRs or by making review comments please do so by adding comments to the PR.
When preparing a pull request, if possible please configure with
--enable-test, and to catch as many coding errors as possible please compile
with:
make CFLAGS="-Wall -Wextra -Werror"and then run the unit test suite:
make checkThe project wiki is "public" and contributions there are also welcome.
Before raising a new issue, please search previous issues (both open and closed), to see if your question has already been answered or problem resolved. If reporting a problem, please clearly state the version of BlueALSA that you are using, and give sufficient information for readers to be able to reproduce the issue.
Please also look at the wiki if you require help as there is a great deal of useful information. Unfortunately the wiki is not indexed by web search engines, so searching on-line for your issue will not discover the information in there.
BlueALSA is licensed under the terms of the MIT license. See the LICENSE file for details.