NAME

bluealsa - Bluetooth Audio ALSA Backend

SYNOPSIS

bluealsa -p PROFILE [OPTION]...

DESCRIPTION

bluealsa is a Linux daemon to give applications access to Bluetooth audio streams using the Bluetooth A2DP, HFP and/or HSP profiles. It provides a D-Bus API to applications, and can be used by ALSA applications via libasound plugins.

OPTIONS

-h, --help
Output a usage message and exit.
-V, --version
Output the version number and exit.
-B NAME, --dbus=NAME
BlueALSA D-Bus service name suffix. Without this option, bluealsa registers itself as an "org.bluealsa" D-Bus service. For more information see the EXAMPLE below.
-S, --syslog
Send output to system logger (syslogd(8)). By default, log output is sent to stderr.
-i hciX, --device=hciX
HCI device to use. Can be specified multiple times to select more than one HCI. Because HCI numbering can change after a system reboot, this option also accepts HCI MAC address for the hciX value, e.g.: --device=00:11:22:33:44:55 Without this option, the default is to use all available HCI devices.
-p NAME, --profile=NAME
Enable NAME Bluetooth profile. May be given multiple number of times to enable multiple profiles. It is mandatory to enable at least one Bluetooth profile. For the list of supported profiles see the PROFILES section below.
-c NAME, --codec=NAME
Enable or disable NAME Bluetooth audio codec. May be given multiple number of times to enable (or disable) multiple codecs. In order to disable given audio codec (remove it from the list of audio codecs enabled by default), the NAME has to be prefixed with - (minus) character. It is not possible to disable SBC and CVSD codecs which are mandatory for A2DP and HFP/HSP respectively. By default BlueALSA enables SBC, AAC (if AAC support is compiled-in), CVSD and mSBC. For the list of supported audio codecs see the "Available BT audio codecs" section of the bluealsa command-line help message.
--initial-volume=NUM
Set the initial volume to NUM % when the device is connected. NUM must be an integer in the range from 0 to 100. The default value is 100 (full volume). Having headphones volume reset to max whenever they connect can lead to an unpleasant experience. This option allows the user to choose an alternative initial volume level. Only one value can be specified and each device on connect will have the volume level of all its PCMs set to this value (%). However, a device with native volume control may then immediately override this level.
--keep-alive=SEC
Keep Bluetooth transport alive for SEC number of seconds after streaming was closed. This option is required when using bluealsa with applications that close and then immediately re-open the same PCM as part of their initialization; for example applications built with the portaudio portability library and many other "portable" applications. It can also be useful when playing short audio files in quick succession. It will reduce the gap between playbacks caused by Bluetooth audio transport acquisition.
--a2dp-force-mono
Force monophonic sound for A2DP profile.
--a2dp-force-audio-cd
Force 44.1 kHz sampling frequency for A2DP profile. Some Bluetooth devices can handle streams sampled at either 48kHz or 44.1kHz, in which case they normally default to using 48kHz. With this option, bluealsa will request such a device uses only 44.1 kHz sample rate.
--a2dp-volume
Enable native A2DP volume control. By default bluealsa will use its own internal scaling algorithm to attenuate the volume. This option disables that internal scaling and instead passes the volume change request to the A2DP device. This feature can also be controlled during runtime via BlueALSA D-Bus API. Note that this feature might not work with all Bluetooth headsets.
--sbc-quality=MODE
Set SBC encoder quality, where MODE can be one of:
•
low - low audio quality (mono: 114 kbps, stereo: 213 kbps)
•
medium - medium audio quality (mono: 132 kbps, stereo: 237 kbps)
•
high - high audio quality (mono: 198 kbps, stereo: 345 kbps) ( default)
•
xq - SBC Dual Channel HD (SBC XQ) (452 kbps)
•
xq+ - SBC Dual Channel HD (SBC XQ+) (551 kbps)

--mp3-algorithm=TYPE
Select LAME encoder internal algorithm, where TYPE can be one of:
•
fast - OK quality, really fast
•
cheap - good quality, fast
•
expensive - near-best quality, not too slow (default)
•
best - best quality, slow

 
If CPU power consumption is not an issue, one might safely select best as the algorithm type. Also, please note that the true quality is determined by the selected bit rate or used VBR quality option ( --mp3-vbr-quality).
--mp3-vbr-quality=MODE
Set variable bit rate (VBR) quality, where MODE can be one of:
•
low - low audio quality (100-130 kbps)
•
medium - medium audio quality (140-185 kbps)
•
standard - standard audio quality (170-210 kbps) (default)
•
high - high audio quality (190-250 kbps)
•
extreme - best audio quality, no low-pass filter (220-260 kbps)

--aac-afterburner
Enables Fraunhofer AAC afterburner feature, which is a type of analysis by synthesis algorithm. This feature increases the audio quality at the cost of increased processing power and overall memory consumption.
--aac-bitrate=BPS
Set the target bit rate for constant bit rate (CBR) mode or the maximum peak bit rate for variable bit rate (VBR) mode. Default value is 220000 bits per second.
--aac-latm-version=NUM
Select LATM syntax version used for AAC audio transport. Default value is 1. The NUM can be one of:
•
0 - LATM syntax specified by ISO-IEC 14496-3 (2001), should work with all older BT devices
•
1 - LATM syntax specified by ISO-IEC 14496-3 (2005), should work with newer BT devices

--aac-true-bps
Enable true "bit per second" bit rate. A2DP AAC specification requires that for the constant bit rate (CBR) mode every RTP frame has the same bit rate and for the variable bit rate (VBR) mode the maximum peak bit rate limit is also per RTP frame. However, a single RTP frame does not contain a single full second of audio. This option enables true bit rate calculation (per second), which means that per RTP frame bit rate may vary even for CBR mode. This feature is not enabled by default, because it violates A2DP AAC specification. Enabling it should result in an enhanced audio quality, but will for sure produce fragmented RTP frames. If RTP fragmentation is not supported by used A2DP sink device (e.g. headphones) one might hear clearly audible clicks in the playback audio. In such case, please do not enable this option.
--aac-vbr
Prefer variable bit rate mode over constant bit rate mode. Please note, that this option does not necessarily mean that the variable bit rate (VBR) mode will be used. Used AAC configuration depends on a remote Bluetooth device capabilities.
--lc3plus-bitrate=BPS
Set LC3plus encoder bit rate for constant bit rate mode (CBR) as BPS. Default value is 396800 bits per second.
--ldac-abr
Enables LDAC adaptive bit rate, which will dynamically adjust encoder quality based on the connection stability.
--ldac-quality=MODE
Specifies LDAC encoder quality, where MODE can be one of:
•
mobile - mobile quality (44.1 kHz: 303 kbps, 48 kHz: 330 kbps)
•
standard - standard quality (44.1 kHz: 606 kbps, 48 kHz: 660 kbps) ( default)
•
high - high quality (44.1 kHz: 909 kbps, 48 kHz: 990 kbps)

--xapl-resp-name=NAME
Set the product name send in the XAPL response message. By default, the name is set as "BlueALSA". However, some devices (reported with e.g.: Sony WM-1000XM4) will not provide battery level notification unless the product name is set as "iPhone".

PROFILES

BlueALSA provides support for Bluetooth Advanced Audio Distribution Profile (A2DP), Hands-Free Profile (HFP) and Headset Profile (HSP). A2DP profile is dedicated for streaming music (i.e. stereo, 48 kHz or more sampling frequency), while HFP and HSP for two-way voice transmission (mono, 8 kHz or 16 kHz sampling frequency). With A2DP, BlueALSA includes mandatory SBC codec and various optional codecs like AAC, aptX, and other. The full list of available optional codecs, which depends on selected compilation options, will be shown with bluealsa command-line help message.
 
The list of profile NAME-s accepted by the --profile=NAME option:
•
a2dp-source - Advanced Audio Source (streaming audio to connected device)
•
a2dp-sink - Advanced Audio Sink (receiving audio from connected device)
•
hfp-ofono - Hands-Free AG/HF handled by oFono
•
hfp-ag - Hands-Free Audio Gateway
•
hfp-hf - Hands-Free
•
hsp-ag Headset Audio Gateway
•
hsp-hs - Headset

 
The hfp-ofono is available only when bluealsa was compiled with oFono support. Enabling HFP over oFono will automatically disable hfp-hf and hfp-ag.

FILES

/etc/dbus-1/system.d/bluealsa.conf
BlueALSA service D-Bus policy file. D-Bus will deny all access to the org.bluealsa service (even to root) unless permission is granted by a policy file. The default file permits only root to own this service, and only members of the audio group to exchange messages with it.

EXAMPLE

Emulate Bluetooth headset with A2DP and HSP support:
 
bluealsa -p a2dp-sink -p hsp-hs


 
On systems with more than one HCI device, it is possible to expose different profiles on different HCI devices. A system with three HCI devices might (for example) use hci0 for an A2DP sink service named "org.bluealsa.sink" and both hci1 and hci2 for an A2DP source service named "org.bluealsa.source". Such a setup might be created as follows:
 
bluealsa -B sink -i hci0 -p a2dp-sink &
bluealsa -B source -i hci1 -i hci2 -p a2dp-source &


 
Setup like this will also require a change to the BlueALSA D-Bus configuration file in order to allow connection with BlueALSA services with suffixed names. Please add following lines to the BlueALSA D-Bus policy:
 
...
<allow send_destination="org.bluealsa.sink" />
<allow send_destination="org.bluealsa.source" />
...


SEE ALSO

bluetoothctl(1), bluetoothd(8), bluealsa-aplay(1), bluealsa-cli(1), bluealsa-plugins(7), bluealsa-rfcomm(1)
Copyright (c) 2016-2021 Arkadiusz Bokowy.
 
The bluez-alsa project is licensed under the terms of the MIT license.