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bluealsa-aplay

a simple bluealsa player

Date

February 2024

Manual section

1

Manual group

General Commands Manual

Version

$VERSION$

SYNOPSIS

bluealsa-aplay [OPTION]... [BT-ADDR]...

DESCRIPTION

Capture audio streams from Bluetooth devices (via bluealsa(8)) and play them to an ALSA playback device.

By default bluealsa-aplay captures audio from all connected Bluetooth devices. It is possible to select specific Bluetooth devices by providing a list of BT-ADDR MAC addresses. Using the special MAC address 00:00:00:00:00:00 will disable device filtering - the same as the default behavior.

OPTIONS

-h, --help

Output a usage message and exit.

-V, --version

Output the version number and exit.

-S, --syslog

Send output to system logger (syslogd(8)). By default, log output is sent to stderr.

--loglevel=LEVEL

Set the priority level threshold for log messages. Only messages of the given level or higher are logged. The LEVELs are, in decreasing order:

  • error - error conditions
  • warning - warning conditions
  • info - informational messages

If bluealsa-aplay was built with debug enabled, then an additional, lowest, level is available:

  • debug - debug messages

If this option is not given then the default is to use the lowest level (i.e., all messages are logged).

-v, --verbose

Make the output more verbose.

-l, --list-devices

List connected Bluetooth audio devices.

-L, --list-pcms

List available Bluetooth audio PCMs on connected devices.

-B NAME, --dbus=NAME

BlueALSA service name suffix. For more information see --dbus=NAME option of bluealsa(8) service daemon.

-D NAME, --pcm=NAME

Select ALSA playback PCM device to use for audio output. The default is default.

Internally, bluealsa-aplay does not perform any audio transformations nor streams mixing. If multiple Bluetooth devices are connected it simply opens a new connection to the ALSA PCM device for each stream. Selected hardware parameters like sampling frequency and number of channels are taken from the audio profile of a particular Bluetooth connection. Note, that each connection can have a different setup.

If playing multiple streams at the same time is not desired, it is possible to change that behavior by using the --single-audio option.

For more information see the EXAMPLES section below.

--pcm-buffer-time=INT

Set the playback PCM buffer duration time to INT microseconds. The default is 500000. It is recommended to choose a buffer time that is an exact multiple of the period time to avoid potential issues with some ALSA plugins (see --pcm-period-time option below). ALSA may choose the nearest available alternative if the requested value is not supported.

If you experience underruns on the ALSA device then a larger buffer may help. However, a larger buffer will also increase the latency. For reliable performance the buffer time should be at least 3 times the period time.

--pcm-period-time=INT

Set the playback PCM period duration time to INT microseconds. The default is 100000. ALSA may choose the nearest available alternative if the requested value is not supported.

The ALSA rate plugin, which may be invoked by plug, does not always produce the exact required effective sample rate because of rounding errors in the conversion between period time and period size. This can have a significant impact on synchronization "drift", especially with small period sizes, and can also result in stream underruns (if the effective rate is too fast) or dropped A2DP frames in the bluealsa(8) server (if the effective rate is too slow). This effect is avoided if the selected period time results in an exact integer number of frames for both the source rate (Bluetooth) and sink rate (hardware card). For example, in the case of Bluetooth stream sampled at 44100Hz playing to a hardware device that supports only 48000Hz, choosing a period time that is a multiple of 10000 microseconds will result in zero rounding error. (10000 µs at 44100Hz is 441 frames, and at 48000Hz is 480 frames).

See also dmix in the NOTES section below for more information on rate calculation rounding errors.

--volume=TYPE

Select the desired method of implementing remote volume control. TYPE may be one of four values:

  • auto - the volume control method is determined by the BlueALSA PCM. This is the default when this option is not given. bluealsa-aplay operates its configured ALSA mixer control to apply volume change requests received from the remote Bluetooth device if and only if the PCM is using native ("pass-through") volume control.
  • mixer - bluealsa-aplay will force the BlueALSA PCM volume mode setting to native ("pass-through") before starting the PCM stream, and then operate the same as for auto above.
  • none - bluealsa-aplay will force the BlueALSA PCM volume mode setting to native ("pass-through") before starting the PCM stream. It will not operate its configured ALSA mixer. This can be used to effectively disable remote volume control; or it can be used to allow some other application to apply remote volume change requests.
  • software - bluealsa-aplay will force the BlueALSA PCM volume mode setting to soft-volume ("software") and then will not operate its configured ALSA mixer. This can be used to enable remote volume control without using an ALSA mixer.

See Volume control in the NOTES section below for more information on volume control.

-M NAME, --mixer-device=NAME

Select ALSA mixer device to use for controlling audio output mute state and volume level. In order to use this feature, BlueALSA PCM can not use software volume. The default is default.

--mixer-name=NAME

Set the name of the ALSA simple mixer control to use. The default is Master.

To work with bluealsa-aplay this simple control must provide decibel scaling information for the volume control. Most, but not all, modern sound cards do provide this information.

--mixer-index=NUM

Set the index of the ALSA simple mixer control. The default is 0.

This is required only if the simple mixer control name applies to multiple simple controls on the same card. This is most common with HDMI devices for which the index indicates the controlled HDMI PCM device.

--profile-a2dp

Use A2DP profile (default).

--profile-sco

Use SCO profile.

Note: Only one of A2DP or SCO can be used. If both are specified, the last one given will be selected.

--single-audio

Allow only one Bluetooth device to play audio at a time. If multiple devices are connected, only the first to start will play, the others will be paused. When that first device stops, then the next to send audio will be played.

Without this option, bluealsa-aplay plays audio from all selected Bluetooth devices. Please note that playing from all Bluetooth devices at a time requires used PCM to be able to mix audio from multiple sources (i.e., it can be opened more than once; for example the ALSA dmix plugin).

NOTES

Volume control

If the Bluetooth PCM is using BlueALSA soft-volume volume control, then volume adjustment will have been applied to the PCM stream within the bluealsa daemon; so bluealsa-aplay does not operate the mixer control in this case.

When using --volume=none or --volume=software, then the mixer options --mixer-device, --mixer-name and --mixer-index are ignored, and bluealsa-aplay will not operate any mixer controls, even if some other application changes the PCM volume mode to native while in use.

When using --volume=auto or --volume=mixer the ALSA mixer control will be operated only when the PCM stream is active, (i.e., the remote device is sending audio). If a connected remote device requests a volume change when no active stream is playing, then bluealsa-aplay will ignore that request. When the audio stream starts then bluealsa-aplay will change the Bluetooth volume to match the current setting of the ALSA mixer control.

Native Bluetooth volume control for A2DP relies on AVRCP volume control in BlueZ, which has not always been reliably implemented. It is recommended to use BlueZ release 5.65 or later to be certain that native A2DP volume control will always be available with those devices which provide it.

See bluealsa(8) for more information on native and soft-volume volume control.

dmix

The ALSA dmix plugin will ignore the period and buffer times selected by the application (because it has to allow connections from multiple applications). Instead it will choose its own values, which can lead to rounding errors in the period size calculation when used with the ALSA rate plugin. To avoid this, it is recommended to explicitly define the hardware period size and buffer size for dmix in your ALSA configuration. For example, suppose we want a period time of 100000 µs and a buffer holding 5 periods with an Intel 'PCH' card:

defaults.dmix.PCH.period_time 100000
defaults.dmix.PCH.periods 5

Alternatively we can define a PCM with the required setting:

pcm.dmix_rate_fix {
    type plug
    slave.pcm {
        type dmix
        ipc_key 12345
        slave {
            pcm "hw:0,0"
            period_time 100000
            periods 5
        }
    }
}

EXAMPLES

The simplest usage of bluealsa-aplay is to run it with no arguments. It will play audio from all connected Bluetooth devices to the default ALSA playback PCM.

bluealsa-aplay

If there is more than one sound card attached one can create a setup where the audio of a particular Bluetooth device is played to a specific sound card. The setup below shows how to do this using the --pcm=NAME option and known Bluetooth device addresses.

Please note that in the following example we assume that the second card is named "USB" and the appropriate mixer control is named "Speaker". Real names of attached sound cards can be obtained by running aplay -l. A list of control names for a card called "USB" can be obtained by running amixer -c USB scontrols.

bluealsa-aplay --pcm=default 94:B8:6D:AF:CD:EF F8:87:F1:B8:30:85 &
bluealsa-aplay --pcm=default:USB C8:F7:33:66:F0:DE &

Also, it might be desired to specify ALSA mixer device and/or control element for each ALSA playback PCM device. This will be mostly useful when BlueALSA PCM does not use software volume (for more information see --volume option above).

bluealsa-aplay --pcm=default 94:B8:6D:AF:CD:EF F8:87:F1:B8:30:85 &
bluealsa-aplay --pcm=default:USB --mixer-device=hw:USB --mixer-name=Speaker C8:F7:33:66:F0:DE &

Such setup will route 94:B8:6D:AF:CD:EF and F8:87:F1:B8:30:85 Bluetooth devices to the default ALSA playback PCM device and C8:F7:33:66:F0:DE device to the USB sound card. For the USB sound card the Speaker control element will be used as a hardware volume control knob.

COPYRIGHT

Copyright (c) 2016-2023 Arkadiusz Bokowy.

The bluez-alsa project is licensed under the terms of the MIT license.

SEE ALSO

amixer(1), aplay(1), bluealsa-rfcomm(1), bluealsa(8)

Project web site

https://github.com/arkq/bluez-alsa