======ALSA-only audio on Linux======
this is a guide on how to setup ALSA to be enjoyable by itself without an audio server.

I will be showing changes to ///etc/asound.conf// as to effect all users (including daemons such as MPD). you can also use //~/.asoundrc// for setup specific to your user.

=====devices=====
multiple commands can list available audio cards and devices.

**alsactl** can be used:
<code bash>
$ alsactl info 1
#
# Sound card
#
- card: 1                    # card number.
  id: sofhdadsp
  name: sof-hda-dsp
  longname: 
  driver_name: sof-hda-dsp
  mixer_name: Realtek ALC233
  components: 
  controls_count: 54
  pcm:
    - stream: PLAYBACK
      devices:
        - device: 1          # device number.
          id: HDA Analog (*) # name.
          name: 
          subdevices:
            - subdevice: 0
              name: subdevice #0
...
</code>
by default //alsactl info// will show card 0. you most likely have multiple cards.

**aplay** will also list sound cards and devices.
<code bash>
$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: HDMI [HDA ATI HDMI], device 0: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
...
card 1: sofhdadsp [sof-hda-dsp], device 1: HDA Analog (*) []
  Subdevices: 1/1
  Subdevice #0: subdevice #0
...
</code>

card 1 and device 1 will be used for this guide. in most places, this is specified with **"hw:1,1"**. the first number is the card and the second is the device.

=====mixing=====
[[https://www.alsa-project.org/wiki/Asoundrc#dmix|dmix]] is a software mixer for audio output. it will allow multiple programs to simultaneously play sound at the same time.

in //asound.conf//, the following configuration could be used to create a software mixer that can be accessed by multiple users.
<file bash /etc/asound.conf>
pcm.mixer {
  type dmix
  ipc_key 1024
  ipc_key_add_uid false  # remove these two lines to only allow
  ipc_perm 0666          #  one user to use the mixer at a time.
  
  slave {
    pcm "hw:1,1"         # hardware output device to use.
  }
}

pcm.!default plug:mixer  # set the default device to the mixer.
</file>

=====Bluetooth=====
[[https://github.com/arkq/bluez-alsa|BlueALSA]] can be used to easily play audio on Bluetooth audio devices.

the pcm and ctl 'bluealsa' is created automatically, and in most cases they can be used directly. see the project's wiki for more information on configuration.

<file bash ~/.asoundrc>
pcm.!default bluealsa
ctl.!default bluealsa
</file>

you can use **bluealsa-cli** to get information on your Bluetooth devices.
<code bash>
$ bluealsa-cli list-pcms
/org/bluealsa/hci1/dev_XX_XX_XX_XX_XX_XX/a2dpsrc/sink

$ bluealsa-cli info -vv /org/bluealsa/hci1/dev_XX_XX_XX_XX_XX_XX/a2dpsrc/sink
...
Format: S32_LE
Channels: 2
Sampling: 96000 Hz
Available codecs:
        ...
	LDAC:... [channels: 1 2 2] [sampling: 44100 48000 88200 96000] # supported sample rates.
Selected codec:
	LDAC:... [channels: 2] [sampling: 96000]
...
</code>

====LDAC====
on Sony and other brand products which support it, LDAC is a codec which provides a high bit depth and sample rate. BlueALSA supports LDAC, but some packages are built without it.

on Arch Linux, the package in the AUR disables LDAC support so you must edit the PKGBUILD or compile it manually. uncomment/pass --enable-ldac.

if wokring correctly, BlueALSA will automatically use LDAC on supported devices, and adjust the sample rate depending on the audio.

=====S/PDIF multichannel=====
the **a52** alsa plugin can be used to output Dolby Digital 5.1 (or lower) multichannel audio through S/PDIF.

you must have the plugin installed. look in your distribution's repositories for a package similar to "alsa-plugins". it may be in a separate package such as "alsa-plugins-a52", as on Alpine Linux.

here is an example configuration:
<file bash /etc/asound.conf>
pcm.surround {
        type a52
        slavepcm "hw:1,1"

        channels 6
        bitrate 1000
        rate 48000
        format S16_LE
}
</file>


=====equalization=====
[[https://github.com/bassdr/alsaequal|alsaequal]] is a 10-band software equalizer in the form of an ALSA plugin.

each user has their own persistent settings, stored in //~/.alsaequal.bin//. if, for example, you are running MPD as its own mpd user, you must either copy or link the //alsaequal.bin// file to its home directory, or manually configure it seperately.

the following configuration builds on the previous section on dmix. an asoundrc using solely alsaequal can be very simple.
<file bash /etc/asound.conf>
pcm.dmix_stereo {
        type dmix
        ipc_key 1024
        ipc_key_add_uid false
        ipc_perm 0666

        slave {
                pcm "hw:1,1"

                period_time 0
                period_size 1024
                buffer_size 4096
                rate 48000
        }
        bindings {                     # channel configuration (stereo, quad, 5.1, ...).
                0 0
                1 1
        }
}
pcm.plug_eq_stereo {
        type equal
        slave.pcm "plug:dmix_stereo"
}
pcm.eq_stereo {                       # this plug is needed to make the alsaequal output suitable for use by most applications.
        type plug
        slave.pcm "plug_eq_stereo"
}

ctl.eq_stereo {                       # this ctl is what allows adjustment in alsamixer (or similar utilities).
        type equal
}

pcm.!default eq_stereo
</file>
with this configuration, the equalizer can be changed with ctl **eq_stereo**:
<code bash>
alsamixer -D eq_stereo
</code>

====multichannel====
here is an example of using alsaequal with **a52**.
<file bash /etc/asound.conf>
...

pcm.surround {
        type a52
        slavepcm "hw:1,1"

        channels 6
        bitrate 1000
        rate 48000
        format S16_LE
}
pcm.plug_eq_surround {
        type equal
        channels 6                         # changes channel configuration to 5.1.
        controls ".alsaequal.surround.bin" # sets the control information file to at ~/.alsaequal.surround.bin. this must be changed if there are to be multiple alsaequals of differing channel configurations.
        slave.pcm "plug:surround"
}
pcm.eq_surround {
        type plug
        slave.pcm "plug_eq_surround"
}

ctl.eq_surround {
        type equal
        channels 6
        controls ".alsaequal.surround.bin"
}

...
</file>
the surround equalizer can be changed with ctl **eq_surround** using this configuration.

{{tag>audio alsa linux}}