Difference between revisions of "How to record audio"

[checked revision] [quality revision]

1 Article purpose[edit]

This article explains how to record audio via the kernel ALSA audio framework in Linux® OS context. The examples below, show how to record audio from the different audio hardware interfaces of the STM32MPU boards.

2 Audio record overview[edit]

The ALSA framework exposes audio devices associated to the board audio hardware interfaces.

The application audio streams are routed by default through the PulseAudio sound server. PulseAudio exposes audio profiles, which are mapped on the ALSA sound card audio devices. The PulseAudio server provides a command line interface to list audio profiles and to select one, in order to record from a specific audio interface.

The audio record examples in following sections are based on ALSA utilities. Some input paths are configured through ALSA controls. These configurations are detailed in sound card configuration article. If an error is issued when running an example, please refer to Audio troubleshooting grid article for debug.

3 Examples[edit]

3.1 Audio record from headset microphone input[edit]

3.1.1 Record from ALSA device[edit]

Start audio record from 'record_codec' ALSA device:

Info white.png Information
'record_codec' is an alias defined in /etc/asound.conf, for headset microphone input device.
 arecord -D record_codec -f S16_LE -d 10 /tmp/rec.wav

3.1.2 Record via PulseAudio[edit]

3.1.2.1 For ecosystem release ≥ v1.2.0 More info.png[edit]
  • Configure Pulseaudio :

Change Pulseaudio default input source to 'analog_input':

Info white.png Information
The Pulseaudio analog_input is defined in /etc/pulse/system.pa configuration file.
 pacmd set-default-source analog_input
  • Start audio record :
Info white.png Information
The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.
 arecord -d 10 /tmp/rec.wav
3.1.2.2 For ecosystem release ≤ v1.1.0 More info.png[edit]
  • Configure Pulseaudio :

Change Pulseaudio active profile of the sound card, to 'analog-stereo' profile:

Info white.png Information
The Pulseaudio analog-stereo profile is the default profile. So next command is not required after boot.
Info white.png Information
Example below is given for sound card index 0. Check sound cards index with "pactl list cards short" command.
 pacmd set-card-profile 0 output:analog-stereo+input:analog-stereo
  • Start audio record :
Info white.png Information
The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.
 arecord -d 10 /tmp/rec.wav

3.2 Audio record from digital microphone input[edit]

Warning white.png Warning
The support of digital microphone input is board dependent. Please, check available inputs with "arecord -l" command.

3.2.1 Record from ALSA device[edit]

Start mono audio record from 'record_dfsdm0' ALSA device:

Info white.png Information
'record_dfsdm0' is an alias defined in /etc/asound.conf, for digital microphone U1 input device.
 arecord -D record_dfsdm0 -r 16000 -f S32_LE -c 1 -d 10 /tmp/rec.wav

3.2.2 Record multiple digital microphones from a virtual ALSA device[edit]

Start stereo audio record from 'multi' ALSA device:

Info white.png Information
'multi' device, based on ALSA multi plugin[1], has to be defined in /etc/asound.conf file.
 arecord -D multi -r 16000 -f S32_LE -c 2 -d 10 /tmp/rec.wav

3.2.3 Record via PulseAudio[edit]

The record via Pulseaudio is only available for ecosystem release ≥ v1.2.0 More info.png.

  • Configure Pulseaudio

Change Pulseaudio default input source to 'dmic1_input':

Info white.png Information
The Pulseaudio dmic1_input is defined in /etc/pulse/system.pa configuration file.
 pacmd set-default-source dmic1_input
  • Start audio record :
Info white.png Information
The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.
 arecord -r 48000 -f S32_LE -c 2 -d 10 /tmp/rec.wav

3.3 Audio record from S/PDIF input[edit]

Warning white.png Warning
The support of S/PDIF input is board dependent. Please, check available inputs with "arecord -l" command.

3.3.1 Record from ALSA device[edit]

Start audio record from 'record_spdif' ALSA device:

Info white.png Information
'record_spdif' is an alias defined in /etc/asound.conf, for S/PDIF input device.
Info white.png Information
A S/PDIF signal must be available on S/PDIF RCA input connector before starting the record command. The record rate must be set according to S/PDIF signal sampling rate.
 arecord -D record_spdif -f S32_LE -c 2 -r 48000 -d 10 /tmp/rec.wav

3.3.2 Record via PulseAudio[edit]

The record via Pulseaudio is only available for ecosystem release ≥ v1.2.0 More info.png.

  • Configure Pulseaudio

Change Pulseaudio default input source to 'iec958_input':

Info white.png Information
The Pulseaudio iec958_input is defined in /etc/pulse/system.pa configuration file.
 pacmd set-default-source iec958_input
  • Start audio record :
Info white.png Information
The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.
 arecord -r 48000 -f S32_LE -c 2 -d 10 /tmp/rec.wav

4 References[edit]



== Article purpose ==
This article explains how to record audio via the kernel [[ALSA overview|ALSA]] audio framework in '''Linux® OS''' context.
The examples below, show how to record audio from the different audio hardware interfaces of the STM32MPU [[:Category:ST boards| boards]].

== Audio record overview ==
The [[ALSA overview|ALSA]] framework exposes audio devices associated to the board audio hardware interfaces. 

The application audio streams are routed by default through the [[PulseAudio]] sound server. PulseAudio exposes audio profiles, which are mapped on the ALSA sound card audio devices. The PulseAudio server provides a command line interface to list audio profiles and to select one, in order to record from a specific audio interface.

The audio record examples in following sections are based on [[ALSA_overview#How_to_use|ALSA utilities]]. Some input paths are configured through ALSA controls. These configurations are detailed in [[Soundcard_configuration|sound card configuration]] article. If an error is issued when running an example, please refer to [[Audio troubleshooting grid]] article for debug.

== Examples ==

=== Audio record from headset microphone input ===

==== Record from ALSA device ====
Start audio record from 'record_codec' ALSA device:

{{Info|'record_codec' is an alias defined in /etc/asound.conf, for headset microphone input device.}}
 {{Board$}} arecord -D record_codec -f S16_LE -d 10 /tmp/rec.wav

==== Record via PulseAudio ====

===== For {{EcosystemRelease | revision=1.2.0 | range=and after}} =====

* '''Configure Pulseaudio :'''
Change Pulseaudio default input source to 'analog_input':
{{Info|The Pulseaudio analog_input is defined in /etc/pulse/system.pa configuration file.}} {{Board$}} pacmd set-default-source analog_input

* '''Start audio record :'''
{{Info|The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.}}
 {{Board$}} arecord -d 10 /tmp/rec.wav
<div class="mw-collapsible mw-collapsed">

===== For {{EcosystemRelease | revision=1.1.0  | range=and before}} =====<div class="mw-collapsible-content">

* '''Configure Pulseaudio :'''
Change Pulseaudio active profile of the sound card, to 'analog-stereo' profile:
{{Info|The Pulseaudio analog-stereo profile is the default profile. So next command is not required after boot.}}
{{Info|Example below is given for {{highlight|sound card index 0}}. Check sound cards index with "''pactl list cards short''" command.}}
 {{Board$}} pacmd set-card-profile 0 output:analog-stereo+input:analog-stereo

* '''Start audio record :''' {{Info|The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.}}{{Board$}} arecord -d 10 /tmp/rec.wav</div></div>


=== Audio record from digital microphone input ===
{{Warning|The support of digital microphone input is board dependent. Please, check available inputs with "''arecord -l''" command.}}

==== Record from ALSA device ====
Start mono audio record from 'record_dfsdm0' ALSA device:
{{Info|'record_dfsdm0' is an alias defined in /etc/asound.conf, for digital microphone U1 input device.}}
 {{Board$}} arecord -D record_dfsdm0 -r 16000 -f S32_LE -c 1 -d 10 /tmp/rec.wav

==== Record multiple digital microphones from a virtual ALSA device ====
Start stereo audio record from 'multi' ALSA device:
{{Info|'multi' device, based on ALSA multi plugin<ref>[https://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html| ALSA PCM plugins]</ref>, has to be defined in /etc/asound.conf file.}}
 {{Board$}} arecord -D multi -r 16000 -f S32_LE -c 2 -d 10 /tmp/rec.wav

==== Record via PulseAudio ====
The record via Pulseaudio is only available for {{EcosystemRelease | revision=1.2.0 | range=and after}}.

* '''Configure Pulseaudio'''
Change Pulseaudio default input source to 'dmic1_input':
{{Info|The Pulseaudio dmic1_input is defined in /etc/pulse/system.pa configuration file.}} {{Board$}} pacmd set-default-source dmic1_input

* '''Start audio record :'''
{{Info|The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.}} {{Board$}} arecord -r 48000 -f S32_LE -c 2 -d 10 /tmp/rec.wav

=== Audio record from S/PDIF input ===
{{Warning|The support of S/PDIF input is board dependent. Please, check available inputs with "''arecord -l''" command.}}

==== Record from ALSA device ====
Start audio record from 'record_spdif' ALSA device:
{{Info|'record_spdif' is an alias defined in /etc/asound.conf, for S/PDIF input device.}}
{{Info|A S/PDIF signal must be available on S/PDIF RCA input connector before starting the record command. The record rate must be set according to S/PDIF signal sampling rate.}}
 {{Board$}} arecord -D record_spdif -f S32_LE -c 2 -r 48000 -d 10 /tmp/rec.wav

==== Record via PulseAudio ====
The record via Pulseaudio is only available for {{EcosystemRelease | revision=1.2.0 | range=and after}}.

* '''Configure Pulseaudio'''
Change Pulseaudio default input source to 'iec958_input':
{{Info|The Pulseaudio iec958_input is defined in /etc/pulse/system.pa configuration file.}} {{Board$}} pacmd set-default-source iec958_input

* '''Start audio record :'''
{{Info|The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.}} {{Board$}} arecord -r 48000 -f S32_LE -c 2 -d 10 /tmp/rec.wav

== References ==<references />

<noinclude>

{{PublicationRequestId | 10588 | 2019-02-06}}
[[Category:How to run use cases]]
[[Category:ALSA]]</noinclude>
Line 25: Line 25:
   
 
* '''Configure Pulseaudio :'''
 
* '''Configure Pulseaudio :'''
 
 
Change Pulseaudio default input source to 'analog_input':
 
Change Pulseaudio default input source to 'analog_input':
 
{{Info|The Pulseaudio analog_input is defined in /etc/pulse/system.pa configuration file.}}
 
{{Info|The Pulseaudio analog_input is defined in /etc/pulse/system.pa configuration file.}}
 
 
  {{Board$}} pacmd set-default-source analog_input
 
  {{Board$}} pacmd set-default-source analog_input
   
Line 40: Line 38:
 
* '''Configure Pulseaudio :'''
 
* '''Configure Pulseaudio :'''
 
Change Pulseaudio active profile of the sound card, to 'analog-stereo' profile:
 
Change Pulseaudio active profile of the sound card, to 'analog-stereo' profile:
{{Info|The Pulseaudio analog-stereo profile is the default profile. So next command is not required after boot.}}
 
 
{{Info|Example below is given for {{highlight|sound card index 0}}. Check sound cards index with "''pactl list cards short''" command.}}
 
{{Info|Example below is given for {{highlight|sound card index 0}}. Check sound cards index with "''pactl list cards short''" command.}}
 
  {{Board$}} pacmd set-card-profile 0 output:analog-stereo+input:analog-stereo
 
  {{Board$}} pacmd set-card-profile 0 output:analog-stereo+input:analog-stereo
   
 
* '''Start audio record :'''
 
* '''Start audio record :'''
  +
{{Info|The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.}}
 
  {{Board$}} arecord -d 10 /tmp/rec.wav
 
  {{Board$}} arecord -d 10 /tmp/rec.wav
 
</div></div>
 
</div></div>
Line 65: Line 63:
   
 
* '''Configure Pulseaudio'''
 
* '''Configure Pulseaudio'''
 
 
Change Pulseaudio default input source to 'dmic1_input':
 
Change Pulseaudio default input source to 'dmic1_input':
 
{{Info|The Pulseaudio dmic1_input is defined in /etc/pulse/system.pa configuration file.}}
 
{{Info|The Pulseaudio dmic1_input is defined in /etc/pulse/system.pa configuration file.}}
 
 
  {{Board$}} pacmd set-default-source dmic1_input
 
  {{Board$}} pacmd set-default-source dmic1_input
   
 
* '''Start audio record :'''
 
* '''Start audio record :'''
 
{{Info|The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.}}
 
{{Info|The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.}}
 
 
  {{Board$}} arecord -r 48000 -f S32_LE -c 2 -d 10 /tmp/rec.wav
 
  {{Board$}} arecord -r 48000 -f S32_LE -c 2 -d 10 /tmp/rec.wav
   
Line 89: Line 84:
   
 
* '''Configure Pulseaudio'''
 
* '''Configure Pulseaudio'''
 
 
Change Pulseaudio default input source to 'iec958_input':
 
Change Pulseaudio default input source to 'iec958_input':
 
{{Info|The Pulseaudio iec958_input is defined in /etc/pulse/system.pa configuration file.}}
 
{{Info|The Pulseaudio iec958_input is defined in /etc/pulse/system.pa configuration file.}}
 
 
  {{Board$}} pacmd set-default-source iec958_input
 
  {{Board$}} pacmd set-default-source iec958_input
   
 
* '''Start audio record :'''
 
* '''Start audio record :'''
 
{{Info|The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.}}
 
{{Info|The Pulseaudio device is the default one, so "-D pulse" option can be omitted in the record command.}}
 
 
  {{Board$}} arecord -r 48000 -f S32_LE -c 2 -d 10 /tmp/rec.wav
 
  {{Board$}} arecord -r 48000 -f S32_LE -c 2 -d 10 /tmp/rec.wav