Difference between revisions of "How to record audio"

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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.png '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

3.1.2 Record via PulseAudio[edit]

3.1.2.1 For ecosystem release v1.2.0 Warning.png[edit]
  • Configure Pulseaudio :

Change Pulseaudio default input source to 'analog_input':

Info.png The Pulseaudio analog_input is defined in /etc/pulse/system.pa configuration file.
Board $> pacmd set-default-source analog_input
  • Start audio record :
Info.png 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
3.1.2.2 For ecosystem release v1.1.0 Warning.png[edit]
  • Configure Pulseaudio :

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

Info.png Example below is given for 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.png 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

3.2 Audio record from digital microphone input[edit]

Warning.png 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.png '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

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

Start stereo audio record from 'multi' ALSA device:

Info.png 'multi' device, based on ALSA multi plugin[1], 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

3.2.3 Record via PulseAudio[edit]

The record via Pulseaudio is only available for ecosystem release v1.2.0 Warning.png.

  • Configure Pulseaudio

Change Pulseaudio default input source to 'dmic1_input':

Info.png The Pulseaudio dmic1_input is defined in /etc/pulse/system.pa configuration file.
Board $> pacmd set-default-source dmic1_input
  • Start audio record :
Info.png 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

3.3 Audio record from S/PDIF input[edit]

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

3.3.1 Get IEC958 status bits[edit]

Some restrictions may apply to IEC958 control, depending on the SPDIFRX device configuration as it is explained in SPDIFRX device tree configuration and SPDIFRX Linux driver articles.

Board $> amixer -c STM32MP1EV cget iface=PCM,name='IEC958 Capture Default'

3.3.2 Record from ALSA device[edit]

Start audio record from 'record_spdif' ALSA device:

Info.png 'record_spdif' is an alias defined in /etc/asound.conf, for S/PDIF input device.
Info.png 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

3.3.3 Record via PulseAudio[edit]

The record via Pulseaudio is only available for ecosystem release v1.2.0 Warning.png.

  • Configure Pulseaudio

Change Pulseaudio default input source to 'iec958_input':

Info.png The Pulseaudio iec958_input is defined in /etc/pulse/system.pa configuration file.
Board $> pacmd set-default-source iec958_input
  • Start audio record :
Info.png 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

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|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.}}

==== Get IEC958 status bits ====
Some restrictions may apply to IEC958 control, depending on the SPDIFRX device configuration as it is explained in [[SPDIFRX device tree configuration]] and [[SPDIFRX Linux driver]] articles.

 {{Board$}} amixer -c STM32MP1EV cget iface=PCM,name='IEC958 Capture Default'

==== 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 21: Line 21:
   
 
==== Record via PulseAudio ====
 
==== Record via PulseAudio ====
 
===== For {{EcosystemRelease | revision=1.2.0 | range=and after}} =====
 
   
 
* '''Configure Pulseaudio :'''
 
* '''Configure Pulseaudio :'''
Line 32: Line 30:
 
{{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 -d 10 /tmp/rec.wav
 
  {{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|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 ===
 
=== Audio record from digital microphone input ===
Line 60: Line 45:
   
 
==== Record via PulseAudio ====
 
==== Record via PulseAudio ====
The record via Pulseaudio is only available for {{EcosystemRelease | revision=1.2.0 | range=and after}}.
 
   
 
* '''Configure Pulseaudio'''
 
* '''Configure Pulseaudio'''
Line 86: Line 70:
   
 
==== Record via PulseAudio ====
 
==== Record via PulseAudio ====
The record via Pulseaudio is only available for {{EcosystemRelease | revision=1.2.0 | range=and after}}.
 
   
 
* '''Configure Pulseaudio'''
 
* '''Configure Pulseaudio'''