查看“How to record audio”的源代码

== 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>