查看“How to play audio”的源代码

== Article purpose ==
This article explains how to play audio through the [[ALSA overview|ALSA]] audio framework in '''Linux<sup>&reg;</sup> OS''' context.
The examples below, show how to play audio on the different audio hardware interfaces of the STM32MPU [[:Category:ST boards| boards]].

== Audio playback 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 which allows to list audio profiles and to select a profile, to play on a specific audio interface.

The audio playback examples in following sections are given for [[ALSA_overview#How_to_use|ALSA utilities]]. However, the audio playbacks can be launched by other applications, such as [[Gst-play|gstreamer]] multimedia framework.

== Examples ==

=== Audio playback on headset output ===

==== Playback on ALSA device ====
Run audio playback on 'playback_codec' ALSA device:
{{Info|'playback_codec' is an alias defined in /etc/asound.conf, for headset output device.}}
 {{Board$}} aplay -D playback_codec /usr/share/sounds/alsa/Front_Left.wav

==== Playback via PulseAudio ====

* '''Configure Pulseaudio'''
Change the 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

* '''Run audio playback:'''
 {{Board$}} aplay /usr/share/sounds/alsa/Front_Left.wav

=== Audio playback on HDMI output ===
{{Warning|The support of HDMI output is board dependent. Please, check available outputs with "''aplay -l''" command.}}

==== Playback on ALSA device ====
Run audio playback on 'playback_hdmi' ALSA device:
{{Info|'playback_hdmi' is an alias defined in /etc/asound.conf, for hdmi output device.}}
 {{Board$}} aplay -D playback_hdmi /usr/share/sounds/alsa/Front_Left.wav

==== Playback via PulseAudio ====

* '''Configure Pulseaudio'''
Change the Pulseaudio active profile of the sound card, to 'hdmi-stereo' profile:
{{Info|Example below is given for {{highlight|sound card index 0}}. Check sound card index with "''pactl list cards short''" command.}}
 {{Board$}} pacmd set-card-profile 0 output:hdmi-stereo

* '''Run audio playback:'''
 {{Board$}} aplay /usr/share/sounds/alsa/Front_Left.wav

=== Audio playback on S/PDIF output ===
{{Warning|The support of S/PDIF output is board dependent. Please, check available outputs with "''aplay -l''" command.}}
{{Info|S/PDIF ALSA device supports only {{highlight|32-bit audio streams}}. As 32-bit wave files are not provided in sample sound files, speaker-test is used instead of aplay, for convenience, here. Speaker-test generates a 440Hz sine wave in following examples.}}

==== Set IEC958 status bits ====
Example: set IEC958 mode bit.
 {{Board$}} iecset -c STM32MP1EV -n device=0 pro on

==== Playback on ALSA device ====
Run audio playback on 'playback_spdif' ALSA device:
{{Info|'playback_spdif' is an alias defined in /etc/asound.conf, for S/PDIF output device.}}
 {{Board$}} speaker-test -D playback_spdif -c 2 -F S32_LE -f 440 -t sine -l 1

==== Playback via PulseAudio ====

* '''Configure Pulseaudio'''
Change the sound card active profile, to S/PDIF 'iec958-stereo' profile.
{{Info|Example below is given for {{highlight|sound card index 0}}. Check sound card index with "''pactl list cards short''" command.}}
 {{Board$}} pacmd set-card-profile 0 output:iec958-stereo

* '''Run audio playback:'''
 {{Board$}} speaker-test -c 2 -F S32_LE -f 440 -t sine -l 1

<noinclude>
{{PublicationRequestId | 10391 | 2019-01-21}}
[[Category:How to run use cases]]
[[Category:ALSA]]
</noinclude>