Difference between revisions of "How to play audio"

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1 Article purpose[edit]

This article explains how to play audio through the ALSA audio framework in Linux® OS context. The examples below, show how to play audio on the different audio hardware interfaces of the STM32MPU boards.

2 Audio playback 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 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 utilities. However, the audio playbacks can be launched by other applications, such as gstreamer multimedia framework.

Warning.png Sound hazards: The user should always be very cautious when testing audio playbacks, as a software misconfiguration may produce strong sound level, which can expose to hearing damages.


3 Examples[edit]

3.1 Audio playback on headset output[edit]

  • Playback on ALSA device

Run audio playback on 'playback_codec' ALSA device:

Info.png '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

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

Info.png The Pulseaudio analog-stereo profile is the default profile. So next command is not required after boot.
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

Run audio playback:

Board $> aplay /usr/share/sounds/alsa/Front_Left.wav

3.2 Audio playback on HDMI output[edit]

Warning.png 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.png '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

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

Info.png Example below is given for 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

3.3 Audio playback on S/PDIF output[edit]

Warning.png The support of S/PDIF output is board dependent. Please, check available outputs with "aplay -l" command.
Info.png S/PDIF ALSA device supports only 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.
  • Playback on ALSA device

Run audio playback on 'playback_spdif' ALSA device:

Info.png '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

Change the sound card active profile, to S/PDIF 'iec958-stereo' profile.

Info.png Example below is given for 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>

{{ArticleMainWriter | OlivierM}}
{{ArticleApprovedVersion | OlivierM | ArnaudP(Passed 17Janv'19) | No previous approved version | AlainF - 21Jan'19 - 10391 | 21Jan'19}}
[[Category:How to run use cases]]
[[Category:ALSA]]</noinclude>

== 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.
{{Warning|Sound hazards: The user should always be very cautious when testing audio playbacks, as a software misconfiguration may produce strong sound level, which can expose to hearing damages.}}

{{ReviewsComments| Arnaud: W38.2: need to clarify from legals point of view if we can communicate this and how to communicate this.}}
== 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'''
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'''
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.}}

* '''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'''
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>
(3 intermediate revisions by 2 users not shown)
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<noinclude>
 
{{ArticleMainWriter | OlivierM}}
 
{{ArticleApprovedVersion | OlivierM | ArnaudP(Passed 17Janv'19) | No previous approved version | AlainF - 21Jan'19 - 10391 | 21Jan'19}}
 
[[Category:How to run use cases]]
 
[[Category:ALSA]]
 
</noinclude>
 
 
 
== Article purpose ==
 
== Article purpose ==
 
This article explains how to play audio through the [[ALSA overview|ALSA]] audio framework in '''Linux<sup>&reg;</sup> OS''' context.
 
This article explains how to play audio through the [[ALSA overview|ALSA]] audio framework in '''Linux<sup>&reg;</sup> OS''' context.
Line 16: Line 9:
   
 
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.
 
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.
  +
  +
{{Warning|Sound hazards: The user should always be very cautious when testing audio playbacks, as a software misconfiguration may produce strong sound level, which can expose to hearing damages.}}
  +
  +
{{ReviewsComments| Arnaud: W38.2: need to clarify from legals point of view if we can communicate this and how to communicate this.}}
   
 
== Examples ==
 
== Examples ==
Line 67: Line 64:
 
Run audio playback:
 
Run audio playback:
 
  {{Board$}} speaker-test -c 2 -F S32_LE -f 440 -t sine -l 1
 
  {{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>

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