Common Usage

This page provides a reference for the shared components of the audio system across Genio platforms.

PipeWire

Supported Platform:

  • Genio 350-EVK

  • Genio 510-EVK

  • Genio 700-EVK

  • Genio 1200-EVK

  • Genio 520/720-EVK

PipeWire is a server and user space API to deal with multimedia pipelines. Starting from IoT Yocto v25.1, PipeWire replaces PulseAudio as the default system audio server on the Genio platform.

The following section introduces PipeWire usage, providing example commands and the expected results on the platforms.

Service Status

PipeWire usually runs as a user service, managed by the WirePlumber session manager.

To check the status of the PipeWire service and the WirePlumber:

systemctl --user status pipewire pipewire-pulse wireplumber

If the services are running correctly, you should see them as active (running).

Output Example:

../../../../_images/sw_yocto_app-dev_audio_pipewire-status.png

PipeWire service status

To start the services:

systemctl --user start pipewire pipewire-pulse wireplumber

To stop the services:

systemctl --user stop pipewire pipewire-pulse wireplumber

Common Command Line Tools

The Genio platform includes several tools for interacting with PipeWire.

Tool

Description

wpctl

The primary CLI for managing volume, routing, and device status.

pw-top

Real-time monitoring of PipeWire nodes and drivers.

pw-dump

Dumps the current state of the PipeWire graph.

pw-play

Simple playback tool.

pw-record

Simple recording tool.

spa-acp-tool

CLI to manage ALSA Card Profiles (ACP) directly.

Usage Examples

Listing Devices

To see all available audio sinks (outputs) and sources (inputs):

wpctl status

Output Example:

Audio
 ├─ Devices:
 │      47. Built-in Audio                      [alsa]
 │
 ├─ Sinks:
 │      48. Built-in Audio I2S output           [vol: 0.40]
 │      49. Built-in Audio PCM output           [vol: 0.40]
 │  *   50. Built-in Audio Earphone speaker + Lineout speaker [vol: 0.40]
 │
 ├─ Sources:
 │      51. Built-in Audio I2S input            [vol: 1.00]
 │      52. Built-in Audio PCM input            [vol: 1.00]
 │  *   53. Built-in Audio Digital microphone   [vol: 1.00]
 │      54. Built-in Audio Analog microphone + Earphone microphone [vol: 1.00]
 │
 ├─ Filters:
 │
 ├─ Streams:

Note: The * indicates the default device.

Setting Default Output/Input

To change the default audio output/input device, identify the ID from wpctl status (e.g., ID 48):

wpctl set-default 48

Playback and Recording Test

Since PipeWire provides ALSA compatibility, standard ALSA tools can be used:

Playback:

aplay -D pipewire /usr/share/sounds/alsa/Front_Center.wav

Recording:

arecord -D pipewire -f S16_LE test.wav

Alternatively, you can use pw-play and pw-record:

pw-play /usr/share/sounds/alsa/Front_Center.wav
pw-record test.wav

Changing Volume

You can set volume using the ID displayed in wpctl status or by using special targets like @DEFAULT_AUDIO_SINK@ and @DEFAULT_AUDIO_SOURCE@.

Set volume using ID (e.g., ID 48):

wpctl set-volume 48 0.5

Set volume for the default sink/source:

# Set default speaker volume to 50%
wpctl set-volume @DEFAULT_AUDIO_SINK@ 0.5

# Set default microphone volume to 80%
wpctl set-volume @DEFAULT_AUDIO_SOURCE@ 0.8

Adjust volume relative to current level:

# Increase volume by 5%
wpctl set-volume @DEFAULT_AUDIO_SINK@ 5%+

# Decrease volume by 5%
wpctl set-volume @DEFAULT_AUDIO_SINK@ 5%-

Mute/Unmute:

To mute or unmute a device, use 1 (mute), 0 (unmute), or toggle.

# Toggle mute status
wpctl set-mute @DEFAULT_AUDIO_SINK@ toggle

# Explicitly mute
wpctl set-mute @DEFAULT_AUDIO_SINK@ 1

# Explicitly unmute
wpctl set-mute @DEFAULT_AUDIO_SINK@ 0

Debugging

Monitoring Latency and DSP Load

Use pw-top to view real-time statistics regarding quantum size (buffer), sample rate, and DSP usage.

pw-top

Output Example:

S   ID  QUANT   RATE    WAIT    BUSY   W/Q   B/Q  ERR FORMAT           NAME
S   29      0      0    ---     ---   ---   ---     0                  Dummy-Driver
S   30      0      0    ---     ---   ---   ---     0                  Freewheel-Driver
S   48      0      0    ---     ---   ---   ---     0                  alsa_output.platform-soc_sound.HiFi__hw_mt8391evk_1__sink
S   49      0      0    ---     ---   ---   ---     0                  alsa_output.platform-soc_sound.HiFi__hw_mt8391evk_6__sink
S   50      0      0    ---     ---   ---   ---     0                  alsa_output.platform-soc_sound.HiFi__hw_mt8391evk_0__sink
S   51      0      0    ---     ---   ---   ---     0                  alsa_input.platform-soc_sound.HiFi__hw_mt8391evk_3__source
S   52      0      0    ---     ---   ---   ---     0                  alsa_input.platform-soc_sound.HiFi__hw_mt8391evk_20__source
R   53   1024  48000  98.3us   0.6us  0.00  0.00    0    S32LE 2 48000 alsa_input.platform-soc_sound.HiFi__hw_mt8391evk_2__source
R   71      0  48000  62.2us  22.8us  0.00  0.00    0    S16LE 2 48000  + pw-record
S   54      0      0    ---     ---   ---   ---     0                  alsa_input.platform-soc_sound.HiFi__hw_mt8391evk_4__source
S   34      0      0    ---     ---   ---   ---     0                  bluez_midi.server

Inspecting the Graph

To generate a visual representation of the current audio pipeline (nodes and links):

pw-dot
dot -Tpng pw.dot -o pipewire-graph.png

(Requires graphviz package installed)

Output Example:

../../../../_images/sw_yocto_app-dev_audio_pipewire-graph.png

pipewire-graph.png