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Audio

RUBIK Pi 3 currently supports the following audio interfaces:

  • 3.5mm headphone (No. 4 in the following figure)
  • HDMI OUT (No. 9 in the following figure)
  • USB Audio (No. 5, 6, 7 in the following figure)

This section describes how to perform audio playback, recording, and input/output interface switching when a UAC device is connected.

Sound card​

  • The mounting order of the onboard sound card and the UAC device sound card mainly depends on the following factors:

    1. The connection interface of the UAC device.
    2. Whether the UAC device is connected before or after device boot-up.

  • On RUBIK Pi 3, run the following command to check the mounted sound cards:

    cat /proc/asound/cards

    warning
    1. The following instructions assume that the onboard sound card is mounted as card 0, and the UAC device is mounted as card 1.
    2. The actual name and supported formats of UAC devices may vary. Please adjust commands accordingly based on your specific device.

  • On RUBIK Pi 3, run the following command to check the allocated PCM stream list:

ALSA​

  • On RUBIK Pi 3, run the following commands to install the ALSA utilities.

    sudo apt update
    sudo apt install alsa-utils

Playback​

warning
  1. Run the following command to ensure the /opt path has read/write permissions.
  2. Make sure the WAV test file (<FileName>.wav) has been pushed to the /opt directory before running the command.
sudo chmod 777 -R /opt
paplay /opt/<FileName>.mp3
  • 3.5mm headphone playback 
    amixer -c 0 cset "name=DAC Playback Volume" 192
    amixer -c 0 cset "name=PRIMARY_MI2S_RX Audio Mixer MultiMedia1" 1
    aplay -Dplughw:0,0 /opt/<FileName>.wav
  • HDMI OUT playback 
    amixer -c 0 cset "name=QUATERNARY_MI2S_RX Audio Mixer MultiMedia2" 1
    aplay -Dplughw:0,1 /opt/<FileName>.wav
  • UAC playback 
    aplay -Dplughw:1,0 /opt/<FileName>.wav

Recording​

warning

Run the following command to ensure the /opt path has read/write permissions.

sudo chmod 777 -R /opt

  • 3.5mm headphone recording

    amixer -c 0 cset "name=MultiMedia3 Mixer PRIMARY_MI2S_TX" 1
    arecord -Dplughw:0,2 -f S16_LE -r 48000 -c 1 -d 10 -t wav /opt/<FileName>.wav

  • UAC recording

    warning

    Adjust the command parameters based on the formats actually supported by the UAC device.

    arecord -Dplughw:1,0 -f S16_LE -r 48000 -c 1 -d 10 -t wav /opt/<FileName>.wav

PulseAudio​

  • On RUBIK Pi 3, run the following commands to install the PulseAudio utilities:

    sudo apt update
    sudo apt install pulseaudio pulseaudio-utils
    note

    Please run the Pulseaudio command under a non-root user. For example, use the su ubuntu command to switch to the ubuntu user.

Set the audio output interface​

warning
  1. PulseAudio automatically switches audio output based on sink priority: UAC > 3.5mm headphone > HDMI OUT.
  2. Users can manually switch using the set-default-sink command. Once switched manually, the automatic strategy will be overridden until the sink is manually set back to the one with the highest priority.
  • On RUBIK Pi 3, use the following command to view sink names and their priorities: 
    pactl list sinks | grep -A5 -B1 -E 'Sink #|priority'

Switch the audio output interface​

pactl set-default-sink <Sink-Name>

Examples

  • Switch output to 3.5mm headphone:
pactl set-default-sink alsa_output.platform-sound.HiFi__hw_qcs6490rubikpi3_0__sink
  • Switch output to HDMI OUT:
pactl set-default-sink alsa_output.platform-sound.HiFi__hw_qcs6490rubikpi3_1__sink
  • Switch output to UAC device:
warning

Adjust the command according to the actual sink name of your UAC device.

pactl set-default-sink alsa_output.usb-GeneralPlus_USB_Audio_Device-00.analog-stereo

Set the audio input interface​

warning
  1. PulseAudio automatically switches audio input based on source priority: UAC > 3.5mm headphone.
  2. Users can manually switch using the set-default-source command. Once switched manually, the automatic strategy will be overridden until the source is manually set back to the one with the highest priority.
  • On RUBIK Pi 3, run the following command to list available sources and their priorities: 
    pactl list sources | grep -A5 -B1 -E 'Source #|priority'

Switch the audio input interface​

pactl set-default-source <Source-Name>

Examples:

  • Switch input to 3.5mm headphone:
pactl set-default-source alsa_input.platform-sound.HiFi__hw_qcs6490rubikpi3_2__source
  • Switch input to UAC device:
warning

Adjust the command according to the actual source name of your UAC device.

pactl set-default-source alsa_input.usb-GeneralPlus_USB_Audio_Device-00.mono-fallback

Playback​

warning
  1. Run the following command to make sure the /opt directory has read/write permissions.
  2. Before running the command, ensure the MP3 test file (<FileName>.wav) has been pushed to the /opt directory.
sudo chmod 777 -R /opt

Recording​

Run the following command to make sure the /opt directory has read/write permissions.

sudo chmod 777 -R /opt
  • On RUBIK Pi 3, run the following command to start recording:
parecord /opt/<FileName>.mp3