Linux Audio record play

DART-Mx8M - Audio Record/Play

Get information on the Sound Cards

Installed devices:

root@imx8m-var-dart:~# cat /proc/asound/cards
 0 [imxwm8904      ]: imx-wm8904 - imx-wm8904
                      imx-wm8904

List device names for playback:

root@imx6ul-var-dart:~# aplay -L
null
    Discard all samples (playback) or generate zero samples (capture)
pulse
    PulseAudio Sound Server
sysdefault:CARD=imxwm8904
    imx-wm8904, 
    Default Audio Device

Audio Playback

Set PCM volume (main volume of audio codec), range :0-63

# amixer set Headphone 30
Play audio:
<pre>
# aplay /usr/share/sounds/alsa/Front_Center.wav

Example:

root@imx8m-var-dart:~# amixer set set Headphone 30
Simple mixer control 'Headphone',0
  Capabilities: volume pswitch
  Playback channels: Front Left - Front Right
  Capture channels: Front Left - Front Right
  Limits: 0 - 63
  Front Left: 30 [48%] [-27.00dB] Playback [on]
  Front Right: 30 [48%] [-27.00dB] Playback [on]

root@imx8m-var-dart:~# aplay /usr/share/sounds/alsa/Front_Center.wav
Playing WAVE '/usr/share/sounds/alsa/Front_Center.wav' : Signed 16 bit Little Endian, Rate 48000 Hz, Mono

Audio Record and Play, Line-in Jack

# amixer set 'Capture' 22
# arecord -f cd -d 10 test.wav
# aplay test.wav 

Example:

root@imx6ul-var-dart:~# arecord -f cd -d 10 test.wav
Recording WAVE 'test.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo
root@imx6ul-var-dart:~# aplay test.wav
Playing WAVE 'test.wav' : Signed 16 bit Little Endian, Rate 44100 Hz, Stereo

Advanced Controls

amixer without a parameter will show all available controls. For example:

root@imx6ul-var-dart:~# amixer
Simple mixer control 'Master',0
  Capabilities: pvolume
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 127
  Mono:
  Front Left: Playback 125 [98%] [4.00dB]
  Front Right: Playback 125 [98%] [4.00dB]
Simple mixer control 'Master Playback ZC',0
  Capabilities: pswitch
  Playback channels: Front Left - Front Right
  Mono:
  Front Left: Playback [off]
  Front Right: Playback [off]
Simple mixer control 'Sidetone',0
  Capabilities: pvolume pvolume-joined
  Playback channels: Mono
  Limits: Playback 0 - 3
  Mono: Playback 3 [100%] [-6.00dB]
Simple mixer control 'Mic',0
  Capabilities: cswitch cswitch-joined
  Capture channels: Mono
  Mono: Capture [off]
Simple mixer control 'Mic Boost',0
  Capabilities: volume volume-joined
  Playback channels: Mono
  Capture channels: Mono
  Limits: 0 - 1
  Mono: 0 [0%] [0.00dB]
Simple mixer control 'Playback Deemphasis',0
  Capabilities: pswitch pswitch-joined
  Playback channels: Mono
  Mono: Playback [off]
Simple mixer control 'Capture',0
  Capabilities: cvolume
  Capture channels: Front Left - Front Right
  Limits: Capture 0 - 31
  Front Left: Capture 31 [100%] [12.00dB]
  Front Right: Capture 31 [100%] [12.00dB]
Simple mixer control 'ADC High Pass Filter',0
  Capabilities: pswitch pswitch-joined
  Playback channels: Mono
  Mono: Playback [on]
Simple mixer control 'Input Mux',0
  Capabilities: enum
  Items: 'Line In' 'Mic'
  Item0: 'Line In'
Simple mixer control 'Output Mixer HiFi',0
  Capabilities: pswitch pswitch-joined
  Playback channels: Mono
  Mono: Playback [on]
Simple mixer control 'Output Mixer Line Bypass',0
  Capabilities: pswitch pswitch-joined
  Playback channels: Mono
  Mono: Playback [off]
Simple mixer control 'Output Mixer Mic Sidetone',0
  Capabilities: pswitch pswitch-joined
  Playback channels: Mono
  Mono: Playback [off]
Simple mixer control 'Store DC Offset',0
  Capabilities: pswitch pswitch-joined
  Playback channels: Mono
  Mono: Playback [off]

Options:

amixer   sset sID P      set contents for one mixer simple control
amixer   sget sID        get contents for one mixer simple control

For example:

 root@imx6ul-var-dart:~# amixer sget 'Capture'                                                                                         
Simple mixer control 'Capture',0
  Capabilities: cvolume
  Capture channels: Front Left - Front Right
  Limits: Capture 0 - 31
  Front Left: Capture 31 [100%] [12.00dB]
  Front Right: Capture 31 [100%] [12.00dB]

HP DAC is a headphones DAC gain currently set to 60%. The optional values are 0-118 equal to 0%-100%.

  root@imx6ul-var-dart:~# amixer sset 'Capture' 25                                                                                      
Simple mixer control 'Capture',0
  Capabilities: cvolume
  Capture channels: Front Left - Front Right
  Limits: Capture 0 - 31
  Front Left: Capture 25 [81%] [3.00dB]
  Front Right: Capture 25 [81%] [3.00dB]

Capture currently now set to 81%.

Save / restore system's audio settings

alsactl store stores all alsamixer settings into a file
alsctl Options:

  store     <card>  save current driver setup for one or each soundcards
                      to configuration file
  restore   <card>  load current driver setup for one or each soundcards
                      from configuration file

Example:

# alsactl store -f 123.conf
# alsactl restore -f 123.conf