Question

I’ve developed a small application that records sound using ALSA driver on an embedded system.
Now I have a problem selecting the device that I want to record from MIC/Line IN .
The application is set to start at system start up but my default recording device is set to MIC. For my app to work I have to go to amixer and set the recording device from MIC to Line IN and then start my app.

Do you guys know a way to do this change from the app or amixer command that will change this recording device and I can put it in a script an run it at start up.

Has I said this app is running on a embedded system and I need a way to conf the system before my app starts.

EDIT1:
here is my amixer output:

root@freescale ~$ amixer
Simple mixer control 'Headphone',0
  Capabilities: volume
  Playback channels: Front Left - Front Right
  Capture channels: Front Left - Front Right
  Limits: 0 - 127
  Front Left: 103 [81%]
  Front Right: 103 [81%]
Simple mixer control 'Playback',0
  Capabilities: volume
  Playback channels: Front Left - Front Right
  Capture channels: Front Left - Front Right
  Limits: 0 - 192
  Front Left: 192 [100%]
  Front Right: 192 [100%]
Simple mixer control 'Capture',0
  Capabilities: cvolume
  Capture channels: Front Left - Front Right
  Limits: Capture 0 - 15
  Front Left: Capture 15 [100%]
  Front Right: Capture 15 [100%]
Simple mixer control 'Capture Vol Reduction',0
  Capabilities: enum
  Items: 'No Change' 'Reduced by 6dB'
  Item0: 'No Change'
Simple mixer control 'ADC Mux',0
  Capabilities: enum
  Items: 'MIC_IN' 'LINE_IN'
  Item0: 'MIC_IN'
Simple mixer control 'DAC Mux',0
  Capabilities: enum
  Items: 'DAC' 'LINE_IN'
  Item0: 'DAC'
Simple mixer control 'MIC GAIN',0
  Capabilities: enum
  Items: '0dB' '20dB' '30dB' '40dB'
  Item0: '0dB'

Thanks a lot,
Gabriel

Answer 1

I finally did it. I’m using amixer with “cset” command to do it.

amixer -c 0 cset numid=7 1

“-c 0” is the first sound card
“numid=7” is the recording device that is active.
“1” is the second intput … in my case 0-MIC 1-LINEIN

amixer info  

Gets all the controls with their numids ex:

    amixer info
Card default 'mxsevk'/'mxs-evk (SGTL5000)'
  Mixer name    : ''
  Components    : ''
  Controls      : 7
  Simple ctrls  : 7
root@freescale ~$ amixer contents
numid=5,iface=MIXER,name='Headphone Volume'
  ; type=INTEGER,access=rw---,values=2,min=0,max=127,step=0
  : values=103,103
numid=7,iface=MIXER,name='ADC Mux'
  ; type=ENUMERATED,access=rw---,values=1,items=2
  ; Item #0 'MIC_IN'
  ; Item #1 'LINE_IN'
  : values=1
numid=3,iface=MIXER,name='Capture Vol Reduction'
  ; type=ENUMERATED,access=rw---,values=1,items=2
  ; Item #0 'No Change'
  ; Item #1 'Reduced by 6dB'
  : values=0
numid=2,iface=MIXER,name='Capture Volume'
  ; type=INTEGER,access=rw---,values=2,min=0,max=15,step=0
  : values=15,15
numid=4,iface=MIXER,name='Playback Volume'
  ; type=INTEGER,access=rw---,values=2,min=0,max=192,step=0
  : values=192,192
numid=6,iface=MIXER,name='DAC Mux'
  ; type=ENUMERATED,access=rw---,values=1,items=2
  ; Item #0 'DAC'
  ; Item #1 'LINE_IN'
  : values=0
numid=1,iface=MIXER,name='MIC GAIN'
  ; type=ENUMERATED,access=rw---,values=1,items=4
  ; Item #0 '0dB'
  ; Item #1 '20dB'
  ; Item #2 '30dB'
  ; Item #3 '40dB'
  : values=0