Recording sound using ALSA from Line IN

alsa, c, linux

Solution

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

Problem

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

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