amixer - How to change recording channel?

Question

So fat, I am setting up microphone settings :

$ amixer set 'Rear Mic' 90% mute cap
$ amixer set 'Rear Mic Boost' 80%

But, after some sys. update, my default recoding chanell changed to 'Front Mic' :

$ amixer sget 'Input Source'
Simple mixer control 'Input Source',0
  Capabilities: cenum
  Items: 'Front Mic' 'Rear Mic' 'Line' 'CD' 'Mix'
  Item0: 'Front Mic'

How to change 'Input Source' to 'Read Mic' with amixer ? (Currently I do it manually with alsamixer or kmix - I would love to automatize it on startup).

Answer 1

I found solution here:

• http://thenerdshow.com/index30e5.html

there I've found :

$ amixer -c0 cset iface=MIXER,name='Input Source',index=1 'Front Mic' # (Record from Front Mic)

slightly modified according to my sound-card and setup (default sound-card, different items ordering) :

$ amixer cset name='Input Source',index=0 'Rear Mic'

Answer 2

You can use sset parameter. From man amixer:

   set or sset <SCONTROL> <PARAMETER> ...
          Sets the simple mixer control contents. The parameter can be the volume either as a percentage  from  0%  to  100%
          with  % suffix, a dB gain with dB suffix (like -12.5dB), or an exact hardware value.  The dB gain can be used only
          for the mixer elements with available dB information.  When plus(+) or minus(-) letter is  appended  after  volume
          value, the volume is incremented or decremented from the current value, respectively.

          The  parameters  cap,  nocap, mute, unmute, toggle are used to change capture (recording) and muting for the group
          specified.

          The optional modifiers can be put as extra parameters to specify the stream direction or channels to  apply.   The
          modifiers playback and capture specify the stream, and the modifiers front, rear, center, woofer are used to spec‐
          ify channels to be changed.

          A simple mixer control must be specified. Only one device can be controlled at a time.

In your case should be as simple as (NOT TESTED)

$ amixer sset 'Input Source',0,'Rear Mic'