Converting mono 32bit input with ALSA

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53

# This section makes a reference to your I2S hardware, adjust the card name
# to what is shown in arecord -l after card x: before the name in []
# You may have to adjust channel count also but stick with default first
pcm.dmic_hw {
  type hw
  card sndrpisimplecar
  channels 2
  format S32_LE
  rate 48000
}

# This is the software volume control, it links to the hardware above and after
# saving the .asoundrc file you can type alsamixer, press F6 to select
# your I2S mic then F4 to set the recording volume and arrow up and down to adjust the volume
# After adjusting the volume - go for 50 percent at first, you can do something like
# arecord -D dmic_sv -c2 -r 48000 -f S32_LE -t wav -V mono -v myfile.wav
pcm.dmic_sv {
  type softvol
  slave.pcm dmic_hw
  control {
    name "Boost Capture Volume"
    card sndrpisimplecar
  }
  min_dB -3.0
  max_dB 30.0
}

# This plugin converts the mono input to stereo.
pcm.mono2stereo {
  type route
  slave.pcm dmic_sv
  slave.channels 2
  # ttable.input_channel.output_channel volume_gain
  ttable.0.0 1
  ttable.0.1 1
}

# The "plug" plugin converts channels, rate and format on request.
# In our case it converts the 32 format to whatever the application request.
pcm.convert {
  type plug
  slave {
    pcm mono2stereo
  }
}

# Default capture and playback devices
pcm.!default {
  type asym
  capture.pcm convert
  playback.pcm "hw:0,0" # Note: the default output may also need a plug.
}