How to change bit depth to 16 of I2S MEMS Microphone?

Question

I have successfully setup adafruit I2S mem microphone on my RPi3 running buster by following this guide .

It records audio well using arecord :

arecord -D 'plughw:2,0' -c1 -r 48000 -f S32_LE -t wav -V mono -v file.wav

But I need 16-bit signed PCM audio for my project. Running arecord -D 'plughw:2,0' -c1 -r 48000 -f S16_LE -t wav -V mono -v file.wav does not record anything.

What changes do I need to make to change bit depth to 16 ?

Thanks.

Answer 1

After going through ALSA documentation, I was able to achieve it by configuring ALSA .asoundrc file to get 16 bit pcm with boosted microphone volume for my project.

Microphone is available as card #2. Therefore in line 4, pcm "hw:2,0"

Here are the contents of ~/.asoundrc :

pcm.mymic_main {
        type plug
        slave {
           pcm "hw:2,0"
           rate 48000
           format S32_LE
    }

}

pcm.mymic  {
        type softvol
        slave.pcm mymic_main
        control {
                name "Boost Capture Volume"
                card sndrpii2scard
        }
        min_dB -3.0
        max_dB 30.0
}

In python project :

sudo pip3 install pyalsaaudio

cat myproject.py

import alsaaudio

mic = alsaaudio.PCM( alsaaudio.PCM_CAPTURE,  alsaaudio.PCM_NONBLOCK,  device='mymic',  channels=1, rate=48000, format=alsaaudio.PCM_FORMAT_S16_LE, periodsize=960 )

_ , frame = mic.read()