android_mic_streamig.md

Android mic streamig

In this text I show how to use your android phone as microphone for your pc desktop using sox over ssh.

1 - Configure the desktop

You need have a pulseaudio server running in your pc desktop. Make a simple virtual microphone device using the following:

pactl load-module module-pipe-source source_name=virtmic file=/tmp/virtmic format=s32 rate=48000 channels=1

All OK.

1.1 - For Load virtual mic always

If you prefer, you can load the virtual mic in start of pulseaudio editing the file /etc/pulse/default.pa (you need as root acess).

sudo su
echo "load-module module-pipe-source source_name=virtmic file=/tmp/virtmic format=s32 rate=48000 channels=1" >> /etc/pulse/default.pa
exit

Now restart pulseaudio.

pulseaudio --kill
pulseaudio --start

2 - Configure the android

In android you need have Termux installed. Now you need sox (audio software) for stream your microphone, pulseaudio for authorize sox to use the microphone and ssh to share the stream to the desktop, install it in termux typing:

apt update
apt install -y sox pulseaudio openssh

If you don't know use ssh, read about it in internet.

To allow that sox use microphone, type:

echo "load-module module-sles-source" >> $PREFIX/etc/pulse/default.pa

Restart pulseaudio.

pulseaudio --kill
pulseaudio --start

Now, start the microphone stram with sox -c 1 -r48000 -d -t s32 - and can pipe to cat, for write in the file /tmp/virtmic, in the desktop using ssh:

sox -c 1 -r48000 -d -t s32 - | ssh -p PC_SSH_PORT PC_USER@PC_IP 'cat > /tmp/virtmic'

All OK.

2.1 - Adding effects to the microphone

The streamer can be rewritten as:

sox \
   --channels 1 \
   --rate 48000 \
   --default-device \
   --type s32 \
   -

Where:

• --channels: 1 for mono, 2 for stereo.
• --rate is the sound frequency in Hz.
  • Note that the rate is the same in module-pipe-source argument in the virtual microphone.
• --default-device is the input device.
• --type is the audio type (s32 = signed 32-bit integer).
  • Note that the type is the same in module-pipe-source argument in the virtual microphone.
• - is the output device, the stdin.

Before output device you can add effects from sox. You can also add effects from pulseaudio editing $PREFIX/etc/pulse/default.pa.

For noise you can record 10 seconds for make a profile:

sox -c 1 -r 48000 -d -t s32 $PREFIX/tmp/noise.wav trim 0 10
sox -c 1 -r 48000 -t s32 $PREFIX/tmp/noise.wav -n noiseprof noise.prof

And use noisered noise.prof 0.1 effect before - in sox.

2.2 - Making a script with notification settings

If you prefer, you can write a script for start and stop sound streamer.

Frist edit ~/.ssh/config for make a alias for your pc desktop. In my case the alias is pc.

For make a notification you need installed termux-api application and termux-api package:

apt install -y termux-api

I put the code bellow in $PREFIX/bin/mic_streamer.

#!/bin/bash

# Make a notification for android microphone streaming
termux-notification \
   --icon settings_voice \
   --id 225 \
   --ongoing \
   --type default \
   --priority high \
   --title 'Microphone streamer' \
   --content 'The microphone is sharing to desktop' \
   --button1 'Stop' \
   --button1-action "kill $$; termux-notification --icon settings_voice --id 225 --title 'Microphone streamer' --content 'The microphone streamer has stopped.'"

# Stream the microphone and pipe it for ssh and cat the pipe in the file of the virtual microphone module
sox \
   --channels 1 \
   --rate 48000 \
   --default-device \
   --type s32 \
   - | ssh pc 'cat > /tmp/virtmic'

exit 0

3 - Read more

You can see all formats suported in documentation.