Changing volume in Python program on Raspbery Pi

Question

I use Raspbery Pi B+ 2. I have a Python program that uses the ultrasonic sensor to measure the distance to an object. What I would like to is change the volume depending on the distance to a human. Having a Python code to obtain the distance, I have no idea, how can I change the Raspbery Pi volume by a code in Python.

Is there any way to do that?

Solution 1

You can use the package python-alsaaudio. The installation and usage is very simple.

To install run:

sudo apt-get install python-alsaaudio

In your Python script, import the module:

import alsaaudio

Now, you need to get the main mixer and get/set the volume:

m = alsaaudio.Mixer()
current_volume = m.getvolume() # Get the current Volume
m.setvolume(70) # Set the volume to 70%.

If the line m = alsaaudio.Mixer() throws an error, then try:

m = alsaaudio.Mixer('PCM')

this might happen because the Pi uses PCM rather than a Master channel.

You can see more information about your Pi's audio channels, volume (etc..), by running the command amixer.

Solution 2

1. Collecting actual mixers available (will provide a list of available cards):

import alsaaudio as audio
scanCards = audio.cards()
print("cards:", scanCards)

In my case I've got following list:

[u'PCH', u'headset']

2. Scanning for the mixers per each card:

for card in scanCards:
    scanMixers = audio.mixers(scanCards.index(card))
    print("mixers:", scanMixers)

In my case I've got the following two lists:

[u'Master', u'Headphone', u'Speaker', u'PCM', u'Mic', u'Mic Boost', u'IEC958', u'IEC958', u'IEC958', u'IEC958', u'IEC958', u'Beep', u'Capture', u'Auto-Mute Mode', u'Internal Mic Boost', u'Loopback Mixing']

[u'Headphone', u'Mic', u'Auto Gain Control']

As you may see, "Master" is not always the mixer available, but traditionally expected an equivalent of the Master mixer to be at index 0. (Doesn't mean always!)

3. To control volume in this case for the USB Headset would be following procedure.

Volume Up

def volumeMasterUP():
    mixer = audio.Mixer('Headphone', cardindex=1)
    volume = mixer.getvolume()
    newVolume = int(volume[0])+10
    if newVolume <= 100:
        mixer.setvolume(newVolume)

Volume Down

def volumeMasterDOWN():
    mixer = audio.Mixer('Headphone', cardindex=1)
    volume = mixer.getvolume()
    newVolume = int(volume[0])-10
    if newVolume >= 0:
        mixer.setvolume(newVolume)

Solution 3

I made a simple python service for a two button volume control. Based on what @ant0nisk put.

https://gist.github.com/peteristhegreat/3c94963d5b3a876b27accf86d0a7f7c0

It shows getting and setting the volume, and muting.

Comments

[Joseph Sheedy]

The package is named pyalsaaudio