how to play audio from python on Raspbian Stretch Lite?

Question

I would like to play selected audio files through the built-in audio port on a Raspberry 3 that is running Raspbian Stretch Lite, from a python program. Unfortunately, none of the libraries or external applications that I have tried for this purpose work.

sudo pip install pygame

results in

Unable to run "sdl-config". Please make sure a development version of SDL is installed.

and

pip install sdl

fails with

Could not find a version that satisfies the requirement sdl (from versions: ) No matching distribution found for sdl

mplayer won’t install.

mpg321 comes closest, installing but then failing when used, with ALSA lib errors, and you can’t install a new version of alas-utils because

Could not find a version that satisfies the requirement alsa-utils (from versions: ) No matching distribution found for alsa-utils

What do people do to play music on this OS?

Answer 1

I have just tested it with two favorite programs: omxplayer and mpv. I used a fresh flashed up to date Raspbian Buster Lite but it shouldn't make a difference to Raspbian Stretch Lite. Playing music with this programs works out of the box without an modifications.

For testing first I plugged in a simple earphone into the analog audio output plug of my Raspberry Pi 4B. Then downloaded a test mp3 file from Sample .mp3 download. I selected the smallest one:

rpi ~$ curl https://file-examples.com/wp-content/uploads/2017/11/file_example_MP3_700KB.mp3 > file_example_MP3_700KB.mp3

Then installed omxplayer:

rpi ~$ sudo apt install omxplayer

and played the test file:

rpi ~$ omxplayer file_example_MP3_700KB.mp3

Same with mpv:

rpi ~$ sudo apt install mpv
rpi ~$ mpv file_example_MP3_700KB.mp3

I would prefer omxplayer because it is lighter than mpv and explicitly supports the hardware acceleration of the Raspberry Pi.

Now play it from python3:

rpi ~$ python3
Python 3.7.3 (default, Apr  3 2019, 05:39:12) 
[GCC 8.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.system('/usr/bin/omxplayer /home/pi/file_example_MP3_700KB.mp3')

or playing it in the background:

>>> import subprocess
>>> subprocess.Popen(['/usr/bin/omxplayer', '/home/pi/file_example_MP3_700KB.mp3'])
exit()
rpi ~$    # exit from python3 but still playing

You may have a look at an omxplayer-wrapper. Look at google with python omxplayer-wrapper.

Answer 2

How to play audio in Python3 on RaspiOS Bullseye lite (I'd recommend to use the current version) - because VLC supports many audio formats, I use this library.

Install pulseaudio:

sudo apt install alsa-oss libasound2-plugins libavresample4 pulseaudio pulseaudio-utils

Start server:

pulseaudio -D

You can display your audio sinks (outputs) with:

pacmd list-sinks

Playing is possible with pacmd as well but only WAV:

pacmd play-file  <path> <sinkno>

You have to specify the full, absolute path for the file.

Troubleshooting for pulseaudio:

Stopping server:

systemctl --user stop pulseaudio.socket
systemctl --user stop pulseaudio.service

Starting server interactively for output to screen:

pulseaudio -v

VLC: Install necessary parts of VLC:

sudo apt install vlc-bin vlc-plugin-base

Install VLC library for Python:

sudo pip install python-vlc

In Python:

import vlc
p = vlc.MediaPlayer("<audiofile>")
p.play()

Volume can be got and set with:

vlc.libvlc_audio_get_volume(p)
vlc.libvlc_audio_set_volume(p,50)

I hope this answer is helpful.

Additional hint: If you plug in your USB device, this device should be the default for audio output.