Play two sounds simultanously in PYTHON without pygame

Question

I'm doing a project with an embedded computer module, the EXM32 Starter Kit and I want to simulate a piano with 8 musical notes. The OS is linux and I'm programming in Python. My problem is that version of Python is the 2.4 without 'pygame' library to play two sounds simultaneously. At now I am using in python "os.system('aplay ./Do.wav')" to play, from linux console, the sound.

The simplificated question is: Can I use another library to do the same as:

    snd1 =  pygame.mixer.Sound('./Do.wav')
    snd2 =  pygame.mixer.Sound('./Re.wav')

    snd1.play()
    snd2.play()

to play 'Do' and 'Re' simultanously? I can use "auidoop" and "wave" library.

I tried use threading but the problem is that the program wait until the console command has been finished. Another library that can I used? or the method to do with 'wave' or 'audioop'?? (this last library I believe is only for manipulated sound files) The complete code is:

import termios, sys, os, time
TERMIOS = termios
#I wrote this method to simulate keyevent. I haven't got better libraries to do this
def getkey():
    fd = sys.stdin.fileno()
    old = termios.tcgetattr(fd)
    new = termios.tcgetattr(fd)
    new[3] = new[3] & ~TERMIOS.ICANON & ~TERMIOS.ECHO
    new[6][TERMIOS.VMIN] = 1
    new[6][TERMIOS.VTIME] = 0
    termios.tcsetattr(fd, TERMIOS.TCSANOW, new)
    key_pressed = None
    try:
            key_pressed = os.read(fd, 1)
    finally:
            termios.tcsetattr(fd, TERMIOS.TCSAFLUSH, old)
    return key_pressed

def keyspress(note):

    if note == DO:
            os.system('aplay  ./notas_musicales/Do.wav')
    elif note == RE:
            os.system('aplay ./notas_musicales/Re.wav')
    elif note == MI:
            os.system('aplay ./notas_musicales/Mi.wav')
    elif note == FA:
            os.system('aplay ./notas_musicales/Fa.wav')
    elif note == SOL:
            os.system('aplay ./notas_musicales/Sol.wav')
    elif note == LA:
            os.system('aplay ./notas_musicales/La.wav')
    elif note == SI:
            os.system('aplay ./notas_musicales/Si.wav')


DO = 'a'
RE = 's'
MI = 'd'
FA = 'f'
SOL = 'g'
LA = 'h'
SI = 'j'
key_pressed = ""
i = 1

#in each iteration the program enter into the other 'if' to doesn't interrupt
#the last sound.
while(key_pressed != 'n'):
    key_pressed = getkey()
    if i == 1:
        keyspress(key_pressed)
        i = 0
    elif i == 0:
        keyspress(key_pressed)
        i = 1
    print ord(key_pressed)

Python 2.4 is waaaay behind the times. You should try very hard to upgrade, preferably to 2.7. — Katriel, Dec 28 '12 at 17:41

score 3 · Answer 1 · edited May 23 '17 at 11:52

3

Your basic problem is that you want to spawn a process and not wait for its return value. You can't do that with os.system() (well you could just spawn dozens of threads).

You can do this with the subprocess module which incidentally is available since 2.4. See here for an example.

edited May 23 '17 at 11:52

Community

1
1

answered Dec 28 '12 at 17:26

Voo

29,040
11
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Roland Smith · Accepted Answer · 2012-12-29T00:29:02.340

3

Due to the global interpreter lock ("GIL") in the default python implementation only one thread will be running at a time. So that won't help you much in this case.

Additionally, os.system waits for the command to finish, and spawns an extra shell to run the command in. You should use suprocess.Popen instead, which will return as soon as it has started the program, and by default does not spawn an extra shell. The following code should start both players as closely together as possible:

import subprocess

do = subprocess.Popen(['aplay', './notas_musicales/Do.wav'])
re = subprocess.Popen(['aplay', './notas_musicales/Re.wav'])

edited Dec 29 '12 at 00:29

answered Dec 28 '12 at 17:30

Roland Smith

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3
64
94

Thx Roland. Question answered. – Iker Ocio Zuazo Dec 28 '12 at 17:47
Actually since `os.system()` just creates a new process, the GIL would be no problem at all. Yes you could only *spawn* one process at a time, but the same is true for `subprocess.Popen`. It just creates quite some overhead if you need more than one or two sounds at the same time. – Voo Dec 29 '12 at 00:14

Play two sounds simultanously in PYTHON without pygame

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