Generating Tones With Python

[Adam Gaskins]

I am pretty sure this shouldn't be as hard as I'm making it to be, but
how does one go about generating tones of specific frequency, volume, and
L/R pan? I've been digging around the internet for info, and found a few
examples. One was with gstreamer, but I can't find much in the
documentation to explain how to do this. Also some people said to use
tksnack snack, but the one example I found to do this didn't do anything
on my machine, no error or sounds. I'd like this to be cross platform,
but at this point I just want to do it any way I can.

Thanks,
-Adam

 

[Matus]

try http://www.pygame.org, as far as I remember there is a way to
generate sound arrays though not sure aboout the pan

m

 

[Dennis Lee Bieber]

I am pretty sure this shouldn't be as hard as I'm making it to be, but
how does one go about generating tones of specific frequency, volume, and
L/R pan? I've been digging around the internet for info, and found a few
examples. One was with gstreamer, but I can't find much in the
documentation to explain how to do this. Also some people said to use
tksnack snack, but the one example I found to do this didn't do anything
on my machine, no error or sounds. I'd like this to be cross platform,
but at this point I just want to do it any way I can.

Sound generation has seldom been easily cross platform -- especially
if you need almost instantaneous response to changes. Otherwise I'd say
generate a .WAV file and feed that to a standalone player that can talk
to the sound card on the system. Or generate MIDI SMF files and feed
them to a player... Or find a MIDI library that can dynamically send
data to the sound card.

What type of tones? Sign waves, square waves, triangle, sawtooth --
combination of them... Fundamental or fundamental plus selected
harmonics...
--
Wulfraed Dennis Lee Bieber KD6MOG
(e-mail address removed) (e-mail address removed)
HTTP://wlfraed.home.netcom.com/
(Bestiaria Support Staff: (e-mail address removed))
HTTP://www.bestiaria.com/

 

[John O'Hagan]

I am pretty sure this shouldn't be as hard as I'm making it to be, but
how does one go about generating tones of specific frequency, volume, and
L/R pan? I've been digging around the internet for info, and found a few
examples. One was with gstreamer, but I can't find much in the
documentation to explain how to do this. Also some people said to use
tksnack snack, but the one example I found to do this didn't do anything
on my machine, no error or sounds. I'd like this to be cross platform,
but at this point I just want to do it any way I can.

[...]

I've done this using the subprocess module to call the sox program (which has
a built-in synth to generate customisable tones, and can play sound files) or
using the socket module to send control messages to a running instance of the
fluidsynth program (which can generate sound using soundfonts). The former is
very simple, the latter is very responsive to quick changes. I think both
programs are cross-platform.

HTH,

John

 

[Tim Harig]

I am pretty sure this shouldn't be as hard as I'm making it to be, but
how does one go about generating tones of specific frequency, volume, and
L/R pan? I've been digging around the internet for info, and found a few

This can be done with SDL which would be my first suggestion.
There doesn't seem to be a direct Python SDL module but pygame seems to
encompass the SDL interface. If that doesn't work for you might be able
to write python wrappers and the C SDL functions.

A second option, on Windows, may be to interface DirectX. This would not
be cross platform and I don't personally know anything about it; but, it
should be possible to work with DirectX. I found this with a Google
search:

http://directpython.sourceforge.net/


Finally, if all else fails you can generate the PCM directly and pipe it to
an external interface. I have never actually written anything that
actually output sounds directly; but, I have written a module to generate
morse tones wave files:

info:
http://ilthio.net/page.cgi?doc=n20
script:
http://ilthio.net/page.cgi?txt=cw.py

Look inside of the oscillator class. I used an 8bit samplewidth with
1 channel to save space (I originally did implement it in 16bit mono).
To do more complex sounds, you will probably need to a 16 bit channel.
Note that 8bit wave files use unsigned integer values, little endian while
16 bit wave files use signed integers, little endian, two's compliment.
For L/R pan, you will also need to create the second channel waveform. You
can easily find good references for the different wave file PCM formats
with a search engine query.

If the SDL interface doesn't work for you, then you might be able to
generate a PCM format and pipe it to an external player. In this scenerio
you would likely ignore actually creating the wave file. You would instead
just create the raw PCM format inside of the array container and then
pipe bits of it out to the wave player program. Without the format data
contained in the RIFF header of the wave file, you will need to inform
the player as to exactly what format you will be feeding it. Most Unix
players have command line options that will allow you to specify the
format. I am not sure whether Windows based players allow similar
options. Under Linux, you could pipe the stream directly to the sound
card device inteface file in the /dev filesystem if you know what bitrate
the soundcard uses internally.

This would likely require a second process or second thread to make sure
that you can feed the PCM output in real time.