[erlang-questions] Generating sine waves and/or audio stream output

[Ivan Uemlianin]

Dear All

I am learning Erlang and one of the things I'm interested in is
generating sine waves, merging them and streaming them to audio output.

I can kind of imagine how generating and merging would work, with a sine
wave represented as a list of numbers. Is there an Erlang library or
project working with sine waves?

I can't imagine how to stream a list of numbers to audio output. Can
anyone point me to projects/libraries/ideas for that one? Writing the
data to a file would be OK for now, but "live" sound would be much nicer.

With thanks and best wishes

Ivan

--
============================================================
Ivan A. Uemlianin
Speech Technology Research and Development

iv...@llaisdy.com
www.llaisdy.com
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"Froh, froh! Wie seine Sonnen, seine Sonnen fliegen"
(Schiller, Beethoven)
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[Willem de Jong]

Hello Ivan,

I have an erlang module that generates sounds. It can generate different wave forms (right now all I need is a saw-like shape and a sinus shape). I am attaching it. It is a bit messy, perhaps, but it should give you an impression of how it can be done.

The synthesize() function uses the sinus() function to create a number of complete waves, and then pastes  these together repeatedly (I assumed that would be more efficient that calculating the sinus() function for each sample).

The syntesize() function returns a couple of sound fragments: an "attaque" bit that starts with an amplitude of zero, a fade-out bit where the volume decreases back to 0, and a long and a short bit of sound with a stable volume. Another module creates a complete sound-fragment of the desired duration by pasting together the attaque, a number of long fragments and short fragments in such a way that it matches the duration (as precisely as possible), and a fade out bit.

As you can see this creates sounds with a fixed pitch and volume (within one sound, that is). Also note that both the length and the pitch of the sound will be approximations.

I created this to generate music for my web-site: http://coria.nl.  You can try the result there, if you want. It is a site that enables me and the other members of my choir (and anyone else who is interested) to practise our music. 

Any comments or suggestions will be quite welcome, 

Good luck,

Willem 

[Ivan Uemlianin]

Dear Willem

Thanks very much for you email and your code. This looks good.

The functions generate binaries. Do you stream the binaries to audio or
do you write them to a file?

Do you have a function that writes wav files? If not I shall write one
(unless a function to stream to audio will be easier but I don't think
it will be).

Thanks and best wishes

Ivan

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[G.S.]

Hello Willem,

Could you also please send me the code if possible? as I am also highly
interested in using Erlang for sound generation.

Regards and thanks,
-Gene

[Willem de Jong]

Hmm, I had forgotten about some of the complexities involved. 

I do not have a function that writes wav files. I put the pcm data that is generated by this into a flash file. For wav files you have to do add a header and framing, I believe. 

I added a function that puts together the parts of the sound. You can write it to a file like this:

> file:write_file("sinus.raw", sound:sound(440, 3, 0.5, sinus)).

(440 hertz, 3 seconds, volume 0.5 (50%), sinus wave form).

This file will be in "raw" format (pcm without headers). With the current settings the sample rate is 22050, mono, sample size 16 bits big endian.

Regards,

Willem

[Ivan Uemlianin]

You've done all the hard work!

Thanks Willem. I'll write a function to write a wav header and report
back: I've got one I wrote in C somewhere; might be interesting to
compare the two.

I'll also look into streaming to audio (there is esdl, an erlang binding
for sdl, but that looks a bit hefty, and doesn'ty work with smp enabled
erlang).

Best

Ivan

On 25/03/2010 19:04, Willem de Jong wrote:
> Hmm, I had forgotten about some of the complexities involved.
>
> I do not have a function that writes wav files. I put the pcm data
> that is generated by this into a flash file. For wav files you have to
> do add a header and framing, I believe.
>
> I added a function that puts together the parts of the sound. You can
> write it to a file like this:
> > file:write_file("sinus.raw", sound:sound(440, 3, 0.5, sinus)).
>
> (440 hertz, 3 seconds, volume 0.5 (50%), sinus wave form).
>
> This file will be in "raw" format (pcm without headers). With the
> current settings the sample rate is 22050, mono, sample size 16 bits
> big endian.
>
> Regards,
> Willem

--

[Ivan Uemlianin]

Dear Willem

This hacky little script (my first in erlang!) will write a sound and
pipe it to audio.

play(Sound) ->
Fn = sinus,
file:write_file(io_lib:format("~p.raw", [Fn]), Sound),
os:cmd(io_lib:format("sox -r ~B -c 1 -w -s ~p.raw ~p.wav",
[?SamplingRate, Fn, Fn])),
os:cmd(io_lib:format("afplay ~p.wav", [Fn])).

sox is a unix tool, here it converts the raw audio file to wav format
file. On a proper unix platform sox can output to audio. On MacOSX you
have to write to a file and use afplay to play the file.

This is not a very nice function. I shall write a function to convert a
raw sound into a wav format binary. It would be v nice to habe
something like an erlang binding for PortAudio. In the meantime, the
function above makes it possible to listen to generated sounds fmor the
erlang shell.

With thanks and apologies

Ivan

On 25/03/2010 19:04, Willem de Jong wrote:

> Hmm, I had forgotten about some of the complexities involved.
>
> I do not have a function that writes wav files. I put the pcm data
> that is generated by this into a flash file. For wav files you have to
> do add a header and framing, I believe.
>
> I added a function that puts together the parts of the sound. You can
> write it to a file like this:
> > file:write_file("sinus.raw", sound:sound(440, 3, 0.5, sinus)).
>
> (440 hertz, 3 seconds, volume 0.5 (50%), sinus wave form).
>
> This file will be in "raw" format (pcm without headers). With the
> current settings the sample rate is 22050, mono, sample size 16 bits
> big endian.
>
> Regards,
> Willem

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