I'm working on an engine for a retro-style game in C. I'm looking for a sound library that would produce chip sounds from code...I want to make my own simple chiptune tracker for the engine to create music. Does such a thing exist?
I'd also be interested in a library to use .nsf files in my project.
I'm using Linux for development.
Probably not a correct answer but here is a library of various audio engines
(Scroll down to the second segment for audio libraries)
At least 9 out of 12 engines go with C. Most of them also support tracker files. Which is not so different than nsf ( I assume these are NES music files ) files.
Sure you can, it's just not trivial to get it sounding "nice".
I don't know how to do it in Linux, but if you can play a PCM buffer, all you have to do is fill it with whatever you want.
So supposing your buffer is set to play in monaural, signed 16-bit samples, at 44100 samples per second, creating a pure (sinusoidal) A4 sound (440 Hz) is as simple as
int16_t buffer[44100];
float frequency = 440.0f;
float sampling_ratio = 44100.0f;
float amplitude = 0.5f;
float t;
for (int i = 0; i < 44100; i++)
{
float theta = ((float)i / sampling_ratio) * PI;
buffer[i] = (int16_t)(sin(theta * frequency) * 32767.0f * amplitude);
}
However, this sound is probably very dull for your interests, so you have to do some more complicated things. In general, there are two types of sound synthesis: Additive and Subtractive. There are many others, but these two are probably the most simple ones. Today I'll just talk about additive synthesis.
For additive synthesis, you do the same thing as I did just up there, but instead of just using one frequency at one amplitude, you add several waves together. This is just like pressing several keys on a piano at the same time. So you modify your code to look something like this:
void add_sine_wave(int16_t* buffer, int buffer_length, float frequency, float sampling_ratio, float amplitude)
{
for (int i = 0; i < buffer_length; i++)
{
float theta = ((float)i / sampling_ratio) * M_PI;
// make sure to correct for overflows and underflows
buffer[i] += (int16_t)(sin(theta * frequency) * 32767.0f * amplitude);
}
}
and then use it like this:
int16_t buffer[44100];
memset(buffer, 0, sizeof(buffer));
// Create an A Major chord
add_sine_wave(buffer, 44100, 440.0f, 44100.0f, 0.5f);
add_sine_wave(buffer, 44100, 554.37f, 44100.0f, 0.5f);
add_sine_wave(buffer, 44100, 659.26f, 44100.0f, 0.5f);
By the way, I'm getting my frequencies from here (I'm using equal temperament, but there are lots of other tunings available).
Notice that so far I've only been using sine waves, but old synthesizers also support square, triangular and saw waves as well, each with its own interesting sound properties. Implementing these is pretty straightforward.
Other things you can do to increase the variety of sounds you can create are:
The point here is that the techniques themselves are not very difficult, so you don't really need a library to abstract them for you. It's using them to create interesting sounds what is difficult.
One final note. When experimenting with sound like this, it may be really useful to save your data to WAV files, and then visualizing them in some software like Audacity. That way you can see what you're doing more clearly.
short before you cast it to a short.
\$\endgroup\$
Commented
Oct 30, 2014 at 4:09
For chiptune sound effects, there's one definite answer: sfxr.
It's a standalone application that you can use to generate samples, but the source code is also available should you want to integrate it to your code.
I can personally recommend Blargg's audio libraries. Something that may be of particular interest to you is his Blip_Buffer.
Blargg's site has several "retro" audio synthesizers, and I am actively using his Game_Music_Emu to play NSF files in a Mega Man clone I am writing.
Many of the libraries are written in C++ but some provide a C interface as well.
