BlipKit

BlipKit is a C library for creating the beautiful sound of old sound chips.

Generate waveforms: square, triangle, noise, sawtooth, sine and custom waveforms
Use an unlimited number of individual tracks
Use stereo output or up to 8 channels
Define instruments to create envelopes and other interesting effects
Use effects: portamento, tremolo, vibrato and some more
Load multi-channel samples and play them at different pitches

🎹 Also consider to check out the bliplay project

Basic Example

This code demonstrates the basic steps to generate audio data of a square wave in the note A with enabled tremolo effect:

// The context object contains the audio buffers.
BKContext ctx;
// The track object generates the waveform.
BKTrack track;
// Initialize context with 2 channels (stereo).
// and a sample rate of 44100 Hz.
BKContextInit(&ctx, 2, 44100);
// Initialize track with square wave.
// By default, the square wave has a duty cycle of 4 (12.5%).
BKTrackInit(&track, BK_SQUARE);
// Set mix and note volume.
BKSetAttr(&track, BK_MASTER_VOLUME, 0.15 * BK_MAX_VOLUME);
BKSetAttr(&track, BK_VOLUME, 1.0 * BK_MAX_VOLUME);
// Set note A in octave 3.
BKSetAttr(&track, BK_NOTE, BK_A_3 * BK_FINT20_UNIT);
// Enable tremolo effect.
BKInt tremolo[2] = { 20, 0.66 * BK_MAX_VOLUME };
BKTrackSetEffect(&track, BK_EFFECT_TREMOLO, tremolo, sizeof(tremolo));
// Attach track to context.
BKTrackAttach(&track, &ctx);
// Define buffer to write audio data to.
// As there are 2 channels used, the buffer must be
// twice the size than number of frames are requested.
BKFrame frames[512 * 2];
// Generate 512 frames, e.g., as they would be requested by an audio output function (SDL).
// Subsequent calls to this function generate the next requested number of frames.
BKContextGenerate(&ctx, frames, 512);
// The channels are interlaced into the buffer in the form: LRLR...
// Which means that the first frame of the left channel is at frames[0],
// the first frame of the right channel at frames[1] and so on...

Building the Library

First execute autogen.sh in the base directory to generate the build system:

sh ./autogen.sh

Next execute configure in the base directory:

./configure

Use the --without-sdl option if you don’t want to link against SDL.

./configure --without-sdl

Then execute make to build libblipkit.a in the src directory:

make

Optionally, you may want to execute to install the library and headers on your system:

sudo make install

Building and Running Examples

All examples use SDL (http://www.libsdl.org) to output sound, so you have to install it first. Execute make examplename to build an example in the examples directory.

# in `examples`
make tone
make divider
make stereo
make scratch
make waveform
make envelope

Finally, run examples like this:

# in `examples`
./tone

License

This library is distributed under the MIT license. See LICENSE.