A library for generating optimized, single-sample audio callbacks in JavaScript. Inspired by gen~ in Max/MSP.
http://www.charlie-roberts.com/genish/playground
genish.js should run in all reasonably modern browsers; however, it runs best in Firefox, Edge, and Chrome due to their support for AudioWorklets. Other browsers will fallback to using a ScriptProcessor node, which runs on the main thread and thus may result in glitches.
A little more detail: genish.js will compile per-sample callback functions from a graph. Given the following code to create a sine oscillator and scale its output:
mul( cycle( 220 ), .1 )...genish will generate the following sample processing loop (reading from a wavetable) inside of an AudioWorklet node:
for( let i = 0; i < len; ++i ) {
var phasor2_value = memory[2]
memory[2] += 0.004988662131519274
if( memory[2] >= 1 ) memory[2] -= 1
if( memory[2] < 0 ) memory[2] += 1
var cycle4_dataIdx = 3,
cycle4_phase = phasor2_value * 1024,
cycle4_index = cycle4_phase | 0,
cycle4_frac = cycle4_phase - cycle4_index,
cycle4_base = memory[ cycle4_dataIdx + cycle4_index ],
cycle4_next = ( cycle4_index + 1 ) & (1024 - 1),
cycle4_out = cycle4_base + cycle4_frac * ( memory[ cycle4_dataIdx + cycle4_next ] - cycle4_base )
var mul5 = cycle4_out * 0.1
memory[0] = mul5
left[ i ] = memory[0]
}To use genish.js, you need to create an AudioContext and an AudioWorklet node that will run the functions genish.js creates. Genish includes a utilities object that provides convenience methods for these tasks. The following example performs the necessary setup and starts a sine oscillator running:
<!doctype html>
<html lang='en'>
<head>
<script src="https://gitcdn.link/repo/charlieroberts/genish.js/master/dist/gen.lib.js"></script>
</head>
<body></body>
<script>
// wait until genish.js has loaded...
window.onload = function() {
// optionally put all genish object in global namespace
genish.export( window )
// schedule our audiocontext to be created when a user
// interacts with the page... this is required by browsers
utilities.createContext()
window.onclick = ()=> {
// now our audiocontext has been created and we
// can create an audioworklet...
utilities.playWorklet( cycle( 330 ) )
}
}
</script>
</html>AudioWorklets only run if your webpage is loaded from a server; http-server is a nice way to quickly start a server running for local testing purposes. More standalone examples are also available in the examples directory. You can either use the prebuilt library in the dist folder, or use a version served by GitCDN.
First, run npm install from within the top level of the repo directory. Next, run npm run build to create the library. The resulting file will be found in dist/gen.lib.js.