tinymidipcm

render MIDIs to PCM with custom soundfonts via tinysoundfont in WASM.

example

import TinyMidiPCM from 'tinymidipcm';

(async () => {
    const midiRes = await fetch('/e1m1.mid');
    const midiBuffer = new Uint8Array(await midiRes.arrayBuffer());

    const channels = 2;
    const sampleRate = 44100;

    let renderEndSeconds = 0;

    const tinyMidiPCM = new TinyMidiPCM({
        channels,
        sampleRate,
        renderInterval: 1000,
        onPCMData: (pcm) => player.feed(pcm),
        onRenderEnd: (ms) => {
            console.log('midi finished rendering.');

            renderEndSeconds = Math.floor(ms / 1000);
            console.log(renderEndSeconds, 'seconds');
        }
    });

    const pcmPlayerOptions = {
        inputCodec: 'Float32',
        channels,
        sampleRate,
        onended: async () => {
            const timeSeconds = Math.floor(
                player.audioCtx.currentTime
            );

            if (
                renderEndSeconds > 0 &&
                Math.abs(timeSeconds - renderEndSeconds) <= 2
            ) {
                console.log('midi finished playing.');
                renderEndSeconds = 0;
            }
        },
        flushTime: 1000
    };

    // https://www.npmjs.com/package/pcm-player
    const player = new PCMPlayer(pcmPlayerOptions);

    tinyMidiPCM.setBufferDuration(2);

    await tinyMidiPCM.init();

    const soundfontRes = await fetch('/scc1t2.sf2');

    const soundfontBuffer = new Uint8Array(
        await soundfontRes.arrayBuffer()
    );

    tinyMidiPCM.setSoundfont(soundfontBuffer);

    window.onclick = async () => {
        await player.pause();
        player.destroy();
        player.init(pcmPlayerOptions);

        player.volume(1);

        tinyMidiPCM.render(midiBuffer);
    };
})();

api

tinyMidiPCM = new TinyMidiPCM(options = {})

create a new rendering instance. options include:

• bufferSize PCM chunk size to render per renderInterval. default to 1 second worth of data.
• renderInterval how often in ms to generate a new bufferSize PCM data event. default 30.
• sampleRate default 44100.
• channels stereo or mono. default 2.
• gain volume gain in decibels (>0 means higher, <0 means lower).
• onPCMData function callback wich emits a Uint8Array of PCM data at renderInterval rate. encoded as 32 bit floats.
• onRenderEnd function callback when the entire MIDI is processed, providing millseconds rendered argument.

async tinyMidiPCM.init()

fetch and load the wasm. required for following methods.

tinyMidiPCM.render(midiBuffer)

start emitting onPCMData callbacks. midiBuffer is a Uint8Array of a MIDI file.

license

TinySoundFont is available under the MIT license.