wav-file-encoder/dist/WavFileEncoder.js

A simple encoder for WAV audio files

export function encodeWavFileFromAudioBuffer(audioBuffer, wavFileType) {
    const numberOfChannels = audioBuffer.numberOfChannels;
    const numberOfFrames = audioBuffer.length;
    const sampleRate = audioBuffer.sampleRate;
    const channelData = Array(numberOfChannels);
    for (let channelNo = 0; channelNo < numberOfChannels; channelNo++) {
        channelData[channelNo] = audioBuffer.getChannelData(channelNo);
        if (channelData[channelNo].length != numberOfFrames) {
            throw new Error("Unexpected channel data array size.");
        }
    }
    return encodeWavFileFromArrays(channelData, sampleRate, wavFileType);
}
export function encodeWavFileFromArrays(channelData, sampleRate, wavFileType) {
    const numberOfChannels = channelData.length;
    if (numberOfChannels < 1) {
        throw new Error("No audio channels.");
    }
    const numberOfFrames = channelData[0].length;
    let bitsPerSample;
    let formatCode;
    let fmtChunkSize;
    let writeSampleData;
    switch (wavFileType) {
        case 0: {
            bitsPerSample = 16;
            formatCode = 1;
            fmtChunkSize = 16;
            writeSampleData = writeSampleData_int16;
            break;
        }
        case 1: {
            bitsPerSample = 32;
            formatCode = 3;
            fmtChunkSize = 18;
            writeSampleData = writeSampleData_float32;
            break;
        }
        default: {
            throw new Error();
        }
    }
    const bytesPerSample = Math.ceil(bitsPerSample / 8);
    const bytesPerFrame = numberOfChannels * bytesPerSample;
    const bytesPerSec = sampleRate * numberOfChannels * bytesPerSample;
    const headerLength = 20 + fmtChunkSize + 8;
    const sampleDataLength = numberOfChannels * numberOfFrames * bytesPerSample;
    const fileLength = headerLength + sampleDataLength;
    const arrayBuffer = new ArrayBuffer(fileLength);
    const dataView = new DataView(arrayBuffer);
    writeWavFileHeader();
    writeSampleData();
    return arrayBuffer;
    function writeWavFileHeader() {
        setString(0, "RIFF");
        dataView.setUint32(4, fileLength - 8, true);
        setString(8, "WAVE");
        setString(12, "fmt ");
        dataView.setUint32(16, fmtChunkSize, true);
        dataView.setUint16(20, formatCode, true);
        dataView.setUint16(22, numberOfChannels, true);
        dataView.setUint32(24, sampleRate, true);
        dataView.setUint32(28, bytesPerSec, true);
        dataView.setUint16(32, bytesPerFrame, true);
        dataView.setUint16(34, bitsPerSample, true);
        if (fmtChunkSize > 16) {
            dataView.setUint16(36, 0, true);
        }
        const p = 20 + fmtChunkSize;
        setString(p, "data");
        dataView.setUint32(p + 4, sampleDataLength, true);
    }
    function writeSampleData_int16() {
        let offs = headerLength;
        for (let frameNo = 0; frameNo < numberOfFrames; frameNo++) {
            for (let channelNo = 0; channelNo < numberOfChannels; channelNo++) {
                const sampleValueFloat = channelData[channelNo][frameNo];
                const sampleValueInt16 = convertFloatSampleToInt16(sampleValueFloat);
                dataView.setInt16(offs, sampleValueInt16, true);
                offs += 2;
            }
        }
    }
    function writeSampleData_float32() {
        let offs = headerLength;
        for (let frameNo = 0; frameNo < numberOfFrames; frameNo++) {
            for (let channelNo = 0; channelNo < numberOfChannels; channelNo++) {
                const sampleValueFloat = channelData[channelNo][frameNo];
                dataView.setFloat32(offs, sampleValueFloat, true);
                offs += 4;
            }
        }
    }
    function convertFloatSampleToInt16(v) {
        return Math.max(-32768, Math.min(32767, Math.round(v * 32768)));
    }
    function setString(offset, value) {
        for (let p = 0; p < value.length; p++) {
            dataView.setUint8(offset + p, value.charCodeAt(p));
        }
    }
}
export { encodeWavFileFromAudioBuffer as encodeWavFile, encodeWavFileFromArrays as encodeWavFile2 };