How to convert Float32Array into mp3 file about lamejs HOT 8 OPEN

const fetchAudio = async (url: string) => {
  const response = await fetch(url, {
    mode: 'cors',
    referrerPolicy: 'no-referrer-when-downgrade',
  });
  const arrayBuffer = await response.arrayBuffer();
  const audioContext = new AudioContext();
  const buffer = await audioContext.decodeAudioData(arrayBuffer);
  return buffer;
};
// Do something to get the url and setup your s3
fetchAudio(url).then((data) => {
    const binary = audioToMp3Binary(data);
    s3.send(new PutObjectCommand({
        Bucket: bucketName,
        Key: `test/${fileName}`,
        Body: binary, // Uint8Array
    }));
});

import lamejs from 'lamejs';
import MPEGMode from 'lamejs/src/js/MPEGMode';
import Lame from 'lamejs/src/js/Lame';
import BitStream from 'lamejs/src/js/BitStream';

(window as any).MPEGMode = MPEGMode;
(window as any).Lame = Lame;
(window as any).BitStream = BitStream;

export function audioToMp3Binary(audioData: AudioBuffer, debug = true) {
    const encoder = new lamejs.Mp3Encoder(1, audioData.sampleRate, 128);
    const leftChannel = audioData.getChannelData(0);
    // Interpolate to -32768 to 32767, which is signed int16
    const interpolated = leftChannel.map((n) =>
        Math.max(-32768, Math.min(32768, n * (n < 0 ? 32768 : 32767)))
    );
    const int16arr = new Int16Array(leftChannel.length);
    // Type coercion, float -> int
    interpolated.forEach((n, i) => (int16arr[i] = n));

    const mp3Data: Int8Array[] = [];
    const sampleBlockSize = 1152;
    for (let i = 0; i < int16arr.length; i += sampleBlockSize) {
        const sampleChunk = int16arr.subarray(i, i + sampleBlockSize);
        const mp3buf = encoder.encodeBuffer(sampleChunk);
        if (mp3buf.length > 0) mp3Data.push(mp3buf);
    }
    mp3Data.push(new Int8Array(encoder.flush())); // Fill gaps in mp3buf
    if (debug) debugDownload(mp3Data);
    return int8ArrayToUint8Array(mp3Data);
}

function debugDownload(mp3Data: Int8Array[]) {
    const blob = new Blob(mp3Data, { type: 'audio/mp3' });
    const mp3Url = URL.createObjectURL(blob);
    const link = Object.assign(document.createElement('a'), {
        href: mp3Url,
        download: 'output.mp3',
    });
    document.body.appendChild(link);
    link.click();
    document.body.removeChild(link);
}

function int8ArrayToUint8Array(int8s: Int8Array[]) {
    const totalLength = int8s.reduce((acc, value) => acc + value.length, 0);
    const result = new Uint8Array(totalLength);
    let offset = 0;
    for (const int8 of int8s) {
        result.set(int8, offset);
        offset += int8.length;
    }
    return result;
}