1. 使用npm已有包
安装包:npm install audiobuffer-to-wav --save
用例:
var toWav = require('audiobuffer-to-wav')
var xhr = require('xhr')
var context = new AudioContext()
// request the MP3 as binary arraybuffer
xhr({
uri: 'audio/track.mp3',
responseType: 'arraybuffer'
}, function (err, body, resp) {
if (err) throw err
// decode the MP3 arraybuffer into an AudioBuffer
audioContext.decodeAudioData(resp, function (buffer) {
// encode AudioBuffer to WAV ArrayBuffer
var wav = toWav(buffer)//实际上是在audio前加wav的头
// do something with the WAV ArrayBuffer ...
})
})
2. 自己实现
export function audioBufferToWav(buffer: AudioBuffer, opt?: any) {
opt = opt || {};
const numChannels = buffer.numberOfChannels;
const sampleRate = opt.sampleRate || buffer.sampleRate;
const format = opt.float32 ? 3 : 1;
const bitDepth = format === 3 ? 32 : 16;
let result;
if (numChannels === 2) {
result = interleave(buffer.getChannelData(0), buffer.getChannelData(1));
} else {
result = buffer.getChannelData(0);
}
return encodeWAV(result, format, sampleRate, numChannels, bitDepth);
}
function encodeWAV(samples: Float32Array, format: number, sampleRate: number, numChannels: number, bitDepth: number) {
const bytesPerSample = bitDepth / 8;
const blockAlign = numChannels * bytesPerSample;
let buffer = new ArrayBuffer(44 + samples.length * bytesPerSample);
let view = new DataView(buffer);
writeString(view, 0, "RIFF");
view.setUint32(4, 36 + samples.length * bytesPerSample, true);
writeString(view, 8, "WAVE");
writeString(view, 12, "fmt ");
view.setUint32(16, 16, true);
view.setUint16(20, format, true);
view.setUint16(22, numChannels, true);
view.setUint32(24, sampleRate, true);
view.setUint32(28, sampleRate * blockAlign, true);
view.setUint16(32, blockAlign, true);
view.setUint16(34, bitDepth, true);
writeString(view, 36, "data");
view.setUint32(40, samples.length * bytesPerSample, true);
if (format === 1) {
floatTo16BitPCM(view, 44, samples);
} else {
writeFloat32(view, 44, samples);
}
return buffer;
}
function interleave(inputL: Float32Array, inputR: Float32Array) {
let length = inputL.length + inputR.length;
let result = new Float32Array(length);
let index = 0;
let inputIndex = 0;
while (index < length) {
result[index++] = inputL[inputIndex];
result[index++] = inputR[inputIndex];
inputIndex++;
}
return result;
}
function writeFloat32(output: DataView, offset: number, input: Float32Array) {
for (let i = 0; i < input.length; i++, offset += 4) {
output.setFloat32(offset, input[i], true);
}
}
function floatTo16BitPCM(output: DataView, offset: number, input: Float32Array) {
for (let i = 0; i < input.length; i++, offset += 2) {
let s = Math.max(-1, Math.min(1, input[i]));
output.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7fff, true);
}
}
function writeString(view: DataView, offset: number, string: string) {
for (let i = 0; i < string.length; i++) {
view.setUint8(offset + i, string.charCodeAt(i));
}
}
但直接用这种方法重采样效果不佳。