Js提取视频中的音频
将视频中的音频轨道分离出来，生成 wav 文件播放或下载（ Vue3 setup ）
代码实现
template
<button>
<label for="file" id="filename">选择视频文件</label>
<input type="file" name="file" id="file" accept="video/*,audio/*" @change="fileChange">
</button>
scss
button {
position: absolute;
top: calc(50vh - 30px);
left: 10%;
width: 80%;
height: 60px;
background-color: transparent;
border: 1px solid gainsboro;
border-radius: 10px;
padding: 10px;
}
input[type=file] {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
opacity: 0;
filter: alpha(opacity=0);
cursor: pointer;
}
setup
const fileChange = (e) => {
const file = e.target.files[0]
if (!file) return
const label = document.getElementById('filename')
label.innerHTML = file.name
videoToAudio(file).then(audio => {
console.log('audio', audio)
audio && (label.innerHTML = audio.fileName)
})
}
/***
* video-to-audio
* creater：qc
* reference：//github.com/mdn/webaudio-examples/tree/master/offline-audio-context-promise
*/
const videoToAudio = async (file) => {
try {
console.log('videoToAudio file', file)
const fileData = new Blob([file]) // video file
const arrayBuffer = await new Promise((resolve) => {
const reader = new FileReader()
reader.onload = () => {
const arrayBuffer = reader.result
resolve(arrayBuffer)
}
reader.readAsArrayBuffer(fileData)
})
console.log('arrayBuffer', arrayBuffer)
const audioContext = new (window.AudioContext || window.webkitAudioContext || window.mozAudioContext || window.msAudioContext)()
const decodedAudioData = await audioContext.decodeAudioData(arrayBuffer)
console.log('decodedAudioData', decodedAudioData)
const fileDuration = durationTrans(decodedAudioData.duration)
console.log('fileDuration', fileDuration)
const offlineAudioContext = new OfflineAudioContext(decodedAudioData.numberOfChannels, decodedAudioData.sampleRate * decodedAudioData.duration, decodedAudioData.sampleRate)
const soundSource = offlineAudioContext.createBufferSource()
soundSource.buffer = decodedAudioData
soundSource.connect(offlineAudioContext.destination)
soundSource.start()
const renderedBuffer = await offlineAudioContext.startRendering()
console.log('renderedBuffer', renderedBuffer) // outputs audiobuffer
const wav = audioBufferToWav(renderedBuffer)
const fileType = `wav`
const fileName = `${
file.name}.${
fileType}`
// -----------下载音频文件---------------------
downloadWav(wav, fileName)
// ------------------------------------------
// -----------播放音频文件---------------------
audioContext.decodeAudioData(wav, function (buffer) {
const source = audioContext.createBufferSource();
source.buffer = buffer;
source.connect(audioContext.destination);
source.start();
// 在这里继续下一步
}, function (error) {
console.error('解码音频数据失败:', error);
});
// ------------------------------------------
return {
fileName, fileType, fileDuration}
} catch (error) {
// {code: 0, name: 'EncodingError', message: 'Unable to decode audio data'} Case：No audio in the video file ? Maybe
console.log('videoToAudio error', error)
return null
} finally {
console.log('videoToAudio finally')
}
}
/**
* audiobuffer-to-wav
* creater：https://github.com/Jam3/audiobuffer-to-wav
*/
const audioBufferToWav = (buffer, opt) => {
opt = opt || {
}
var numChannels = buffer.numberOfChannels
var sampleRate = buffer.sampleRate
var format = opt.float32 ? 3 : 1
var bitDepth = format === 3 ? 32 : 16
var result
if (numChannels === 2) {
result = interleave(buffer.getChannelData(0), buffer.getChannelData(1))
} else {
result = buffer.getChannelData(0)
}
return encodeWAV(result, format, sampleRate, numChannels, bitDepth)
}
const encodeWAV = (samples, format, sampleRate, numChannels, bitDepth) => {
var bytesPerSample = bitDepth / 8
var blockAlign = numChannels * bytesPerSample
var buffer = new ArrayBuffer(44 + samples.length * bytesPerSample)
var view = new DataView(buffer)
/* RIFF identifier */
writeString(view, 0, 'RIFF')
/* RIFF chunk length */
view.setUint32(4, 36 + samples.length * bytesPerSample, true)
/* RIFF type */
writeString(view, 8, 'WAVE')
/* format chunk identifier */
writeString(view, 12, 'fmt ')
/* format chunk length */
view.setUint32(16, 16, true)
/* sample format (raw) */
view.setUint16(20, format, true)
/* channel count */
view.setUint16(22, numChannels, true)
/* sample rate */
view.setUint32(24, sampleRate, true)
/* byte rate (sample rate * block align) */
view.setUint32(28, sampleRate * blockAlign, true)
/* block align (channel count * bytes per sample) */
view.setUint16(32, blockAlign, true)
/* bits per sample */
view.setUint16(34, bitDepth, true)
/* data chunk identifier */
writeString(view, 36, 'data')
/* data chunk length */
view.setUint32(40, samples.length * bytesPerSample, true)
if (format === 1) {
// Raw PCM
floatTo16BitPCM(view, 44, samples)
} else {
writeFloat32(view, 44, samples)
}
return buffer
}
const interleave = (inputL, inputR) => {
var length = inputL.length + inputR.length
var result = new Float32Array(length)
var index = 0
var inputIndex = 0
while (index < length) {
result[index++] = inputL[inputIndex]
result[index++] = inputR[inputIndex]
inputIndex++
}
return result
}
const writeFloat32 = (output, offset, input) => {
for (var i = 0; i < input.length; i++, offset += 4) {
output.setFloat32(offset, input[i], true)
}
}
const floatTo16BitPCM = (output, offset, input) => {
for (var i = 0; i < input.length; i++, offset += 2) {
var s = Math.max(-1, Math.min(1, input[i]))
output.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7FFF, true)
}
}
const writeString = (view, offset, string) => {
for (var i = 0; i < string.length; i++) {
view.setUint8(offset + i, string.charCodeAt(i))
}
}
const downloadWav = (wav, fileName = 'audio') => {
try {
const blob = new window.Blob([new DataView(wav)], {
type: 'audio/wav'
})
if ('download' in document.createElement('a')) {
const url = window.URL.createObjectURL(blob)
const anchor = document.createElement('a')
document.body.appendChild(anchor)
anchor.style = 'display: none'
anchor.href = url
anchor.download = fileName
anchor.click()
window.URL.revokeObjectURL(url)
document.body.removeChild(anchor)
} else {
navigator.msSaveBlob(blob, fileName)
}
} catch (error) {
console.log('downloadWav error', error)
} finally {
console.log('downloadWav finally')
}
}
const durationTrans = (a) => {
let b = ''
let h = parseInt(a / 3600),
m = parseInt(a % 3600 / 60),
s = parseInt(a % 3600 % 60)
if (h > 0) {
h = h < 10 ? '0' + h : h
b += h + ':'
}
m = m < 10 ? '0' + m : m
s = s < 10 ? '0' + s : s
b += m + ":" + s
return b
}