我想对AudioBuffer进行切片,所以我首先从blob创建了ArrayBuffer,因为无法将blob直接转换为audioBuffer,但是,很多时间试图将AudioBuffer转换回ArrayBuffer但没有用...我首先将音频Blob转换为Arraybuffer,然后将其转换为AudioBuffer,但无法将其转换回ArrayBuffer。我想要ArrayBuffer,因为我无法从audioBuffer生成Blob,因此首先需要ArrayBuffer,可以将其转换为BLOB,因此可以从中创建ObjectURL,然后下载它。
let rec = new Recorder(async(chunks) => {
var blob = new Blob(chunks, {
type: 'audio/mp3'
});
var arrayBuffer = await blob.arrayBuffer();
const audioContext = new AudioContext()
await audioContext.decodeAudioData(arrayBuffer, (audioBuffer) => {
//but now can't convert audioBuffer back to Arraybuffer
}
一个AudioBuffer包含每个解码音频通道的非交织Float32Array
PCM样本。对于立体声AudioBuffer,它将包含2个通道。这些通道需要首先进行交错,然后交错的PCM必须附加一个WAV标头,以便您可以下载并作为WAV播放。
// Float32Array samples
const [left, right] = [audioBuffer.getChannelData(0), audioBuffer.getChannelData(1)]
// interleaved
const interleaved = new Float32Array(left.length + right.length)
for (let src=0, dst=0; src < left.length; src++, dst+=2) {
interleaved[dst] = left[src]
interleaved[dst+1] = right[src]
}
// create WAV file
const wavBytes = getWavBytes(interleaved, {
numFrames: interleaved.length, // you may need to divide by 2 here
numChannels: 2,
sampleRate: 44100, // you may need to adjust to 48000
isFloat: true
})
const wav = new Blob([wavBytes], { type: 'audio/wav' })
// create download link and append to dom
const downloadLink = document.createElement('a')
downloadLink.href = URL.createObjectURL(wav)
downloadLink.setAttribute('download', 'my-audio.wav') // name file
以下支持功能:
function getWavBytes(pcmSamples, options) {
const headerBytes = getWavHeader(options)
const wavBytes = new Uint8Array(headerBytes.length + pcmSamples.length);
// prepend header, then add pcmBytes
wavBytes.set(headerBytes, 0)
wavBytes.set(pcmSamples, headerBytes.length)
return wavBytes
}
// adapted from https://gist.github.com/also/900023
// Returns Uint8Array of WAV bytes
function getWavHeader(options) {
const numFrames = options.numFrames
const numChannels = options.numChannels || 2
const sampleRate = options.sampleRate || 44100
const bytesPerSample = options.isFloat? 4 : 2
const format = options.isFloat? 3 : 1
const blockAlign = numChannels * bytesPerSample
const byteRate = sampleRate * blockAlign
const dataSize = numFrames * blockAlign
const buffer = new ArrayBuffer(44)
const dv = new DataView(buffer)
let p = 0
function writeString(s) {
for (let i = 0; i < s.length; i++) {
dv.setUint8(p + i, s.charCodeAt(i))
}
p += s.length
}
function writeUint32(d) {
dv.setUint32(p, d, true)
p += 4
}
function writeUint16(d) {
dv.setUint16(p, d, true)
p += 2
}
writeString('RIFF') // ChunkID
writeUint32(dataSize + 36) // ChunkSize
writeString('WAVE') // Format
writeString('fmt ') // Subchunk1ID
writeUint32(16) // Subchunk1Size
writeUint16(format) // AudioFormat
writeUint16(numChannels) // NumChannels
writeUint32(sampleRate) // SampleRate
writeUint32(byteRate) // ByteRate
writeUint16(blockAlign) // BlockAlign
writeUint16(bytesPerSample * 8) // BitsPerSample
writeString('data') // Subchunk2ID
writeUint32(dataSize) // Subchunk2Size
return new Uint8Array(buffer)
}