67 lines
2.0 KiB
JavaScript
67 lines
2.0 KiB
JavaScript
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/**
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* Recorder EncodeWAV Worker
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* Note: only the recordWorker function's body codes will be loaded as worker.
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* 注意：仅该函数内部代码会被引入到 worker
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*/
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const recordWorker = function () {
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/**
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* Created by lycheng on 2019/8/9.
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*/
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let self = this
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this.onmessage = function (e) {
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switch (e.data.command) {
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case "transform":
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transform.transaction(e.data.buffer);
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break;
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}
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}
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var transform = {
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transaction (buffer) {
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let bufTo16kHz = transform.to16kHz(buffer)
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let bufTo16BitPCM = transform.to16BitPCM(bufTo16kHz)
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// let bufToBase64 = transform.toBase64(bufTo16BitPCM)
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self.postMessage({ 'buffer': bufTo16BitPCM })
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},
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to16kHz (buffer) {
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var data = new Float32Array(buffer)
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var fitCount = Math.round(data.length * (16000 / 44100))
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var newData = new Float32Array(fitCount)
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var springFactor = (data.length - 1) / (fitCount - 1)
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newData[0] = data[0]
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for (let i = 1; i < fitCount - 1; i++) {
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var tmp = i * springFactor
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var before = Math.floor(tmp).toFixed()
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var after = Math.ceil(tmp).toFixed()
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var atPoint = tmp - before
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newData[i] = data[before] + (data[after] - data[before]) * atPoint
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}
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newData[fitCount - 1] = data[data.length - 1]
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return newData
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},
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to16BitPCM (input) {
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var dataLength = input.length * (16 / 8)
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var dataBuffer = new ArrayBuffer(dataLength)
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var dataView = new DataView(dataBuffer)
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var offset = 0
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for (var i = 0; i < input.length; i++ , offset += 2) {
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var s = Math.max(-1, Math.min(1, input[i]))
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dataView.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7FFF, true)
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}
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return Array.from(new Int8Array(dataView.buffer))
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},
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toBase64 (buffer) {
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var binary = ''
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var bytes = new Uint8Array(buffer)
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var len = bytes.byteLength
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for (var i = 0; i < len; i++) {
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binary += String.fromCharCode(bytes[i])
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}
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return window.btoa(binary)
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}
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}
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}
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export default recordWorker
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