yuanian-ai-component/lib/transformpcm.worker.js

js common function

/**
 * Created by caihua on 2019/9/3.
 */
let self = this;
this.onmessage = function(e) {
    switch (e.data.command) {
        case "transform":
            transform.transaction(e.data.buffer);
            break;
    }
};

var transform = {
    transaction(buffer) {
        let bufTo16kHz = transform.to16kHz(buffer);
        let bufTo16BitPCM = transform.to16BitPCM(bufTo16kHz);
        // let bufToBase64 = transform.toBase64(bufTo16BitPCM)
        self.postMessage({ buffer: bufTo16BitPCM });
    },
    to16kHz(buffer) {
        var data = new Float32Array(buffer);
        var fitCount = Math.round(data.length * (16000 / 44100));
        var newData = new Float32Array(fitCount);
        var springFactor = (data.length - 1) / (fitCount - 1);
        newData[0] = data[0];
        for (let i = 1; i < fitCount - 1; i++) {
            var tmp = i * springFactor;
            var before = Math.floor(tmp).toFixed();
            var after = Math.ceil(tmp).toFixed();
            var atPoint = tmp - before;
            newData[i] = data[before] + (data[after] - data[before]) * atPoint;
        }
        newData[fitCount - 1] = data[data.length - 1];
        return newData;
    },

    to16BitPCM(input) {
        var dataLength = input.length * (16 / 8);
        var dataBuffer = new ArrayBuffer(dataLength);
        var dataView = new DataView(dataBuffer);
        var offset = 0;
        for (var i = 0; i < input.length; i++, offset += 2) {
            var s = Math.max(-1, Math.min(1, input[i]));
            dataView.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7fff, true);
        }
        return Array.from(new Int8Array(dataView.buffer));
    },
    toBase64(buffer) {
        var binary = "";
        var bytes = new Uint8Array(buffer);
        var len = bytes.byteLength;
        for (var i = 0; i < len; i++) {
            binary += String.fromCharCode(bytes[i]);
        }
        return window.btoa(binary);
    },
};