@voice-ping/cognitive-services-speech
Version:
VoicePing Cognitive Services Speech SDK for JavaScript forked from Microsoft
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JavaScript
// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT license.
/**
* Represents audio stream format used for custom audio input configurations.
* @class AudioStreamFormat
*/
export class AudioStreamFormat {
/**
* Creates an audio stream format object representing the default audio stream
* format (16KHz 16bit mono PCM).
* @member AudioStreamFormat.getDefaultInputFormat
* @function
* @public
* @returns {AudioStreamFormat} The audio stream format being created.
*/
static getDefaultInputFormat() {
return AudioStreamFormatImpl.getDefaultInputFormat();
}
/**
* Creates an audio stream format object with the specified pcm waveformat characteristics.
* @member AudioStreamFormat.getWaveFormatPCM
* @function
* @public
* @param {number} samplesPerSecond - Sample rate, in samples per second (Hertz).
* @param {number} bitsPerSample - Bits per sample, typically 16.
* @param {number} channels - Number of channels in the waveform-audio data. Monaural data
* uses one channel and stereo data uses two channels.
* @returns {AudioStreamFormat} The audio stream format being created.
*/
static getWaveFormatPCM(samplesPerSecond, bitsPerSample, channels) {
return new AudioStreamFormatImpl(samplesPerSecond, bitsPerSample, channels);
}
}
/**
* @private
* @class AudioStreamFormatImpl
*/
// tslint:disable-next-line:max-classes-per-file
export class AudioStreamFormatImpl extends AudioStreamFormat {
/**
* Creates an instance with the given values.
* @constructor
* @param {number} samplesPerSec - Samples per second.
* @param {number} bitsPerSample - Bits per sample.
* @param {number} channels - Number of channels.
*/
constructor(samplesPerSec = 16000, bitsPerSample = 16, channels = 1) {
super();
this.setString = (view, offset, str) => {
for (let i = 0; i < str.length; i++) {
view.setUint8(offset + i, str.charCodeAt(i));
}
};
this.formatTag = 1;
this.bitsPerSample = bitsPerSample;
this.samplesPerSec = samplesPerSec;
this.channels = channels;
this.avgBytesPerSec = this.samplesPerSec * this.channels * (this.bitsPerSample / 8);
this.blockAlign = this.channels * Math.max(this.bitsPerSample, 8);
this.privHeader = new ArrayBuffer(44);
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView
const view = new DataView(this.privHeader);
/* RIFF identifier */
this.setString(view, 0, "RIFF");
/* file length */
view.setUint32(4, 0, true);
/* RIFF type & Format */
this.setString(view, 8, "WAVEfmt ");
/* format chunk length */
view.setUint32(16, 16, true);
/* sample format (raw) */
view.setUint16(20, 1, true);
/* channel count */
view.setUint16(22, this.channels, true);
/* sample rate */
view.setUint32(24, this.samplesPerSec, true);
/* byte rate (sample rate * block align) */
view.setUint32(28, this.avgBytesPerSec, true);
/* block align (channel count * bytes per sample) */
view.setUint16(32, this.channels * (this.bitsPerSample / 8), true);
/* bits per sample */
view.setUint16(34, this.bitsPerSample, true);
/* data chunk identifier */
this.setString(view, 36, "data");
/* data chunk length */
view.setUint32(40, 0, true);
}
/**
* Retrieves the default input format.
* @member AudioStreamFormatImpl.getDefaultInputFormat
* @function
* @public
* @returns {AudioStreamFormatImpl} The default input format.
*/
static getDefaultInputFormat() {
return new AudioStreamFormatImpl();
}
/**
* Closes the configuration object.
* @member AudioStreamFormatImpl.prototype.close
* @function
* @public
*/
close() { return; }
get header() {
return this.privHeader;
}
}
//# sourceMappingURL=AudioStreamFormat.js.map