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node_modules/prism-media/src/opus/Opus.js

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+// Partly based on https://github.com/Rantanen/node-opus/blob/master/lib/Encoder.js
+
+const { Transform } = require('stream');
+const loader = require('../util/loader');
+
+const CTL = {
+  BITRATE: 4002,
+  FEC: 4012,
+  PLP: 4014,
+};
+
+let Opus = {};
+
+function loadOpus(refresh = false) {
+  if (Opus.Encoder && !refresh) return Opus;
+
+  Opus = loader.require([
+    ['@discordjs/opus', opus => ({ Encoder: opus.OpusEncoder })],
+    ['node-opus', opus => ({ Encoder: opus.OpusEncoder })],
+    ['opusscript', opus => ({ Encoder: opus })],
+  ]);
+  return Opus;
+}
+
+const charCode = x => x.charCodeAt(0);
+const OPUS_HEAD = Buffer.from([...'OpusHead'].map(charCode));
+const OPUS_TAGS = Buffer.from([...'OpusTags'].map(charCode));
+
+// frame size = (channels * rate * frame_duration) / 1000
+
+/**
+ * Takes a stream of Opus data and outputs a stream of PCM data, or the inverse.
+ * **You shouldn't directly instantiate this class, see opus.Encoder and opus.Decoder instead!**
+ * @memberof opus
+ * @extends TransformStream
+ * @protected
+ */
+class OpusStream extends Transform {
+  /**
+   * Creates a new Opus transformer.
+   * @private
+   * @memberof opus
+   * @param {Object} [options] options that you would pass to a regular Transform stream
+   */
+  constructor(options = {}) {
+    if (!loadOpus().Encoder) {
+      throw Error('Could not find an Opus module! Please install @discordjs/opus, node-opus, or opusscript.');
+    }
+    super(Object.assign({ readableObjectMode: true }, options));
+    if (Opus.name === 'opusscript') {
+      options.application = Opus.Encoder.Application[options.application];
+    }
+    this.encoder = new Opus.Encoder(options.rate, options.channels, options.application);
+
+    this._options = options;
+    this._required = this._options.frameSize * this._options.channels * 2;
+  }
+
+  _encode(buffer) {
+    return this.encoder.encode(buffer, this._options.frameSize);
+  }
+
+  _decode(buffer) {
+    return this.encoder.decode(buffer, Opus.name === 'opusscript' ? null : this._options.frameSize);
+  }
+
+  /**
+   * Returns the Opus module being used - `opusscript`, `node-opus`, or `@discordjs/opus`.
+   * @type {string}
+   * @readonly
+   * @example
+   * console.log(`Using Opus module ${prism.opus.Encoder.type}`);
+   */
+  static get type() {
+    return Opus.name;
+  }
+
+  /**
+   * Sets the bitrate of the stream.
+   * @param {number} bitrate the bitrate to use use, e.g. 48000
+   * @public
+   */
+  setBitrate(bitrate) {
+    (this.encoder.applyEncoderCTL || this.encoder.encoderCTL)
+      .apply(this.encoder, [CTL.BITRATE, Math.min(128e3, Math.max(16e3, bitrate))]);
+  }
+
+  /**
+   * Enables or disables forward error correction.
+   * @param {boolean} enabled whether or not to enable FEC.
+   * @public
+   */
+  setFEC(enabled) {
+    (this.encoder.applyEncoderCTL || this.encoder.encoderCTL)
+      .apply(this.encoder, [CTL.FEC, enabled ? 1 : 0]);
+  }
+
+  /**
+   * Sets the expected packet loss over network transmission.
+   * @param {number} [percentage] a percentage (represented between 0 and 1)
+   */
+  setPLP(percentage) {
+    (this.encoder.applyEncoderCTL || this.encoder.encoderCTL)
+      .apply(this.encoder, [CTL.PLP, Math.min(100, Math.max(0, percentage * 100))]);
+  }
+
+  _final(cb) {
+    this._cleanup();
+    cb();
+  }
+
+  _destroy(err, cb) {
+    this._cleanup();
+    return cb ? cb(err) : undefined;
+  }
+
+  /**
+   * Cleans up the Opus stream when it is no longer needed
+   * @private
+   */
+  _cleanup() {
+    if (Opus.name === 'opusscript' && this.encoder) this.encoder.delete();
+    this.encoder = null;
+  }
+}
+
+/**
+ * An Opus encoder stream.
+ *
+ * Outputs opus packets in [object mode.](https://nodejs.org/api/stream.html#stream_object_mode)
+ * @extends opus.OpusStream
+ * @memberof opus
+ * @example
+ * const encoder = new prism.opus.Encoder({ frameSize: 960, channels: 2, rate: 48000 });
+ * pcmAudio.pipe(encoder);
+ * // encoder will now output Opus-encoded audio packets
+ */
+class Encoder extends OpusStream {
+  /**
+   * Creates a new Opus encoder stream.
+   * @memberof opus
+   * @param {Object} options options that you would pass to a regular OpusStream, plus a few more:
+   * @param {number} options.frameSize the frame size in bytes to use (e.g. 960 for stereo audio at 48KHz with a frame
+   * duration of 20ms)
+   * @param {number} options.channels the number of channels to use
+   * @param {number} options.rate the sampling rate in Hz
+   */
+  constructor(options) {
+    super(options);
+    this._buffer = Buffer.alloc(0);
+  }
+
+  async _transform(chunk, encoding, done) {
+    this._buffer = Buffer.concat([this._buffer, chunk]);
+    let n = 0;
+    while (this._buffer.length >= this._required * (n + 1)) {
+      const buf = await this._encode(this._buffer.slice(n * this._required, (n + 1) * this._required));
+      this.push(buf);
+      n++;
+    }
+    if (n > 0) this._buffer = this._buffer.slice(n * this._required);
+    return done();
+  }
+
+  _destroy(err, cb) {
+    super._destroy(err, cb);
+    this._buffer = null;
+  }
+}
+
+/**
+ * An Opus decoder stream.
+ *
+ * Note that any stream you pipe into this must be in
+ * [object mode](https://nodejs.org/api/stream.html#stream_object_mode) and should output Opus packets.
+ * @extends opus.OpusStream
+ * @memberof opus
+ * @example
+ * const decoder = new prism.opus.Decoder({ frameSize: 960, channels: 2, rate: 48000 });
+ * input.pipe(decoder);
+ * // decoder will now output PCM audio
+ */
+class Decoder extends OpusStream {
+  _transform(chunk, encoding, done) {
+    const signature = chunk.slice(0, 8);
+    if (signature.equals(OPUS_HEAD)) {
+      this.emit('format', {
+        channels: this._options.channels,
+        sampleRate: this._options.rate,
+        bitDepth: 16,
+        float: false,
+        signed: true,
+        version: chunk.readUInt8(8),
+        preSkip: chunk.readUInt16LE(10),
+        gain: chunk.readUInt16LE(16),
+      });
+      return done();
+    }
+    if (signature.equals(OPUS_TAGS)) {
+      this.emit('tags', chunk);
+      return done();
+    }
+    try {
+      this.push(this._decode(chunk));
+    } catch (e) {
+      return done(e);
+    }
+    return done();
+  }
+}
+
+module.exports = { Decoder, Encoder };