opus-decoder/src/OpusDecoder.js

Web Assembly streaming Opus decoder

import { WASMAudioDecoderCommon } from "@wasm-audio-decoders/common";

import EmscriptenWASM from "./EmscriptenWasm.js";

export default function OpusDecoder(options = {}) {
  // static properties
  if (!OpusDecoder.errors) {
    // prettier-ignore
    Object.defineProperties(OpusDecoder, {
      errors: {
        value: new Map([
          [-1, "OPUS_BAD_ARG: One or more invalid/out of range arguments"],
          [-2, "OPUS_BUFFER_TOO_SMALL: Not enough bytes allocated in the buffer"],
          [-3, "OPUS_INTERNAL_ERROR: An internal error was detected"],
          [-4, "OPUS_INVALID_PACKET: The compressed data passed is corrupted"],
          [-5, "OPUS_UNIMPLEMENTED: Invalid/unsupported request number"],
          [-6, "OPUS_INVALID_STATE: An encoder or decoder structure is invalid or already freed"],
          [-7, "OPUS_ALLOC_FAIL: Memory allocation has failed"],
        ]),
      },
    });
  }

  // injects dependencies when running as a web worker
  // async
  this._init = () =>
    new this._WASMAudioDecoderCommon(this)
      .instantiate(this._EmscriptenWASM, this._module)
      .then((common) => {
        this._common = common;

        this._inputBytes = 0;
        this._outputSamples = 0;
        this._frameNumber = 0;

        this._input = this._common.allocateTypedArray(
          this._inputSize,
          Uint8Array,
        );

        this._output = this._common.allocateTypedArray(
          this._outputChannels * this._outputChannelSize,
          Float32Array,
        );

        const mapping = this._common.allocateTypedArray(
          this._channels,
          Uint8Array,
        );

        mapping.buf.set(this._channelMappingTable);

        this._decoder = this._common.wasm.opus_frame_decoder_create(
          this._sampleRate,
          this._channels,
          this._streamCount,
          this._coupledStreamCount,
          mapping.ptr,
          this._preSkip,
          this._forceStereo,
        );
      });

  Object.defineProperty(this, "ready", {
    enumerable: true,
    get: () => this._ready,
  });

  // async
  this.reset = () => {
    this.free();
    return this._init();
  };

  this.free = () => {
    this._common.free();
    this._common.wasm.opus_frame_decoder_destroy(this._decoder);
    this._common.wasm.free(this._decoder);
  };

  this._decode = (opusFrame) => {
    if (!(opusFrame instanceof Uint8Array))
      throw Error(
        "Data to decode must be Uint8Array. Instead got " + typeof opusFrame,
      );

    this._input.buf.set(opusFrame);

    let samplesDecoded =
      this._common.wasm.opus_frame_decode_float_deinterleaved(
        this._decoder,
        this._input.ptr,
        opusFrame.length,
        this._output.ptr,
      );

    let error;

    if (samplesDecoded < 0) {
      error =
        "libopus " +
        samplesDecoded +
        " " +
        (OpusDecoder.errors.get(samplesDecoded) || "Unknown Error");

      console.error(error);
      samplesDecoded = 0;
    }

    return {
      outputBuffer: this._common.getOutputChannels(
        this._output.buf,
        this._outputChannels,
        samplesDecoded,
      ),
      samplesDecoded: samplesDecoded,
      error: error,
    };
  };

  this.decodeFrame = (opusFrame) => {
    let errors = [];

    const decoded = this._decode(opusFrame);

    if (decoded.error)
      this._common.addError(
        errors,
        decoded.error,
        opusFrame.length,
        this._frameNumber,
        this._inputBytes,
        this._outputSamples,
      );

    this._frameNumber++;
    this._inputBytes += opusFrame.length;
    this._outputSamples += decoded.samplesDecoded;

    return this._WASMAudioDecoderCommon.getDecodedAudioMultiChannel(
      errors,
      [decoded.outputBuffer],
      this._outputChannels,
      decoded.samplesDecoded,
      this._sampleRate,
    );
  };

  this.decodeFrames = (opusFrames) => {
    let outputBuffers = [],
      errors = [],
      samplesDecoded = 0,
      i = 0;

    while (i < opusFrames.length) {
      const opusFrame = opusFrames[i++];
      const decoded = this._decode(opusFrame);

      outputBuffers.push(decoded.outputBuffer);
      samplesDecoded += decoded.samplesDecoded;

      if (decoded.error)
        this._common.addError(
          errors,
          decoded.error,
          opusFrame.length,
          this._frameNumber,
          this._inputBytes,
          this._outputSamples,
        );

      this._frameNumber++;
      this._inputBytes += opusFrame.length;
      this._outputSamples += decoded.samplesDecoded;
    }

    return this._WASMAudioDecoderCommon.getDecodedAudioMultiChannel(
      errors,
      outputBuffers,
      this._outputChannels,
      samplesDecoded,
      this._sampleRate,
    );
  };

  // injects dependencies when running as a web worker
  this._isWebWorker = OpusDecoder.isWebWorker;
  this._WASMAudioDecoderCommon =
    OpusDecoder.WASMAudioDecoderCommon || WASMAudioDecoderCommon;
  this._EmscriptenWASM = OpusDecoder.EmscriptenWASM || EmscriptenWASM;
  this._module = OpusDecoder.module;

  const MAX_FORCE_STEREO_CHANNELS = 8;
  const isNumber = (param) => typeof param === "number";

  const sampleRate = options.sampleRate;
  const channels = options.channels;
  const streamCount = options.streamCount;
  const coupledStreamCount = options.coupledStreamCount;
  const channelMappingTable = options.channelMappingTable;
  const preSkip = options.preSkip;
  const forceStereo = options.forceStereo ? 1 : 0;

  // channel mapping family >= 1
  if (
    channels > 2 &&
    (!isNumber(streamCount) ||
      !isNumber(coupledStreamCount) ||
      !Array.isArray(channelMappingTable))
  ) {
    throw new Error("Invalid Opus Decoder Options for multichannel decoding.");
  }

  // libopus sample rate
  this._sampleRate = [8e3, 12e3, 16e3, 24e3, 48e3].includes(sampleRate)
    ? sampleRate
    : 48000;

  // channel mapping family 0
  this._channels = isNumber(channels) ? channels : 2;
  this._streamCount = isNumber(streamCount) ? streamCount : 1;
  this._coupledStreamCount = isNumber(coupledStreamCount)
    ? coupledStreamCount
    : this._channels - 1;
  this._channelMappingTable =
    channelMappingTable || (this._channels === 2 ? [0, 1] : [0]);
  this._preSkip = preSkip || 0;

  this._forceStereo =
    channels <= MAX_FORCE_STEREO_CHANNELS && channels != 2 ? forceStereo : 0;

  this._inputSize = 32000 * 0.12 * this._channels; // 256kbs per channel
  this._outputChannelSize = 120 * 48;
  this._outputChannels = this._forceStereo ? 2 : this._channels;

  this._ready = this._init();

  return this;
}