wasm-media-encoders v0.6.4

wasm-media-encoders

The LAME MP3 and Ogg Vorbis audio encoders, compiled to WebAssembly and ready for use in the browser or Node.

Installation

yarn add wasm-media-encoders

or

npm install wasm-media-encoders

Getting started

With webpack:

import { createMp3Enoder, createOggEncoder } from "wasm-media-encoders";

createOggEncoder().then((encoder) => {
  /* Configure and use the encoder */
});
createMp3Encoder().then((encoder) => {
  /* Configure and use the encoder */
});

With a <script> tag:

<script src="https://unpkg.com/wasm-media-encoders/umd/WasmMediaEncoder.min.js"></script>
<script>
  // The UMD package will fetch() the WASM binaries from
  // unpkg.com by default to reduce size

  WasmMediaEncoder.createMp3Encoder().then((encoder) => {
    /* Configure and use the encoder */
  });
</script>

With Node:

const { createMp3Encoder } = require("wasm-media-encoders");
createMp3Encoder().then((encoder) => {
  /* Configure and use the encoder */
});

Reducing bundle size

By default, this package inlines the WASM binary as a base64-encoded data URL. This make importing the encoder easy, but also increases the bundle size by about 30%. With webpack, you can use file-loader and load the WASM directly (found in wasm-media-encoders/wasm/(mp3|ogg).wasm), passing the URL as the second parameter to createEncoder():

import { createEncoder } from "wasm-media-encoders";
import wasm from "file-loader!wasm-media-encoders/wasm/mp3.wasm";

createEncoder("audio/mpeg", wasm).then((encoder) => {
  /* Now mp3.wasm will be copied to output dir by webpack and fetch()ed at runtime*/
});

Example usage

createMp3Encoder().then((encoder) => {
  encoder.configure({
    sampleRate: 48000,
    channels: 2,
    vbrQuality: 2,
  });

  let outBuffer = new Uint8Array(1024 * 1024);
  let offset = 0;

  while (true) {
    const mp3Data = moreData
      ? encoder.encode([
          pcm_l /* Float32Array of left channel PCM data */,
          pcm_r /* Float32Array of right channel PCM data */,
        ])
      : /* finalize() returns the last few frames */
        encoder.finalize();

    /* mp3Data is a Uint8Array that is still owned by the encoder and MUST be copied */

    while (mp3Data.length + offset > outBuffer.length) {
      const newBuffer = new Uint8Array(outBuffer.length * 2);
      newBuffer.set(outBuffer);
      outBuffer = newBuffer;
    }

    outBuffer.set(mp3Data, offset);
    offset += mp3Data.length;

    if (!moreData) {
      break;
    }
  }

  return new Uint8Array(outBuffer.buffer, 0, offset);

  /* Or encoder can be reused without calling createEncoder() again:

  encoder.configure({...new params})
  encoder.encode()
  encoder.finalize() */
});

API

Named exports:

createMp3Encoder(): Promise<WasmMediaEncoder>

createOggEncoder(): Promise<WasmMediaEncoder>

createEncoder(mimeType, wasm: Promise<WasmMediaEncoder>

The first two named exports use inline base-64 encoded WASM binaries (or fetch() from unpkg.com in the case of UMD). Tree-shaking on webpack should prevent unused encoders from being included in the final bundle.

WasmMediaEncoder

configure(options): void

Configures the encoder. This method can be called at any time to reset the state of the encoder, including after finalize().

The options object is a union of common properties and encoder-specific ones. All common options are required.

Common options: | Property | Type | Description | |-|-|-| | channels | Number | The number of channels to be encoded. Currently only 1 or 2 channels are supported.| |sampleRate | Number | Sample rate of data to be encoded, in hertz. |

Options for MIME type audio/mpeg (MP3):

vbrQuality and bitrate are mutually exclusive. | Property | Type | Default | Description | |-|-|-|-| |vbrQuality| Number \| undefined | 4.0 | Variable Bitrate (VBR) quality for the LAME encoder, from 0.0 (best quality) to 9.999 (worst quality). See here for details.| |bitrate| Number \| undefined | | Constant bitrate in kbit/s. Valid bitrates are 8, 16, 24, 32, 40, 48, 64, 80, 96, 112, 128, 160, 192, 224, 256, or 320.|

Options for MIME type audio/ogg (Ogg Vorbis):

encode(samples): Uint8Array

Encodes PCM samples and returns a Uint8Array. May return a Uint8Array of length zero. The returned Uint8Array is owned by the encoder and MUST be copied before any other encoder methods are called. | Parameter | Type | Description | | - | - | - | |samples| Float32Array[] | A channels-length array of Float32Array representing the PCM data to encode. Each sample must be in the range of -1.0 to 1.0 |

finalize(): Uint8Array

Flushes the encoder and returns the last few encoded samples. May return a Uint8Array of length zero. The returned Uint8Array is owned by the encoder and MUST be copied before any other encoder methods are called.

License

This project is licensed under the terms of the MIT license.