@speechmatics/web-pcm-player

Web PCM audio player

Package for playing PCM audio in the browser. Both signed 16-bit int and 32-bit float encodings are supported.

The player requires a given AudioContext to play audio within. It does not manage/change the lifecycle of the audio context (this is left to the consumer).

Installation

NPM

This package can be installed from NPM

npm i @speechmatics/web-pcm-player

Import map

You can also fetch the code from UNPKG for use in an import map:

<script type="importmap">
  {
    "imports": {
      "@speechmatics/web-pcm-player": "https://unpkg.com/@speechmatics/web-pcm-player@1.0.0-rc/dist/index.min.js"
    }
  }
</script>

Usage

This library can be used to play PCM data from either an:

• Int16Array for 16-bit unsigned integer PCM or
• Float32Array. for 32-bit float PCM

These formats correspond to pcm_s16le and pcm_f32le respectively, as described in the FFMPEG guide to PCM formats here. If you'd like more PCM formats to be added, feel free to raise an issue.

Base64 audio example

Below is an example usage playing pcm_s16le audio rendered as Base 64.

For a full working example, open the file examples/example.html in the browser.

import { PCMPlayer } from "@speechmatics/web-pcm-player";

async function playTestAudio() {
  const audioContext = new AudioContext({ sampleRate: 16_000 });
  await audioContext.resume();
  const player = new PCMPlayer(audioContext);

  for (const audioChunk of base64Data) {
    const buffer = Uint8Array.from(atob(audioChunk), (c) =>
      c.charCodeAt(0)
    );
    const data = new Int16Array(buffer.buffer);
    player.playAudio(data);
  }
}

window.onload = () => {
  document.getElementById("play-button").addEventListener("click", () => {
    playTestAudio();
  });
};

const base64Data = [
  // See data in the examples/ folder
];