<stemplayer-js>

A streaming, low latency Stem Player Web-Component

See this live example of our stem player

This webcomponent follows the open-wc recommendation.

Contributing

This repo is a subtree split of our monorepo which will be made public in due course. We cannot process any pull-requests to this repo. Please contact us for help.

Installation

npm i @stemplayer-js/stemplayer-js

Usage

<script type="module">
  import '@stemplayer-js/stemplayer-js/element.js';
</script>

<stemplayer-js>
  <stemplayer-js-controls label="A label"></stemplayer-js-controls>
  <stemplayer-js-stem
    label="Drums A"
    src="https://your-cdn-com/drums.m3u8"
    waveform="https://your-cdn-com/drums.json"
    volume="0.1"
  >
  </stemplayer-js-stem>
  <stemplayer-js-stem
    label="Vocals"
    src="https://your-cdn-com/vocals.m3u8"
    waveform="https://your-cdn-com/vocals.json"
    muted="true"
    volume="0.2"
  ></stemplayer-js-stem>
</stemplayer-js>

See here for further options, events and CSS variables

Browser Support

The Player works in browsers supporting the Web Audio API. This includes most modern browsers.

The stem player is built as a web-component which is supported natively by most modern browsers.

For targeting older browsers, you can utilise your own build system.

Polyfills for web-components exist for support for older browsers.

Audio

The player consumes m3u8 playlist files known from the HLS protocol.

The audio is split up into chunks and served (over simple HTTP) separately.

Why HLS and not just download whole files? Downloading and decoding, for example, 10 5minute audio files will consume bandwith and bloat memory: each minute of every audio file worth of mp3 data is decoded into 44k PCM data and will consume roughly 100mb. By using live streaming we not only speed up playback, we also reduce the memory footprint.

Why not progressive download? We need to use the web audio API to achieve precise synchronized playback.

See also

• https://ffmpeg.org/ffmpeg-formats.html#toc-hls-1
• https://ffmpeg.org/ffmpeg-formats.html#toc-segment_002c-stream_005fsegment_002c-ssegment

See also this Docker image to help you segment your audio.

If you have an AWS environment, we have also created a Serverless Backend that will do this for you.

Waveforms

Because we don't download the entire audio file, we cannot analyse the audio so that we can display a nice waveform. So unfortunately these also need to be pre-generated. Although inconvenient, it is probably good practice anyway as a waveform in json format is very small in size; there is no need to re-compute it time and time again.

See here for info on how to generate compatible waveforms. Make sure you limit the --pixels-per-second to around 20, since by default the library will output that contains too much detail.

The output will have to be normalized so the waveform will be represented by an array of numbers that is between -1 and +1.

See here for a Docker image which should (hopefully) help.

If you have an AWS environment, we have also created a Serverless Backend that will do this for you.

Linting and formatting

To scan the project for linting and formatting errors, run

npm run lint

To automatically fix linting and formatting errors, run

npm run format

Testing with Web Test Runner

To execute a single test run:

npm run test

To run the tests in interactive watch mode run:

npm run test:watch

Tooling configs

For most of the tools, the configuration is in the package.json to minimize the amount of files in your project.

If you customize the configuration a lot, you can consider moving them to individual files.

Local Demo with web-dev-server

npm start

To run a local development server that serves the basic demo located in demo/index.html

License

Copyright (C) 2019-2024 First Coders LTD

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.