hls-stream

A readable/writable stream that can be used for manipulating a live/VOD HLS stream

Features

• Provides a readable stream that can be used for extracting particular variants/renditions from a running live/VOD HLS stream
  • Downloads and parses HLS playlist and segment files based on the spec.
  • Enables clients to choose specific variant(s) with specific rendition(s) to download.
  • Provides parsed playlists and segments as structured JS objects.
• Provides a writable stream that can be used for generating HLS playlist/segment files in realtime
  • Enables clients to describe playlists/segments as JS objects.
  • Converts the JS objects into HLS playlist and segment files that conform to the spec.

Usage

Readable stream

const {createReadStream} = require('hls-stream');
// Create a readable stream from a URL
const stream = createReadStream('https://foo.com/bar.m3u8', {concurrency: 7});

stream.on('variants', (variants, cb) => {
  // Choose variants
  const variantsToLoad = [];
  for (let [index, variant] of variants.entries()) {
    if (variant.bandwidth >= MIN_BITRATE) {
      variantsToLoad.push(index);
    }
  }
  return cb(variantsToLoad);
  // If not specified, all the variants will be loaded.
})
.on('renditions', (renditions, cb) => {
  // Choose renditions
  const renditionsToLoad = [];
  for (let [index, rendition] of renditions.entries()) {
    if (rendition.type === 'AUDIO') {
      renditionsToLoad.push(index);
    }
  }
  return cb(renditionsToLoad);
  // If not specified, all the renditions will be loaded.
})
.on('data', data => {
  // The streams chosen above will be delivered here
  if (data.type === 'playlist') {
    const playlist = data;
    if (playlist.isMasterPlaylist) {
      console.log(`Master playlist`);
    } else {
      console.log(`Media playlist`);
    }
  } else if (data.type === 'segment') {
    const segment = data;
    console.log(`#${segment.mediaSequenceNumber}: duration = ${segment.duration}, byte length = ${segment.data.length}`);
  }
})
.on('end', () => {
  // For VOD streams, the stream ends after all data is consumed.
  // For Live streams, the stream continues until the ENDLIST tag.
  console.log('Done');
})
.on('error', err => {
  console.error(err.stack);
});

// To emit 'variants' and 'renditions' events again
stream.updateVariant();

Writable stream (still under development...)

const {createWriteStream, types: {MediaPlaylist}} = require('hls-stream');
// Create a writable stream from a filepath
const stream = createWriteStream('./sample.m3u8');

stream.write(new MediaPlaylist({
  targetDuration: 9,
  playlistType: 'VOD',
  segments: [
    new Segment({uri: '', duration: 9})
  ]
}));

API

These features are provided via a ReadStream.

createReadStream(url[, options])

Creates a new ReadStream object.

params

Name	Type	Required	Default	Description
url	string	Yes	N/A	Playlist URL
options	object	No	{}	See below

options

Name	Type	Default	Description
concurrency	number	6	Max number of requests concurrently processed
rawResponse	boolean	false	If true, Segment data is returned as a readable stream, default is as a Buffer

return value

An instance of ReadStream.

ReadStream

A subclass of stream.Readable with additional events and methods as follows.

events

'variants'

variants event is emitted to let clients specify which variants to be loaded. The event listener is called with the following arguments:

Name	Type	Description
variants	[Variant]	A list of available variants
cb	function	A callback function used by the client to specify which variants to be loaded. cb takes a single argument of type Array which contains the index within variants.

'renditions'

renditions event is emitted to let clients specify which renditions to be loaded. The event listener is called with the following arguments:

Name	Type	Description
renditions	[Rendition]	A list of available renditions
cb	function	A callback function used by the client to specify which renditions to be loaded. cb takes a single argument of type Array which contains the index within renditions.

'data'

data event is emitted when a playlist or segment is available. The event listener is called with the following arguments:

Name	Type	Description
data	Data	An instance of either of Segment, MasterPlaylist or MediaPlaylist

methods

updateVariant()

Emits variants/renditions events again so that the client can choose other variants/renditions. The method takes no params and returns no value.