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.
