48 lines
2.0 KiB
Markdown
48 lines
2.0 KiB
Markdown
|
# Playlist Loader
|
||
|
|
|
||
|
|
## Purpose
|
||
|
|
|
||
|
|
The [PlaylistLoader][pl] (PL) is responsible for requesting m3u8s, parsing them and keeping track of the media "playlists" associated with the manifest. The [PL] is used with a [SegmentLoader] to load ts or fmp4 fragments from an HLS source.
|
||
|
|
|
||
|
|
## Basic Responsibilities
|
||
|
|
|
||
|
|
1. To request an m3u8.
|
||
|
|
2. To parse a m3u8 into a format [videojs-http-streaming][vhs] can understand.
|
||
|
|
3. To allow selection of a specific media stream.
|
||
|
|
4. To refresh a live m3u8 for changes.
|
||
|
|
|
||
|
|
## Design
|
||
|
|
|
||
|
|
### States
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
- `HAVE_NOTHING` the state before the m3u8 is received and parsed.
|
||
|
|
- `HAVE_MAIN_MANIFEST` the state before a media manifest is parsed and setup but after the main manifest has been parsed and setup.
|
||
|
|
- `HAVE_METADATA` the state after a media stream is setup.
|
||
|
|
- `SWITCHING_MEDIA` the intermediary state we go though while changing to a newly selected media playlist
|
||
|
|
- `HAVE_CURRENT_METADATA` a temporary state after requesting a refresh of the live manifest and before receiving the update
|
||
|
|
|
||
|
|
### API
|
||
|
|
|
||
|
|
- `load()` this will either start or kick the loader during playback.
|
||
|
|
- `start()` this will start the [PL] and request the m3u8.
|
||
|
|
- `media()` this will return the currently active media stream or set a new active media stream.
|
||
|
|
|
||
|
|
### Events
|
||
|
|
|
||
|
|
- `loadedplaylist` signals the setup of a main playlist, representing the HLS source as a whole, from the m3u8; or a media playlist, representing a media stream.
|
||
|
|
- `loadedmetadata` signals initial setup of a media stream.
|
||
|
|
- `playlistunchanged` signals that no changes have been made to a m3u8.
|
||
|
|
- `mediaupdatetimeout` signals that a live m3u8 and media stream must be refreshed.
|
||
|
|
- `mediachanging` signals that the currently active media stream is going to be changed.
|
||
|
|
- `mediachange` signals that the new media stream has been updated.
|
||
|
|
|
||
|
|
### Interaction with Other Modules
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
[pl]: ../src/playlist-loader.js
|
||
|
|
[sl]: ../src/segment-loader.js
|
||
|
|
[vhs]: intro.md
|