jtBaseApp/node_modules/@videojs/http-streaming/docs/playlist-loader.md

Playlist Loader

Purpose

The PlaylistLoader (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 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