An HLS master playlist describes alternative ways to play a presentation, such as video variants at different bitrates and groups of audio or subtitle renditions. It acts as a directory for those choices rather than a sequential list of all video segments itself. A player uses its declarations and its own capabilities to choose appropriate media playlists. A single entry address can therefore lead to several available qualities. Those alternatives exist only when the publisher supplies them; merely having a master playlist does not guarantee every resolution, language or device-compatible codec is available.
Master playlist and Media playlist
The master describes alternatives; a media playlist lists the segments for a selected presentation.
How selection reaches actual media
The player reads variant information such as bandwidth and codec declarations, selects a compatible option and retrieves the associated media playlist. It can also select an audio rendition from a declared group. The selected media playlist then identifies timed segments. A failure at the second stage can occur even when the original master address returned a valid document quickly.
Diagnosing one broken alternative
If automatic playback works at one quality but fails when another supplied quality is selected, compare those variants rather than treating the whole stream as unavailable. One variant might reference missing media, exceed decoder capabilities or require a different codec. Record the selected quality and any explicit error. A forced high setting changes both data demand and potentially the decoder workload.
Master versus media playlist
The master describes alternatives and their relationships. A media playlist describes the timeline and segments of a chosen rendition. Confusing those roles can lead to using a single variant address and unintentionally bypassing adaptive selection or alternative audio. Use the provider's supported entry address, since manually choosing a child playlist can also bypass metadata or access behavior the application expects.
An illustrative example
A master playlist offers two video variants and an alternative audio group. The player starts the lower variant, but selecting the higher one consistently fails. The relevant report includes that variant and error, because a working master document does not prove every child playlist, codec configuration or segment path is valid.
Practical actions
- Use the documented presentation entry address
- Record the failing supplied variant
- Compare master and selected media-playlist requests