Architecture

dash.js is organized in layers with a strict direction of dependencies: the streaming/ layer implements the playback engine and the public API, the dash/ layer encapsulates everything MPD-related, and the core/ layer provides the infrastructure both build on. Smooth Streaming (mss/) and offline playback (offline/) are optional satellites with their own bundles.

The layers

• core/ — dependency injection (FactoryMaker), the EventBus, Settings, Debug/logging and the error definitions. No media logic.
• dash/ — the MPD world: manifest parsing (parser/), DashAdapter (the facade the streaming layer uses to query the manifest — see Manifest Handling), DashHandler (segment request generation) and DashMetrics.
• streaming/ — the playback engine and the entire public API surface (MediaPlayer.js). Contains the playback pipeline, the controllers, the ABR rules (see Adaptive Bitrate Streaming), the EME/DRM stack (protection/) and the HTTP loading stack (net/).
• mss/ — Microsoft Smooth Streaming support, shipped as a separate bundle (dash.mss.min.js).
• offline/ — offline download and playback.

Data flow at a glance

1. The application calls player.initialize(video, url, autoPlay).
2. The manifest is loaded and parsed; the streaming layer queries it exclusively through DashAdapter.
3. StreamController creates one Stream per period; the active Stream creates one StreamProcessor per media type (video, audio, text).
4. Each StreamProcessor runs a schedule/load/append loop: DashHandler generates segment requests, the net/ stack loads them, SourceBufferSink appends them to the Media Source Extensions buffers.
5. Metrics from every step feed the ABR rules, which adjust the selected Representation continuously.

Entry points

dash.js ships two entry points:

• index.js (full build, dash.all.min.js) — everything: DRM (Protection), metrics reporting, text/subtitle support, MediaPlayerFactory for declarative setup.
• index_mediaplayerOnly.js (dash.mediaplayer.min.js) — the lightweight core: MediaPlayer, FactoryMaker and version info only. DRM, offline and text modules can be added at runtime as needed.

The following pages describe the individual building blocks in detail:

• Dependency Injection - the FactoryMaker pattern and per-player contexts
• Event Bus & Wiring - how modules communicate
• Playback Pipeline - from schedule decision to appended segment
• Manifest Handling - loading, parsing and the DashAdapter facade
• Error Model - error events vs. synchronous throws