.MPD

MPEG-DASH Media Presentation Description

Introduction

An .mpd file is the manifest of MPEG-DASH, Dynamic Adaptive Streaming over HTTP, the international standard for adaptive streaming, ISO/IEC 23009-1. Like an HLS playlist it tells a player which versions of a video exist and where to fetch each segment, so the player can change quality as the connection changes. DASH is widely used by large streaming services and plays in browsers through JavaScript players.

The manifest is an XML document. It describes the media but holds none of it: the segments themselves are usually fragmented MP4 or WebM files.

Software

Structure

The root element is MPD. Its attributes say whether the presentation is static, like a film, or dynamic, like a live broadcast, and give its duration and the minimum buffer a player should keep.

Inside it, one or more Period elements divide the presentation in time, for example a programme and an advert. Each period holds AdaptationSet elements, one for each kind of content such as the video, the audio in each language and the subtitles. Each adaptation set holds Representation elements, the alternative encodings of that content, each with its bandwidth, codecs and, for video, resolution. A SegmentTemplate, SegmentList or SegmentBase tells the player how to find the segments of each representation.

  1. MPDMPD type, duration, buffer and profilesroot
    1. PeriodPeriod a span of the presentationrepeated
      1. SetAdaptationSet one kind of content: video, an audio language, subtitlesrepeated
        1. RepRepresentation one encoding, with its segment templaterepeated
The element tree of an MPEG-DASH manifest.