CODEWITHSUNDEEP
javascriptvideo-streamingvideo-encodingtranscodingmpeg-dash
Chris Calo
Chris Calo

Reputation: 456

Start MPEG-DASH Stream at Arbitrary Segment

Say there are 20 segments in an MPEG-DASH stream, and the stream typically starts at index 0. Is it possible to start at index 13, assuming an init file/byte sequence has already been queued into the Media Source buffer? An example, in which this use-case would be practical, is for something like Netflix' resumption feature – where someone could continue streaming on another device/browser. (Presumably with the same init data as when started from the beginning.)

My only thought is that my assumption is wrong, and there would be a different initialization chunk for each various point in which the media could be paused… but that would just be silly… right?

Upvotes: 1

Views: 727

Answers (1)

Mick
Mick

Reputation: 25481

The simple answer is that yes it is possible and as you suggest this can be used for resume playback features. It can also be used for 'start-over' on live streams and to jump forwards or backwards to a particular point in a video.

MPEG DASH supports two main file formats (or video container formats) - ISO Base Media File Format (ISOBMFF - which is often referred to as MP4 although it is strictly speaking a generalisation of MPEG-2) and MPEG-TS.

The MPEG DASH standard uses the concept of 'Periods' as one of its fundamental building blocks - the periods represents a part of the content stream and include a start time and a duration. To be able to playback the content in a given period you still need some initialisation data.

Looking at ISOBMFF, there is an init segment as you suggest which contains this required data and which is defined by W3C as:

Initialization Segment A sequence of bytes that contain all of the initialization information required to decode a sequence of media segments. This includes codec initialization data, Track ID mappings for multiplexed segments, and timestamp offsets (e.g., edit lists).

Upvotes: 1

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