Harmonic Inc

By: Harmonic Inc on February 4th, 2013

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MPEG-DASH: How Does it Work?

MPEG-DASH is a new ISO standard poised to help operators create a more efficient multiscreen delivery ecosystem. But what does it actually do DASH offers a playlist mechanism that supports either fragmented transport streams (derived from the Apple HLS  specification) or MPEG-4 (derived from the Microsoft Smooth Streaming specification).

Inside each of those formats, it’s possible to have a common encryption scheme that allows content to be encoded and encrypted just once, with a single master key that can be used by several DRM servers and clients.This is good because it lets content/service providers use one defined format (TS or MPEG-4) for a lot of different DRM specifications, increasing device support without increasing costs. Another plus is that  the fragmented MPEG-4 format has been widely endorsed by the industry (see HbbTV in Europe, 3GPP for mobile devices and soon DECE).

A DASH system will have several elements:

Transcoding: You need this for live and file-based content. It transcodes in H.264 format for every required profile. Dual encapsulation is needed in case both TS and MPEG-4 formats are required, though we think that eventually MPEG-4 will win out.

  • Content Encryption and DRM: This will encrypt the TS and MPEG-4 files with a single key. The DRM server will add metadata related to content rights on top of the encrypted file.
  • Streaming: With the unified DASH playlist mechanism, this will only have to be in two formats: fragmented MPEG-4 or TS.
  • Storage: This is needed for VOD and catch-up files. With all that put together, an operator can start DASHing towards a superior multiscreen delivery model.

– Harmonic Marketing