First Live MPEG-DASH Large Scale Demonstration
During the 2012 London Olympics, VRT has been offering its audience the chance to experience the Olympic Games broadcast on their personal devices via MPEG-DASH. The public trial allowed for a maximum of 1000 concurrent viewers to watch their favourite sport events on a laptop, smartphone or tablet.
The commercial deployment of the MPEG-DASH (Dynamic Adaptive Streaming over HTTP) standard is one step closer with the first live public trial, presented by Belgian public broadcaster VRT. This trial has been supported by a number of DASH Promoters Group members: encoding has been provided by Elemental, Harmonic and Media Excel; streaming origins was courtesy of Wowza and CodeShop, who also provided encryption; web clients for PC and Android have been supplied by Adobe; and BuyDRM provided applications for iOS and Android, which incorporate its DRM solution.
This proof of concept was initiated by the European Broadcasting Union, which strongly supports the development of MPEG-DASH as it is a key enabler allowing broadcasters to use a single file and streaming format to deliver content to multiple devices on multiple platforms.
Supported Devices
VRT offered users the following choices for viewing the London Games:
- PCs and MAC running Adobe Flash.
- Web browser for Android provided by Adobe.
- iPhone / iPads from iOS version 4.3, with a special app from the iTunes store. The app is currently pending Apple approval.
- Android smartphones from version 4.0, via Sporza Olympic Games available from the Google Play store.
Used MPEG-DASH Profile
The demonstration featured a live video stream encoded using the MPEG-DASH ISO Base Media File Format Live Profile, delivered through Belgacom’s Content Delivery Network to a range of device categories including tablets, smartphones and PCs running iOS, Android and Windows operating systems. This represents the first large-scale multivendor deployment of MPEG-DASH.
The demonstration was based on an early version of the DASH-264 interoperability guidelines, specifically developed by the DASH Promoters Group for interoperable deployment of the MPEG-DASH standard. DASH-264 provides a general interoperability framework aligned with the HbbTV 1.5 specification and other consortia recommendations. HbbTV 1.5 will be widely used by European broadcasters for interactive services on connected televisions.
DASH details:
- File Format: ISO BM FF
- Profile: Live
- Template: Time based
- Codecs: H.264 Baseline (ABR) / Audio AAC-LC (SBR)
Encoding settings:
The video consists of 6 different streams that can be chosen by the player to adapt the video playout automatically to the available bandwidth. The highest quality is 1500 kbs for the video quality, and there is also an audio-only stream available when there is inadequate Internet speed for video.
The settings of the various adaptive switchable streams in this proof of concept have not been defined for optimal audiovisual quality. Simplicity was the key driver in selecting the Baseline profile for H.264 encoding and 64 kbs audio bitrate limitation. This will ensure that switching between the different streams will run smoothly.
Logic Flow
The logical flow of online distribution based on MPEG-DASH is very similar to what is currently deployed in adaptive streaming systems. One needs only an encoded/packaged stream and an HTTP server to get the job done and play out video to a player that supports MPEG-DASH natively.
The simple part of the workflow is demonstrated by the chain starting with the Elemental Live encoder, which captures the audiovisual content from the SDI feed at the VRT premises. The Apache server located at the CDN of Belgacom picks up the data packages via HTTP GET from the encoder and makes it available by a URL and an MPD file describing how the packages should be interpreted by the player. The Adobe player reads out the MPD, buffers the packages and plays out the video on a device of the end user.
It gets more complicated when one involves dedicated applications that play out video to devices that do not yet support MPEG DASH natively. Additionally, to secure premium content, content protection using DRM technology needs to be implemented in the server and the client. In this trial, a group of equipment suppliers are working together to make this happen.
The Harmonic ProMedia Live encoder encodes the IP feeds. The Wowza server, also located at the VRT premises, acts as an origin server, making the packages available for the Wowza cache server in the CDN. This content is then played out by the BuyDRM Android and iOS players.
In order to also showcase the Common Encryption support for MPEG-DASH with Microsoft’s PlayReady DRM, another distribution chain is set up in which the Media Excel HERO encoder works with CodeShops’s Unified Streaming server acting as an origin to produce live encrypted content. For proof of concept purposes, the BuyDRM Android and iOS applications in this distribution chain switch seamlessly between protected and unprotected content.
Source: DASH Promoters Group
