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FEATURE


viewing is content shifting. This stage, which might occur within the next three to four years, will be one of extreme personalisation and will give viewers the power to change the fundamental nature of the content. We are used to watching news


programmes from a single camera angle, but that can become monoto- nous. Why can’t we have the power to change the camera angles? Why can’t we play around with the lan- guage of a film and hear the same dialogue in different languages? Wouldn’t it be great to watch a cricket match from different angles? The possibilities are endless. Many of these applications require


an interactive channel to provide the desired level of user experience, but there are technical limitations. Most IP video broadcasts use


adaptive bit rate streaming technol- ogy. This works on the principle of varying the resolution of the video by switching to streams of identical content containing a higher or lower bit rate, depending on the available network and processing resources. To make this work, the head end outputs the same content multiple times at different bit rates. For a given channel to support


the three most popular adaptive streaming formats (Apple HTTP Live Streaming, Microsoft Smooth Streaming and Adobe Flash Dynamic Streaming), the head end needs to support an average of six profiles for each format. This means around 18 profiles per channel. So an IPTV transmission of 200


channels would have 200 x 18 profiles – or 3,600 profiles in total. This requires the use of the densest trans- ponders and significant operating and capital expenditure. The situation


42 | Broadcast TECH | May/June 2012


SHIFTING POWER A


fter time shifting and place shifting, the next phase of TV


Broadcast TECH


Amit Kumar explains the technical challenge of giving viewers more control over what they watch


Howzat!: cricket would benefit from allowing viewers to watch from different angles


‘Why can’t we have the power to change the camera angles? The possibilities


are endless’ Amit Kumar


is even worse for content shifting as the encoders and transcoders need to receive multiple profiles for the same channel on the input side. On the output side, a similarly complex system of profiles is needed to implement the content-shifting concepts. The input audio and video file formats can be different, and transcoders should be competent enough to seamlessly generate profiles for the content-shifted broadcast. All these channel line- ups, profiles and input-output matrices also pose a significant management challenge and complex testing procedures.


Return channel Many of the content-shifting appli- cations, such as requesting more information from an advertiser, voting for contestants in real time, requesting statistics on a player dur- ing a sporting event, or playing along with a TV game, need a return channel to the head end to pass information to the broadcaster. This problem is easier to handle in an IP scenario, but in a cable environment, it is challenging. However, compa-


nies have come up with different solutions to this problem that pro- vide true interactivity to the user. One of the solutions is to use the Enhanced TV Binary Format (EBIF) framework, proposed by Cable Labs. Solutions that combine EBIF and MPEG broadcasting to provide interactivity on most basic set-top boxes are available. Other compa- nies have proposed solutions where most of the interactive applications run on the head end side and DOC- SIS or out-of-band IP connections are used for the return channel. However, these systems are not


popular and their functions are lim- ited. For the kind of interactivity and personalisation needed in a content- shifting context, there are still many technical challenges to be overcome. Another significant issue is copy-


right: if users are empowered to play around with the content, there will be serious content protection issues to consider. And there is likely to be a tussle between content producers and content distributors to share the extra revenues generated by the process. ➤ Amit Kumar is product manager at MindTree Digital Media


www.broadcastnow.co.uk/techfacils


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