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special report adaptive streaming


It's often said that change is disruptive, and that's certainly true for the most significant media distribution development in recent memory, which is the advent of new viewing devices for content delivery. With the extension of video viewing from standard TVs to smart phones, tablets, connected TVs, DVRs, and game consoles, over-the-top (OTT) media has become a major factor in content distribution, making today's media landscape radically different from that of just a few years ago. What used to be all but impossible - the delivery of consistently acceptable image and sound quality despite often uncertain and fluctuating bandwidth - is now taken for granted by viewers on these devices. Adaptive bit- rate (ABR) streaming is the key technology to making it all work. JimDuval, director of new products and strategy at Telestream, reports.


Adaptive streaming in an OTT world


investment that content owners and distributors have made in recent years to extend media distribution beyond the confines of traditional broadcast and cable television. It would be a mistake to think of the content preparation side of that investment solely in terms of discrete devices for transcoding video into the correct format for various outlets. Instead, efficient high-volume content preparation demands a comprehensive workflow approach that addresses archiving, digital asset management, transcoding, and delivery in an intelligent workflow. ABR has direct and significant impacts on this workflow.


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he emergence of ABR - Apple HTTP Adaptive Streaming, Microsoft Smooth Streaming, and Adobe Dynamic Streaming, and MPEG DASH - coincides with the significant


Telestream Lightspeed


accelerates video processing and H.264 encoding on parallel GPUs and multicore CPUs.


With ABR growing in importance, it's


imperative for content owners and others who prepare media for distribution to fully understand how ABR files differ from conventional streaming files, the implications of those differences for conventional media preparation processes, and how those processes may be successfully adapted to create highly-efficient, cost- effective workflows addressing both ABR and conventional deliverables.


Understanding adaptive streaming


In conventional streaming, once a connection is established between an end user and a media file, that file streams at a fixed bitrate and displays at its inherent resolution (eg 640 480). ABR streaming instead tailors streams to the resolution of the playback device


and the available bandwidth of the connection. Connect via a tablet over a strong Wi-Fi signal, and you'll get a larger picture and higher bitrate. Connect via a smart phone in your car and you'll get a smaller (lower resolution) picture at a lower bitrate. If your connection improves as you drive, the system will adapt on the fly to the changed conditions, increasing the bitrate at which the content is streamed. To enable this flexibility, an ABR file


isn't really an individual file at all, but rather a package of files. An ABR package includes a manifest file, which holds the stream metadata, and a set of multiple ‘layers’, each made up of the media data for a different target bitrate. To enable switching between layers as conditions change during streaming, the content for each layer is fragmented into files of only a few seconds in duration. One aspect of preparing an ABR


package is to prepare the half-dozen or so streams corresponding to each of the package's layers. Using conventional hardware, transcoding for an ABR package with a half-dozen layers will typically take about six


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