The ABC Player for the iPad launched with much fanfare and success. Building on this success, ABC set out to develop a dedicated ABC News application for the iPad, designed to provide a rich, interactive end-user experience in which text and video work together to inform and entertain. The free application's debut targeted an installed base of more than 3 million iPad users.
Background: ABC'S expansive video assets
As new media platforms proliferate, content producers like ABC are increasingly challenged to supply archived and first-run video for playback in a variety of formats on a wide range of devices over bandwidth-constrained networks. When a new device like the iPad is introduced into the market, large content providers must be prepared to convert video assets for compatible format and display. But formatting and display are only part of the equation.
Today, multiple copies, and therefore multiple transcodes of the same content, are needed to deliver the highest possible quality experience on a wide array of devices.
Smart video delivery
Adaptive bit-rate streaming is literally seamless in that the video consumer does not need to adjust settings to cope with variability in network conditions. Bit-rate changes occur as both network and client resources fluctuate while maintaining smooth delivery of streaming video without buffering or other interruption.
Adaptive bit-rate streaming to the iPad, therefore, requires not only conversion of existing content to a variety of display resolutions and bit rates optimized for the device, but also requires a mix of files to be available for real-time stream switching. To achieve this, content providers must convert video assets to new file formats across a range of settings rather than relying on a single encoded file to address all network and client conditions before delivering to a CDN.
Under the hood
In the case of the iPad, ABC must encode and segment years of video into the fragments required for Apple's HTTP adaptive streaming protocol. To meet this challenge, ABC deployed Elemental Technologies' Elemental Server into its production workflow. (See Figure 1.)
Elemental Server is a file-based video processing system that performs high-speed video transcoding for multiscreen video applications. At the heart of the system is patent-pending software that harnesses the power and programmability of modern graphics processing units (GPUs). By harnessing the power of the GPU, the time required for video processing and conversion is greatly reduced.
The Linux-based system is designed to perform transcoding. The key functions include decoding, video processing and conversion, and file formatting. It offers universal input support and can accept a broad range of incoming file formats and core codecs, including Apple ProRes 422, MPEG-2, VC-1 and MPEG-4. It provides advanced preprocessing, including inverse telecine and motion-adaptive deinterlacing, noise reduction, and color correction. Image insertion is also available. Other video processing functions include antialias scaling, scene change detection, MPEG-2 deblocking and temporal frame rate conversion. Video conversion can be performed using a variable, average or constant bit rate with options for single or multipass encoding.
Supported codecs include H.264, VC-1 and MPEG-2. Converted files can be wrapped in a variety of containers for Flash or Windows Media, or in an MPEG-2 transport stream. Media can also be formatted for adaptive bit-rate protocols, including ISMV for Smooth Streaming, F4V for Flash Media Server, or m3u8 for Apple Adaptive. CableLabs-compliant streams are also an available option.
Elemental Server also addresses the Apple App Store requirement to use the m3u8 file extension as well as to provide a 64kb/s bit stream for all video apps. Files are generally either 640 × 360 or 480 × 360, 24fps, with a 48 GOP size and incremented in 10-second segments. Each input file is formatted to five outputs — 700k: 652k video + 48k audio; 500k: 452k video + 48k audio; 300k: 252k video + 48k audio; 150k: 118k video + 32k audio; and 64k: 36k video + 24k audio (JPEG overlay + audio).
The system significantly streamlines content conversion for the iPad with a substantial increase in transcoding efficiency compared with existing solutions. Built-in presets for the iPad eliminate the need for customized encoding settings and save operator time. The performance available with a single encoding system reduces the number of units required for large-scale transcoding, therefore lowering operations cost and overhead.
In addition, the system's flexibility allows effective conversion of video for the iPad today and ensures support for video delivery standards and protocols such as HTML5 and WebM in the future. Its massively parallel architecture can easily handle the processing required to transcode simultaneous inputs and outputs in real time. With Elemental Server, ABC can convert more than 20 640 × 360 or 480 × 360 files in real time for on-demand adaptive bit rate streaming.
Elemental Server merges the performance benefits of a massively parallel hardware platform with the versatility and forward compatibility of intelligent software to give video publishers and distributors unmatched price/performance for video compression. By harnessing the power of graphics processors, it offers greater density and throughput than other solutions. The system delivers simultaneous, faster-than-real-time conversion of multiple HD and SD video streams across an array of devices, including TVs, PCs, tablets and mobile phones.
Lisa Epstein is senior marketing manager of Elemental Technologies.
