In Broadcast - December 2011/January 2012 - 84

InFILE
Crushing Need For A Massive Squeeze Cont.

Viewcast Niagara 7550

an almost-instantaneous second pass is a hazardous process so Harmonic’s broadcast encoder, the Electra and its real-time multiscreen software transcoder, ProMedia Live, employ sophisticated techniques to compete in pure image quality terms with its post production cousins. In the battle to overcome the inherent limitations in live repurposing, different solutions are utilised. For Harmonic, it is the concept of look-ahead multipass processing, which employs two MPEG encoders. The second encoder’s buffer delays the input so that the first encoder can analyse the picture first. The second encoder uses the analysis of the first encoder as a guide to generating the final bitstream. In broad terms, this concept of multi-pass analysis and forwardlooking encoding is used by other leading developers such as Ericsson and Cisco. Similarly, Thomson Video Networks’ “enriched logic” in the ViBE EM4000 HD encoder does “much more computation on the picture in the encoding process, thus leading to a more efficient encoding and less bit rate”. At the transmission side of the

market, this kind of sophisticated, intelligent pre-encoding sits alongside highly evolved preprocessing to ensure that compressed signals are as high in quality as possible. The key is for the encoder to make intelligent decisions about compression, based upon an understanding of the composition of the pictures. Encoders can pick out areas of the picture that contain excessive unwanted noise and unnecessary detail while maintaining definition in sequences that contain radical scene changes, such as crossfades between scenes. The combination of preprocessing and multi-pass technology has seen enormous efficiency gains – in short higher quality content at ever lower bitrates.

Tailored to the streaming needs of the broadcast market, Viewcast’s Niagara 7550 HD picture preprocessing is restricted to scaling, cropping, de-interlacing, inverse telecine and closed-caption rendering. Instead of optimising for ultimate image quality, the emphasis of the Niagara – and similar products in this field – is on a broad range of simultaneous output options.

Multiple Formats

Live Webcasts

Very similar constraints – low bitrates and the necessity for live transmission – confront webcasters and live internet streaming providers. Because streaming media often operates at a different financial level to TV transmission, the level of pre-processing and image optimisation is inevitably more limited.

In order to cope with the multitude of formats such as Adobe® Flash® H.264, Flash dynamic streaming, Apple® HTTP live streaming, Microsoft Live IIS Smooth Streaming, Silverlight and MPEG-4, live IP solutions are the clearly decathletes of the encoding world, compared with the specialist thoroughbreds of the DVB world. IP encoders are available as rack-mounted units, PCI cards or in portable dedicated units, like Digital Rapids’ TouchStream appliance. This packages live streaming technology into a mobile device and, like the Niagara, offers multiformat, multi-resolution delivery. With advanced motion adaptive de-interlacing algorithms, Digital Rapids claims to offer superior

image quality alongside video adjustments that can enhance image quality for internet delivery. Smaller still are Teradek’s range of encoders. Its Odyssey, Citadel and Chimera offer H.264 output in cases little bigger than a DVD case. Even these seem bulky next to the company’s Cube range, a product that would fit into a cigarette box. However, before being carried away by the miniaturisation mantra, it’s worth noting that these small packages cannot yet compare in features to the image enhancing, multi-stream and adaptive bitrate capabilities of their more heavily built counterparts.

In the Clouds

Digital Rapids Touchstream

With Encoding.com, Haivision’s HyperStream, Though Equity Motion and other online suppliers, video encoding can now be a hands-off process. The concept is simple: upload your media to a service provider where it is transcoded into whatever formats you require before it is distributed back to you or to any network you specify. The benefits are many: no need to invest in transcoding solutions; no need to continually update and support existing systems; roundthe-clock access to world-class high-speed technology. The cloud promises increased speed, lower overheads and maximum future-proofing. Encoding.com boasts the option of transcoding video as it is being uploaded; Haivision’s system offers live encoding for playout in the cloud – a broadcaster in the field can upload a 1Mbps stream that is transcoded live into adaptive multi-bitrate, multi-platform, multiformat video. For speed and cost efficiencies, the cloud approach is a tempting proposition. Where it cannot currently compete, however, is where a broadcaster has particular pre-processing requirements for image enhancements, peculiar aspect ratios, logo insertion or
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