In Broadcast - April 2012 - 48


WWW.INBROADCAST.COM | ISSUE 7 - APRIL 2012

InREPLY
Renaud Desportes, Director of Wohler’s Ancillary Data Management Product Line addresses the question of subtitling content challenges
Renaud Desportes

48

Mandates from industry regulators worldwide are requiring a growing number of broadcasters and other distributors of programming – to provide a minimum number of hours of subtitled programming per day, week, or calendar quarter. Though there is no one, uniformly adopted standard for subtitling across Europe, the Middle East, and Africa, broadcasters across these regions face similar challenges in handling subtitling data within their internal workflows for media distribution, contribution, and recording. While these broadcasters must ensure that their facilities encode and output programming that adheres to the different subtitling standards – such as WST, OP47, and SMPTE2031-based WST governing their broadcasts, they can implement similar internal models for inserting, extracting, and otherwise handling subtitling data efficiently and accurately across the transmission chain. Four fundamental challenges face broadcasters that work with subtitling content. The first of these is the development of an effective subtitling production workflow for subtitles prepared in advance of the broadcast, as well as those generated for live events. In addressing requirements regarding the delivery of subtitling within digital television services, broadcasters can choose from two subtitle production models. Larger broadcast networks typically establish in-house services, with staff at dedicated workstations performing offline captioning and live captioning for news, sports and other live events. A second fundamental challenge is the storage of subtitling information along with the broadcaster’s media assets. In addressing this challenge, the broadcaster must determine the stage at which to encode subtitles, taking into account distribution, contribution, and recording of live events for later re-playout and direct broadcast. Wohler has addressed this issue with its HDCC Series captioning / subtitling cards, which offer complete, independent dual-

A subtitler at work

channel operation for encoding, decoding and monitoring of subtitles for every major global standard. Within a streamlined workflow, the subtitling system – also called an inserter – encodes actual subtitle data and associated control data into the video signal, ensuring compliance with required standards, as well as integrity with the video signal. A subtitle management system ensures interconnection and interaction with the subtitle data sources, handles incoming subtitle data files or streams, and interfaces with the playout automation system, the MAM, and the playlist management system, so that the required subtitle data is loaded and played out in sync with the video time code, or that the live captioning source is connected in time. Because subtitle data is not encoded within the video file, the subtitle data file can be delivered to the broadcaster or altered / corrected at any moment prior to

the actual playout. In some cases, subtitle processing is performed at the ingest stage, with subtitles embedded into files that eventually will be transformed into a broadcast. Assuming the in-house video file format and wrapper can carry ancillary data including subtitle data, such as MXF, the MAM system can handle audio, video, and related subtitle data as a single asset, in turn simplifying management and movement throughout the rest of the workflow. The limitation of this approach is that it fails to provide for live subtitling and the need to record live programmes along with synced captions for later re-broadcast. Thus, a hybrid approach would be necessary to accommodate both prepared and live subtitles effectively. The flexibility of the subtitling system helps broadcasters address a third challenge: future-proofing and optimising their investments in subtitle-management equipment. With the industry’s

ongoing transition to DTV and HD operations, as well as the move into multiplatform distribution via new outlets, broadcasters need solutions that can evolve along with their operations. For broadcasters delivering programming concurrently in HD and SD, a dual-channel subtitle inserter can handle encoding both in SD and HD at once. With this model, the broadcaster can employ a single-format (SD or HD) video storage and playout server architecture and implement an up or down converter before the inserter to feed the inserter’s second channel. Pre-encoded subtitle data from within the native video SDI stream would be copied and transcoded on the fly by the inserter to the up or down converted SDI stream that goes through its second channel. The inserter thus enables the broadcaster to encode and insert live or external file-based captions in both SD and HD streams simultaneously. Finally, the fourth central challenge for broadcasters is addressing subtitling for VOD and Web-based programme delivery. This process involves different formats, different video and audio encoding processes, different asset management systems, and different ways of making captions available. This also presents the difficulty of accommodating added delay introduced by the encoding of streaming media. In summary, the insertion of subtitles into the broadcast signal can be a complicated process, but flexible subtitling solutions go far in simplifying this small yet critical aspect of a facility’s operations. ■

Subtitle workflow


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Table of Contents for the Digital Edition of In Broadcast - April 2012

In Broadcast - April 2012
Contents
Broadcast Networks Delivers for Arqiva
Swedish Hockey Safe in the Bank
Viewcast Launches Niagara 9100 Series
Cavena: Enhancing the Value of Content
Broadcast Pix Announces Video Control Center 3.0
Telecast’s Latest Innovations
Glidecam Introduces XR-Series Stabilisers
Qvest Media Live With Code One Streaming
Volicon Extends Observer Utility
Petrol Bags Add to Audio & DSLR Range
In Broadcast - April 2012 - In Broadcast - April 2012
In Broadcast - April 2012 - Cover2
In Broadcast - April 2012 - Contents
In Broadcast - April 2012 - Broadcast Networks Delivers for Arqiva
In Broadcast - April 2012 - 5
In Broadcast - April 2012 - Swedish Hockey Safe in the Bank
In Broadcast - April 2012 - 7
In Broadcast - April 2012 - 8
In Broadcast - April 2012 - 9
In Broadcast - April 2012 - 10
In Broadcast - April 2012 - 11
In Broadcast - April 2012 - 12
In Broadcast - April 2012 - 13
In Broadcast - April 2012 - 14
In Broadcast - April 2012 - 15
In Broadcast - April 2012 - 16
In Broadcast - April 2012 - 17
In Broadcast - April 2012 - 18
In Broadcast - April 2012 - 19
In Broadcast - April 2012 - 20
In Broadcast - April 2012 - 21
In Broadcast - April 2012 - Viewcast Launches Niagara 9100 Series
In Broadcast - April 2012 - 23
In Broadcast - April 2012 - 24
In Broadcast - April 2012 - 25
In Broadcast - April 2012 - 26
In Broadcast - April 2012 - Cavena: Enhancing the Value of Content
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In Broadcast - April 2012 - 29
In Broadcast - April 2012 - 30
In Broadcast - April 2012 - 31
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In Broadcast - April 2012 - Broadcast Pix Announces Video Control Center 3.0
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In Broadcast - April 2012 - Telecast’s Latest Innovations
In Broadcast - April 2012 - 55
In Broadcast - April 2012 - Glidecam Introduces XR-Series Stabilisers
In Broadcast - April 2012 - 57
In Broadcast - April 2012 - 58
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In Broadcast - April 2012 - 60
In Broadcast - April 2012 - 61
In Broadcast - April 2012 - 62
In Broadcast - April 2012 - Qvest Media Live With Code One Streaming
In Broadcast - April 2012 - 64
In Broadcast - April 2012 - 65
In Broadcast - April 2012 - Volicon Extends Observer Utility
In Broadcast - April 2012 - 67
In Broadcast - April 2012 - 68
In Broadcast - April 2012 - 69
In Broadcast - April 2012 - Petrol Bags Add to Audio & DSLR Range
In Broadcast - April 2012 - Cover3
In Broadcast - April 2012 - Cover4
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