DOWNLOAD BEYOND THE HEADLINES Accessible TV Viewers expect broadcasters to provide more than just pictures and sound. BY PETER BLATCHFORD

losed-caption subtitling The past cue the subtitle fi le with the matching and audio description are Historically, there was an occasional video fi le name on the transmission two increasingly popular requirement to add closed-caption system, and the two fi les would play service additions to mod- subtitles to selected programs, typical- out synchronically . A hardware inser- Cern TV channel output. Providing tion device would insert the subtitle ly high-profi le dramas and documen- access for people with hearing and taries. Consequently, subtitle manage- fi le in real time — typically onto line sight impairments is not the only ment developed as a manual process. A 335 using the World System Teletext driving factor. Programs subtitled videotape recording would be dubbed (WST). To ensure redundancy, there with multiple languages enable TV to produce a VHS copy, and this would would typically be two hot-swappable channels to increase their audience be delivered to the subtitle authoring inserters, possibly with an automated fi gures through wider distribution, department for fi le preparation . failover capability. For occasional which is especially useful in Eastern The completed subtitle fi le, contain- program subtitling, this system oper- ated successfully, although not entirely Channel program schedule without problems .

Things have changed UK government legislation has Check existing incrementally raised the level of sub- Extract subtitle subtitle archive requirement titling required from terrestrial chan- nels. The BBC has committed itself to

Collect required browse providing subtitles on all of its output Create subtitle job list media or create browse by 2008. This includes subtitling live with required delivery media from broadcast media date programming, such as news and sport, which brings with it a whole set of other issues beyond the scope of this Deliver job list and article. For a high percentage of pro- browse media, and Transmission system recieve completed files grams to contain closed captioning, Media playout server Traditional open caption or closed caption/ the manual process is ineffi cient and teletext inserter prone to human error. Monitor file delivery, If you add to this requirement the warn if files are not delivered to required desire to offer subtitling in a number shedule Auto QC subtitle files of languages, then the workfl ow and and report errors management issue is elevated directly

Subtitle playout server to the realms of an automated system or file embedding Automation and asset management control with sophisticated monitoring to en- sure high reliability of service provi- sion. To this, also add the desire to Figure 1. In a typical subtitle workfl ow for broadcast and playout centers, automated systems, such as the Starfi sh Technologies ProTask, can perform and monitor these functions. include audio description, and hope- fully the complexities of the access Europe, where many languages are ing subtitle text and associated time services provision start to become spoken. code reference, would be delivered clear. The cost to add multiple languag- back to the transmission area where There are a number of issues regard- es to the broadcast signal through an engineer would load the fi le into ing the transmission of multiple-lan- closed captioning (using line 21, a subtitle server. This server would be guage subtitle fi les within a single pro- teletext or DVB) is relatively low. time code-locked to the transmission gram. It is possible to transmit as many Also these additional services can be system, be it a tape-based cart machine as eight separate subtitle fi les, support- highly automated . or a playout server. The system would ing eight different languages, in a WST

10 broadcastengineeringworld.com | May 2007 DOWNLOAD BEYOND THE HEADLINES

system. However, there are time delays complete and no downstream process- Audio description and refresh rates to consider. Therefore, ing is required. The required format of the audio there is no simple hard and fast rule. • The embedded subtitle fi le can be description fi le will vary depending The requirements for managing viewed for quality assurance before on the transmission system employed. subtitle and audio description fi les transmission. This allows the user to The fi le can be supplied as a separate can be designed into fi le-based trans- play back the broadcast fi le, decoding commentary WAV fi le with associated mission systems to take advantage the closed captions into visible cap- control track (that includes pan and of the inherent workfl ow enhance- tions for review. This is particularly fade information) or as a premixed ments. To ensure maximum effi cien- useful when an existing subtitle fi le audio fi le containing normal pro- cy, this should be designed as part of will be used with a program that has gram sound with the audio descrip- the complete system and not simply been through minor editorial changes, tion commentary added. treated as an afterthought. e.g., for prewatershed transmission. Software utilities can transcode de- With the changes in fi le-based tech- • The closed captions become an in- scription fi les into the various forms nology and the increasing access ser- tegral part of the program fi le. When required, and therefore fi le conver- vice requirement becoming apparent, the material is archived, it contains sion is simply another process that there is a need for an access service the embedded subtitles, so the pro- can be designed into the transmission management system that can either cess doesn’t need to be repeated when system workfl ow. Audio description be used as a standalone application the material is recalled for subsequent is either incorporated into the trans- or integrated into a modern media transmission. mission media as a separate audio fi le management system as a specialized In addition to server-specifi c ca- that end users control via their set-top task management module designed pabilities, software can also embed boxes, or it is transmitted as another around fi le-based media. subtitles into generic IMX-encoded complete audio track (premixed) that media. This allows the users select, as they would with an al- technique to operate ternative language audio track. with any playout server capable of transmitting Workfl ow considerations IMX fi les. IMX fi les con- In the example workfl ow in Figure 1 tain VBI data within the on page 10, the subtitle fi le requirement picture as a waveform list is generated directly from the origi- in the nonvisible lines. nal program schedule. The delivery of The IMX variant em- fi les to fulfi ll this requirement is moni- beds the subtitle data as tored from either an in-house depart- a VBI waveform directly ment or an external specialist supplier. into the MPEG picture. Automated QC is applied to the Only the VBI lines are delivered fi les to minimize possible er- The ProTask user interface indicates fi le progress through the touched, so there is no rors, such as overlapping time codes or monitored system. picture degradation incorrectly labeled language fi les. The during the process. latter is especially important when used File-based embedding By comparison, server-specifi c ver- in a system with multiple-language ac- Rather than embedding at the sions add subtitle data to the broad- cess service fi les, as the fi nal transmis- point of transmission, subtitles can cast fi le set, and the server is respon- sion monitoring staff may not be able be added in the fi le domain. This sible for creating a VBI waveform to interpret the many languages that redefi nes the offl ine closed-caption from that data on playout. Additional need to be broadcast simultaneously. transmission workfl ow, eliminating functionality includes the ability to In other words, it may be evident that the need for downstream hardware encode the V-Chip information used a subtitle fi le exists at the appropriate inserters and their associated redun- in North America to mark a program position in the broadcast package, but dancy schemes. with appropriate content labelling. is it the correct language? Subtitle embedding writes the sub- Software products have been devel- This fi gure also includes monitor- title data directly into the media fi le oped to embed subtitles into trans- ing of fi le delivery status by compari- (the precise location varies depending port stream encoded material in the son to the transmission requirement on the type of fi le and playout server form of either teletext or DVB sub- derived from the scheduling system. in use). The numerous advantages of titles. This is aimed at broadcasters This ensures that all missing fi les are this software-based process include: who wish to include access services in automatically tracked and the people • Embedding takes place prior to material repurposed for use in areas responsible for operation are in- transmission, so the fi nal playout fi le is such as VOD or IPTV. formed well in advance. This includes

12 broadcastengineeringworld.com | May 2007 DOWNLOAD BEYOND THE HEADLINES in-house transmission staff, who are • High-level broadcast monitor- All of these developments will result warned of the nonavailability of the ing systems will increasingly be used in more of the transmission workfl ow fi le, as well as the author of the access to maximize reliability, warn of im- being automated and monitored. Con- service fi les. Both groups can be auto- pending problems and identify exact sequently, solutions to manage and matically e-mailed to inform them of points in the workfl ow where failures monitor access services will become missing fi les or fi le errors. occurred. These systems will demand increasingly important to broadcasters When the appropriate access service sophisticated two-way communica- and suppliers of video content. BE fi les are available to the transmission tion with task management systems Peter Blatchford is sales and marketing system, they can be embedded into for access services. director at Starfi sh Technologies. the broadcast media whilst stored on nearline storage, before the fi nal media wrapper is moved to the transmission server and is controlled by the tradi- tional transmission automation . The Starfi sh Technologies Pro- Task, for example, can also run as a standalone task management system where the media processing functions are not required to be incorporated into a media management system or where a media management system does not exist. This requirement can exist where the fi le preparation pro- cess is handled in-house by a televi- sion channel, but the actual transmis- sion of fi nal content is managed by a third-party transmission provider.

The Future My humble attempts to predict the future developments in this area of technology err on the side of cau- tion. However, I believe it is very safe to predict the following: • Legislation for broadcasters to in- clude access services to some degree will expand internationally. • The requirement for carrying access services on a higher percentage of pro- grams will continue to increase. • Broadcasters will continue to want to broaden the market appeal for their output with channels carrying closed captioning in multiple languages. • Broadcast transmission systems will become increasingly fi le-based with conventional videotape being used only for fi nal archive storage. • Increased reliability of transmission is a goal for all providers and service level agreements will become increas- ingly demanding. • Media management systems will in- crease in complexity and coverage of transmission systems.

May 2007 | broadcastengineeringworld.com 13