Issues of closed captioning and digital television

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1 Issues of closed captioning and digital television Deborah I. Fels, and Charles Silverman Ryerson University 350 Victoria St., Toronto, CANADA M5B 2K3 Abstract. The digital revolution has finally had a significant impact on the broadcast industry. In many countries television broadcasters (over-the-air, cable and satellite) are required to migrate to digital broadcast technologies for production and distribution. This convergence of television with computing technologies offers a significant opportunity to provide increased accessibility options to television content for people with disabilities similar to the variety of access solutions available for computer software and web-based access. However, there are many issues that must be addressed in a timely fashion. Example issues include, effectively using multimedia techniques to provide access to television content so that users have improved entertainment experiences, and creating international standards and development guidelines so that differing digital broadcast protocols do not restrict access. Some international and national efforts are beginning to appear but much more is required if access to digital television is to improve from its analogue cousin. 1 Introduction The television industry is undergoing the most significant revolution since the origin of the NTSC standard in Television is without exception the last partner in the communications industry to embrace digital delivery of its transmission signal. The United States (US) and Canada have only recently begun the process of converting to digital transmission while European Union (EU) countries have been working on standards and services for digital and interactive television since The EU has released the Digital Video Broadcast (DVB) standards and implementation specifications and more recently has embraced the Multimedia Home Platform (MHP) as its itv authoring environment [1]. The United States is implementing a separate and different standard, ATSC [2] from the DVB platform adopted in Europe and by many cable and satellite enterprises throughout the world. These different standards may spell important interoperability challenges for access solutions that already exist for the analogue systems (e.g., difference between NTSC and PAL video formats). Direct to Home satellite services embraced digital in the mid 1990 s, with cable and multi-channel, multi-point distribution service (MMDS) operators, such as Sprint and MCI WorldCom, have already begun changing over to digital and a complete change is expected within the next two years. These services have been using the

2 DVB standard as its transmission standard. In the US, the FCC has imposed a deadline of 2004 for commercial television stations to transition from analogue to digital for over-the-air broadcasting services [3]. With all of this change in the television industry, many of the limitations of existing access solutions for television can be addressed and new solutions can be developed. However, we must proceed quickly to devise improvements in technologies, procedures, standards and interoperability or risk having access solutions become a retrofitting exercise with limited opportunities to explore new and creative ideas that take advantage, integrate with and perhaps even direct some of the new technologies rather than just comply with them. In this paper we will present some of the issues for access surrounding the change from analogue to digital television and highlight some of the international efforts being made to address some of these issues. Efforts such as using multimedia techniques to create enhanced access to digital video content. Enhancements include graphical objects (shapes, colours and symbols), animation (text and graphical objects) and tactile equivalents of the sound information (e.g., sound effects, music, and paralanguage) that is currently missing from text-based closed or open captions. 2 Captioning for Analogue Television Current analog television closed captioning in North America relies upon an industryagreed standard, EIA 608. This standard is designed to be carried in the vertical ancillary blanking interval (VBI line 21) of the analog television signal. The bandwidth offered by VBI line 21 is restrictive hence EIA-608 can only sustain a maximum data throughput of 960 bits per second. This throughput can only support limited text captions and perhaps changes in colour and font. However, it cannot support animated, graphical or other displays for captioning. In Europe, Teletext was developed in the 1970s to provide television viewers with selectable access to additional information services such as news, weather, and sports. It is designed around a text-based page model where pages can be subtitles (UK equivalent to closed-captions), news, weather, sports pages or pages on other subjects [4]. Viewers pay for and choose the types of pages that they want to access. However, subtitling is provided as a public service and there are no charges to use it. Teletext allows for use of colour, and graphics to represent information although the predominant medium is text along with provision for different fonts, sizes and mixed-case [5]. 3 Captioning and Digital Television Since the mid-1990 s, the broadcast industry worldwide has agreed to adopt a digital transport stream for digital television based on MPEG-2. Video carried by MPEG-2 is substantially more efficient than analog NTSC/PAL multiplexing for television signal carriage and as a result more bandwidth is available within the broadcast channel for

3 future data services. A new captioning standard for digital television in North America, EIA-708, was designed with to take advantage of this expanded bandwidth. EIA-708 supports a data rate of up to 9600 bits per second of captioning data. This extra throughput will allow many of the restrictions of EIA-608 to be lifted such as limitations on fonts, colours, caption borders and caption positioning. EIA-708 does indeed have provisions for using alternative fonts, colours, caption positioning and other options related to text-based enhancements [6]. Robson and Hutchins [7] provide a detailed account of some of the technical issues that arise with EIA-708. However, there have been few research initiatives investigating ways of incorporating enhancements such as colour, and font. There are also few available captioned examples that demonstrate even simple enhancements for broadcast content. Digital subtitling in the UK uses the existing teletext model, inserting the bitmapped imaged of the closed-captions into the VBI of the MPEG-2 digital video signal [8]. Colour, speed specifications (supports up to 192 kbps) and insertion techniques are different from the analogue version but the subtitling process remains essentially the same. There is no provision or implementation guidelines that take advantage of the multimedia capabilities offered by the digital environment to enhance the subtitles. 4 Issues to address Advances in digital television technologies require important exploration of issues around providing complete access to broadcast-based entertainment and information. We have a rare window of opportunity to examine the strengths and weaknesses of existing practices for providing accessible broadcast content, and explore ways to improve the quality and quantity of access options. There are three main issues that we must consider in the context of closedcaptioning/subtitling and digital television: 1) interoperability of international DTV access standards; 2) expansion of capabilities beyond text to better suit needs of individuals who are deaf or hard of hearing and/or overcome the limitations of existing systems; 3) explore the need for new or updated standards to reflect the integrative nature of computing, the Internet and television. 4.1 Expansion of capabilities With closed-captioning models, the deaf or hard of hearing caption viewer must rely on visual-only cues such as body language and gesture combined with the words and short text descriptors of other information to understand a television program. Mehrabian [9] suggests that human-to-human communication consists of seven percent words, thirty-eight percent non-verbal linguistic modifiers (paralanguage), and fiftyfive percent visual cues or gestures. While television viewers are not active participants in the human conversation of a television program, they are the intended receivers of this communication. It is through the interaction between humans onscreen, background sounds and music that much of a television program s semantics

4 are conveyed. Without continual access to conversation modifiers and access to the paralinguistic components of human conversation, people who are deaf and hard of hearing may misinterpret or misunderstand the semantics of television, be unable to discuss the program with hearing viewing partners, and come away with an unsatisfactory experience. Limitations in viewer reading speed [10] and vocabulary levels [11] also contribute to the limitations in the quantity and speed of text presentation. There is often only enough time and space to provide the verbatim translation of what is being said. We must therefore consider using alternative display strategies such as with graphical, animated and tactile displays to convey the additional non-verbal information such as paralanguage, music and sound effects. Fels et al [12] have begun to investigate the use of alternative displays for expressing emotion, music and sound effects for digital television. Their initial results are very positive and viewers who are deaf and hard of hearing seem to have a different and more satisfactory experience of the captioned video content. 4.2 Efforts in new standard setting and internationalization activities A task force of the W3C, the timed text task force [13] has been struck to examine some of the issues of creating accessible text for time-based media such as video and audio. The scope of the activities of the task force includes text associated with video such as captions (closed or open), and moving credits, animated text (Flash or Swish), and hyperlinks. The intention of this task force is to establish an operational standard that would allow digital media producers. The current proposal call for use of SMIL 2.0 as the common authoring language creating XML expressions. SVG, MathML and other standard markup languages are recommended for using for enhancements to text (e.g., graphics and equations). The proposal also suggests incorporating the timed-text standard into authoring environments such as QuickTime, and RealMedia and Windows Media so that developers can produce and play text in this standardized format rather than in the proprietary format currently used in these authoring environments. However, these authoring environments are designed to produce compressed web-based video and audio, and not video and audio for television or film. In television and film, text is often inserted with specialized editors such as captioning and subtitling systems, or digital video editing software such as Adobe Premiere, Final Cut Pro and high-end professional editors. We need to better understand the impact of a web-oriented timed-text standard on the different international television and film standards and practices. Some of the issues that remain to be considered are: how to incorporate animated text, how text authored using this standard will integrate with DVB and EIA-708 digital television protocols, and captioning or subtitling software and industry practice, and the impact on the production industries. In addition, considerable research is required to determine whether current industry conventions are still suitable or even desirable by the deaf and hard of hearing viewers/users, and the impact of enhanced text on the viewing population.

5 References 1. Daly, W.B., H. (eds), MHP out of the box. European Broadcast Union: Grand Saconnex (2002) p Advanced Television Systems Committee, ATSC Document A/53B (2002) 3. Federal Communications Commission, FCC issues further order in digital television transition (2001) 4. McMordie, R., A brief history of the development of teletext and viewdata. (1998) 5. Weitzel, P.H., J.R. Teletext - old digits in a new age. in International Broadcast Convention. (1999) Amsterdam 6. Robson, G.D., FCC adopts caption standards for digital television. (2000) 7. Robson, G.D.H., J. The advantages and pitfalls of closed captioning for advanced television. in International Conference on Consumer Electronics (1998) BBC, Subtitling & audio description, in BBC R&D Open Day 1999 Information Brochure. (1999) 9. Mahrabian, A., Communication without words. Psychology Today, (4): p Jensema, C., McCann, R., & Ramsey, S., Closed-captioned television presentation speed and vocabulary. American Annals of the Deaf, (4): p Jensema, C.J., Viewer reaction to different television captioning speeds. American Annals of the Deaf, 1998: p Fels, D.I., Polano, L, Harvey, T., Degan, S.S., & Silverman, C.H. Towards emotive captioning for interactive television. in Universal Access and Human-computer Interaction New Orleans. 13. Freed, G., Standardized timed-text format

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