Providing Sign Language Service in Audiovisual Media

Providing Sign Lenguage Service - Introduction pic

Author: Carlos Alberto Martín Edo – Senior Project Engineer. ATOS

Audiovisual accessibility services for people with disabilities have been becoming increasingly widespread throughout the world in recent years. In view of the importance of multimedia content and, most particularly, on TV, audiovisual accessibility aims at getting people with disabilities have access on equal terms to information, training and entertainment as enabled by such content. In other words, lack of accessibility in multimedia content may cause social exclusion of people with disabilities. This article deals with the provision of sign language interpreting services aimed at deaf people and people with a hearing impairment.

This issue is a hot topic, as in November 2018 the European Parliament and the EU Council passed a new version of the “Audiovisual Media Services Directive” [1] that delves on the obligations of making audiovisual content available. This AVMSD (Audiovisual Media Services Directive). The AVSMD Directive cannot directly impose accessibility services but invites all EU Member States to adopt the necessary accessibility measures in their respective territories. The directive makes express mention of hearing or visually impaired people and, amongst the services identified, the first one being mentioned is precisely sign language. As for the Member States, there are laws in place imposing on TV operators interpreting services quotas for sign language.

TV sign language has a distinct feature not found in any other services such as subtitling or audio-description: while the latter two can be provided on a closed mode (i.e. only activated if/when so decided by users), sign language has been traditionally provided on an open-service basis (i.e. available for all spectators, whether they require it or not). In view of the fact that the sign language interpreter can be a nuisance for users not requiring the service or not being acquainted with deaf people, sign language has been relegated to time slots featuring lower TV consumption, which article [2] of EBU terms as ‘unsocial scheduling’.

Figure 1 - Providing Sign Language Service in Audiovisual Media Figure
Figure 1 – Customizable sign language pioneering experience in German channel RBB within the HBB4ALL project. By means of an HbbTV application, users would select the interpreter’s position for a video-on-demand program. The interpreter on the left-hand side of this video capture is Jan Sell.

As the same article [2] reminds, some myths about sign language must be clarified. Sign language is not universal, as there may be one or maybe more languages within a country. As in any other language, there may be dialects within the same sign language. And these are living languages that evolve as the social environment in which they are used does (for example for naming new phenomena). Worth noting also is the fact that a sign language is not subordinated to the oral language spoken in the relevant territory, but it is instead an independent language with its own grammar rules. As [2] says, defining it as ‘interpreting’ might be more appropriate than ‘translation’.

Though TV digitalization brought about new technological opportunities that resulted in improved quantity and quality of other accessibility-related services (such as subtitling and audio-description), this did not happen with sign language interpreting, which kept a free-to-air service provision. However, the number of channels available did enable the possibility of devoting a channel to simultaneous sign language interpreting while the main channel was offering the program with no interpreting at all. This is the case with the British BBC NEWS channel, which offers simultaneous sign language interpreting for some programs being broadcast in BBC ONE.

Figure 2 - Providing Sign Language Service in Audiovisual Media Figure
Figure 2. TVE’s HbbTV application for on-demand sign language services in live programs.

The widespread presence of Connected TV (that is, TV screens capable of receiving and playing content either from a broadcast network or the Internet) does entail a real opportunity for offering an on-demand sign language interpreting service. Whilst the broadcast channel offers a service with no sign language interpreting for all users, the relevant TV operator makes available to viewers sign language interpreting through the Internet. In this way, any users needing it, may select the sign language option by means of their remote controls and then switch to sign language through live streaming broadcast on their Internet connection. The video signal transmitted via the Internet comprises both the program’s signal and the interpreter’s image. In an ideal case, both video signals would be independent, in such a way that users could choose in what area of the screen and image size that the sign language interpreter may be shown. The downside is that this would require two video-decoding circuits in the same receiver, something that is not usual.

The European R&D HBB4ALL (Hybrid Broadcast Broadband 4 All) project was a development of this idea. German operator RBB (a public radio and television broadcaster for the Berlin and Brandenburg regions) launched a pilot project for sign language by using the HbbTV connected TV standard in which viewers could choose from various sizes, positions and service composition options. The capture shown in Figure 1 is one of said options, which were available for video-on-demand programs.

At present, the Spanish public TV channel TVE is also providing an on-demand sign language interpreting service based on the HbbTV standard, but with the peculiarity that it is available for live content, which entails simultaneous interpreting and Internet transmission as live streaming [3]. Figure 2 shows two screen captures of this service, which is activated by pressing the green button in the remote control in the selected programs (upper-hand side of the figure). In view of the above-described restriction in the number of video decoders in the screens, the video signal reaching the TV screens through the Internet includes both the program’s video input and the sign language interpreter (lower-hand side of the figure).

Figure 3 - Providing Sign Language Service in Audiovisual Media Figure
Figure 3. Ideal example of layout as proposed by the handbook.

The “Handbook on Good Practices for Inclusion of Spanish Sign Language in TV Broadcasting” [4] prepared by the Centre for Language Standardization of Spanish Sign Language and published by the Royal Trust on Disabilities, aims at becoming a document of reference for TV operators for launching quality services. This handbook contains amongst many others, the following recommendations:

  • Broadcasting of the service on demand and the possibility of user-customizable settings for position and size of the person performing the interpreting (if allowed by technology).
  • Syncing between the audio signal and the interpreting (although sign languages have their particular ordering of signs).
  • On-screen layout of sign language and subtitles, in such a way that the latter do not get in the way of the former.
  • Diversification of TV genres and time slots in which the sign language service is being provided, including prime time broadcasts.
  • Ensuring throughout the acquisition and transmission chain good contrast between the skin tone of the interpreters and their own clothing, as well as with the background, in such a way that the sign language can be properly understood.
  • Codification of sign language in proper lighting conditions, as well as proper camera parameters, resolution and bit rate settings so as to make it intelligible. The use of a chroma-key technique (enabling insertion of the interpreter as a silhouette over the program) deserves special attention at the time of video signal acquisition in order to avoid any artifacts. Additionally, due to the movements of hands and arms, the use of progressive (non-interlaced) formats is preferable, as well as observing the customary safety margins used for TV broadcasting.
  • A frontal plane is recommended, keeping the camera at the interpreter’s eye height and in a framing such as to ensure capture of all the space that will be used for sign language, taking into account movements of hands, arms and face.
  • Marking of sign language is very important as well in order to keep the target audience informed about the availability of the service. The handbook also suggests an icon in order to communicate availability of the service throughout any means as, for instance, the EPGs.

Figure 3 shows an image layout for an ideal interpreting service conforming to the handbook, although a service targeting deaf-blind people would require a higher contrast.

The aim of this article was to tackle sign language interpreting on TV from the standpoint of provision of an accessibility service, dealing with issues such as technical opportunities and quality recommendations, in view of the importance of audiovisual means in depicting a social reality. Should operators not increase visibility of deaf people and raise awareness of sign languages in programs targeting the whole population, thus promoting social integration of this group and contributing towards a richer, more diverse representation of society?


[1] Directive (EU) 2018/1808 of the European Parliament and of the Council of 14 November 2018 amending Directive 2010/13/EU on the coordination of certain provisions laid down by law, regulation or administrative action in Member States concerning the provision of audiovisual media services (Audiovisual Media Services Directive) in view of changing market realities. Available here:

[2] Frans de Jong. “Access Services for digital television”. EBU Technical Review, October 2004, no. 300. Available here:

[3] Manuel Gómez Zotano, Pere Vila Fumas, Enrique Martin Laguna. “Components of a cloud-based solution for sign language accessibility: the España Directo use case”. IOSR Journal of Computer Engineering (IOSR-JCE) e-ISSN: 2278-0661, p-ISSN: 2278-8727, Volume 20, Issue 3, Ver. IV (May. -June. 2018), PP 15-24.

[4] Centre for Language Standardization of Spanish Sign Language. “Handbook on Good Practices for Inclusion of Spanish Sign Language in TV Broadcasting”. Edited by: Royal Trust on Disabilities. 2017. NIPO: 689-17-006-0. Available at:

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