In Broadcast - May/June 2011 - 30

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New developments in broadcast subtitling and captioning
by David Kirk
Many television programmes, particularly the low-budget presenterto-camera variety, make so little use of the visual medium that they would work just as well on radio. But if the audio track is in an unfamiliar language or the listener’s hearing is impaired, then television really comes into its own. It is capable of carrying subtitles. These come in two forms: • Text superimposed as a permanent part of the video image. • Viewer-selectable subtitles, normally called ‘closed captions’. Prior to the digital switchover, these were traditionally delivered as data encoded in one or more spare lines of the analogue video field. Now they are embedded in the digital signal stream. So what is new or notable in this sector of the broadcast business? Quite a lot: Introduced at NAB 2011, Cavena’s Cimpress is a 1 RU video subtitle keyer for inserting open or teletext subtitles into broadcast applications in a digital video environment. It is controlled by the Cavena STU subtitle transmission unit via an IP connection. The STU receives timecode from Cimpress and returns pre-rendered subtitles for frame-accurate insertion into the video. Each group of two outputs can have one or up to four graphic layers added. It is therefore possible to subtitle one programme with two different languages keyed onto the image and presented on separate feeds. Each output can also accommodate a separate logo. In addition, Cavena’s Tempo is a Windows-based subtitle preparation system intended for use with all languages, including right to left scripts such as Arabic and Hebrew. Multiple languages can be integrated on a single subtitle page. Text files can be directly imported for editing and timing. Capabilities include playback of video files with subtitles, instant rehearsal of audio and video with subtitles, single-keystroke instant replay, loop play to allow for fast location of audio cuts, and frameaccurate control/playback of MPEG-1 files. Tempo is designed for use with the Cavena Toolbox which can be used to convert subtitle files from one format to another or between different transmission standards. Given the rapidly falling price of 2D/3D-compatible television displays and computer monitors, many developers of subtitling and closed-caption systems are adding 3D capability to their products.
Cavena’s Tempo

The recently approved DVB-3DTV specification is accompanied by a Subtitling Systems specification (EN 300 743). This provides a standard way of allowing subtitles and other on-screen graphics to be positioned in the stereoscopic picture. EZTitles’ 3DTitles allows the addition of depth to standard 2D subtitles for inclusion in stereoscopic programmes. 3DTitles runs on Microsoft Windows Vista or Windows 7 in conjunction with an NVidea 3D Vision processing and display package, a compatible video card and a 3D screen. The software can open .ezt files created with EZTitles or converted between different subtitle file formats in EZConvert. Each output file can be exported as a single clip to Adobe Premiere or Avid editing software. Subtitles can also be saved in Sony’s Blu-ray BDN XML stereoscopic extension format along with Final Cut’s XML and EDL file formats. EEG Enterprises’ new CCPlay FilePro software encoding tool for MPEG-2 and MXF XDCAM video file formats extends the capabilities of the company’s CCPlay software suite which was previously available only on the HD485 HD/SD closed captioning encoder. It accepts all common closed captioning and subtitling file formats including ECF, SCC, Timed Text and CAP. The software performs AFD encoding into file-based video assets and can export caption files in the form of an AAF caption track suitable for import into Avid Media Composer 5.

FAB’s Subtitler Broadcast Edition subtitling software allows automatic transmission of subtitles synchronised with timecode and controlled by VPS/PDC signal or an automation system. Features include subtitle file transmission playlist, interface to automation systems, support for VPS/PDC decoder, interface to FAB Subtitle Database for automatic download of requested subtitle files, and station logo handling. Screen Subtitling’s new Poliscript 3DITOR is designed to offer the subtitler or stereographer instant rendering with full stereoscopic control, including the ability to control and manipulate full 3D subtitles in live and pause mode. It supports passive and active shutter viewing. Formats include 3D Blu-ray, Digital cinema, 3D broadcast, Mobile, VOD and IPTV. Poliscript 3DITOR is retrocompatible with 2D subtitle files and with Screen’s Polistream Black. Softel is now offering 3D subtitle and caption creation as well as rendering, in partnership with Pixel Power whose 3D-equipped graphics products import Softel subtitle files together with subtitle, timecode and z-axis metadata. Subtitles are then rendered automatically in real-time, synchronised with timecode and controlled via graphic templates. The z-axis metadata can also be used to animate the perceived depth of a displayed subtitle. It dynamically positions the subtitles to match the underlying action and avoid distracting the viewer. Softel has also developed an upgrade to its Swift Create subtitle workstation to allow z-axis placement metadata to be stored for each subtitle while ensuring that this is within a pre-specified 3D object space. The combined system can be used to re-purpose 2D subtitles or create them from scratch. SoftNI’s new Live Subtitling Suite consists of three modules: LiveCap delivers live stenotyped closed captions to a local or remote closed caption encoder via serial port,
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