Subtitle workflow

Cavena offers a range of products for the total workflow of subtitling. The preparation of subtitles is done using a workstation for subtitlers called Tempo where they can play a browse copy of the program, translate and type the text for subtitles. In Tempo the subtitles are also timed so that each subtitle gets the in- and out-time for display. Files created contains the subtitles for one language. The first subtitle file is often used for a second language translator to edit subtitles without working with the program material, saving production time but sometimes causing more of the original dialogue to be lost in the second translation step.


Subtitle files are sent to the broadcaster for transmission often several days in advance. File can be sent manually, via automated FTP or via e-mail, directly into the SAM, Subtitle Archive and Management product. SAM can perform technical checks on subtitle files before accepting them into the archive and report any errors back to the supplier and optionally to local administrators.


The transmission of subtitle files is most often automated. This is done by integrating the subtitling transmission system with the transmission system. Interfacing is needed to the planning and automation systems so that the correct subtitle files are played out at the correct time using the station playlists. The automation controls the Cavena STC, Subtitle Transmission Controller. This is similar to how automation controls other playout devices, often the automation system can display more detailed information about the status of the subtitle transmission system. Monitoring of STC is normally done in the master control room as the STC displays status about the full transmission system. From the STC, manual override can also be done at any time.


The STC controls the STUs, Subtitle Transmission Units, for playing out the subtitle files. STC will control which files to load and when to go on air and off air, based on the automation commands received. One STU is used for each program video channel. When on air, the subtitles from one or more language files for a program are synchronized in STU using the time code from the playout devices and transmitted in one or more transmission formats in parallel. Thus the same subtitle file can be played out for PAL teletext, NTSC closed captions and HD DVB bitmap subtitles all at the same time. The format and appearance can also be changed dynamically per event based on GPI or automation commands. The STU interfaces to most transmission systems.


Other functions can also be integrated in the Cavena transmission system, like transcoding of subtitles in STU. For example, teleprompter output being sent directly to an STU can be reformatted into subtitles and transmitted using any transmission format. Live typing stations used for news subtitling interfaces directly to STU the same way. This can also be used to convert one transmission format to another, for example EBU teletext on an SDI feed can be transcoded into DVB bitmap subtitles or a US feed containing Line-21 closed captions can be transcoded to EBU teletext. The STU is flexible so that any input formats can be transcoded to any output format.



In short the workflow is:

  • Browse video is sent to a subtitle translator together with a workorder.
  • The translator prepares the subtitle file which is sent to Cavena SAM the subtitle archive
  • Subtitles are automatically loaded to the subtitle playout system using the playlist as the reference.
  • The automation system sends commands to the Cavena system to start and stop the subtitles for each channel.
  • The STU uses time code as reference to playout the subtitles.
  • The settings of the STU decides in which format the subtitles should be transmitted.
  • The formats include: in-vision SD or HD, Teletext, EIA-608, SD or HD Bitmap for DVB, EIA 708, additional formats are easy to add to the STU.
  • The subtitles are transmitted together with the program signal
  • The subtitles are displayed on the viewers TV-set