When DeckLink output is selected and you have applied it in Preferences->Output you may configure it by going to Output/Setup Output. The DeckLink setup dialog is displayed:
Video Standart
Select the video standard which passes through the DL board or will be output in case of External Keying or No Keying output. Available standards depend on actual DeckLink board used. Some of the available standards in this list are: PAL, NTSC, 1080i 24, 1080i 25, 720p 50, etc.
If you make changes to the video standard you have to restart SubtitleNEXT in order changes to take in account.
Internal: Subtitles will be burned over passed through video signal (burned over video)
External: Subtitles will be output on one DL output and on second will be output the key signal (their transparency). External video mixer can be used with this type of output.