FAB Subtitler BCAST/XCD can output open subtitles as “Fill & Key” signal which is fed to a video mixer which then overlays subtitles over the video. The video mixer has one input for video, one input for the fill and one input for the key signal. The video output then contains the video with the overlaid subtitles which are present on the Fill/Key input.
The “Fill” signal contains the following bitmap of the subtitle:
The “Key” signal contains the “alpha” information of the subtitle:
The video mixer then combines the subtitle with the video:
FAB Subtitler supports the following hardware for output of SDI Fill & Key signal:
- Decklink 4K Extreme PCIe Card
- Dektec DTA-2152 PCIe Card
FAB Subtitler can also output Fill & Key using the NDI (Network Device Interface) protocol over Ethernet so that no special hardware from FAB is required. The video mixer however has to support receiving Fill&Key over the NDI protocol.