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Subtitling - Broadcast
FAB DVB Interface

FAB DVB Interface FT-DVB is a software package for PC that receives DVB Subtitles over TCP/IP from FAB Subtitler BCAST/XCD and converts and synchronizes them to a PCR present on ASI/IP input and transmits them over TS/IP or TS/ASI to a DVB multiplexer. The software can transmit a teletext stream generated by FT-DVBTSG FAB Teletext Subtitle Generator over TS/IP or TS/ASI to a DVB multiplexer and synchronize it to a PCR present on ASI/IP input.

Instead of using ASI cards one or more additional network cards can be used in the PC to use TS over IP without any special hardware. One FT-DVB software license is required for every ASI Input/Output and for one Ethernet port. Multiple ASI cards and network cards are supported per PC.

Main functionalities of FAB DVB Interface:

  1. DVB Subtitling Transmission
  2. Teletext Subtitling Transmission
  3. PTS Restamping
  4. SDI Teletext to ASI/IP Conversion
  5. Transmission of hbbtv signalisation and stream events



Fig.1: DVB and Teletext subtitling transmission over IP

Fig.2: DVB and Teletext subtitling transmission over ASI


DVB subtitling is used in satellite and terrestrial DVB (Digital Video Broadcast) transmissions. Only Set Top Boxes (DVB decoders) that support DVB subtitles are capable of displaying DVB subtitles.

DVB subtitles are transmitted in a separate DVB stream with a separate PID. Every subtitle contains a PTS (presentation time stamp) which is defined by the subtitle transmission system. The PTS is calculated from the PCR/video stream which comes from the DVB ASI output of the DVB multiplexer and is connected to the input of FAB DVB Interface.

The DVB encoder/multiplexer must be configured so that the subtitle streams with correct PIDs are passed through and the PMT (Program Map Table) must be configured correctly so that Set Top Boxes will associate subtitle streams to video streams correctly.

Multiple FT-DVB licenses with multiple ASI cards and multiple Ethernet cards can be installed in one PC: One FT-DVB license is required for every ASI Input/Output and for every Ethernet port.



Fig.3: Teletext subtitling transmission over SDI and TS/ASI and TS/IP

FAB DVB Interface can generate one or more teletext streams and transmit every teletext stream to multiple outputs. One FT-DVBTSG software license is required for every generated teletext stream.

The generated teletext stream can be transmitted as TS/IP or TS/ASI to one or more DVB multiplexers. The teletext stream with the teletext PID can be synchronized to a PCR which is present on the TS/ASI or TS/IP input. One FT-DVB license is required for every DVB multiplexer.

The generated teletext stream can also be inserted into SD/HD-SDI. In such case one or more FAB PCIe cards must be installed in the PC. By installing two cards into the PC the same teletext stream can be inserted into SD and HD signal simultaneously.



Fig.4: PTS restamping functionality

FAB DVB Interface supports a special feature for PTS restamping of DVB subtitling and teletext streams. This function receives multiple DVB subtitling and teletext streams and calculates the time and PTS offset between the packets of the received DVB subtitle/teletext stream and the referenced PCR stream. The DVB subtitle/teletext stream is retransmitted on the output but referenced with the same time and PTS offset to a different PCR stream. The DVB subtitling/teletext stream can also be delayed for a constant time defined in miliseconds.

This function is necessary when video/audio is received, reencoded and retransmitted so that the PTS of the retransmitted DVB subtitling/teletext stream is correctly referenced to the PCR of reencoded video/audio.

In the above example 2 ASI/IP inputs and one ASI/IP output are necessary:

- One ASI/IP input is used for receiving the DVB stream from the DVB receiver. The stream must include the PCR/Video PID and the DVB Subtitling or Teletext PID that should be restamped.

- The connection to the DVB Multiplexer is using one ASI Input to read the PTS and PCR from the Video PID to which the DVB Subtitling or Teletext PID should be restamped. The ASI Output will contain only the DVB Subtitling or Teletext PID with correctly restamped PTS so that they will correspond to the PCR/PTS of the Video PID on the DVB Multiplexer.



Fig.5: SDI Teletext to TS/ASI or TS/IP conversion

FAB DVB Interface can receive teletext over SD/HD-SDI and convert it to ASI/IP synchronized to a PCR which is present on the ASI/IP input. One SDI input can be converted to multiple ASI/IP output streams which are synchronized to different PCRs. One or more FAB FT-HT 12 FAB PCIe cards must be installed in the PC. Each card has two SD/HD-SDI inputs.

FAB DVB Interface always uses the ASI ports on the FT-ASI cards so that one is input and one is output. The FT-ASI 1 card has one input and one output. The FT-ASI 2 card has two inputs and two outputs. However a license for FT-DVB software is only required if the output is actually used. Therefore the above configuration requires only one FT-DVB license. Additional FT-DVB licenses are required for every DVB Multiplexer to which the subtitles have to be sent to. Additional ASI/IP inputs for receiving DVB Subtitling or Teletext Streams do not require additional FT-DVB licenses.



FAB DVB Interface can transmit signalisation for hbbtv applications and transmission of stream events as defined in ETSI TS 102 809 can be triggered by a simple HTTP request.

Multiple hbb-tv apps can be included in the signalization within the transmitted TS with the link to the App URL, App ID and all other necessary parameters:

- AIT PID, App language, App name, App URL, App ID, Boundary extensions, Control code, Priority, Service bound, Digital text, Object carousel, Component tag, Remote, ONID, TSID, SID

To signalize a stream event the parameters in the HTTP request define the type and content of the stream event. The following parameters can be defined for a stream event:

- Events PID, Component tag, Event range

Example of a trigger for a hbbtv stream event:


Detailed parameters for stream events are defined in the configuration of FAB DVB Interface.


Screenshot of FAB DVB Monitor Application


  • Windows 7 64 Bit or higher, 4GB RAM, Quad core CPU
  • or Windows Server 2008 R2 64 Bit or higher, 8GB RAM, Quad core CPU



FAB DVB Interface
Software for transmission of DVB subtitles with FT-SUBTITLER BCAST/XCD. Requires FT-ASI 1 card for ASI or network card for IP interface. Supports reception of TS data from one FT-ASI card or from one network card. Required is a standalone PC with Windows 7 or higher. One unit per DVB Multiplexer is required. Standard software for 1 PC incl. 12 months software updates and 12 months technical support.


FAB ASI Interface Card
PCI-Express x1 card for low profile and high profile slot with ASI input and ASI output, incl. driver for Windows.


FAB ASI Interface Card
PCI-Express x4 card for high profile slot with 2xASI input and 2xASI output, incl. driver for Windows.

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