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72 01-0870-401B 01/03
Tiernan VBI Data Transmission
MPEG and VBI Originally, the MPEG video compression scheme discarded all VBI information
and included only the compressed, active video portion of the picture for
transmission. This caused all VBI data to be lost when the video was digitally
compressed for transmission using MPEG.
Today, however, enhancements to the original MPEG compression system have
provided two methods for including VBI data in digital-compressed MPEG
streams:
■ The first method is to extract the data from the baseband video input and
insert that data digitally into the transport stream as either a dedicated PES
stream on a dedicated PID, as in DVB-Teletext, or as an extended data field in
the video frame header information as in ATSC-CC.
■ The second method is to shift, or expand, the active video portion of the
picture to include the VBI lines in the compressed picture frame, as in DVB
4:2:2 expanded windows.
For either of these methods to work, it is required that both the encoder and
decoder are:
■ Functionally capable of processing the required video
■ Correctly configured, either manually or via auto-sensing functionality, for
the employed VBI method
All of the VBI schemes described in this document, with the exception of Tiernan
Proprietary Closed Captions, adhere to industry standards and formats, defined
either by ATSC or DVB. Tiernan Radyne ComStream equipment does inter-
operate with all other vendor’s equipment that is found to be compliant with these
industry standards.
Tiernan’s TDR6 decoder can process data contained in the VBI region of a video
signal according to the following methods and standards:
■ Tiernan-CC – A Tiernan proprietary scheme for transmission of Line 21
closed captions included on a composite analog NTSC or component digital
(525) format video signal.
■ DVB 4:2:2 Expanded Windows – DVB standard for transmission of 16 or 32
lines of VBI data included on a composite analog or component digital (SDI)
format video signal. This standard supports both PAL/625 and NTSC/525
format video standards.