DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

I use the subscript h to denote a
hexadecimal (base 16) integer.
Sample values in this chapter
are expressed in 10 bits.
Digital sync, TRS,
ancillary data, and interface 33
Along with picture information, a video system needs
to convey information about which time instants – or
which digital samples – are associated with the start of
each frame and the start of each line. In digital video,
this information is conveyed by timing reference signals
(TRS) that I will explain in this chapter.
I outlined the Serial digital interface (SDI), on page 130.
SDI has capacity to transmit ancillary (ANC) data. The
serial data transport interface (SDTI) resembles SDI, but
has no uncompressed active video – instead, the full
data capacity of the link is dedicated to carrying ANC
packets. Compressed digital video, such as DV25 or
DV50, can be conveyed in these ANC packets.
In Digital video interfaces, on page 127, I introduced
DVB-ASI, SMPTE SSI, and IEEE 1394/DV. These interfaces
have no ancillary data, and do not use TRS.
Standard serial interfaces transmit 10-bit samples; a
transmitter must encode all 10 bits (even if the two
LSBs are zero).
TRS and ANC sequences are introduced by 10-bit codewords
0 and 3FF h . For compatibility with legacy parallel
interfaces such as SMPTE RP 125 and EBU Tech. 3246,
a receiver must ignore the two LSBs in identifying TRS
and ANC. Apart from their use to delimit TRS and ANC,
codewords 0, 1, 2, 3, and 3FC h, 3FD h, 3FE h, and 3FF h,
are prohibited from digital video data.
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