A Comparison of Digital Video Standards - Digital Video and Audio Broadcasting Technology - page 177

stream interface, however, any data going beyond 188 bytes are only
dummy bytes and their content can be ignored. Many devices can be con-
figured to these various packet lengths or have the capability of handling
all formats.

Clock

Data [0..7] sync sync

16d 1 187 1d 16d 1

DVALID

PSYNC

Fig. 10.5. Transmission format with 188 byte packets and 16 dummy bytes (=204
Bytes) [DVG]

Fig. 10.6. TS-ASI

10.3.3 Asynchronous Serial Transport Stream Interface (TS
ASI)

The asynchronous serial transport stream interface (Fig. 10.6.) is an inter-
face with a constant data rate of 270 Mbit/s. Data bytes (8 bits each) will
be transmitted via this interface at a maximum rate of 270 Mbit/s, i.e. the
data rate on this interface is not synchronous with the actual MPEG-2
transport stream but always a constant 270 Mbit/s. The advantage of this
is, however, that the same distribution system system can be used as with
the SDI. Each byte is supplemented by 2 additional bits in accordance with
a standardized table. On the one hand, this identifies the data bytes
(dummy bytes) which are irrelevant but necessary for filling up the data
rate of 270 Mbit/s and, on the other hand, it prevents the occurrence of a
DC component in the serial signal.