Ensemble Designs 4500 ASI and SMPTE 310M Converter and MPEG Transport Processor - Manual (Page 7)

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Model 4500 MPEG Stream Processor
MAJOR FUNCTIONAL CAPABILITIES OF THE 4500
Signal Conversion
The 4500 converts DVB-ASI to SMPTE 310M or SMPTE 310M to DVB-ASI. Using the reference input, the
output bitstream can be synchronized to a video or 10 MHz reference signal.
Set the output of the 4500 module to the desired signal type. The module auto-senses what type of
signal is on the input and converts as needed. Additionally, it will pass DVB-ASI to DVB-ASI, and SMPTE
310M to SMPTE 310M.
DVB-ASI is a worldwide standard, whereas SMPTE 310M is broadcast in North America only because it
is highly specific to NTSC broadcast standards.
Stream Analysis
The idea of stream analysis in this context is similar to what the 4455 and 7455 can do, yet the
capabilities of the 4500 go above and beyond those products.
The built-in transport stream analyzer detects whether the input constitutes a valid signal by checking
for PAT, PMT, and PID packets. In addition to the ETR 290 test protocols, you can configure tests to
define the minimum number of video and audio packets expected per second in a given service.
Clock Cleaner
Transport Stream Time Base Corrector
There are reclocking techniques that can be used to reduce jitter in a serial bitstream. But they cannot
correct any underlying frequency error, and ultimately their effectiveness is limited by the bandwidth
inherent in their design.
In contrast, the Avenue 4500 overcomes underlying frequency error by separating the content from
the original clock and generating a new output based upon more accurate and more stable clocks.
Although the data rate of the actual content is constantly varying in response to the compressibility
of that content, the overall data rate is held constant at 19.39 Mb/s. The 4500 accomplishes this by
adjusting the number of null packets (which contain no data) to keep the packet count at precisely
12,894 per second.