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Old 06-27-2007, 11:50 AM   #21  
drdumont
Long Journey into HD
 

Join Date: May 2007
Location: Dallas Area
Posts: 40
Default Transport and compression

Indeed, there is usually some form of compression used in long haul transport of digital signals. In the case of remote telecasts, I hand off the signal from the truck to a transport medium. THe signal I hand them is native uncompressed 1080, 720 or 480, depending on the wishes of my customer. In the case of most SDI trasmissions, audio is embedded in the datastream.

The transport then uses encryption and some form of compression to get the signal from the origination point (the side of my mobile unit) to the network HQ or other aggregation point. Then there is decoding, processing, branding, whatever else is done in packaging the final product before it is sent for distribution to local stations, the Head End In The Sky (trade mark), or however else the signal is sent to the transmission device prior to your reception via CATV, satellite receiver, fiber optics or off the air.

Local TV stations, Cable head ends, Satellite transmission companies, etc all may use some form or another of compression according to their business practice.

All, however, except for Verizon FiOS. In a conversation with several of the Senior Engineers and the Project Engineer overseeing the install of the head end for the North Texas area as we stood in their NOC, I was told several times "No additional compression is applied to any of the signals presented to us for inclusion in the Fiber Optic stream". "Whatever bitrate, whatever bandwidth is received, we retransmit it exactly as received". There is local commercial insertion on some channels, but other than that, they don't alter the incoming data stream except to translate it to their fiber transmission scheme.

So either the engineers were standing in their control room lying through their teeth or there is some part of this thread that is being misunderstood. The FiOS system doesn't need to degrade the signals they pass. The bandwidth of the fiber system is wayyyyy wider than that needed to send all the data than they presently send, leaving them plenty of room for expansion.
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