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Old 12-12-2009, 06:09 PM   #28  
Broadcast Engineer
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Join Date: Nov 2009
Location: Central New York
Posts: 36

Originally Posted by jim5506 View Post
WE have a local CW/MYTV/UNI digital with 2 720p's and a 480i. Needless to say the 720ps are a bit soft from running about 8 Mbits, but it is still noticably better than 480i.
We're just now setting up a brand new box by Harris called a NetVX... it's basically a card frame you populate with all of the devices you need to create a multi-program ATSC transport stream (there are other applications for it, but that's what a broadcast station would use it for). Ours happens to have a pair of HD encoders and a multiplexer to combine their outputs with PSIP data to produce a SMPTE 310 output to send to the transmitter. It's an impressive device: we are finding that we can fit two 720p/59.94 signals into one channel at about 9 megabits per second each, and the subjective quality is at least as good as our older Tandberg E5821 encoders running at 14 or 15... even with rapid and highly random motion.

Several recent posts have correctly observed that broadcast 1080i runs at 30 frames per second (actually, 29.97); 1080p/60 would yield four times the data rate of 1080i/30, not double. Still, it's a moot point: even this brand new NetVX can only fit two HD streams into an ATSC signal if they are both 720p/59.94.

But as several folks have already observed, none of this is pertinent to the original question about the bandwidth (which would be the data rate) of raw uncompressed 1080i... and per SMPTE 292M, it's 1.485Gb/s.

-- Jeff
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