Revisiting 1080p and beyond
Dec 15, 2006 9:00 AM
Delivery channels and display resolution
The true benefit of 1080p display is not 60p necessarily, but the fact that all 1920 pixels are present on each line. And if 2K displays really come to exist for the home theater, both formats need a delivery mechanism.
An e-mail from reader Joe Gombos of JBA Consulting Engineers asked for more information about how existing delivery channels could support 1080p.
A potential OTA delivery solution could be to use the ATSC A/53 High Data Rate (HDR) mode, which employs a 38.78Mb/s Transport Stream (TS) and 16-VSB modulation. This would facilitate squeezing a 1080 60p, MPEG-2, 4:2:0 color sample structure into 6MHz. Of course, there is a more stringent signal to noise requirement of 28.3dB, as compared to 14.9dB for 8-VSB with a corresponding decrease in coverage area.
A cable system can go to 256-QAM, while DBS would have to allocate a complete satellite transponder. Both methods would eat up valuable channel capacity. In addition, the resulting signal could be less robust and therefore result in less image stability.
Telco IPTV and FiOS delivery systems are approaching 100Mb/s. And although 40Mb/s may or may not be a practical, guaranteed bit rate to the home now, in the future, it may prove to be sufficient for 1080p given that a High Data Rate TS is at 38.78Mb/s, provided that it is a guaranteed, sustainable QoS.
Broadband cable Internet connections have not yet reached sustained data rates at the 40Mb/s level. So, a download mechanism may do the trick; however, it will take 12 hours at 10Mb/s to download a three-hour 1080 60p movie. This may prove to be unacceptable. Cable operators may have to turn to a switched video implementation. In this way, similar to VoD, only the one stream of content requested by a customer is delivered. HD VoD and PPV capabilities exist, but again, going to 1080 60p will take up channel capacity and limit the amount of content that can be delivered. Maybe the near-video-on-demand model will work, starting 1080p content every 15 minutes.
With the emergence of more efficient compression engines such as AVC and VC-1, however, bit rates for 1080 60p may be reduced to manageable numbers in the near future. Will AVC/VC-1 compress native 1080 60P content sufficiently to enable delivery over existing channels? Will a Super HD-DVD come into existence, or will quad-core media PCs handle native 1080p?
Regardless, content availability will still be the fundamental issue. So, as discussed last month, the digital cinema production industry may be the only source for content in these higher resolution formats.
Technology necessitates change
In the end, naturally, a 1080p display/DTV receiver will be required. This necessitates new 16-VSB/256-QAM demodulators. The High Data Rate TS will have to be parsed. New decompression engines will be needed. And for 2K pixel grids, new display manufacturing techniques or technologies may be necessary. Seeing how true 1920 pixels per line capabilities are just now being introduced, I wouldn’t hold my breath waiting for higher display grid formats and advances in processing circuitry.
By now, just about everyone in broadcasting realizes that “broadcasting” isn’t just about broadcasting any more. Multichannel delivery and multiformat production have completely altered the business. There is no “user manual” that can keep up with the speed at which the industry is changing. The responsibility rests with industry professionals to find the solutions to these engineering problems as they arise. As some have said, this is a new engineering discipline born of the union of broadcast engineering and information technology.
Happy Holidays to all!
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