As the North American Advanced Television System Committee (ATSC) works to define the second iteration of its digital terrestrial television (DTT) broadcast standard - ATSC 2.0 - Korean electronics manufacturer LG has developed a non-real-time (NRT) caching technology that it hopes to see incorporated within the new standard. The NRT system takes advantage of the fact that within a 6MHz-wide, MPEG-2 ATSC broadcast signal, the use of variable bit-rate (VBR) encoding requires the insertion of null packets to maintain a constant, total bitrate of 19.39 Mbits per second. NRT defines the means to supplant these necessary null packets with data which may be cached on the hard disk of the viewer's set-top box (STB). Over time, the drip-feed specified by NRT allows content - such as a data-intensive 3D movie - to be pushed to the STB within spare capacity found in the broadcast bandwidth.
The idea of using a modicum of bandwidth, spare or otherwise, to deliver content to the STB is not new, and is precisely the principle which underlies the current implementation of push video-on-demand (push-VoD) services. NRT's novelty derives not from its founding principle, but from the uptake that LG hopes to assist: by incorporating NRT within ATSC, standardization of the push technology will allow any ATSC 2.0-compliant STB to access non-real-time-delivered content.
There is little question that within the bandwidth-starved world of ATSC DTT broadcast, a standardized method for delivering data-intensive content over the top (OTT) of the real-time broadcast is useful. However, given that ATSC 2.0 is likely to be standardized around 2012, and unlikely to be used to broadcast a DTT multiplex before 2013/2014, a NRT OTT delivery mechanism may, by such time, have to contend with a real-time, broadband-based OTT mechanism. The ATSC countries - Canada, Mexico and the US - have yet to push an HbbTV or Canvas analogue which would define and standardize this IP-based delivery. However, within the ATSC 2.0 time window, it is not inconceivable that a broadcast/broadband standard could crowd out the utility of NRT.