effective bandwidth of 1080i is lower because it sends 540 lines per sync signal, whereas 720p has to send 720 lines.
At first this took me by surprise as well, but we should really thank our lucky stars that this is what many broadcasters picked because it leaves the door wide open for 1080p.
As this standard is obviously going to be with us for a long long time, it's best that it contains as much possible data to accomodate the next decade (at the very least). 1080i does just that by allowing us to use just 540p now, and "upgrading" (via processing) to 1080p relatively effortlessly.
It is just a matter of time before more scaling engines are created to allow for 1080i deinterlacing. The technology is well known, it's just a matter of market availability and processing power. Both DCDi and DVDO's algorithm (Pure Progressive) can be adapted to 1080i, and I believe they probably will at one point or another.
At first this took me by surprise as well, but we should really thank our lucky stars that this is what many broadcasters picked because it leaves the door wide open for 1080p.
As this standard is obviously going to be with us for a long long time, it's best that it contains as much possible data to accomodate the next decade (at the very least). 1080i does just that by allowing us to use just 540p now, and "upgrading" (via processing) to 1080p relatively effortlessly.
It is just a matter of time before more scaling engines are created to allow for 1080i deinterlacing. The technology is well known, it's just a matter of market availability and processing power. Both DCDi and DVDO's algorithm (Pure Progressive) can be adapted to 1080i, and I believe they probably will at one point or another.