[opendtv] Re: 1080p transmission
- From: "Albert Manfredi" <bert22306@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 03 May 2007 20:42:47 -0400
Tom Barry wrote:
What sort of bandwidth are you talking about wasting? Certainly not
transmission since the digital formats are transmitted as compressed
frames of video where nothing need be wasted in the overscan area.
The bandwidth figures are baseband to the screen. And you need to add
chrominance to that, to get the total figure. Of course, since 1080i and
720p are both 4:2:0, the ratio will remain identical. So this is completely
independent of any codec difference or any display technology. It's a
measure of the information transfer limit of the two formats. 1080i wins
out, if only by 12.5 percent.
And it makes sense. You would not expect to be able to send more pixels per
unit time to the display without requiring more total bandwidth to the
display. You're sending 62.2 Mpixels/sec at 1080i, and 55.3 Mpixels with
720p. Ergo, 1080i involves a greater amount of information rate to the
screen. This can only result from more baseband bandwidth.
So I'm saying that if, for some reason, 720p and 1080i in reality require
the same amount of baseband bandwidth to the display, obviously 720p has
more wasted overhead. Same baseband pipe size, less useful information
transfer, must be less efficient for some reason.
I think that sort of Luminance bandwidth measurement is an artifact
of legacy scanning CRT's
I think of this as "information to the display." It can be measured in
different ways, but the ultimate answer does not change.
Bert
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