[opendtv] Re: News: CEA FORECASTS CONSUMER ELECTRONICS REVENUE
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 12 Jan 2007 19:10:41 -0500
Olivier Houot wrote:
> Your HDTV bandwidth is for an uncompressed signal.
Salut Olivier. Oui, bien sur, but that makes it comparable with the
analog TV standard image quality limitation, and it also sidespteps all
the digital compression algorithm variables. I am simply assuming that
1080i or 1080p at 60 fields/frames per second are available.
> Where is the mathematical tool to compare - an initial
> "704x480" analog SD signal occupying 6 Mhz of bandwidth
> - a signal with a 1920x1080 resolution that has 6
> times more pixels but goes through a 50:1 compression
> step to finally force it down into the SAME 6 Mhz signal
> as its SD counterpart?
>
> Theoretically, there can be some doubt as to how much
> better the second option is. After all, shannon will limit
> the amount of information that you can squeeze through
> this limited bandwidth in a given time interval.
If you keep the compression algorithms the same, then the bit rate
provides a perfectly good comparison, between digital signals. But not
so easy to compare numerically against PAL, unless you again go through
the cycles/line computation.
> And of course, a really significant calculation would be
> more tricky, as you would have to consider the 10x
> horizontal color bandwidth reduction in analog signals,
> the limitation of the luminance bandwidth to get room for
> color, halved vertical colour reduction in european
> systems... Also, would you take an initial 4:4:4 or 4:2:0
> signal for HD? And which part of this information is
> really significant for the human eye?
>
> I am afraid mathematics are not the shortest way to the
> truth in this case.
I agree that including color adds the variables to be considered.
However, isn't 4:2:0 similar to how color is transmitted over PAL, in
terms of how much of the video bandwidth (or bit rate) is used for the
color information, compared with luminance information? I think it works
out to the same thing. I'll give it some more thought.
> It would be interesting to evaluate, after all the pain
> suffered to finally make HDTV a reality, how much we have
> REALLY gained.
I think the improvement is entirely obvious. When I first set up my HDTV
STB, I used the composite interface to the monitor. I just wanted to
make sure I could receive stations. (And thankfully, I could.)
What I saw was a good, clean image, but I was not amazed by the razor
sharpness of the image compared with, say, DVD. Still, I was very
pleased.
Then I tried the HDMI interface. Too bad, it didn't work.
So then I went to component analog, not expecting a huge improvement
over the composite (remember: 26" screen, not all that big).
Instead, the difference was like this is not TV anymore. This is more
like a good movie source. Subjectively, it's like going from looking at
a butter knife to looking at a razor blade.
Bert
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