[opendtv] Re: Philips ClearLCD technique for motion sharpness
- From: Craig Birkmaier <craig@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 20 Jan 2005 10:14:50 -0500
Thanks for this educational post Jeroen!
At 8:51 AM +0100 1/20/05, jeroen.stessen@xxxxxxxxxxx wrote:
>Hello all,
>
>Craig wrote:
>> Sounds like Philips just can't let go of scanning screens.
>
>??
>
>This is not by choice. The fact is that all LCD screens are
>refreshed top to bottom, using the largest possible fraction
>of the frame time. It simply can not be done any faster.
>It takes time to charge each pixel capacitance to its opposite
>polarity. Trying to do it too fast leads to uniformity errors,
>a "dirty screen".
>
>So the bottom of the screen is refreshed some 15 ms later than
>the top, and the pulsing of the backlight must match that delay,
>in order to sample the transmitivity of the LCD at the moment
>when it is most stable. It is the only proper way...
How does this compare to the time difference from top to bottom for a
scanning CRT.
If my calculations are correct it is very close.
> > As Bert may recall, there have been several recent announcements
>> about new chips that do motion compensated prediction to improve the
>> temporal presentation of lower frame rate sources such as 24P (film
>> or video).
>
>Yes, it is very important for film sources, at least if you
>believe that it was not a deliberate artefact, intended by
>the director... "Suspension of disbelief" and all.
>
>But it is still a major hurdle to do this for HD resolutions
>and beyond, as many displays are now offered with 1920x1080p.
>That is a pixel bandwidth of at least 120 MHz at 60 Hz frame
>rate. And then there's that issue that the manufacturers just
>won't specify these panels at more than 60 Hz. Yet.
Glad you have added "yet," as some of your competitors have announced
chips that work at these clock rates.
> > As for re-writing the ATSC or DVB standards, it is mostly an
>> editing job, and a rather easy one at that.
>> You simply delete all the stuff after the modulator and
>> definition of the transport stream - the market place is
>> driving the rest.
>
>And in the process you lose compatibility with only a couple
>of million receivers and displays out there... :-(
Not at all.
I am not suggesting that the existing DVB formats be abandoned; the
marketplace ALREADY supports them.
But existing DVB receivers will be just as "broken" if a service
provider adds HD formats - actually I think theDVB specs already
includes them.
It is absurd to think that either DVB or ATSC are going to have a
life span of 50 or more years. Both of these standards are ALREADY
showing signs of age. The false premise upon which these standards
are based is that broadcasters and CE manufacturers can hold back
technical innovation.
Here we are less than a decade into history of DTV and the MPEG-2
compression standard is outdated. While MPEG-2 will be supported
moving forward, H.264, VC-1 and other compression formats are going
to be deployed in the next few years.
The real question is WHY should a terrestrial broadcast system be
constrained with respect to the bits that it carries? Defining
modulation and the transport stream is sufficient. Applications
determine what those bits should represent.
To provide an analogy.
Where would personal computing be today if we were all using 286
processors with 512KB or RAM?
The CE industry has driven innovation to the consumer - often at
considerable expense. That expense is justified by the improved
performance and new capabilities that are possible when the consumer
decides it is time to upgrade.
If broadcasters are going to survive, they must get in sync with
modern realities. Trying to lock down the system parameters - again -
is already putting broadcasters at a competitive disadvantage.
Already DirecTV has announced that they will migrate to H.264 for
local HD signals; this assumes an upgraded receiver for existing
subscribers. Cable will start using H.264 in the near future as well,
introducing it first for HD and VOD services.
The issue is not about protecting the consumers investment in an OTA
receiver. The issue is how broadcasters will survive if they do not
start innovating and giving their "subscribers" good reasons to stay
tuned...
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