[opendtv] Re: RGB mania

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Mon, 17 Jan 2005 09:27:35 -0500

At 5:06 PM +0000 1/16/05, Alan Roberts wrote:
>Have you any idea how hard analogue circuit design is? You're asking for
>video amplifiers with at least 75MHz bandwidth and over 90dB SNR. The Sony
>HDW900 has 12-bit adcs and achieves about 58dB, but that circuitry consumes
>about 20% of total power in the camera. Dropping from 12- to 10-bit in the
>750 is virtually the only reason why its power consumption is lower.
>Astronomical cameras achieve that sort of performance by using very long
>exposure periods and liquid gas cooling, neither is appropriate for shooting
>real life.

Yes. Acquisition is perhaps the most difficult part of the process, 
as Alan rightly points out that we must start in the analog realm.

By the way, pushing around 2 million samples  is part of what makes 
this task all the more difficult. Not that 1 million samples at 60P 
is a piece of cake, but at least there are more photons available at 
each CCD sensor sight.

There are MANY ways to design acquisition systems, and many trade-offs.

We can push the spatial resolution;

We can push the temporal resolution;

Or we can balance one against the other. 1024 x 576 at 72P has a 
pixel clock that is about 2/3's that of 1080@30i. Now which one do 
you think will provide better slo-mo playback?

Regards
Craig
 
 
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