[opendtv] Re: Europe now debates i vs p

  • From: Craig Birkmaier <craig@xxxxxxxxx>
  • To: opendtv@xxxxxxxxxxxxx
  • Date: Tue, 14 Sep 2004 14:53:06 -0400

At 10:46 AM -0400 9/14/04, Mark Schubin wrote:
>Craig Birkmaier wrote:
>
>>Mark Schubin may correct me if I am wrong, but the 55% MTF at 27 MHz
>>suggests that a fine black detail at 27MHz will be captured as a
>>midtone grey.
>>
>55% MTF means 55% of the contrast ratio at zero detail (i.e., the whole
>screen white or black).  Midtone grey will still be midtone grey.  Black
>will be roughly half as far from that as it would at zero detail.  Of
>course, bias may be applied so black is black and white is a midtone
>grey or so white is white and black is a midtone grey.

Thanks Mark.  So the resulting image will be more accurate than I 
suggested, but the contrast will be reduced.

>
>
>>  The lack of contrast will make it difficult to perceive
>>the detail. For example a B& W herringbone pattern may turn into a
>>solid grey pattern.
>>
>That statement is not supported by a 55% MTF.  The pattern would not be
>solid; it would just have slightly more than half the usual contrast.

And this is under ideal display conditions. When the MTF of the 
display and its actual resolution (ability to present these high 
frequency details) are added to the equation, the ability to perceive 
this detail may be impaired as I suggested.  Much will depend on the 
integrity of the samples after they pass through the distribution and 
emission chain, and the quality of the image processing that takes 
place after the MPEG compressed video has been decoded.

Regards
Craig

>
>TTFN,
>Mark
>
>
>
>
>
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