[opendtv] Re: Optimizing the system

  • From: "John Shutt" <shuttj@xxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Tue, 21 Dec 2004 10:53:20 -0500

Perhaps.  I've seen that effect mostly with LCD projectors, and it is truly 

However, That effect does not surround person's head as it moves across the 
screen.  But a person's head is usually covered (except in my case) with 
hair, and the fine hair moving against a more or less stationary background 
results in macroblocks with much detail and little correlation from frame to 
frame, and so usually are the first to be DCT truncated by the encoder, 
causing the cloud of bees.

If you have access to an MPEG encoder, you can make the effect more and more 
pronounced as you encode the same scene over and over with decreasing 
bitrate.  HD or SD, the only difference is the relative size of the 
macroblocks to overall picture size, and the relative size of the 'bees.' 
As I said, the effect is constant on MSNBC's ticker at the bottom of the 
screen when viewed from DirecTV.  The edge of each letter and number is 
surrounded by a similar cloud of truncated macroblocks.

However, I suppose the only real way to tell for sure is to meet Tom at 
***The Technology Retreat*** and view material together to discuss what is 
being seen.  ;^)


----- Original Message ----- 
From: "Craig Birkmaier" <craig@xxxxxxxxx>

> Based on an earlier comment from Tom Barry, he may also be seeing the
> "screendoor" effect of the LCD raster, since he is sitting too close
> to the display...
> ;-)
> Regards
> Craig

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