View Full Version : Noise around the lettering?


6GH8cowboy
02-09-2014, 09:03 PM
I have noticed that around some lettering on flat screen DTV sets there is what I will call video noise around the letters in a square area. Also in some dark areas the is this same effect. Cant capture it with a camera or I'd post a pix. Is it being broadcast that way. Is it the receiver RF or the way its decoded?
At times there seems to be a ghost around such lettering or logo some of the time, all the way around. I was thinking it might be the way the TV software dithers the pixels to make a picture but the effect is a bit too extreem to me.
Any body know.

ChrisW6ATV
02-09-2014, 10:56 PM
Hi-

If you are referring to what I could call a "wrinkled" look in the area closely surrounding text or other sharp, higher-contrast details on digital TV broadcasts (and much worse if it is from satellite or cable), that is a side effect of the limits on digital date rates in the TV signals.

jr_tech
02-09-2014, 11:13 PM
Read about "Gibbs Effect" (mosquito noise) here:
http://www.embedded.com/design/real-time-and-performance/4013028/Video-compression-artifacts-and-MPEG-noise-reduction
jr

Username1
02-11-2014, 02:10 PM
This must appear mostly in flat HD tvs. My Fatherinlaw's house (boy spellcheck put a red line under that new word) they replaced their analog 21" tv with a 30" flatter and the picture and color look so bad I don't even want to turn it on.... They have cable, same controller on both sets.... But the old tv, before it died, looked really good....

Chip Chester
02-11-2014, 03:44 PM
Start your "investigation" by watching network programming via an antenna -- not by cable or satellite. Re-broadcasters will cough up only enough bandwidth as is necessary to minimize complaints. And non-network programming could have non-HD beginnings. (I suppose local live news would be OK.) Then you can see if it's the content or the display.

(This would be on the primary HD channel, not a sub-channel.)

Chip