[mythtv-users] OT: LED or Plasma (was Advice on choosing a TV)

Indulis Bernsteins indulis.b at au1.ibm.com
Thu May 27 15:52:34 UTC 2010

> Are you seeing a lot of posterization from yours in darker images,
> especially on walls and faces? At first I thought it was just the
> TV being larger than I was used to showing up poor sources, but
> I'm seeing it in all sources. Also, if I pause and adjust the
> brightness, the colour bands move, which also indicates that it's
> the TV not the source. It's bad enough that I'm considering
> returning it. Although maybe this is a problem with all modern
> TVs.

> Paul.


I think this is normal.  I am trying to remember where I saw a really good 
discussion about this in the last few weeks.

If you imagine the input is 256 levels, and your brightness and contrast 
settings "crunch" these into 170 levels on the actual display (say the 
bottom 40 levels of input all translate to output of 0 or dead black), 
then with a full range of input levels (say a blue sky or the blue Mythtv 
theme!) you'll get adjacent input levels the picture moving in between the 
170 levels (1 level of input change "clicks over" 2 or 3 levels of 
output), and you'll see the "bands" move.

  input 50 = output 75 due to your brightness/contrast settings
  and input 51 = output 78
but if you change contrast/brightness a bit, 
  input 50 might = 78
  and input 51 also = 78
so the "bands" between the colours move around.  I have probably done a 
cr at p job of explaining this!

You will find the high contrast "demo" or "vivid" settings on a TV do a 
LOT of crunching of the video data into a small subset of levels, so the 
quantisation becomes more apparent- the banding is worse.  You lose 
definition in shadows and fine detail for the same reason.

The best I can suggest, is to get a copy of the Digital Video Essentials 
(DVE) DVD or Blueray.  Use it to set up the right brightness and contrast 
settings for your TV.  If you have Terminator 2 on DVD, it and some others 
have a short version of the Digital Video Essentials type of guided setup 
("THX setup menu").

Often video rental stores have a copy of DVE you can rent for a day, but I 
think it is good to have one around all the time.

You may also be seeing two different effects- one is posterisation from 
lousy overcompressed sources, the other is the bands moving when you 
adjust brightness.contrast, the two are not necessarily related, so you 
can't draw the conclusion it is just the TV.  Personally I think you're 
seeing two different things.

If you can find a very good video source (good progressive scan DVD 
player- pioneer, Sony, Oppo, try looking at "secrets of home theater" 
http://www.hometheaterhifi.com/ which has a lost of good progressive scan 
DVD players.. and there is a lot of difference even between a $80 and a 
$150 player with progressive scan) and a good DVD disc (check avsforum for 
examples of good test discs, some of the animation films from Pixar are v 
good, and if you can score a "superbit" DVD on eBay, these were DVDs with 
no extras and remastered for the maximum amount of just film video+audio 
data that could squeeze onto a DVD).

Once you've done the setup and view the picture and you'll find it is 
pretty impressive (it was even on my old Pana 50" from 4 years ago- I had 
a Sony prog scan DVD player about $200, but the new Pioneers are also v 
good).  And I am fussy when it comes to video and audio quality.  Good 
setup of the TV is key to a good image!  I think that there is a THX 
setting on the Pana TV you have?  That is supposed to be good (I was 
reading about it in the review). 

Use HDMI over component, and component over s-video, and s-video over 
composite connections.  DOn't bother with "m0nster cable" HDMI or 
component, a waste of money! 

Finally, you could beg/borrow a Blueray player and see how it goes 
attached to the set.

Good luck!

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