Ivor's Blog Page

Blog #1                          Why all LCD and Plasma HD digital Tv's picture quality sucks in this joint!

17 March 2009

My old 32" widescreen CRT (tube) TV packed up end of last year. It was non fixable so it was time for new. Once widescreen, no going back to 4:3 square TV.

All the LCD and Plasma sets looked great in HD, but their picture quality sucked under normal conditions. I thought they all looked terrible. Oh well, CRT was the way for me, and since it was going to cost more to get the set here than the price of the actual set, why not go for state of the art CRT with digital tuner, half a dozen AV inputs and High Definition to boot. (yes, they make HD tube TV's!)

So it arrived last month and I plugged everything in...woooohaaaaaa! What a dreadful picture! May as well have bought LCD here at half the price!!! 

Trees blowing in the background leaves all smeared, as the camera pans across the rugby field following the guy with the ball, it's all juddery, the ticker running across the bottom of the news channel is not clear and difficult to read if it's moving fast. Some peoples faces distort on occasion and a fast action scene is sometimes "heh what just happened bru?, it was all a blurr" and so on. I found out this phenomena is called Digital Artifacts.

Sent it back to Samsung twice, moaned and complained you name it! What is going on in this place. This TV had excellent reviews!

Well, I eventually found out. Here is basic explanation. It is not entirely accurate either. I studied electrical engineering many years ago so only half understand the technical reasons and have tried to make it a bit easier to understand with simple analogies. My problem is slightly more complex been CRT since it's natively analog, but the explanation should apply to any digital TV.

First thing to understand is the difference between Analog and Digital. Below is a refresher so take a good look.

Analog Wave form:                                                                                                                http://en.wikipedia.org/wiki/File:Waveforms.svg

Digital Wave form:                                                                                                                    http://en.wikipedia.org/wiki/File:Waveforms.svg

The first thing you will notice is that there is a hell of a lot of information "missing" from the digital signal compared with it's analog counterpart.

Let's for one minute forget about the picture video thing. You have probably heard that mp3's never sound as good as the original analog sound. This is because a certain amount of the info has been stripped from it. You just don't notice it is not there - or the human ear doesn't realise it's missing. Of course the higher the sampling rate, bigger the file, less the compression, the better it sounds - but what is missing will always be missing because you have taken an original smooth sine wave, and converted it to a square one - digital. And if you try convert it back to analog, it will never be the same. You cannot put back what was never there.

Now you plug in your DSTV decoder, Non HD DvD player etc via anything other than a digital port (dvi, hdmi) you have a problem and here's why.

Your normal AV composite input (the yellow video RCA plug or SCART or S-video or any other composite input) is an analog signal. The TV now buffers and stores this signal for processing to convert to digital so it can output the picture. Only thing is, some of the original information is missing! (unlike sound from an mp3, you can now SEE it)  So now what you ask. Well - the TV circuitry guesses what is missing via various complex algorithms from what was happening in the previous "frames" for lack of a better word, and checks the frames coming up (because it has buffered the info for a split second so it can compare) and sometimes it guesses all wrong.

Yip - that's your digital artifacts and general messy or jerky juddering non focused picture! When it totally screws things up you get all the blocks on the screen which you even get on an analog TV thanks to poor signal from dstv decoder messing up the D/A conversion from thunderstorm etc.

To make matters even worse as far as DSTV goes: Digital signal (already shocking quality highly compressed like a 32kbps mp3) comes in to decoder from dish - gets converted back to analog for AV out - goes to TV and gets converted a second time back to digital. Result = shocking picture! And I'm sure some channels have better quality than others. The SABC channels for example are always yucky.

The ideal is no conversion eg latest multiscum decoders - digital in - digital out via hdmi strait to tv, tv doesn't have to convert anything = stunning picture. Upscaler DvD players (ie a normal SD dvd player but it has a hdmi out) also vastly improves the picture. It's not HD, but it has at least not gone through any conversion processes.

Also as Sentech / SABC keep on going on about the so called non existent "Digital Switch on" that was supposed to have been 1 November 2008 at the same time they are saying to the public "don't worry, all tv's will be able to view the signal by means of a set top box". Ha ha ! Digital signal in, just to be converted back to analog!!! ie same crummy picture! How nice! Only a TV with a built-in digital tuner (or a STB with digital hdmi /dvi out) is going to look any good and take advantage of the better quality.

WHERE ARE OUR DIGITAL TV's ALREADY ??? (by that i mean tv with digital tuner built-in).

So right now we have a dilemma in this country. 4 grand for new MonoChoice HD decoder with currently only ONE HD channel, and new cables and second LNB etc or a poor picture from your beautiful new TV. And the bigger the picture - the more noticeable the digital artifacts. Think carefully before you buy. Do you need a 60" plasma when a 32" will do and so on etc. The high end Tv's will have better processing power and better technology so naturally better conversion processes and ultimately a better picture. But soon today's 50 grand sets will be tomorrows 5 grand sets.

May be better to save your money and buy a 72cm standard CRT television.

I'm somewhat lucky in that I can still watch the TV in analog mode if I wish, I just have to sit with the annoying 50hz flicker std CRT tv's all suffer from. Like I said - may as well have saved my pennies :-( 

I'm certainly not forking out another 5 G's getting a new decoder and LNB's and paying best part of R600/month for their shoddy picture without even the SciFi Channel (and all i want to see is F1), and all the while I'm blaming the poor TV.

Hope that sheds some light.

Ivor.

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