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Dr. Dark Current

Tue Oct 17 2006, 06:25PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

hi all,
I'm planning to buy a cheap LCD TV, however there's one thing worrying me: All TV's in my price range have a display resolution of 640x480 or 800x600 pixels. Now, how does it display a 625 line (PAL) TV broadcast?? There must be done some nasty interpolation, resulting in a crappy picture, right?

Nik

Tue Oct 17 2006, 10:38PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

I have found that 90% of LCD TVs (that I have seen in stores or peoples homes) have very poor images when displaying regular cable tv. If you buy a cheap TV you will get a very cheap picture. CRT's arent as popular but this makes them cheap and the picture is better then an equivilantly priced LCD (or plasma) TV.

Avalanche

Tue Oct 17 2006, 11:02PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

I know not many will agree with me here, but -

I'd still recommend CRTs, and in fact I did a few months ago to someone. They are designed for the 625-line system, whereas LCDs are not. The colour, viewing angle, everything is going to be better on a CRT, and call me crazy but if you are on a budget I would also recommend a second hand sony or panasonic or something from the 90s, it will cost nothing and will go on and on forever. I find modern budget electronics usually comes with creaky cases, crappy speakers and the silver paint that wears off after 6 months

Bjørn

Tue Oct 17 2006, 11:06PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

You will not notice any interpolation, the original signal is not sharp enough that you will notice even pretty bad interpolation.

The main problem is that the LCD is much sharper than a CRT and you will tend to see all sorts of noise and artifacts that are invisible on a CRT. The black level is not very good either so if you ever watch something that depends on details in the dark areas of the picture you will not be very pleased.

Another problem is that most LCD TVs have default settings that are fairly useless unless you have perfect signal quality.

Steve Conner

Tue Oct 17 2006, 11:30PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Avalanche is right, you can get a second hand CRT TV for like $20 and it's hard to beat that. I guess LCDs are more "El1te" though on account of being flat. As far as I know, they use a framebuffer to do 2-D digital interpolation.

I have seen some models with a native resolution related to the video, like 352 x 288 or 768 x 576. But usually they make them multi-standard for PAL or NTSC, and a native resolution that fit one standard wouldn't fit the other, so scaling and interpolation is still needed. Also, the 625 line thing is interlaced, and having the framebuffer de-interlace while it's interpolating makes the picture flicker a lot less.

We have an apparatus in our lab with a small colour LCD monitor. Someone managed to break the screen, and the official replacement was $900. I figured out that it was analog RGB video with NTSC scan rate, and managed to graft the guts of a cheap $100 mini LCD TV in there, but the picture quality was indeed a lot worse than the $700 monitor, even though I had bypassed the video decoder and fed the RGB signals straight to the LCD driver chip.

Sulaiman

Wed Oct 18 2006, 02:23AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Copying from Wikipedia
The PAL colour system is usually used with a video format that has 625 lines per frame (576 visible lines, the rest being used for other information such as sync data and captioning)

So 800 x 600 is plenty.

Dr. Dark Current

Wed Oct 18 2006, 02:24PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

The TV I want to buy, the Acer AT2001, has a SHARPNESS setting in the OSD, maybe this can be used to "mask" the interpolation artifacts?

Also, what about LCD vs. CRT lifetime?

Avalanche

Wed Oct 18 2006, 03:24PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

I would guess the sharpness setting would alter something in the interpolation stage to average out or emphasise the colour between adjacent pixels, or something like that. Not sure.

As for lifetime, CRT will always win there. The first thing to go in an LCD TV is most likely going to be the backlight or the backlight inverter. They usually degrade over time, so your image will have a yellow tint. It's not that hard to fix, but you still need to be able to find the right replacement parts in a few years. LCDs are too new to be able to make an accurate judgement on how long they would last, but I bet one wouldn't last anything near 14 years, which is when I got my current TV. Another potential problem is dead pixels and missing lines on the screen, caused by a variety of things usually expansion and contraction of the set over time, not a problem with CRTs.

I am biased towards CRT also

Bored Chemist

Wed Oct 18 2006, 04:56PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

There's a side to LCDs that hasn't been mentioned. I use the same PC as I'm typing this on, as a TV as well. There's a card in the pc that does the tuning etc (doubles up as digital box and video recorder too).
The quality is limited by the poor aerial I'm using rather than anything else.
One really noticable difference between this 19" LCD and a 19" CRT is that I picked this thing up in the shop, put it under my arm and carried it home on the bus. I really don't think I could have done that with a CRT. Allied to this benefit (which only matters if you move the thing) is that there's space behind it on the table for the printer.
If you want a good picture that will stay good for years buy a second-hand, good CRT. If you are short of space and/ or planning to move a lot, buy an LCD.

Dr. Dark Current

Wed Oct 18 2006, 05:19PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Well, thanks for all your replies,
I think I'll buy some nice tube screen TV after all, since it has for me more pros than LCD. I saw a nice real flat screen Panasonic TV, that I'm most probably going to buy.

J.M.

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