The good and the bad of HD TVs

[Frank]

There are basically three types of wide screen televisions: CRT, plasma and LCD. And there are some subtypes for all of them.

CRT (analog)
Pros:
- Automatic anti-aliasing
- Good color representation
- Automatic smoothing of colored surfaces
- Very good scaling
- Good contrast
- Very long lifetime
- Cheap
Cons:
- Very big and heavy
- Consume a lot of energy
- Low native resolution
- Visible flickering / less easy on the eyes
- Risk of burn-in
- Hard to get the geography right and the subpixels to match up

Plasma (analog/hybrid)
Pros:
- Flat
- Very good color representation
- Automatic smoothing of colored surfaces
- Very good contrast
- Very good luminance
- Very long lifetime
(depending on subtype: )
- Big
- Good scaling
- Automatic anti-aliasing
Cons:
- Low to very low native resolution
- Risk of burn-in
- Big pixels with border
(depending on subtype: )
- Bad scaling

LCD (digital)
Pros:
- Flat and light
- Long lifetime
- Very crisp picture
- Useable as a monitor
- Very easy on the eyes
- High native resolution
Cons:
- Risk of defective pixels
- Low refresh speed (ghosting)
- Bad scaling
- Medium luminance
- Medium color representation
- Automatic aliasing

But, a display is nothing without a video source. There are quite a lot of those, so I keep it to the most commonly used ones:

NTSC (broadcast)
Pros:
- Cheap
- Low bandwidth
Cons:
- Low resolution (~270 × 480)
- Bad color representation
- No widescreen
- Interlaced

PAL/SECAM (broadcast)
Pros:
- Medium resolution (~350 × 576)
- Reasonable color representation
Cons:
- Medium bandwidth
- No widescreen
- Interlaced

DVD
Pros:
- Better resolution than broadcast, 720 × 480 (NTSC) or 720 × 576 (PAL)
- Support for widescreen
- Optional better color representation
Cons:
- Non-square pixels
- Scaling

HDTV 720p
Pros:
- Non-interlaced!
- Good resolution (1280 × 720)
- Very good color representation
- Support for widescreen
Cons:
- No support for 4:3

HDTV 1080i
Pros:
- Very good resolution (1920 × 1080)
- Very good color representation
- Support for widescreen
Cons:
- Interlaced
- No support for 4:3


As it happens, almost all the affordable wide and flat tv's have a resolution that is less than optimal and isn't equal to any of the specs above. Which is probably no surprise, seeing the list of available formats. Looking at the wide screen displays, most CRT tv's have the native amount of lines depending on if they're to be used for NTSC or PAL/SECAM. Most plasma tv's have a native resolution of 640 x 480 (even many of the really big ones!) or 1024 x 768, and most LCD tv's have a native resolution of 1360 x 768.

While the actual amount of pixels per line is less important for correct display than it is for color depth and distinction of fine details for an analog display, it is for a digital one. And the amount of lines is paramount.

CRT displays scale very well (although the actual resolution and color depth suffer), plasma displays can go either way, and LCD displays scale very bad. A CRT display is analog, while a LCD display is digital. A CRT display is like an oscilloscope, where you can vary the thickness and speed of the beam, while a LCD display is like a computer with monitor, where you have a fixed amount of pixels in a rectangle.

The main problem seems to be the embedded computer. You pay about twice the amount of money for the same LCD tv with a twice as powerful computer and program that does the actual rendering. And you need to pay a lot more than that to have a picture that looks as good as when you use a game console or pc to render the display at the native resolution.

Another problem is that most input signals (especially broadcast) carry too little information to be able to determine the right color for each pixel. That is actually quite alike scaling, but you need to interpolate whole blocks of pixels with only a very tiny amount of color information. Which is with regular broadcasts very suspectible to noise. Like, what you see when you don't have any signal selected, but finer grained.

To counter those problems, most LCD (and some plasma) tv's have a digital noise filter. This smooths the picture, and sharpens the edges. Most of it seems to work like a MPEG2 decoder: combine the interlaced halves of a picture, if appropriate, smooth the jpegs, calculate the borders and sharpen them. Which often introduces more ugly artifacts than it removes, if you ask me.

Another thing to take into account is the cabling:

Antenna
Pros:
- Always works
Cons:
- Bad signal quality
- Needs a modulator/tuner

SCART
Pros:
- Most A/V devices have it
- Allows controlling of the other devices (with a single remote control)
Cons:
- Not very good signal quality

Component
Pros:
- Most A/V devices have it
- Good signal quality
- Analog (good scaling)
Cons:
- Analog (low actual resolution)

DVI
Pros:
- Very good signal quality
- Better SCART
- Allows you to use the tv as a monitor
Cons:
- Not all A/V devices have it
- The maximum resolution is limited

VGA
Pros:
- Good signal quality
- Allows you to use the tv as a monitor
Cons:
- Not many A/V devices have it

HDMI
Pros:
- Very good signal quality
- Serial and digital
- Allows you to use the tv as a monitor
Cons:
- Only recent A/V devices have it
- More or less requires HDCP as well


For HD TV, you need at least DVI or HDMI, and also a HDCP decoder inside the television. Which decodes the scrambled input signal. And only HDMI offers no (or little) signal loss.

HDMI is a wild card: your chances of successfully hooking up two pieces of equipment that both offer it are pretty low at the moment. Often, you need to go back to the shop with both of them for a firmware update, and hope it'll work afterwards. Don't count on it actually working when you need it.


Phew. Enough for now, a next part will have to wait.

 

[Tahir2]

I would add that scaling is independant of panel type with regards to Plasma and LCD but more to do with the processor used.
E.g. a cheap brand Plasma/LCD will use a solution vastly inferior to the latest top of the range Bravia Engine.
Of course doesnt affect CRT's that do not have scalers... but I believe some also use scalers for resolution changes.

Vertical lines (or pixels) are much more important that then the Horizontal pixels when viewing a screen. The amount of pixels is still not as important as the quality of the pixels - i.e. the video processing engine (which includes the scaler).

 

[Frank]

Regarding the CPU, memory and program: the hardware is pretty cheap as it is. An ARM processor that is twice as poweful might be ten dollars more expensive, but that's about it. Add about an equal amount for the increase of the RAM. And there are so very many OpenSource programs that show how to do good video rendering, that I'm hard pressed to see that as the major cost difference.

So, it's basically a price distribution mechanism: all parties involved make only about 20-50% of profit on the cheap models, while they make the big bucks on the expensive models.

 

[Tahir2]

It may not be cost at all but market differentiation that has the biggest say. E.g. the best model suppliers (like Sony/Panasonic/Pioneer) do a lot of their own R&D. And they are probably initially paying for setup costs and could enforce exclusivity terms on their suppliers (e.g. the top of the range Xilleon from AMD/ATI).

Using these top of the range video processors then means that they can charge a massive premium - passing on costs to customers and making tons more money from saps like me.

The cheaper guys will buy off the shelf, whatever is in their budget.. then package and distribute and mostly hope for the best.

 

[Frank]

Agreed. But they're still far from the quality level I can reach with OpenSource software solutions on a basic pc. Which is quite a bit cheaper.

 

[Geo]

Dlp?

 

[Frank]

Dlp?

I might put that in part 3.

 

[Tahir2]

Should add LCoS as well then

By the way nice job on the first post DiGuru.. maybe a Beyond3D article could go Beyond3D and into 2D displays in the future?

 

[Geo]

We absolutely are hoping to plant a flag in the ground for anything pixel driven, including HDTV. Tho probably this thread should have been in the other sub-forum. . .

 

[Frank]

We absolutely are hoping to plant a flag in the ground for anything pixel driven, including HDTV. Tho probably this thread should have been in the other sub-forum. . .

What are you waiting for?

 

[Frank]

Should add LCoS as well then

By the way nice job on the first post DiGuru.. maybe a Beyond3D article could go Beyond3D and into 2D displays in the future?

Thanks!

 

[pascal]

For me LCD is more like that:

LCD (digital)
Pros:
- Flat and light
- Long lifetime
- Very crisp picture
- Very bright
- Useable as a monitor
- Very easy on the eyes
- High native resolution
Cons:
- Risk of defective pixels
- Risk of panel nonuniformity problems and Mura defects
- Low refresh speed (ghosting)
- Bad scaling (depending on the combination of panel/scaller)
- Low contrast (depending on the quality of panel and electonic drivers)
- Medium luminance
- Medium color representation (depending on the quality of the backlight/panel)
- Automatic aliasing

Good job DiGuru

 

[Martin Eddy]

Anybody got any info on Laser TV's, due out in 2007. All I cand find is press releases that state they'll be better and cheaper than Plasma.
http://www.arasor.com.au/consumer/consumer.asp

 

[Ty]

Anybody got any info on Laser TV's, due out in 2007. All I cand find is press releases that state they'll be better and cheaper than Plasma.
http://www.arasor.com.au/consumer/consumer.asp

The fact that we haven't heard anything about it speaks volumes IMO about the chances of it actually making it to the market in 2007. AFAIK, there hasn't been a single major electronics firm who has openly committed to this technology so don't hold your breath. I have the feeling you'll never see one of these sets on the market.

 

[Capeta]

The fact that we haven't heard anything about it speaks volumes IMO about the chances of it actually making it to the market in 2007. AFAIK, there hasn't been a single major electronics firm who has openly committed to this technology so don't hold your breath. I have the feeling you'll never see one of these sets on the market.

Mitsubishi is commited to laser driven DLPs which they've already showed at CES or was that CEDIA? That should eliminiate the color wheel and RBE and allow single chip DLPs to perform equal if not better than 3-chip DLPs at a fraction of the cost. That technology could be used with LCOS too.

We should also add SED to that list of display types.

 

[Ty]

Mitsubishi is commited to laser driven DLPs which they've already showed at CES or was that CEDIA? That should eliminiate the color wheel and RBE and allow single chip DLPs to perform equal if not better than 3-chip DLPs at a fraction of the cost. That technology could be used with LCOS too.

If you go to Arasor's website, you won't see any Press Release mentioning Mitsubishi (or any other TV manufactuer). From what I remember of a previous article on them, their TV was more SED than a marriage of DLP and Lasers therefore I'm not sure the two are even related.

 

[jamesnmandy]

For HD TV, you need at least DVI or HDMI, and also a HDCP decoder inside the television. Which decodes the scrambled input signal. And only HDMI offers no (or little) signal loss.

HDMI is a wild card: your chances of successfully hooking up two pieces of equipment that both offer it are pretty low at the moment. Often, you need to go back to the shop with both of them for a firmware update, and hope it'll work afterwards. Don't count on it actually working when you need it.


Phew. Enough for now, a next part will have to wait.

nice writeup, very direct and to the point, would like to see links to actual data, references of reputable nature if you will, but nice writeup overall,...... but i have to take exception to the last part

you don't "need at least" DVI or HDMI for HD TV, HDTV can be delivered to a HDTV via Component cabling just fine, matter of fact, Component can provide the same resolution as HDMI, including 1080p, but there are other limiting factors introduced by a third party such as ICT, while HDMI may be superior on paper, i have yet to see any distinguishable advantage in using HDMi over Component, especially since i always run a separate audio cable, Toslink or Coax to my surround receiver, the only advantage i could see if if i had a A/V Reciever with DD True HD audio and HDMI passthrough, that seems to be the only way to get DD True HD sound, via HDMI

i have a Toshiba 46H84 CRT-RP-HDTV with HDMI and Component and have tested all the available connections possible using a Toshiba SD-5980U Upconverting DVD player, Motorola DCT 6412 III DVR/HD Dual Tuner Comcast box (have had three generations of these over the years), Xbox 360, etc....and have never had a problem getting the TV and any component with HDMI to handshake successfully.....maybe i am just lucky?

 

[Snyder]

Nice list, DiGuru.

2 things I noticed:

- Consume a lot of energy
Definitely not restricted to CRT - Plasmas and LCDs have similar power draw (Plasmas used to be worse and got better, with LCD it's been the reverse)

- SCART doesn't necessarily have bad signal quality - RGB over SCART (with a good cable) isn't far away from YUV. (After all, it's a component signal as well...)

 

[MfA]

Plasma better contrast than CRTs?

 

[SugarCoat]

I'm not entirely sure i'd put ghosting as a negative for LCDs since most brand models (meaning Sony not Soni) from 2003-2004 on dont experiance it. It would have to be a seriously old LCD to ghost an image after the frame has passed. I'm actually quite sure you ment image streaking instead of ghosting, thats also been eliminated on most sets these days.

Ghosting to an LCD is like a fast burn in that dissipates, something like if a logo was displayed in the end of a comcercial then another comercial came up and for a second or two you could still see the outline of the logo in the previous comercial. Streaking is when a frame doesnt update fast enough and leaves a remnants of it seeming to bleed into the picture. Such as if you were moving down a dark hall with lights spaced over head in a video game, and every time you moved it made the lights bleed or streak together making them appear to be linked when they arent. The latter was noticed far more in your fast paced games then the former and the former was one of the first things eliminated as LCDs progressed.

Two other things that arent there are picture quality at wide viewing angles (CRT/Plasma > LCD) and advantages under certain light conditions, such as LCD still displaying a good quality picture in a heavily lit room where as people might see the Plasmas picture obviously superior in a low light room.

Another thing that could be added is many of the flat panel TV's (LCD and Plasmas alike and some super cheap CRTs) tend to use sub-par internal speakers that many people find weak.

Nice list, DiGuru.
- Consume a lot of energy
Definitely not restricted to CRT - Plasmas and LCDs have similar power draw (Plasmas used to be worse and got better, with LCD it's been the reverse)

Not true. LCDs at ~42" mark are generally listed between 200-250W typical draw. Plasmas for the same size are 300-400W. Its totally dependant on the brand (Sony specifically seem to be conservative) and the audio features included. Plasmas that cut out speakers or use junky 7Watt speakers tend to have power draws of about 300 Watts while LCDs that include 2 20W speakers + a subwoofer would be around 320-340W which is problably where that myth came from. LCDs do still hold between a 25-40% lead over plasma for power consumption if we just factor in the power for the picture, once you add audio features (or take them away in the case of Plasma) you throw it out of wack. I can find a 42" LCD that draws between 200-280W easily while looking for a Plasma at the same size that draws below 300W and still has its (half-way decent) speakers could take me some time. Most of them are listed at 350-400W.

As far as sizes over 42" i wouldnt suggest an LCD anyway but that power consumption of Plasma magically dropping over the last year is becoming a bad myth. If anything its attributed directly to manufacturers almost totally cutting out onboard audio.