DivX Quality On Different Televisions

sellsolid · Jun 23, 2005

Hi guys,

I have a Philips DVP630 DivX player, I have encoded alot of DivX files which play perfectly on my television set, but they play poorly on my PC. On my PC you could see that it is poor, BUT could this be because I encoded it with DivX 5 Home Theatre mode?

These are captured TV shows, which are in DivX format. If I was to buy a new television how would the quality be? Would it appear like the way it appears on my PC or the way it appears on my PC screen?

My TV is old, its a panasonic. There seems to be television sets which specifically states they have digital specialality. What do they exactly mean by this?

If you guys have any experience please post it here. So basically is the quality that is displayed due to my TV or is it because of my DivX player?

Thanks for any help.

Oriphus · Jun 24, 2005

Dont worry about termonology with the TV's. The reason for your query is quite simple. A television, depending on the make or model has around 500 or slightly more horizontal lines running across the screen that make up the image. There are a similar amount (500 in equivalent widescreen format) running vertically. This is what makes the image on the television.

You are finding that a DivX movie works brilliantly on the Television, but not so well on the PC.

Your PC has a screen resolution of say 1280x1024, well thats what mine is at. However, it is likely that the DivX movie is only encoded at a resolution of around 525x??? or even less at around 400x???, meaning that the image is going to look poor on your screen.

You can test this theory out by changing your resolution to 800x600 and you should notice a good improvement in the image. However, it probably still wont be as good as your TV.

So, your predicament is what TV to buy. Basically, get one with a CRT tube and around the 525 lines, which is pretty standard. If you go get a plasma with a higher resolution than SVGA you will find the image of DivX movies to be degraded. Basically, any modern CRT TV will play the movies fine...

Chris

sellsolid · Jun 24, 2005

Thanks you were right about the resolution. Thanks for your input. The Encoded files have a resolution of 720 X 576.

If it would work on a CRT TV, would it work on the following Projector TV:

http://www.argos.co.uk/webapp/wcs/s...n+televisions&categoryId=21955&clickfrom=name

Thanks for all your help.

Oriphus · Jun 24, 2005

Yeah, it would work fine on that Sony Rear Projection system.

The only problem with rear projection TV is the viewing angle at which you can watch it. A normal CRT TV has a viewing angle somewhere in the region of 100 degrees, with distortion. This is because the screen curves and the further wide you go, the more distorted the image becomes for you. With a Plasma screen, the viewing angle, and indeed any flat CRT screen, etc, the viewing angle becomes a lot wider, to somewhere around 170 degrees.

This is not the case with rear projection. Although you do have a flat screen, the way in which rear projection works means that you basically have to be sitting directly in front of the TV with your eyes height set for around the middle of the screen.

Test this out by going to look at one. Stand up close to the image, and if the tv is on the floor on a stand, it will look very dark when you are standing. Go down on your knees then and you will see the image gets very bright and good. Do the same by stepping left and right when viewing from a distance of about 6 feet. You will again notice the picture changing.

Its just something to be aware of when buying a TV with rear projection. Hope this helps

Chris

sellsolid · Jun 25, 2005

Orphius thanks for your help.

The only thing that is bothering me is that is it worth buying a rear projection TV which has CRT functionality?

Is there any plasma screen TV's with this functionality? Isn't it possible to change the settings of a plasma to display DivX files like a CRT TV would?

Also with the above TV, is the CRT a standard or is it like a normal rear projection TV, but with a CRT mode which can switch on or off?

Oriphus · Jun 26, 2005

As with many Plasma screens, the ability to display varying resolutions is usually possible, but there is a native setting (the actual output on the plasma screen). I think that you would end up having compatibility problems unless you got a plasma with a resolution close to the 720 X 576, which would then mean a great picture quality.

Im heading off to Jamaica in the morning, so unfortunately dont quite have the time to help you out fully (gotta pack). But here is some info from the HowStuffWorks website that ive copied across for you:

If you're thinking about assembling a home theater system, you may be looking at large screen televisions as the heart of your system. Projection TV could give you the size that you want -- CRT screens generally top out at 40" (101 cm) or so, and at that size, they are huge and heavy. Plasma screens can be bigger than that and still manageable, but they can be extremely expensive. Projection TV technology can create large screen sizes at a reasonable price.

Or maybe you need to equip a room, like a classroom or conference room, for multimedia presentations with a large audience. A projection TV gives you a lot of flexibility and is usually much better than the standard combination of a 35mm slide projector, overhead projector and TV/VCR.

Projection vs. Conventional TV
A conventional TV uses a device called a cathode ray tube (CRT) to display its image.

The negatively-charged cathode makes a beam of electrons that is drawn toward the screen by the positively charged anode. The beam strikes at the front of the CRT, which is coated with special chemicals called phosphors. When the beam strikes the phosphor, it lights up that area of the tube (a pixel). For a color TV, there are three electron beams and three types of phosphors on the tube for each pixel -- red, blue and green -- which, when excited, can make any color. The electron beam moves along the tube, either horizontally or vertically, using magnetic coils alongside the tube (see How Television Works for details).

Because the CRT is made of glass, there are limits to its maximum size. Today's CRT TVs usually measure less than 40 inches (101 cm) diagonally. This size is not practical for a home theater or large auditorium.

In contrast to conventional TVs, projection TVs form a small image on a device inside the projector -- either a CRT or LCD -- and then shine that image onto a large screen located elsewhere. In one type of projection TV, the screen is located within the TV box itself. This type of projection TV is called a rear or reflective projection. In this type, light reflects off the projection display panel and is then projected onto the screen.

In another type of projection TV, the screen is located across the room. In this type of projection TV, called a front or transmissive projection, light passes through the image-forming display panel and is then projected onto a screen.

Creating Projection TV
A projection TV has four basic parts:

* Projector
* Screen - separate or built-in
* Control panel - separate or built-in
* Sound system - separate or built-in

The arrangement of these parts varies with the different types of projection TV. Most rear projection TVs for home theater systems tend to look like very large-screen conventional televisions. Each one is basically a large box that contains all of the above parts. Rear projection TVs for conference rooms can have a separate projection room behind the screen.

In contrast, front projection TVs are spread out. The projector is at one end of the room, the screen is at the other end, the control panel may be in the middle (on a table or as a mobile device such as a laptop computer) and the speakers may be located in different parts of the room.

Each of these components will be examined in detail in the following sections.

Projectors
The projector is the heart of the projection TV system -- this is where the technological advancements have centered. The projectors used in these systems rely on two general approaches:

* Transmittive projectors - Shine light through the image-forming element (CRT tube, LCD panel)
* Reflective projectors - Bounce light off the image-forming element

In both types of projectors, a lens collects the image from the image-forming element, magnifies the image and focuses it onto a screen. Also, it is important not to confuse reflective projectors with rear projection. The terms "transmittive" and "reflective" refer to the optoelectronics inside the projector, not to how the projector is arranged within the projection TV system.

Some of the most progressive technologies use the reflective approach, but the transmittive approach has been around longer and appears in many of the small portable projectors on the market today. We'll look at transmittive technologies here and then look in depth at several different reflective technologies.

Transmittive Projectors
Transmittive projectors use two basic image forming elements:

* CRTs
* LCDs

Both types are discussed below.

CRT
Like conventional TVs, some projectors have smaller CRT tubes built into them. These tubes are small (perhaps 9-inch diagonal), expensive and extremely bright. In the basic layout, you have one or more CRT tubes that form the images. A lens in front of the CRT magnifies the image and projects it onto the screen. There are three CRT configurations used in CRT projectors:

* One color CRT tube (red, blue, green phosphors) displays an image with one projection lens.

* One black-and-white CRT with a rapidly rotating color filter wheel (red, green, blue filters) is placed between the CRT tube and the projection lens. The rapid succession of color images projected onto the screen forms an apparently single color image (the images are projected too quickly for your brain to distinguish between them).

* Three CRT tubes (red, green, blue) with three lenses project the images. The lenses are aligned so that a single color image appears on the screen.

One of the problems with CRT projectors is that, with anywhere from one to three tubes and accompanying lenses and/or a filter wheel built in, the projectors can be quite heavy and large. Also, CRT devices do not have the fine resolution that LCD devices do, especially when projected.

LCD
To make projectors lighter and increase their resolution, newer LCD technologies have been developed (see How LCDs Work for details on LCD panels). Transmitted LCD projectors use a bright light to illuminate the LCD panel, and a lens projects the image formed by the LCD onto a screen. There is not a huge difference between the LCD panels used in projectors and those found in something like a PDA, except that the LCD is smaller and backlit by a very bright halogen lamp. The LCD acts very much like a color slide in a slide projector. The advantage of this approach is that the projector can be very small.

The most exciting advances in projector technology can be found in reflective projectors.

Reflective Projectors
In reflective projectors, the image is formed on a small, reflective chip. When light shines on the chip, the image is reflected off it and through a projection lens to the screen.

Recent innovations in reflective technology have been in the the following areas:

* Microelectromechanical systems (MEMS)
o Digital micromirror device (DMD, DLP)
o Grating light valve (GLV)

* Liquid crystal on silicon (LCOS)

Click to expand...

Hope this helps
Chris

sellsolid · Jun 27, 2005

Thanks for all your help, have a nice trip by the way.

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DivX Quality On Different Televisions

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