Display Wars: Digital Vs Analog

Today, every one is going crazy over high-definition technology and the

demand for enhanced digital picture quality and visual feel has prompted

industry experts to look beyond the traditional analog display options.

Emergence of HDMI and DVI has given people the option to enjoy high quality

digital display minus any distortion. These technologies have obliterated the

demand for analog options such as S-Video and Component. The move towards more

options may see a complete exit of analog displays in the near future. In this

story we show what makes digital displays such a rave and what's the future of

analog displays.

Why digital?



Digital signal transfer is assumed to be error free, while analog signals

are always subject to some sort of degradation in signal quality and information

loss. This is true to a large extent but when you consider the usage scenario,

there's no reason why any predictable degradation of an analog component video

signal should occur for a small distance; for example, even for a home theater

installation, it doesn't present a challenge for analog cabling if built to

professional standards. Hence there is no reason why there would be information

loss or any substantial degradation which would be noticeable to the naked eye.

It's also not correct to suppose that digital signal handling is always error

free. Both HDMI and DVI signals aren't subject to error correction; hence if

information is lost, it's lost forever.

Digital display has its own importance in today's scenario but it doesn't

mean the end of the day for analog technology. There is still some time left

before analog displays see the end of the day.

DVI or HDMI



HDMI has been the latest buzzword in the digital market. So much so that people
have sidelined DVI and are focusing on HDMI. Is it better than DVI? What's the

difference between the two? To be honest, the only difference between the two is

that HDMI has the capability of carrying audio signals along with video, whereas

DVI can carry only video. Let's analyze them in detail.

Digital Video Interface (DVI) is a predecessor of HDMI and so both are based

on the same specifications. The original design for DVI included conversion of

analog signals to digital signals. The main reason for this conversion was to

accommodate both analog and digital monitors by DVI. Data is transmitted using

transition minimized differential signaling (TMDS) protocol and provides a

digital signal from a PC's graphic subsystem to the display unit.

DVI can be categorized into three categories. There is a DVI-A which is used

for analog signals like VGA. Then there is DVI-D which is used for digital

signals and is the one which is being used in most of the home theater systems

and in other commercial products intended for home use. The third is DVI-Integrated

(I) which is a combination of both DVI-A and DVI-D. Two levels of performance

are supported by DVI-I -- Single Link and Dual Link. Most of the current

electronic products are designed around the Single Link standard. The Dual Link

cable is future ready and is compatible with wide bandwidth applications that

are currently present or shall come into existence in the near future. DVI-I is

complete, fully digital video transport protocol that is supportive of all

digital video formats including 480p, 480i, 540p, 720p, 1080p and 1080i.

High Definition Multimedia Interface, is an uncompressed digital audio/video

interface, supported by the electronics industry. It supports high-definition

video, standard video and enhanced video along with multiple channels of digital

audio. So you won't need additional cables for audio capability. HDMI has plenty

of bandwidth so any future requirement and enhancement can be easily

accommodated. It has support for up to 8-channel uncompressed digital audio at

192 KHz sample rate with 24 bits/sample as well as compressed stream such as

Dolby Digital or DTS. HDMI is backward compatible with single link DVI carrying

digital video used on current monitors and graphics cards. Hence, DVI-D or DVI-I

source can drive an HDMI monitor or vice versa, by means of a suitable adapter

or cable, but the audio and remote control feature of HDMI will be missing. HDMI

also has support for High-Bandwidth Digital Content Protection (HDCP) which

allows the end use to view or record certain restricted content.

Broadly speaking, both HDMI and DVI are the same, barring the lack of audio

and HDCP support in DVI. Also the number of cables required for DVI is more than

that for HDMI; in fact, in HDMI the same cable can get you access to both video

and audio signals.

Analog technologies



Component Video



Component Video splits up color information over three components, as

is the case with DVI and HDMI, but the actual content of the three video

components is different from the three data channels in a DVI or HDMI cable

interconnect. In popular use it refers to a type of analog video information

that is transmitted or stored as three spate signals. It can be contrasted with

composite video in which all video information is combined into a single line

level signal. Component video cables, like DVI, do not carry audio and is common

in most of the current LCD monitors and plasma TVs.

All the LCD and Plasma TVs come with multiple display interfaces such as Component, DVI and HDMI

S-Video



Separate Video commonly known as S-Video is also an analog video

signal that carries video data as two separate signals--brightness and color

unlike composite Video that carries the video signals mixed in one line. The

Component Video cables are commonly used to carry video resolutions higher than

those supported by an S-Video cable. S-Video also does not carry audio on the

same cable.

The new kid: Display Port



Display Port is the new entrant to the already crowded display market. It's

a digital display interface standard promoted by the Video Electronics Standards

Association (VESA). It defines a new license free, royalty free, digital

audio/video interconnect intended to be used primarily between a computer and

its display monitors or a home theater system. It's a direct competitor to the

HDMI connector. It has support for an embedded clock, unlike DVI/HDMI which

requires a separate clock pair. The data transmission protocol in Display Port

is Micro-Packet based, to which more features can be added in future. One of the

important advantages it has over HDMI/DVI is that it consolidates both external

and internal display connections. It includes option DPCP (DigitalPort Content

Protection) copy protection from AMD, which uses 128-bit AES encryption with

modern Cryptography ciphers, very similar to what HDCP does. It allows backward

compatibility with single link DVI/HDMI, dual link DVI/HDMI and analog VGA. Dell

and AMD have already announced support for Display Port in their upcoming

products and many others like NVIDIA, INTEL, HP, Lenovo are planning to follow

suit. It will be interesting to see what all challenges this technology would

bring for HDMI.

VGA to DVI converter	Notebooks also come with multiple display interfaces such VGA, S-video and HDMI

Conclusion



There is a clear transition toward digital displays with almost all

electronic gadgets coming with either a DVI or an HDMI port. Be it a graphics

card or a notebook or an LCD, you are bound to find at least one digital display

option. So, the shift is clearly toward a more enhanced digital experience

rather than regular analog displays. The emergence of Display Port, where you

can send audio and video signal on the same cable, is another kind of digital

display that is becoming quite popular. But still there is some more time before

analog finally sees the end of the day. We still find many products coming with

just a VGA display option. One positive in favor of analog displays is that not

only are they cost effective, but their over all visual experience is also

pretty pleasing. Even with the emergence of several digital display options,

analog will co-exist in the foreseeable future. But the race is hotting up to

give the end user, the best visual experience. Keep waiting for more such

options to unfold in the near future.