Display Wars: Digital Vs Analog

BANGALORE, INDIA: 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.

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.

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.

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.