HDMI™

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HDMI™ stands for High-Definition Multimedia Interface. This technology carries the same video information as DVI but adds the capacity for digital audio and control signals as well. The current version of HDMI™ carries one TMDS link of digital video. Found on many home-theater/consumer electronics devices, HDMI™ uses a 19-pin connector that is held in place by friction. This connector is technically described as a Type A HDMI™ connector. The Type B connector is larger (28 pins), but it is not currently used by any devices in the marketplace. HDMI™ is the interface of choice for most newer HD A/V devices. Not only does it provide outstanding audio and video performance, but it also supports High-bandwidth Digital Content Protection (HDCP), a technology built into consumer electronic equipment that prevents illicit duplication of copyrighted material.

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Component Video

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Component video is the most common type of connection used for high-quality images. A component video signal has three parts, or “components”. These are commonly called Y, Pb, and Pr. The Y signal is luminance — just like S-video. The Pb and Pr signals are called color difference signals. Basically, Pb is blue minus the Y signal, and Pr is red minus the Y signal. These “components” are put back together by a display to produce a bright, highly detailed image. Most DVD players produced nowadays have component outputs; and all HD tuners and HD sets have component connections. Component video is capable of producing High Definition signals - composite and S-video cannot.

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S-Video

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S-video is a video signal format that used to be known as S-VHS or Super VHS. It was developed in the 80s by JVC as a response to attempts by Sony to corner the VCR market with their Beta technology. S-video is superior to composite video in that it separates the brightness/resolution (luminance) and color (chrominance) into separate signals for a sharper picture. This lets the video signal bypass the circuitry in the display (called a comb filter) that separates luminance & color signals, which helps maintain signal integrity. S-video typically uses a 4-pin mini-DIN connector.

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Composite Video

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The most basic type of video signal is composite video. All of the picture information is carried on a single conductor. Most composite video cables use 75Ohm coaxial wire, with a single RCA connector on each end. This RCA plug is usually colored yellow.

Composite video is found on many types of devices. Virtually every TV will have composite inputs, as well as VCRs, DVD players, and cable boxes. Other devices that use composite video include camcorders, RF modulators, and security cameras.

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Digital Coax Audio (S/PDIF) & Toslink Digital Optical Audio

The interface for digital audio in the consumer market is called S/PDIF, or Sony & Philips Digital Interface Format (S/PDIF). Development of the digital format began in the 80s, when the Compact Disc hit the market, and manufacturers sought a way to keep the information on a CD in the digital realm for as long as possible in order to preserve signal quality.

There are two primary connections used by digital audio — coaxial and optical. A digital coax connection is a single RCA jack, and uses a 75Ohm coax cable. The optical interface uses a rounded connector commonly called Toslink. There isn’t a performance advantage to either method — bits are bits, and the same digital information is carried. Optical cables are not electrically conductive, so there is no possibility of a ground loop that could potentially cause hum/buzz in the amplifier, while digital coax has an edge when it comes to cable length. Digital optical cables are limited to about 5 meters in length, while digital coax can go much longer — up to 100 feet and beyond.

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Dual Channel RCA Audio

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There are two main types of analog audio signals used in home theater applications — low level (also called line-level) and high level (or speaker level). The difference between the two is where the amplification of the signal occurs. Line-level signals carry sound from one place to another before it is amplified; after amplification, the sound becomes a speaker-level signal that moves from the amp/receiver to the speakers.

Line-level interfaces are found on many kinds of equipment. You have probably seen them on VCRs, DVDs, cable boxes, DVRs — anything that produces an analog audio signal. The most common connection is an RCA jack, and they are usually colored red & white (for left & right channels). Some equipment has more than two jacks — if a component (like a DVD player) can produce a 5.1 surround signal, then it will have at least 6 output jacks — one for each channel of audio.

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What is resolution?

720p, 1080i, and 1080p — making sense of numbers and letters

The big reason why HDTV looks so much better than regular old TV is because of resolution. Resolution is a measure of how much detail a video screen can produce. The higher the resolution, the better the picture looks. Normal TVs have a resolution of 480 lines. That means that if you imagine tiny horizontal lines stretching across a TV screen, there will be 480 of them stacked from top to bottom. In contrast, a high-definition TV produces either 720 or 1080 lines, depending on the way it was designed and manufactured.

Either resolution setting (720 or 1080) gives you an astonishing improvement in picture quality. What do the p and i stand for in resolution settings like 720p, 1080i, or1080p? Those letters stand for progressive and interlaced, respectively. A progressive display shows all lines in an image several times per second, while an interlaced display only shows half of the lines (every other one) during the same time. Progressive displays typically look better than interlaced, especially when there’s a lot of motion on the screen.

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What is aspect ratio?

Size does matter!

One of the first things you may have noticed about your HDTV is that it isn’t shaped like older TV sets. Your new set is more rectangular in shape — a design called widescreen. The technical term for the shape of a screen is called aspect ratio — the relationship between the width and height of the TV’s display. Standard, older model TV sets use a 4:3 aspect ratio, while newer, widescreen sets have a 16:9 aspect ratio. Check out the figure below. Most movies are filmed in widescreen aspect ratio, and many TV shows are now being shot this way as well. A widescreen picture is more comfortable to look at — think of your own field of vision, for example. You basically see the world as a big rectangle, so a widescreen TV picture is a more natural adjustment for your eyes.

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What is surround sound?

Hear what you've been missing!

When you go to a first-rate movie cinema, you know that what you see is only half of the experience. Sitting in a darkened theater watching a World War II movie, you can get a feeling of storming the beaches at Normandy by hearing bullets whizzing behind you while explosions rumble in the distance. Or imagine a scene in a suspense thriller, where the heroine is walking alone in the woods at night — you know in a second that the monster is lurking off to the left, because that’s where the sound of a twig snapping comes from. The fact that you are “surrounded” by sound makes the action seem closer and really adds to the emotional impact of the movie. This concept of being immersed in sound is called surround sound.

The surround sound technology was pioneered back in the 1950s by Dolby Laboratories and actually became a widespread practice in the 1970s. Movie studios added extra audio tracks to a film that played on speakers located at the rear and sides of a cinema, creating a more realistic “sound field” that enveloped the audience and enhanced the whole experience.

In 1997, Dolby introduced a sophisticated format for surround sound called Dolby Digital. Dolby Digital can send up to six channels of sound to different speakers positioned throughout your home theater: left, right, center, right surround, left surround, and subwoofer. Check out the placement of a 5.1 surround sound in the figure below.

Most A/V equipment comes with decoders that can handle both Dolby Digital and other surround sound formats, such as DTS. Deciding which one works best for you is a matter of personal taste; your best option is to find a DVD or other source material that’s encoded with different sound formats, and play them. You can then decide for yourself which one you prefer.

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What is DTV and HDTV?

One letter makes a big difference.

Are HDTV and digital TV the same thing? It’s a confusing question. The basic answer is that all HDTV broadcasts are digital, but not all digital TV (DTV) broadcasts are high-def. Does that clear everything up? Didn’t think so. Here’s some more details.

A standard broadcast format for color TV, called NTSC (National Television System Committee), was put in place in 1953. Having a standard TV format is important, because then people know that their TV set is going to work properly. The NTSC standard broadcast format uses an analog signal, where the wave form of the electrical signal composes the message that is being sent. Analog relies on the characteristics of an electrical wave (such as frequency, wavelength, and amplitude) to transmit information. Well, for a variety of reasons, it became necessary to upgrade the system to something that works a bit better for more people.

In the 1990s, a new standard called ATSC (Advanced Television Systems Committee) was developed based on digital signals, where TV broadcasts were sent in the form of digital 1s and 0s. This ATSC format provides the capability for high-definition TV broadcasts. This committee was made up of a group of engineers and other technical people who developed a set of rules that define digital television. High-definition TV was one of the technologies that they helped to develop.

When the ATSC group got together years ago, they decided that one of the provisions of the new digital signal format would be enhanced resolution, widescreen aspect ratios, and high-quality surround sound. In other words, high-definition TV! However, not every single program or event broadcast using this digital format is recorded or displayed in HD. A lot of content, especially locally produced shows and reruns, is shown in plain old standard definition. The show may look good on your HDTV, but technically it’s still not high definition.

So digital TV is a way of broadcasting TV signals. HDTV is a form digital TV that offers higher resolution. All HDTV is DTV. Not all DTV is HDTV.

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