Simple glossary of video and connection terms:
Click on the following to jump to its definition:
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A-to-D Converter (Analog-to-Digital):
Electronic equipment used to change or convert an analog (waveform style) signal into a digital signal (made up of 1s and 0s). Analog signals take the form of a wave like a sine wave. If you take a pen and draw on a sheet of paper a continuous line that bends up and down like a wave or serpent you will see a graphic depiction of an analog signal. Analog signals are constant, continuous waveforms.
Digital signals, on the other hand, are made up of discrete ones and zeroes. The ones stand for an "on" state and the zeroes for an "off" state. They do not form continuous waves like the analog signal, however, they are much easier to manipulate than analog signals and they do not degrade with such manipulation. For instance, it is very simple to multiply a digital signal, split it up, invert it and then send it to multiple locations. An analog signal, however, is much more difficult to affect in a similar way and during the process the waveform is altered and noise is added resulting in an impure signal.
Analog signals are converted to digital signals for a variety of reasons including to improve processing power (the ability to manipulate the signals), to encode analog signals for later playback through a digital medium (such as a CD or DVD), and more. The conversion process entails breaking up the analog waveform into thousands of narrow, individual pieces. Each of these pieces is the height of the wave at that point. By cutting the wave into many, many sections the heights of the pieces very closely track the wave. Think of a pyramid in Egypt - from a distance the pyramid's sides look like they are solid, straight lines. However, when you get close to the pyramid you see that the angles are actually made up of hundreds or thousands of individual blocks. The lines up the pyramid are not exactly straight but are actually stair-stepped. The digital signal derived from an analog waveform operates in the same way. It is stair-stepped like the pyramid but has so many steps that it seems to form a continuous line like the pyramid from a distance.
The job of the analog-to-digital converter is to take the waveform (the analog signal) and split it up into the thousands of tiny "stairs" which simulate the wave. Once the signal is in the digital domain, it can be easily copied nd manipulated with no degradation and with enhanced capabilities.
Also see D-to-A
Method of transferring video information using multiple, individual signals such as red, green and blue (RGB) or luminance, luminance minus blue, and luminance minus red (Y-Y/B-Y/R or Y-Pb-Pr) resulting in the highest quality signal transfer and lowest distortion.
Component video is a feature of DVDs allowing video information to be transmitted in its individual pieces for perfect reproduction without errors due to combining and then separating the various parts of the color video signal. Component video uses three coaxial video cables with RCA connectors (some components use BNC connectors) to transfer the three signal components. This allows the signal to bypass the distortion-prone process of breaking the signal up into its various components and instead go cleanly to reproduction of the image. Component video is the best method presently available to the consumer for transferring video signals. Only some DVD players and a relatively few number of video displays feature component video connections.
Component jacks; red, green, blue
Component plugs; red, green, blue
Video information is carried in a single signal combining color and brightness information into the one signal. Composite video is transferred between video devices using a single interconnect cable with an RCA connector
DAC (Digital-to-Analog Converter):
Electronic device that decodes digital data (ones and zeroes) into an analog waveform electrical signal that can be amplified and played by loudspeakers (or that can be used by a video display to form an image in the case of video DACs).
When an analog signal is recorded onto a digital medium, it is split up into thousands of very thin slices. Each of these slices is given a height and an order, and then the information is digitally stored. When digital signals are played back, the thousands of slices are lined up in the proper order. The digital to analog converter forms a solid, flowing line from the tops of the slices to create a continuous, analog waveform. This process can be seen in the pyramids. Each pyramid is made of thousands of blocks forming a stair-step pattern up the side of the structure. However, from a distance, the individual blocks blend together to form what appears to be a straight, continuous line. If you drew a line up the ends of the blocks, you would get that same straight line. Digital encoding works the same way. It would save a triangle like a pyramid as a series of slices or blocks of varying height. When decoded, a line would be drawn from block top to block top recreating the pyramid.
The important thing is having enough individual slices to accurately portray the analog data. The digital medium must have a high resolution - just like with a video display you can see the individual picture elements at low resolutions but at high resolutions they merge to form a complete, high-quality image. The number of samples (individual slices) varies by the sampling rate, which is given in kilohertz (44.1 kHz is the sampling rate for common CDs). The higher the sampling rate, the more individual slices of the signal are created. The digital-to-analog converter uses the individual pieces to recreate the original analog signal and thus allows digital music to be played over analog loudspeakers (all speakers and amplifiers operate on an analog level).
The other important aspect when decoding an analog signal from a digital format is the quantisation. The quantisation is measured in bits. The number of bits used is often referred to as the word length. For each sample or slice of the analog signal, the height of the sample must be given. Quantisation works by taking the maximum signal level and dividing it up into pieces. These pieces are used to measure the height of the sample similar in effect to using a ruler with inch markings. The greater the word length (more bits used), the finer the measurement markings. Using a small number of bits is like measuring using only inches while using a high number of bits is like measuring uses millimeters - using more, smaller units allows more precision and equates to a more accurate signal.
Most digital playback devices (CD, DVD, laserdisc, etc.) include a digital-to-analog converter. There are also separate DACs available that use higher quality components than those typically found in digital playback devices allowing an improvement in sound quality. Any CD player, DVD player, laserdisc player or other digital playback component with the proper digital output can be linked to an external DAC to improve its sound quality.
Also see A-to-D Converter
DVI : digital video interface:
This is a digital only connection which is not commonly in use at this time. It requires that the display device and the source device have compatible DVI connectors and that an appropriate 24-pin cable be used. Currently, its use is limited to computers and the displays connected to them
HD vs digial:
HD simply refers to the lines of resolution that a device can record, transmit and display which is either 720 or 1080. [Standard, or SD, is 480 (viewable).] HD is digital, but digital is not necessarily HD. As of this writing, the federally mandated change-over to digital to take place by 2007 is simply the digitization of an SD signal (480). Please be aware that today's existing analog display devices (mostly tube TVs) will not be able to display a digital signal. Either the device will need to be replaced, or a converter will be required to change the digital signal to analog (at a loss of image quality)
Also see resolution
The High-Definition Multimedia Interface (HDMI) is an all-digital audio/video interface capable of transmitting uncompressed streams. HDMI is compatible with High-bandwidth Digital Content Protection (HDCP) Digital Rights Management technology. HDMI provides an interface between any compatible digital audio/video source, such as a set-top box, a DVD player, a PC, a video game console, or an AV receiver and a compatible digital audio and/or video monitor, such as a digital television (DTV). In 2006, HDMI began to appear as a feature on "prosumer" HDTV camcorders and even high-end digital still cameras.
t is a modern replacement for older analog standards such as RF - coaxial cable, composite video, S-Video, SCART, component video and VGA, and the consumer electronics replacement for older digital standards such as DVI (DVI-D & DVI-I).
Firewire (also know as IEEE1394, i.Link and Lynx):
An interface standard adopted by the Institute of Electrical and Electronics Engineers for very fast (400 megabits per second) digital data transfer, especially of streaming video. In A/V applications, tiny but robust 1394 connectors have so far been used mostly for digital camcorder outputs, but they will become extremely important in computer controlled home entertainment or communication or appliance networks.
For the purposes of this glossary, it is meant to refer to the number of horizontal lines are to be displayed by a given device (TV, LCD, plasma, etc.) The two numbers that refer to lines of resolution we're interested in are 480 and 1080, although there are others between these two. Each number can be either i or p (as in 480i or 480p). i means that the display device is interlacing the image you see, only "drawing" half the picture per sweep of the electron gun across the face of the picture tube. p means the entire picture is "drawn" all at once. Generally, p type displays create a better image. [Note: Line doublers take an i device and change it into a p -- it does not actually double the number of lines of resolution!] All solid state devices (plasma, LCD, etc.) are p. Solid state device also have a "native resolution". This means they can ONLY display the data from a source device (DVD, cable, VCR, etc.) at the resolution it is rated for -- which is NOT necessarily the same resolution the source device is supplying. So, if a 1080p plasma is being fed data from a source that is sending it less than 1080p, the display device must extrapolate the extra data needed to fill the screen - thereby creating artifacts, pixellation and various other unwanted noise phenomena. Please keep in mind that the lines of resolution for various sources are: VCR tapes - 200, cable and broadcast TV - 480, DVD discs - 525. The point is that there is virtually nothing on the market, at this time, in terms of sources, that is capable of adequate driving a 1080p (or 1080i, for that matter) display device. Therefore, buying the latest greatest 1080 product (also referred to as a 1024x1024 device in the plasma world) would only really be practical when there is a reasonable number of sources that can drive it properly
Method of transmitting video signals by separating out the chrominance (color) and luminance (brightness) portions of the video signal resulting in superior picture quality versus composite video
Also see Y/C
VGA (also know as SVGA, XGA, QVGA and others):
A connection type maily used for computers and computer monitors. Some plasma and LCD screens have VGA inputs to allow a computer to use such a display device as a big screen
Y/C : Luminance (Y) and chrominance (C):
Type of video signal transmission format that separates the color portion of the signal (chrominance) from the brightness portion of the signal (luminance) resulting in higher picture quality compared to composite video, which combines the two into a single signal. A Y/C connection is often known as a S-Video connection. These cables carry the brightness and color information on two separate wires.
When the two pieces of information are combined, as in a composite connection, they must be separated at the television by a comb filter or a notch filter. This separation results in some level of distortion. By separating the chrominance (color) from the luminance (brightness), the distortions encountered by separating them can be eliminated.
S-Video VCRs store video information as separate chrominance and luminance signals so that they benefit particularly from using Y/C or S-Video connections. Laserdiscs store video information as a composite signal so Y/C connections may or may not benefit the picture quality. If the laserdisc player's filter for separating the Y/C information is better than the television's then using the Y/C connection is beneficial, but if the television's filter is better then using composite video is preferred allowing the superior TV filter to separate out the signals. DVDs store video information in yet another format.
DVD video signals are split up into three components (hence the name used - component video). The three signal components are the luminance (Y), luminance minus red (Y/R or Pr), and luminance minus blue (Y/B or Pb). These three components are labeled on the player as YUV, Y-Y/B-Y/R, or Y-Pb-Pr. The component video signals can create a picture free of distortions from dot crawl, color bleed, and other common distortions from combining and then separating the video signal components. A DVD player combines the luminance minus red and luminance minus blue signals into the chrominance signal for Y/C video. This results in excellent quality, but the ultimate in picture quality from DVD can be had by using component video outputs (which use three separate coaxial interconnects with RCA connectors instead of a Y/C's single connector with two individual conductors in one wire).
Also see S-Video
Last updated: September 4, 2009