Audio and Video Definitions Part 4 of 4
Wed Feb 09, 2011 09:11
Audio and Video Definitions Part 4 of 4
VCR Plus -- A licensed proprietary system built into a VCR to make programming easy. The user punches in one number of up to eight digits, and the start time, day, duration, channel, etc. are computed and filled into the VCR's memory automatically. Generally the number that goes with each TV show is published in newspaper and magazine TV listings.
VCR/TV Switch -- See TV/VCR Switch
Vertical Banding -- An undesirable effect most noticed as visible vertical stripes of slightly different shades of a color where a solid color should be seen. Can be due to different causes, such as inherent shortcomings of a particular brand of LCD panel, or interference in a video signal.
Vertical Filtering -- Video production method used for such purposes as reducing flickering of very thin horizontal lines or objects particularly when they are part of subject matter moving up or down. It consists of blending the content of adjacent scan lines which of course reduces vertical resolution. It can be done optically, for example the telecine's flying spot is a bit larger than what should correspond to one scan line and captures the average of what it spans on the film, or it can be done electronically, for example scan line 1 as output is the mixture of lines 1 and 2 from the camera, scan line 2 is the mixture of lines 2 and 3, etc.
Vertical Retrace Interval; Vertical Blanking Interval -- The time during which the electron beam is moved from the lower right corner to the upper left corner of the screen to draw the next field. In NTSC video, 1.4 milliseconds, or enough time to draw 21 scan lines, has been set aside for this purpose and to insert information to synchronize the electron beam with the transmitted picture for maintaining vertical hold. Typically the electron beam draws 240 odd lines from top to bottom, then 23 lines while it returns to the top, then draws 240 even lines, then 22 lines during retrace, and so on. The exact number of lines blacked out by the TV during retrace and exactly where and how the 525'th line is drawn varies slightly depending on the program content and the make and model of the equipment. Once in awhile you see a TV picture criss crossed with several spurious diagonal lines slanting up from left to right. These are the vertical retrace scan lines mentioned above but due to a defect they were not made black enough. Vertical Blanking Interval is also used to refer to the non-visual-content data (if any) placed separating the blocks of data that represent fields or frames of video content in digital video.
Vertical Squeeze Trick -- (A.k.a. 16:9 mode on a 4:3 TV set) Adjusting the vertical size control (height control) downward so all the scan lines (the raster) occupy a space of the desired aspect ratio (usually 16:9). Used to play 16:9 enhanced DVD's on 4:3 TV sets yielding increased sharpness compared with using the 4:3 setting on the DVD player. Whether a particular TV set not intended to do so can use this technique is a matter of luck since the adjustment may be complicated or may have undesirable side effects such as misconvergence.
VESA (Video Electronics Standards Association) -- An organization which developed standards for video signals, in particular timing standards (in millisconds, microsecnds) for video signals used for computers and computer monitors. Also the standards developed by said organization.
VGA -- Video Graphic Array or ... Adapter -- An analog computer video signal format or equipment to produce or display same, using 480 visible scan lines each normally representing 640 pixels. The significance of this format is that the video signal is made up of the same total number of scan lines (525) transmitted at the same rate (scan rate) as NTSC video converted to a progressive scan format. If not confined to a broadcast channel, an (interlaced) NTSC video signal can also hold the detail of 640 or more pixels across. VGA signals cannot be sent directly into a standard NTSC video input. SVGA; Super VGA -- A computer video signal format with 800 pixels horizontally and 600 pixels vertically. We believe that this format was defined based on a video memory size of half a megabyte for 256 colors, or one 8 bit byte per pixel. XGA; Extended Graphics Array -- A computer video format with 1024 pixels horizontally and 768 pixels vertically. WXGA; Wide XGA -- A computer video format, 1366 x 768, for 16:9 aspect ratio screens. UXGA; Ultra XGA -- A computer video format, 1280 x 1024.
VHF-High, VHF-Low -- There is a frequency gap between the group of VHF TV channels 2-6 and the group 7-13. The former is referred to as VHF-Low and the latter as VHF-High. On some TV sets, the tuner controls treat these as two separate frequency bands and include a switch to select one or the other (and also the UHF band channels 14-69 as a third switch setting).
VHF vs. VHS vs. VCR -- Don't confuse these three terms. VCR refers to any video cassette recorder, including 8mm or Beta. VHS stands for Video Home System, first marketed by the Japanese Victor Co. (JVC). VHS refers to videocassettes with specific physical dimensions, tape dimensions, and recording format, and the recording equipment that uses such cassettes. A VHS cassette can contain programs in any of the formats NTSC, PAL, or SECAM, and purchasers of videos in gift shops should be aware of this. VHF (very high frequency) refers to a portion of the frequency spectrum, approx. 32 to 316 megahertz, used for broadcasting and includes TV channels 2-13.
Many uses of the word "Video" -- (1) "I see" in Latin, (2) Any electronic signal that represents visual information, or the electronics that process such signals, (3) A short three minute or so motion picture with a soundtrack typically consisting of a single popular song and usually presented on broadcast television programs or on videotape.
Video Processor -- Currently (2006) refers to a unit that converts interlaced video into progressive scan video (de-interlacing) and/or scales video (to have a different scan line count and/or different frame rate) and/or converts from one color space to another e.g. Y,R-Y,B-Y to RGB and/or may perform other processing. Currently the term specifically excludes units that do just comb filtering or do just the simplest de-interlacing by repeating (doubling, etc.) scan lines or do just color space conversion. Devices that do just the latter are called transcoders.
VTR -- Video Tape Recorder.
VOD -- Video On Demand. System which can carry television broadcasts but also allowing a viewer/subscriber to request a specific program to be transmitted to him at a specific time.
WAF (not a military term regarding women) -- Wife Acceptance Factor, q.v.
Water Heater Sub -- Subwoofer system in a cylindrical enclosure or cabinet, resembling a typical hot water tank.
Weave -- Method of de-interlacing where intervening scan lines are taken from the next field. A disadvantage of using the weave techique exclusively is that, when subject motion has occurred between two fields, the finished full frame will have moving subjects with fuzzy (comb-like) side edges. See, also, Bob.
White Flag -- The means whereby a (12") CAV laser disk of a 24 fps film program is encoded so that the even and odd fields match when the player displays a still frame. Without white flagging, the laser player may do a still frame with the odd interlaced field taken from what was one film frame and the even interlaced field taken from the next film frame. The result is a flickering double exposure effect. One consequence of correctly white flagged movies is that the laser player's frame counter will count 24 frames for one second's worth of playing time. NTSC programs not from film sources or that are not white flagged will count 30 frames for one second's worth of playing time. Similar flags are also sometimes encoded on DVD so the player can reconstruct full frames for progressive scan output.
White Level Control -- The contrast control on a TV set, sometimes labeled "picture". More specifically this control should vary the intensity level of white on the screen while not altering the intensity of what should be black, and should alter the various gray shades to maintain proportions. The effect is almost by definition varying the contrast.
Wide Screen -- Refers to a video program or movie whose picture has a wider aspect ratio than approximately 4:3.
Windowbox -- Refers to a video program where the picture is zoomed out so far that unused screen area appears on all four sides. The purported reason for doing this intentionally is to ensure that the entire picture can be seen even on TV sets with a lot of overscan. See, also, Letterbox, Pillarbox.
Wife Acceptance Factor -- A subjective measure of, or rather, explanation of, reluctance to purchase elaborate technology. So named because it is usually the husband who is more deeply interested in the equipment and its benefits and it is usually the wife who is more concerned about the cost of the equipment or how the equipment fits into the room decor when not in use.
Wobulation -- Hewlett Packard's trademark for its DMD technology (also a DLP manufactured by Texas Instruments) where the tiny mirrors have two to four slightly different active positions allowing one DMD panel to project superimposed slightly staggered sub-images of lesser resolution and therefore achieve twice(or even four times) the native resolution of the DMD panel. A current (2005) application is using a 960 x 1080 pixel panel to provide a 1920 x 1080 pixel picture. Since the better DLP (DMD) projectors already project 120 sub-images of each of the three colors every second for 60 fps video to reduce rainbow effects, this vertical interlacing is unlikely to produce artifacts that most people would notice. In order to achieve the best resolution the mirrors themselves must be small enough so that the pixels projected for one subimage do not overlap the pixels projected for another; there are already a few models where the pixels projected are too large.
Wow -- Repeated increase and decrease of pitch of the reproduced audio, under about two repetitions per second, due to non-uniform rotation of a (n analog) record or non-uniform linear speed of analog tape. (A higher repetition rate is referred to as flutter.)
Wow and Flutter -- A measure, expressed in percent of speed change where lower is better, of the expected non-uniformity of tape movement or turntable rotation for a given tape recorder or player or for a given phonograph.
WS -- Wide Screen, refers to pictures with aspect ratio greater than about 1.33:1.
X-Box -- Sony's trademark for a line of its video game units that include built in DVD players.
XGA -- 1024x768 resolution. See, also, VGA.
XM -- Trademark for a subscription satellite delivered wireless radio broadcast service, also shorthand for the name of the company (XM Satellite Radio, Inc.) that provides the service.
Y -- Video signal representing luminance, which by itself would represent the picture in black and white. Quantitatively, Y = 0.299R + 0.587G + 0.114B for NTSC, it is slightly different for U.S. HDTV.
Y/C -- Another name for S-Video.
Y/Cb/Cr -- Luminance and color difference video signals in digital form. See, also, Analog Component Video. Due to differing normalizing constants (proportioning) to optimize the video signal for digital or analog transmission, simply converting a standard Y/Cb/Cr signal to analog does not result in a standard analog (Y/Pb/Pr) signal and vice versa. Occasionally analog component video connections are incorrectly labeled Y/Cb/Cr.
YIQ -- The system of representing video as three subsignals, a kind of "component video": luminance, I or reddish orange to greenish blue color content, and Q or yellow green to purple content. See I, Q.
Y/Pb/Pr -- Luminance and color difference video signals in analog form. See Analog Component Video
YUV -- The system of representing video as luminance, U or approximately blue to yellow color content and V or approximately red to cyan color content.. Another name, not rigorously correct, for analog component video or Y, Pb, Pr. See U, V
Zoom -- Expansion or shrinking of a picture uniformly both horizontally and vertically, possibly cropping the sides and/or top and bottom, or the control on a TV set or projector or DVD player or scaler for performing said function. We refer to the spacing out or scrunching in of scan lines on a CRT as optical zoom. Electronic zoom, on an LCD or other fixed pixel display or keeping the scan lines on a CRT in the same places, requires scaling (upconversion, downconversion).