Glossary for Professional Video

3:2 Pull-down
Method used to map the 24fps of film onto the 30fps (60 fields) of 525 line NTSC video, so that one film frame occupies three video fields, the next two, etc. In this way the film can play at a standard video rate. It means the two fields of every other video frame come from different film frames, this can cause problems in the editing process.

4:1:1 Sampling
A ratio used to describe the sampling frequency of a digitized signal. The ratio describes luminance as being sampled 4 times at 3.37 MHz, while color is sampled 1 time at 3.37 MHz in each of it's separate parts. DV,DVCAM and DVCPRO25 use 4:1:1 color sampling. Formulated as:Y (luminance) is sampled at 13.5 MHz (or 3.37 x 4), R-Y (color) is sampled at 3.37 MHz (or 3.37 x 1), B-Y (color) is sampled at 3.37 MHz (or 3.37 x 1) equals 4:1:1.

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AGC (Automatic Gain Control)
Circuitry that automatically adjusts the gain level providing optimum signal output and preventing potentially damaging circuit overload. AGC circuits are used in cameras and recording devices to maintain proper signal levels without requiring an operator to manually monitor controls.

Aliasing
During the quantization or re-quantization process, unnecessary artifacts may be generated due to interpolation (a method for generating inter-sample data using compulation). This phenomenon is called "aliasing", and the distortion it causes is called "aliasing distortion" or "fold-back noise". Aliasing distortion can cause smear or flicker on the image. 

Aperture
The iris opening in a lens that regulates the amount of light passing into a camera. The size of the aperture opening determines the amount of light that will get to the imager (CCD). The larger the opening, the more light that will enter. Aperture is usually defined in f/stops.
(See f/Stop, CCD)

Aspect Ratio
The ratio of height over width of an image: a standard video monitor has an aspect ratio of three units of height (vertical) to four units of width (horizontal). This is expressed as a 3:4 aspect ratio. Images will become distorted if forced into a different aspect ratio during enlargement, reduction, or transfer. The aspect ratio for HDTV is 16:9.

ATW (Auto Trace White Balance) (Camera feature)
ATW enables the white balance setting to change automatically according to lighting conditions. White balance will change quickly and undetected even when moving from an interior lit with practicals to an exterior lit with the noon sun. 

Authoring
The editing process used to create DVD software is called "authoring". Authoring includes the procedures necessary to encode the movie, graphics, text and sound data, etc. and to convert the encoded data as well as various control data into DVD-Video format data. The system used to perform authoring is called "Authoring System". 

Auto Iris (Camera feature)
A lens iris equipped with a photosensitive detector that can read changes in lighting conditions and automatically open or close the iris to compensate for the changes.

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Bandwidth

Beam Current Feedback (Sony) (Monitor feature)
A Beam Current Feedback circuit is built-in to make corrections for monitor white
balance drift. White balance on monitors without beam current feedback tends to drift during continuous use over long periods of time. 

Betacam SX (Sony) (Video Format)
The Betacam SX format is a digital broadcast format with exceptional quality and flexibility. Features a recording of 8-bit, 4:2:2 component digital signals using an advanced algorithm. Betacam SX uses Inter-frame, MPEG-2 4:2:2 Profile @ Main Level (MPEG-2 4:2:2P@ML), and a 9:1 compression technology on a 1/2" Metal Particle cassette. This compression scheme uses only I-frames and B-frames. The 4:2:2 color sampling structure helps to maintain the chrominance information necessary for postproduction, keying, and multi-layered effects. The format also includes four 16-bit/48 kHz, uncompressed digital audio channels. Betacam SX uses a Metal Particle formulation on a 1/2" tape stock, which is the same 1/2" size cassette as analog Betacam and Betacam SP giving the Betacam SX "A" designated VTR's playback capabilities with analog Betacam or Betacam SP. In fact, BCT and UVW analog tape stock can be used to record a digital Betacam SX signal. This feature gives current analog Beta users the ability to use existing analog stock footage for a digital edit, and helps to maintain the long-term value of an existing Betacam SP camcorder. Playback of analog DT (Dynamic Tracking) from -1 to +3 speed is maintained as well as playback of AFM (Audio FM) audio. The tape format includes an auxiliary track, video track, time code track, control track, and 4 audio sectors.
(See B-frame, I-frame MPEG)

B-frame (Bi-directional-frame)
Predictive frames composed by checking the difference between the previous and the following frames in a MPEG-2 signal. By itself a B-frame does not make up a complete picture. An entire sequence of MPEG-2 frames must be decoded to form a whole picture. A B-frame can also act as a uni-directional frame, if there is only one I-frame to reference in an edit. This is known as a BU-frame.
(See Betacam SX, I-frame, MPEG)

BIT (Binary DigiT)
Each bit represents either "0" or "1" and these can be combined to represent any number or character. In a digital system, the number of bits defines the accuracy of sampling; conventional CDs use 16-bit quantization, and this results in 16-bit "words".

BIT Rate
The amount of data transmitted in 1 second. The larger the number, the faster the transfer and the greater the amount of digital data that can be used for recording and storage. The DVD system uses the Variable Transfer Rate system for its MPEG-2 data compression (encoding), while the Video CD format uses the Fixed Transfer Rate with MPEG-1 compression. 

Bitstream
A sequence of digital data.BPI (Bits Per Inch)
Number of bits that can be recorded per inch of recording medium. 

BPS (Bits Per Second)
Number of bits that can be transmitted in 1 second

Black Stretch/Compress Function (Sony) (Camera feature)
With this function you can variably adjust contrast in the Black area of the image. Black Stretch emphasizes contrast in the dark area, while Black Compress enhances or deepens darkness. 

Byte
A group of bits – usually consisting of 8 bits – which a computer treats as a single unit. Normally one character is represented by one byte.

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C-47
Wooden clothespins. That’s right, every day wooden clothespins. C-47s are perfect devices for attaching diffusion material or gels to a lights barndoors (Never Use Plastic ClothesPins On A Light!). C-47s have a very low burn threshold and are surprisingly very strong. 

CCD (Charged Coupled Device)
A semiconductor that can produce an electrical output analogous to the amount of light striking each of its elements. CCD sensors (imager) are used in both motion video and still video cameras.
(See FIT, HAD, Hyper HAD, IT) 

CCIR (International Radio Consultative Committee)
Was a global organization responsible for establishing television standards. CCIR 601 was the standard for transmitting Digital Video Component information. The CCIR has now become the ITU.
(See, ITU)

Chrominance
The signals that represent the color components of an image. A black and white (monochrome) image has a chrominance value of zero.
(See Component Video, Color Difference Signal, Vectorscope, 4:1:1 Sampling)

Chroma Signal
Portion of a video signal that contains color information. 

Clear Scan (Sony) (Camera feature)
Clear Scan function enables recording of computer monitors without horizontal bands. This is done by precisely selecting a shutter speed to match the scanning frequency of the computer display. Shutter speeds from 60.4 Hz to 200.3 Hz can be selected in 183 increments.
(See Synchro Scan, Variable Scan) 

Color Difference Signal
The signal remaining after the Y (luminance) signal is subtracted from each of the R/G/B signals. The color difference signal represents the hue (tint) and color density. Generally represented by PB and PR .
(See Component Video, R-Y B-Y, Y)

Comb Filter (Monitor feature)
Chrominance and Luminance detail are preserved with the built-in Comb Filter. Prior to reaching the electron gun, the composite video signal is broken down into its separate luminance and chrominance signals as it passes through the comb filter, which reduces dot crawl and signal error.

CMOS (Complementary Metal–Oxide–Semiconductor) and CCD (Charge-Coupled Device) technology were developed roughly at the same time. By some accounts, CMOS technology pre-dates the CCD by six years; (1963 and 1969 respectively.) Source B&H Email Newsletter (To CCD or to CMOS, That is the Question By Kyle Doris)

Component Video
Each individual component of the video signal is transmitted separately. Transmission methods include the R/G/B method, which transmits the R (red), G (green), and B (blue) signals separately, and the Y/PB/PR method that transmits Y (luminance) signal and PB/PR (color difference) signals separately.
(See Color Difference Signal, R-Y B-Y, Y)

Composite Video
A single video signal that contains luminance, color and synchronization information.
(See Sync)

Compression Ratio
The ratio of the amount of data in the original (uncompressed) digital video signal to the amount of data after compression. The resulting picture quality can vary considerably, depending on both picture content and compression method.

CP (Content Package)
(See SDTI-CP)

Crosstalk
Spillover of audio or video information from one recorded track to another.

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D9/Digital S (JVC) (Video Format)
D9 (Digital S) records on 1/2" D9 digital tape stock. The D9 component digital format uses 4:2:2 color sampling, 8 bit component processing, a data rate of 50 Mbps, and 3.3:1 DCT (Discrete Cosine Transfer) based compression. All of which add up to give you a very clean, digital broadcast quality.

D/A Converter (DAC) (Digital-to-Analog Converter)
Converts (decodes) a digital signal into an equivalent analog signal.

Decibel (dB)
A logarithmic unit used to express the ratio between any two levels; normally used to show the difference between two sound levels. Because it is expressed on a logarithm scale, it is convenient for comparing values, which are considerably different.

DPR (Dual Pixel Readout) (Sony) (Camera feature)
Combines the luminance output of two adjacent pixels. With DPR, the light sensitivity is doubled (equivalent to +6 dB Gain) without an increase in noise. This is unlike conventional cameras where the use of electronic gain up in low light amplifies noise as well as the video signal. DPR can be used in combination with Gain-Up modes of +18 dB, +24 dB for video level equivalents of +24 dB and +42 dB, while suppressing the noise level. In Hyper Gain, the camera's gain automatically sets itself to +42 dB, and DPR kicks in, giving a gain equivalent to +48 dB without the extra noise.

DPR Plus (Sony) (Camera feature)
DPR Plus (Dual Pixel Readout) will increase sensitivity to four times of normal by reading an electronic charge of four adjoining CCD pixels. A high signal-to-noise ratio can be obtained with only a small loss of quality when Turbo Gain is used in conjunction with DPR Plus.

DVCAM (Sony) (Video Format)
The DVCAM format uses 8-bit component digital recording at 25 Mbps, with Intra-frame 5:1 compression and 4:1:1 color sampling. A 15-micron track pitch provides superior picture quality, superb multi-generation capability and production flexibility. Two 1/4" ME cassette sizes are available: Standard and Mini. The Standard size cassette will hold up to 184 minutes of information while the Mini cassette will hold up to 40 minutes of information.
(See Compression Ratio)

DVCPRO-25 (Panasonic) (SMPTE 321M) (Video Format)
The DVCPRO-25 format specifications were developed in 1994. The format uses a 1/4" MP tape stock to record a digital component signal. The data is sampled at a 4:1:1 rate and uses 8-bit quantization at 25 Mbps. With an 18-micron track pitch and an analog control track, DVCPRO-25 is a very accurate format for editing.
(See Compression Ratio)

DVCPRO-50 (Panasonic) (Video Format)
The DVCPRO-50 format uses a 1/4" MP tape stock to record a broadcast digital component signal. The data is sampled at a 4:2:2 rate and uses 8-bit quantization at 50 Mbps. 4:2:2 color sampling is useful for clean chroma keys, and multi-layered effects. With an 18-micron track pitch and an analog control track, DVCPRO-50 is a very accurate format for editing.
(See Compression Ratio)

DynaLatitude (Sony) (Camera feature)
Based on the TruEye system, DynaLatitude adaptively manages the contrast of each pixel according to analysis of the video signal level distribution. This brings a new dimension to technologies like Dynamic Contrast Control (DCC) which controls the dynamic range of video signals. DynaLatitude optimizes video level distribution based on signal histograms to make the most of the limited dynamic range of the video signal. Even in difficult lighting situations picture quality will be greatly improved. DynaLatitude is adjustable in four steps via a GUI (Graphic User Interface) and menu system: LOW, MID, HIGH, and OFF.
(See TruEye)

Dynamic Range
The difference between the maximum signal level and the noise floor in electronic equipment, represented in dB.
(See Decibel)

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EZ Focus Function (Sony) (Camera feature)
Let’s you focus precisely without stopping down the lens. EZ Focus automatically opens the iris, reducing the depth-of-field, making critical focusing easier. At the same time, the shutter is automatically set to obtain the correct light level. EZ Focus is overridden while recording.

EZ Mode (Sony) (Camera feature)
By pressing the EZ Mode button, the camera is instantly set to a standard or auto position. The camcorder has a choice of two EZ Modes - Standard or Custom. When set to Custom, the camera setting is changed in accordance with the selected menu setting. There is a Switch Guard to prevent misoperation of EZ Mode, Auto Iris and ATW buttons. The guard has tiny holes so you can see the LED indicators for the buttons while shooting.

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Field
In NTSC, each frame of video is made up of 525 lines. Two 262.5 horizontal line fields equal one frame. Each field represents either the even or the odd lines of a complete frame. A scanning system that uses even/odd field pairs is defined as an interlaced scanning system. A field equals one-half of a complete television scanning cycle (1/60 of a second NTSC; 1/50 of a second Pal/SECAM). When interlaced, two fields combine to make one video frame with a scanning cycle of 1/30 of a second at a rate of 1/30 of a second in NTSC.
(See Frame, Interlaced, NTSC, PAL, SECAM)

Firewire(Apple Computer) (IEEE-1394)
A communications protocol developed by Apple Computer, which provides for the fast transmission of data, video, audio, and power over a single cable. Data is transmitted at 400 Mbps (400 million bits per second).
(See i.Link)

FIT (Frame Interline Transfer)
A type of CCD technology, which dramatically reduces vertical smear as compared to IT, type CCDs.
(See CCD, IT)

Frame
A complete TV picture consisting of two interlaced fields. The NTSC system scans 525 lines with an electron beam and occurs at a frequency of once every 1/30 of a second.
(See Field, Interlaced)

f/Stop
A calibrated measure of aperture lens opening. f/Stop is a numerical relationship between the diameter of the lens opening and the focal length of the lens. Common f/Stops include f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22. The higher the number, the smaller the lens opening and the less light falling on the imager (CCD). In low-light situations, a large aperture (e.g. f/1.4) would be needed.
(See Aperture)

Full Auto Shooting (JVC) (Camera feature)
Full Auto Shooting (FAS) mode for point-and-shoot ease of operation. You simply zoom and focus. Activating the Full Auto Shooting sets the camera to the Auto Iris Mode, even if the lens is set to manual. Automatic video level control (ALC) is also activated, along with Extended Electronic Iris (EEI) and Full Auto White, which provide both variable gain and variable shutter. Shoot continuously from a dark area to a bright area without changing Gain, Iris or ND filter.

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Genlock
Circuitry that synchronizes the television signal source of two or more devices at the vertical, horizontal, and chroma phase levels such that the signals may be cut, mixed, or cross-faded without noticeable roll, jump, or chroma shift. All video signals contain synchronization pulses that are used to reconstruct the picture on a CRT (monitor). When several signals are used together through a common device such as a production switcher, they all must be operating on the same sync. A Master Sync generator provides genlock to signal generating devices (cameras, VTRs, switchers) so that they can operate in sync.
(See Sync)

Good Shot Marker (Sony) (Camera feature)
Data such as Date, Time, Camera ID, Cassette Number and Shot Number can all be recorded during the acquisition process. Shot Data can be used to quickly retrieve material during editing. A "Record Start Mark" is automatically placed on the tape each time the VTR Start button is pressed while the VTR is in standby mode. A Good-Shot Marker can be added at any time by pressing the return button on the side of the lens while in the record mode. These marks will appear highlighted as picture stamps (thumbnails) on the GUI of the Sony Non-linear Editors. Using picture stamps helps to eliminate tedious searching through recorded material, and saves hard disk space by downloading only the scenes selected by editors.

GOP (Group of Pictures)
P and/or B-frames between successive I-frames in an MPEG signal. A GOP is usually about 15 frames long in an NTSC system. The length of a GOP can vary depending on editing needs. The length of a GOP represents the editing capability of an MPEG signal. If an edit accurs within a GOP, an MPEG decoder/recoder will be needed to reclose the GOP. A GOP must begin with an I-frame and end with an I-frame, therefore if a cut accurs in the middle of a GOP, the signal needs to be reconstructed with a decoder/recoder.
(See B-frame, I-frame, MPEG P-frame)

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HAD (Hole Accumulated Diode)
A CCD sensor developed by Sony with improved performance in spectral response, vertical smear, and sensitivity. The introduction of the HAD sensor also allowed for electronic shuttering capabilities to IT type sensors.
(See CCD, HyperHAD, IT)

Horizontal Blanking (Retrace)
The process of bringing the electron beam in a CRT back to the left side of the screen after a left to right line has been traced on the screen. The beam is shut off (blanked), during the period of retrace. About 83% of the total horizontal line time is spent writing the line. The remaining 17% is spent bringing the beam back to the left side; retrace, before starting the next line.
(See Field, Frame, Interlaced, Waveform Monitor)

Horizontal Resolution
The ability of a system to reproduce closely spaced alternating black and white vertical lines of detail across the screen. The number of alternating black and white lines is divided by the aspect ratio to make comparisons between horizontal and vertical resolution easier. This number is usually expressed as TV lines per picture height.
(See Aspect Ratio)

HyperHAD
A derivative of the HAD sensor that incorporates On Chip Lensing (OCL) technology, and the use of microscopic lenses mounted over each sensing pixel. Hyper HAD sensors with OCL have no perceptible smear and nearly doubled sensitivity.
(See CCD, HAD, IT)

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IF Lens