| 16x9 |
(16
by 9) A wide screen television format in which the aspect ratio of the
screen is 16 units wide by 9 high as opposed to the 4x3 of normal TV. |
| 3:2 Pulldown |
The
technique used to convert 24 frames per second film to 30 frames per
second video. Every other film frame is held for 3 video fields resulting
in a sequence of 3 fields, 2 fields, 3 fields,2 fields, etc. (See Fields,
Frames). |
| 4:1:1 |
The
sampling ratio used in the DV or DVC (Digital Video, Digital Video Tape)
digital video signal. For every 4 samples of luminance there is 1 sample
each of the colour difference signals, R-Y (Red minus Luminance) and B-Y
(Blue minus luminance). |
| 4:2:0 |
The
sampling ratio used in some variations of DV digital video signal. For
every 4 samples of luminance there is a sample of one of the colour
difference signals, followed by a sample of the other colour difference
signal on the next luminance sample. |
| 4:2:2 |
The
sampling ratio used in the D1 (CCIR 601) digital video signal. For every 4
samples of luminance there are 2 samples each of the colour difference
signals, R-Y (Red minus Luminance) and B-Y (Blue minus luminance). |
| 4:4:4 |
A
sampling ratio that has equal amounts of the luminance and both
chrominance channels. Can also be used for RGB sampling, the colour space
used in most computer programs. |
| A/B roll edit |
An
edit in which two or more players are used to create special effects such
as dissolve and wipe, and one recorder is used to record the results of
the edit. Using an editing controller allows efficient control of the VTRs
and very precise editing. |
| AES/EBU |
The
digital audio standard set by the Audio Engineering Society and European
Broadcast Union and used by most forms of digital audio from CDs to D1. |
| Aliasing |
Defects
in the picture caused by too low a sampling rate or poor filtering.
Usually seen as "jaggies" or stair steps in diagonal lines. |
| Anti-aliasing |
The
process of removing aliasing artefacts. |
| Artefact |
A
visual effect caused by an error or limitation in the system. |
| Aspect Ratio |
The
ratio of width to height in a picture. Cinema screens generally have an
aspect ratio of 1.85 to 1, widescreen TV (16x9) is 1.77 to 1, and normal
TV (4x3) is 1.33 to 1. |
| Bandwidth |
Bandwidth
The amount of information that can be passed through a given circuit in a
given time. In the case of video, the larger the bandwidth the greater the
picture detail can be. It is a measure of the finest detail that can be
recorded and played back (resolution). |
| Blanking |
The
part of the video signal that contains no picture information. Used for
synchronising, timecode, closed captions, etc. |
| Bridging connection |
A
connection that allows a signal input to an input terminal to pass through
the unit and exit from an output terminal as input to external equipment.
Also called loop-through connection. |
| Broadcast Quality |
A
nebulous term used to describe the output of a manufacturer's product .
Usually at least means that the technical specifications meet the FCC
rules for broadcasting. |
| B-Y signal |
A
chrominance signal determined by subtracting the Y (luminance) signal from
the B (blue) signal. This is one of the component signals. |
| CBR |
Constant
Bit Rate. A variety of MPEG video compression where the amount of
compression does not change. |
| CCIR 601 |
The
standard for digitising component video. Also sometimes called D1 after
the VTR format that first used this signal. (see also 4:2:2) |
| Chrominance |
The
signal which carries the colour information in video. |
| Chrominance signal |
Colour
signal containing colour information such as hue and saturation. Also
called C signal. |
| Colour Frame |
A
sequence of four fields (2 frames) of NTSC video. Since the phase of the
colour sub-carrier reverses every frame in NTSC (which makes the colour
information essentially invisible on a black-and-white receiver) two
complete frames are required to carry a complete sequence of colour
information. So the cycle consists of two frames (four fields) in NTSC
format and four frames (eight fields) in PAL format. |
| Colour framing |
Maintenance
of continuity in the colour sub-carrier phase between one frame and the
next, for the purpose of avoiding noise on the picture. |
| Colour Sub-carrier |
The
portion of the video signal that carries the colour information. Colour
signals are quadrature modulated onto a sub-carrier of 3.579545 MHz in
NTSC. |
| Component Video |
A
video signal in which the Luminance and Chrominance signals are kept
separate. This requires a higher bandwidth, but yields a higher quality
picture. |
| Composite Video |
The
luminance and chrominance signals are combined in an encoder to create the
common NTSC, PAL or SECAM video signals. Allows economical broadcasting of
video. |
| Control Track |
The
is a signal recorded on the video tape which is used to sync up the VCR
during playback. It allows a video tape to play back at a precise speed in
any VTR. |
| D1 |
is
a component format. The extremely high cost of D1 recorders limits their
use to only the very elite production facilities that incorporate many
special effects with multiple layering of the video signal. Such special
effects layering does not degrade the image quality in the pure D1 digital
environment. While most professional grade digital video is sampled at a
rate of 4:2:2, or 4 samples of Y, 2 of (R-Y), 2 of (B-Y), D1 is 4:2:2:4.
This 4:2:2:4 sampling permits an alpha (transparency, or linear keying)
channel to be recorded. (Sampling Ratio 4:2:2:4; max. Data Rate= 270Mbps;
Bits Per Sample= 8 or 10; Compression= none) |
| D2 |
This
is a composite format, but the quality is so high that signal degradation
due to the mixing of video information is kept to a minimum. D2 is not a
pure digital format, as the inputs and outputs are standard analog
composite ports. Although this may degrade the digital signal somewhat, it
does offer the advantage of integrating D2 with other existing equipment.
Professional composite recorders use 4:0:0, because they sample the
composite picture-imbedded colors and all-4 times, then 4 more times, etc.
Since there are no color components, to sample, the other numbers are
zero. (Sampling Ratio 4:0:0; max. Data Rate= 143Mbps; Bits Per Sample= 8;
Compression= none). |
| D3 |
D3
is also a composite format like D2. (Sampling Ratio 4:0:0; max. Data Rate=
143Mbps; Bits Per Sample= 8; Compression= none) |
| D5 |
This
is a component format rather than composite. D5 is the newest digital
format and its common use and acceptance have yet to be determined. All
digital formats on this page sample the Y component at 13.5 MHz but D5 is
switchable to 18 MHz for HDTV. (Sampling Ratio 4:2:2; max. Data Rate=
170Mbps; Bits Per Sample= 10; Compression= none) |
| DV (DV25) |
This
is the lesser of the 'low-end' DV formats. MiniDV consumer cameras are the
least desireable. I will only give specs for the more ‘professional’
forms of DV25. |
| DVCAM |
(Sampling
Ratio 4:1:1 –NTSC, 4:2:0 -PAL; max. Data Rate= 25Mbps; Bits Per Sample=
8; Compression= 5:1). |
| DVCPRO |
(Sampling
Ratio 4:1:1 –NTSC, 4:1:1 -PAL; max. Data Rate= 25Mbps; Bits Per Sample=
8; Compression= 5:1). |
| DVCPRO50 |
Panasonic's
DVCPRO50 use two DV codecs, thereby doubling the data rate to 50
Mbps. (Sampling Ratio 4:2:2;
max. Data Rate= 50Mbps; Bits Per Sample= 8; Compression= 3.3:1) |
| Field |
One
half of a complete interlaced video picture (frame), containing all the
odd or even scanning lines of the picture. |
| Frame |
One
complete video image, containing two fields. There are 30 frames in one
second of NTSC video and 25 frames in one second of PAL video. |
| Frame Code |
Absolute
address system for each frame from 0 to 29,999 recorded in the vertical
blanking interval. |
| Guard Band |
Space
between adjacent recorded tracks (fields) to eliminate crosstalk. |
| Horizontal Resolution |
This
is the resolution of the video picture measured across a horizontal line. |
| Interlace |
A
process in which the picture is split into two fields by sending all the
odd numbered lines to field one and all the even numbered lines to field
two. This was necessary when there was not enough bandwidth to send a
complete frame fast enough to create a non-flickering image. |
| Keycode |
A
machine-readable code printed on the edge of motion picture film which
allows the film edge numbers to be electronically read and inserted into
an edit list. Very useful for generating a negative cut list from a video
off-line EDL. |
| Luminance |
The
black and white, or brightness, part of a component video signal. Also
called the "Y" signal. |
| MPEG |
Moving
Picture Experts Group. A group of standards for compressing moving
pictures. MPEG 1 uses a data rate of 1.5 Mbps (Mega Bits per Second), the
speed of CD-ROM. MPEG 2 supports higher quality with a data rate (also
called bit rate) of from 2 to 10 Mbps. MPEG 2 is the format used for
satellite broadcasting (DSS), digital terrestrial broadcasting, and DVD. |
| Non-Linear Editor |
An
editing system based on storage of video and audio on computer disk, where
the order or lengths of scenes can be changed without the necessity of
re-assembling or copying the program. |
| NTSC |
NTSC
National Television Systems Committee. The name of the television and
video standard in use in the United States. Consists of 525 horizontal
lines at a field rate of 60 fields per second. (Two fields equals one
complete Frame). Only 486 of these lines are used for picture. The rest
are used for sync and extra information such as VITC and Closed
Captioning. This is the colour video standard used in the United States
and Japan. Compare with PAL and SECAM. |
| PAL |
Phase
Alternate Line. The television and video standard in use in most of
Europe, Hong Kond and the Middle East. Consists of 625 horizontal lines at
a field rate of 50 fields per second. (Two fields equals one complete
Frame). Only 576 of these lines are used for picture. The rest are used
for sync or extra information such as VITC and Closed Captioning. |
| PALplus |
A
widescreen (16x9) television standard in use in Europe that is compatible
with existing 4x3 TV sets. Non-16x9 TVs show the picture in a letterboxed
form. |
| Pixel |
Short
for Picture Element. The basic unit from which a video or computer picture
is made. Essentially a dot with a given colour and brightness value. D1
images are 720 pixels wide by 486 high. NTSC images are 640 by 480 pixels. |
| Resolution |
The
amount of detail in an image. Higher resolution equals more detail.
Generally expressed in "lines". It is the number of VERTICAL
line pairs that the system can distinguish, and has no relationship to the
number of horizontal scan lines. Also used to describe the size of a
computer image, usually in pixels. |
| Resolution Independent |
A
term to describe equipment that can work in more than resolution. For
example, most equipment can do film resolution or video resolution, but
not both. Resolution independent equipment can work in both. |
| RGB |
Red,
Green, Blue. The primary colours of light. Computers and some analogue
component devices use separate red, green, and blue colour channels to
keep the full bandwidth and therefore the highest quality picture. |
| R-Y signal |
A
chrominance signal determined by subtracting the Y (luminance) signal from
the R (red) signal. One of the component signals. |
| Sampling Frequency |
The
number of sample measurements taken from an analogue signal in a second,
generally expressed in megahertz. These samples are then converted into
digital numeric values to create the digital signal. |
| SIN ratio |
Abbreviation
of Signal-to-Noise ratio. The higher the S/N ratio, the less noise and
higher the picture quality. |
| SMPTE |
Society
of Motion Picture and Television Engineer. A major standards-setting
organisation for the motion picture and television industries. Established
the standards for time code and for all the major video tape formats. |
| S-video Input connector |
A
connector that inputs Y (luminance) and C (chrominance) signals separately
to reduce interference between Y and C signals, and to help reproduce
noiseless images. |
| Sync signal |
A
reference signal consisting of vertical and horizontal sync signals used
for synchronising the scanning patterns of the video camera and the
monitor. |
| Tracking |
Electrically
controlling the video head so that the playback phase matches the
recording phase of the tape. Especially when playing back the tape with a
VTR other than the one used for recording, adjusting the tracking prevents
noise from appearing on the picture. |
| V-blanking |
The
portion of the video signal that occurs between the end of one field and
the beginning of the next. During this time, the electron beams in the
cameras and monitors are turned off so that they can return from the
bottom of the screen to the top without showing traces of movement on the
screen. When the position of V-blanking is not adjusted correctly, a
horizontal black bar appears on the screen. |
| VBR |
Variable
Bit Rate. MPEG video compression where the amount of compression can be
varied to allow for minimum degradation of the image in scenes that are
harder to compress. |
| Vertical Interval |
Non-visible
(off-screen) part of a video picture signal. |
