Commonly Used Terms

4:1:1 - A more economical form of sampling for 525-line video pictures, used to digitize the luminance and color difference components (Y, R-Y, B-Y) of a video signal.  The '4' represents 13.5 MHz, the sampling frequency of Y, and the '1' represents 3.75 MHz for R-Y and B-Y.  Both the luminance and color difference are sampled on every line so the color information has half the horizontal resolution of a 4:2:2 signal while the vertical resolution of the color information is the same.

4:2:0 - The equivalent to 4:1:1 sampling for 625-line video systems.  The '4' represents 13.5 MHz, the sampling frequency of Y, while the R-Y and B-Y components are sampled at 6.75 MHz (between every other line).  Therefore one line is sampled at 4:0:0 (luminance only) and the next at 4:2:2.

4:2:2 - Another term for the component digital video format, it is the ratio of sampling frequencies used to digitize the luminance and color difference components (Y, R-Y, B-Y) of a video signal.  For every 4 samples of Y there are 2 samples of R-Y and B-Y.  The '4' represents 13.5 MHz, the sampling frequency of Y, and the '2' represents 6.75 MHz for R-Y and B-Y.   4:2:2 is commonly used synonymously with ITU-R 601 to describe digital equipment in the video studio. 

AVI - Audio Video Interleaving, the Microsoft Windows file format for combining video and audio into a single stream.  It is intended to replace this with DirectShow

Component - An analog form of video that separates the video into luminance and chrominance using  Y, R-Y and B-Y signals.  This is typically used with MII and Betacam broadcast video equipment.

Composite - An analog form of video signal that combines luminance (brightness) and chrominance (color) along with timing reference (sync) information.  It can be coded in NTSC (the standard used in the United States), PAL (more commonly used in Europe) or SECAM (a variant of PAL) for transmission and playback.  Typically used with VHS and 8mm consumer video equipment.

DirectShow - Microsoft's replacement for AVI and ActiveMovie, this file format supports the capture and playback of a number of media types including MPEG-1/MPEG-2/MPEG-4/WAV/DVD/etc..

DV - The digital video format developed by JVC, Sony, Hitachi, Toshiba and others.  It records video for the consumer (DV) and professional (DVCAM, DVCPRO) markets.  DV compression is fixed at approximately 5:1 using 4:1:1 sampling (for consumer NTSC equipment) with two 16-bit (48 kHz or 44 kHz) or four 12-bit (32 kHz) audio channels.  The recording rate is 25 Megabits per second (Mbps).  Products that use this format include DVRex-M1, DV500, RT2000 and EditDV.

DVD - Digital versatile disc, stores from 4.7GB (single sided, single layer) to 17.0GB (dual sided, dual layer) on a single disc the same physical size as a CD.  A two hour movie can fit onto one side of a DVD.  It can be used to store data, movies, audio, etc.  

Elementary Stream - The way to export MPEG2 video for use in DVD authoring.  It creates two separate files, one for the MPEG2 video and one for the audio.  The alternative is known as Program Stream, where the video and audio are multiplexed together into the same file.  DVD authoring programs cannot use MPEG2 exported as Program Stream.

IEEE-1394 - A low cost digital interface first widely used by Apple under the name FireWire and now universally accepted for transferring digital video to and from video equipment and computers.  Sony uses it under the name i.Link.  It can also be used to hook up storage devices.

M-JPEG - Motion-Joint Photographic Experts Group, the standard for compression of still images adapted to the moving video.  Each individual video frame is compressed and then joined with the previous frame.  Products that use this include miroVIDEO DC30, TARGA 2000 and EditBay.

MPEG - Motion Pictures Expert Group, the compression standard for moving pictures and audio now replacing the earlier M-JPEG.  MPEG-1 is mainly used for multimedia authoring such as CD-ROMs.  MPEG-2 has a much higher resolution and is the basis for digital television/satellite transmission and is the standard for DVDs.  Each frame of video is compared with the previous one and then only the blocks of video that are different are kept allowing for much more efficient compression.  Products that use this include RT2000, Amber and DC2000. 

OHCI - Open Host Controller Interface, the Microsoft Windows specification for interfacing IEEE-1394 devices (aka FireWire or i.Link) and now USB devices.  The driver is included in Windows 98 SE, Me, 2000 and XP.  Some computers come with the IEEE-1394 or USB interface built in but some may require the interface be added on.  Examples of OHCI compliant IEEE-1394 digital video capture cards include the PYRO PlatinumDV and OrangeLink FireWire PCI.   

QuickTime - Apple's file format for combining video, sound and animation that is available for both the Mac OS and Windows.

SDI - Serial Digital Interface, this is a 10-bit, scrambled interface for component ITU-R 601 and composite digital with four channels of digital audio.  It uses standard 75 ohm BNC connector and coax cable like that used for analog video.  It supports recording rates of 270 Mbps.

USB - Universal Serial Bus, a low cost computer interface that allows data rates up to 12 Mbps, it is hot swappable (so that devices and be added and removed while the computer is on) and connection of up to 127 devices is supported.  It is compatible with both the PC (under Windows 98, Me and 2000) and the Mac and is replacing the parallel, serial, keyboard and mouse ports on newer systems.

Y/C - Another analog form of video signal that separates the luminance (Y) and chrominance (C) for higher bandwidth and therefore greater resolution.  Typically used with S-VHS and Hi8 consumer and professional video equipment.

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