Glossary D-I

By Admin - Posted on 08 September 2008

D1
A format for component digital video tape recording working to the ITU-R 601, 4:2:2 standard using 8-bit sampling. The tape is 19 mm wide and allows up to 94 minutes to be recorded on a cassette. Being a component recording system it is ideal for studio or post production work with its high chrominance bandwidth allowing excellent chroma keying. Also multiple generations are possible with very little degradation and D1 equipment can integrate without transcoding to most digital effects systems, telecines, graphics devices, disk recorders, etc. Being component there are no color framing requirements. Despite the advantages, D1 equipment is not extensively used in general areas of TV production, at least partly due to its high cost. (Often used incorrectly to indicate component digital video.)

D2
The VTR standard for digital composite (coded) NTSC or PAL signals that uses data conforming to SMPTE 244M. It uses 19 mm tape and records up to 208 minutes on a single cassette. Neither cassettes nor recording formats are compatible with D1. D2 has often been used as a direct replacement for 1-inch analog VTRs. Although offering good stunt modes and multiple generations with low losses, being a coded system means coded characteristics are present. The user must be aware of cross-color, transcoding footprints, low chrominance bandwidths and color framing sequences. Employing an 8-bit format to sample the whole coded signal results in reduced amplitude resolution making D2 more susceptible to contouring artifacts. (Often used incorrectly to indicate composite digital video.)

D3
A composite digital video recording format that uses data conforming to SMPTE 244M. Uses 1/2-inch tape cassettes for recording digitized composite (coded) PAL or NTSC signals sampled at 8 bits. Cassettes are available for 50 to 245 minutes. Since this uses a composite signal the characteristics are generally as for D2 except that the 1/2-inch cassette size has allowed a full family of VTR equipment to be realized in one format, including a camcorder.

D4
A format designation never utilized due to the fact that the number four is considered unlucky (being synonymous with death in some Asian languages).

D5
A VTR format using the same cassette as D3 but recording component signals conforming to the ITU-R BT.601-2 (CCIR 601) recommendations at 10-bit resolution. With internal decoding D5 VTRs can play back D3 tapes and provide component outputs. Being a non-compressed component digital video recorder means D5 enjoys all the performance benefits of D1, making it suitable for high-end post production as well as more general studio use. Besides servicing the current 625 and 525 line TV standards the format also has provision for HDTV recording by use of about 4:1 compression (HD D5).

See also: DVCPRO50, DVCPROHD, DVCPRO P.

D8
There is no D8. The Television Recording and Reproduction Technology Committee of SMPTE decided to skip D8 because of the possibility of confusion with similarly named digital audio or data recorders (DA-88).

D9 (Formerly Digital-S)
A 1/2-inch digital tape format developed by JVC which uses a high-density metal particle tape running at 57.8mm/s to record a video data rate of 50 Mbps. The tape can be shuttled and search up to 32x speed. Video sampled at 4:2:2 is compressed at 3.3:1 using DCT-based intra-frame compression (DV). Two or four audio channels are recorded at 16-bit, 48 kHz sampling; each is individually editable. The format also includes two cue tracks. Some machines can play back analog S-VHS. D9 HD is the high definition version recording at 100 Mbps.

D9 HD
A high definition digital component format based on D9. Records on 1/2-inch tape with 100 Mbps video.

Data compression
Reducing the size of a data file by reducing unnecessary information, such as blanks and repeating or redundant characters or patterns.

Data recorders
Machines designed to record and replay data. They usually include a high degree of error correction to ensure that the output data is absolutely correct and, due to their recording format, the data is not easily editable. This compares with video recorders which will conceal missing or incorrect data by repeating adjacent areas of picture and which are designed to allow direct access to every frame for editing. Where data recorders are used for recording video there has to be an attendant "workstation" to see the pictures or hear the sound, whereas VTRs produce the signals directly. Although many data recorders are based on VTRs´ original designs, and vice versa, VTRs are more efficient for pictures and sound while data recorders are most appropriate for data.

D-Cinema (also E-Cinema)
Digital cinema. Typically the process of using video at 1080/24p instead of film for production, post production and presentation.

DCT
1. Discrete cosine transform. A widely used method of data compression of digital video pictures basically by resolving blocks of the picture (usually 8 x 8 pixels) into frequencies, amplitudes, and colors. JPEG and DV depend on DCT. 2. Also an Ampex data videotape format using discrete cosine transform.

Decoder
A television set-top device which enables the home subscriber to convert an electronically scrambled television picture into a viewable signal. This should not be confused with a digital coder/decoder known as a CODEC which is used in conjunction with digital transmissions.

Digital
Conversion of information into bits of data for transmission through wire, fiber optic cable, videoconference, or over air techniques. Method allows simultaneous transmission of voice, data or video.

Down converting
The process which changes the number of pixels and/or frame rate and/or scanning format used to represent an image by removing pixels. Down converting is done from high definition to standard definition.

DV
This digital VCR format is a cooperation between Hitachi, JVC, Sony, Matsushita, Mitsubishi, Philips, Sanyo, Sharp, Thomson and Toshiba. It uses 6.35 mm (0.25-inch) wide tape in a range of products to record 525/60 or 625/50 video for the consumer (DV) and professional markets (Panasonic´s DVCPRO, Sony´s DVCAM and Digital-8). All models use digital intra-field DCT-based "DV" compression (about 5:1) to record 8-bit component digital video based on 13.5 MHz luminance sampling. The consumer versions, DVCAM, and Digital-8 sample video at 4:1:1 (525/60) or 4:2:0 (625/50) video (DVCPRO is 4:1:1 in both 525/60 and 625/25) and provide two

16-bit/48 or 44.1 kHz, or four 12-bit/32 kHz audio channels onto a 4 hour 30 minutes standard cassette or smaller 1 hour "mini" cassette. The video recording rate is 25 Mbps.

DVB
Digital video broadcasting. The group, with over 200 members in 25 countries, which developed the preferred scheme for digital broadcasting in Europe. The DVB Group has put together a satellite system--DVB-S--that can be used with any transponder, current or planned, a matching cable system--DVB-C, and a digital terrestrial system--DVB-T. Internet: www.dvb.org.

DVCAM
Sony´s development of native DV which records a 15 micron (15x10-6m, fifteen thousandths of a millimeter) track on a metal evaporated (ME) tape. DVCAM uses DV compression of a 4:1:1 signal for 525/60 (NTSC) sources and 4:2:0 for 625/50 (PAL). Audio is recorded in one of two forms--four 12-bit channels sampled at 32 kHz, or two 16-bit channels sampled at 48 kHz.

DVCPRO
See: D7.

DVD
Digital versatile disk: A high density development of the compact disk. It is the same size as a CD but stores from 4.38 GB (seven times CD capacity) on a single sided, single layer disk. DVDs can also be double sided or dual layer-storing even more data. The capacities commonly available at present: DVD-5: 4.7 GB (1 side, 1 layer)

DVD-9: 8.5 GB (1 side, 2 layers)
DVD-10: 9.4 GB (2 sides, 1 layer each)
DVD-18: 17.0 GB (2 sides, 2 layers)
DVD-R: 4.7 GB (1 side, 1 layer) (write once)
DVD-RAM: 2.6 GB (per side, 1 layer) (rewritable)
*DVD-RAM: 4.7 GB (per side, 1 layer) (rewritable)
*Expected in 2000.

Embedded audio
Digital audio that is multiplexed and carried within an SDI connection--so simplifying cabling and routing. The standard (ANSI/SMPTE 272M-1994) allows up to four groups each of four mono audio channels. Generally VTRs only support Group 1 but other equipment may use more, for example Quantel´s Clipbox server connection to an edit seat uses groups 1-3 (12 channels). 48 kHz synchronous audio sampling is pretty well universal in TV but the standard also includes 44.1 and 32 kHz synchronous and asynchronous sampling. Synchronous means that the audio sampling clock is genlocked to the associated video (8,008 samples per five frames in 525/60, 1,920 samples per frame in 625/50). Up to 24-bit samples are allowed but mostly only up to 20 are currently used. 48 kHz sampling means an average of just over three samples per line, so three samples per channel are sent on most lines and four occasionally--the pattern is not specified in the standard. Four channels are packed into an Ancillary Data Packet and sent once per line (hence a total of 4 x 3 = 12 or 4 x 4 = 16 audio samples per packet per line).

Encryption
The process of coding data so that a specific code or key is required to restore the original data. In broadcast, this is used to make transmissions secure from unauthorized reception as is often found on satellite or cable systems.

Fibre Channel (also Fiber Channel)
A high speed data link planned to run up to 2 Gbps on a fiber optic cable. A number of manufacturers are developing products to utilize the Fiber Channel--Arbitrated Loop (FC-AL) serial storage interface at 1 Gbps so that storage devices such as hard disks can be connected. Supports signaling rates from 132.8 Mbps to 1,062.5 Mbps, over a mixture of physical media including optical fiber, video coax, miniature coax, and shielded twisted pair wiring. The standard supports data transmission and framing protocols for the most popular channel and network standards including SCSI, HIPPI, Ethernet, Internet Protocol, and ATM.

FireWire
Apple Computer´s trademark for IEEE 1394.
See: IEEE 1394. IEEE 1394 (FireWire)
A low-cost digital interface originated by Apple Computer as a desktop LAN and developed by the IEEE 1394 working group. Can transport data at 100, 200, or 400 Mbps. One of the solutions to connect digital television devices together at 200 Mbps.

Serial Bus Management provides overall configuration control of the serial bus in the form of optimizing arbitration timing, guarantee of adequate electrical power for all devices on the bus, assignment of which IEEE 1394 device is the cycle master, assignment of isochronous channel ID, and notification of errors.

There are two types of IEEE 1394 data transfer: asynchronous and isochronous. Asynchronous transport is the traditional computer memory-mapped, load and store interface. Data requests are sent to a specific address and an acknowledgment is returned.

In addition to an architecture that scales with silicon technology, IEEE 1394 features a unique isochronous data channel interface. Isochronous data channels provide guaranteed data transport at a pre-determined rate. This is especially important for time-critical multimedia data where just-in-time delivery eliminates the need for costly buffering.

Fixed data rate compression
Techniques designed to produce a data stream with a constant data rate. Such techniques may vary the quality of quantization to match the allocated bandwidth.

Format conversion
The process of both encoding/decoding and resampling digital rates to change a digital signal from one format to another.

Frame store
A system capable of storing complete frames of video information in digital form. This system is used for television standards conversion, computer applications incorporating graphics, video walls and various video production and editing systems.

Full-CIF (FCIF)
Common Intermediate Format, an international standard for video display formats developed by TSS. The QCIF format, which employs half the CIF spatial resolution in both horizontal and verticle directions, is the mandatory H.261 format. QCIF is used for most desktop videoconferencing applications where head and shoulder pictures are sent from desk to desk. QCIF displays 176 pixels grouped in 144 non-interlaced luminance lines.

Full-motion video
Video reproduction at 30 frames per second (fps) for NTSC signals or 25 fps for PAL signals. Also known as continuous-motion video. In the videoconferencing world, the term "full-motion video" is often used, and often misunderstood. Videoconferencing systems cannot provide 30 fps for all resolutions at all times nor is that rate always needed for a high-quality, satisfying video image. Picture quality must sometimes be sacrificed to achieve interactive visual communication across the telephone network economically. Videoconferencing vendors often use "full-motion video" to refer to any system that isn´t still-frame. Most videoconferencing systems today run 10 to 15 frames per second at 112 Kbps.

GIF
Graphics interchange format. A computer graphics file format developed by CompuServe for use in compressing graphic images, now commonly used on the Internet. GIF compression is lossless, supports transperancy, but allows a maximum of only 256 colors. Images that will gain the most from GIF compression are those which have large areas (especially horizontal area) with no changes in color.

H.320
A recommendation of the ITU-T based on Discrete Cosine Transform, CCM and motion compensation techniques. It can be a video system´s sole compression method or supplementary algorithm, used instead of a proprietary algorithm when two dissimilar codecs have need to interoperate. H.320 includes a number of individual recommendations for coding, framing, signaling and establishing connections. It also includes three audio algorithms, G.721, G.722 and G.728.

HDTV
High definition television. The 1,125-, 1,080- and 1,035-line interlace and 720 and 1,080-line progressive formats in a 16:9 aspect ratio. Officially a format is high definition if it has at least twice the horizontal and vertical resolution of the standard signal being used. There is a debate as to whether 480-line progressive is also high definition. It is the opinion of the editors that 480-line progressive is not an HDTV format, but does provide better resolution than 480-line interlace, making it an enhanced definition format.

Hertz (Hz)
The name given to the basic measure of radio frequency characteristics. An electromagnetic wave completes a full oscillation from its positive to its negative pole and back again in what is known as a cycle. A single Hertz is thus equal to one cycle per second.

HFC
Hybrid fiber coax. A type of network that contains both fiber-optic cables and copper coaxial cables. The fiber-optic cables carry TV signals from the head-end office to the neighborhood; the signals are then converted to electrical signals and then go to coaxial cables.

IEEE 1394 (FireWire)
A low-cost digital interface originated by Apple Computer as a desktop LAN and developed by the IEEE 1394 working group. Can transport data at 100, 200, or 400 Mbps. One of the solutions to connect digital television devices together at 200 Mbps.

Interactive television
A combination of television with interactive content and enhancements. Interactive television provides better, richer entertainment and information, blending traditional TV-watching with the interactivity of a personal computer. Programming can include richer graphics, one-click access to Web sites through TV Crossover Links, electronic mail and chats, and online commerce through a back channel.

Interlaced
Short for interlaced scanning. Also called line interlace. A system of video scanning whereby the odd- and even-numbered lines of a picture are transmitted consecutively as two separate interleaved fields. Interlace is a form of compression.

Interpolation (spatial)
When re-positioning or re-sizing a digital image inevitably more, less or different pixels are required from those in the original image. Simply replicating or removing pixels causes unwanted artifacts. For far better results the new pixels have to be interpolated--calculated by making suitably weighted averages of adjacent pixels--to produce a more transparent result. The quality of the results will depend on the techniques used and the number of pixels (points--hence 16-point interpolation), or area of original picture, used to calculate the result.

Interpolation (temporal)
Interpolation between the same point in space on successive frames. It can be used to provide motion smoothing and is extensively used in standards converters to reduce the judder caused by the 50/60 Hz field rate difference. The technique can also be adapted to create frame averaging for special effects.

I/O: Input/output.
Typically refers to sending information or data signals to and from devices.

IP: See TCP/IP.

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