D
DAC(audio): Digital to Analog Converter. DACs in DVD players, audio receivers, CD players, etc. convert digital data into analog audio signals. The quality of the DAC can impact sound quality, for better or worse. See Burr-Brown, Wolfson.
Db/Wm: Decibels per watt-meter. See Sensitivity.
DBS: Direct Broadcast Satellite. See C-Band, DirecTV, and Dish Network.
DBX:
Decibel: Unit of sound measurement.
D-ILA: JVC’s brand name for its implementation of LCoS technology. See LCoS.
Digital Video Express: See DIVX
Dipole Antenna: Wire antenna included with most audio receivers. It connects to the press connector terminals on the back of the receiver. Dipole antennas have limited performance compared to rabbit ears antennas and outdoor antennas. See Rabbit Ears.
Dipole Speaker: Speaker that radiates opposite (out-of-phase) soundwaves from two (usually direct opposite) directions. Found in many surround-sound speakers as the combination of in-phase and out-of-phase sound radiating in multiple directions can improve surround effects and create a sense of space. See Dipole Speaker and Out of Phase.
Direct View (television): Television using a CRT picture tube. See CRT.
Distortion (audio): See THD.
DivX: Video codec used for web video applications. Some DVD players can play DivX files burned on a disc. DivX is not to be confused with Circuit City’s DIVX, or Digital Video Express. See Digital Video Express.
DIVX: Digital Video Express, a Circuit City-sourced pay-per-view DVD rental format that featured a DVD player with a phone connection. Customers could buy DIVX discs for under $5.00, but the discs could only be played for a 48 hour window, at which point the player would dial a central server and your credit card would be charged if you tried to play it again. DIVX was originally supported by RCA, Panasonic, and ___ and studios Paramount, Disney and Fox . Negative coverage in the media and a very strong backlash from enthusiasts and the marketplace made DIVX a very short lived product. It racked up tremendous losses for Circuit City in its short existence. DIVX is not to be confused with DivX.
D-VHS: Digital tape format that records a digital signal on to special D-VHS tapes, which look like ordinary VHS tapes. D-VHS VCRs are used primarily to record over-the-air HDTV broadcasts via a tuner connected by a FireWire connection. While providing very high quality, D-VHS never became a mass market product due to the expense and its use of a tape in an increasingly optical disc world. See D-VHS Theater.
D-VHS Theater: Sub-format of D-VHS using movies pre-recorded on D-VHS tapes. Required special D-VHS Theater VCRs for playback- ordinary D-VHS VCRs would not work due to copy protection on the tapes. Provided far better quality than DVD, but never met mainstream success due to expense and its use of a tape in an increasingly optical disc world. See D-VHS.
Deinterlacing: Video process where an interlaced image is taken apart and re-assembled as a progressive scan image. For example, a progressive scan DVD player takes 480i video from the disc, deinterlaces it and sends out a 480p signal. A 1080p TV receiving a 1080i signal from a cable box would deinterlace the signal and display it as 1080p.
Depth of Field: The amount of the foreground and background that is in focus in relation to the subject. Depth of field extends about 1/3 in front of the subject and 2/3 behind it. Greater depth of field is achieved with small apertures (high f-stop numbers) and wide-angle lenses; shallow depth of field occurs with wide apertures (small f-stop numbers) and telephoto lenses. See f-stop, Aperture Priority.
Dialogue Enhancer: See Dynamic Range Control.
Digital 8: Digital camcorder format that records DV signals on 8mm or Hi8 tape.
Digital Zoom: Artificial zoom effect created by a digital camera or camcorder by cropping the image. Digital zooms cut image quality dramatically and should not be used if possible.
DirecTV:
Direct Drive: Turntable drive method using an electric motor coupled directly to the turntable platter. Direct drive provides very stable and accurate speed, but is not favored by most audiophiles because the coupling of the motor directly to the platter can cause undesirable vibration that harms sound quality. See Belt Drive.
Discrete Surround: Surround sound using a separate audio track for each channel. See Matrix Surround.
Dish Network
DLP: Digital Light Processing, a projection TV technology developed by Texas Instruments. It uses a chip with millions of tiny mirrors and either a lamp with a spinning color wheel or LED light sources (some Samsung models) to create the image. See Rainbow Effect.
DNR Perfect:
Dolby B: Noise reduction system developed by Dolby Labs, used primarily on cassette tapes to reduce tape hiss. Dolby B is the most popular noise reduction system in use and if a player has “Dolby” listed without mentioning Dolby C, it uses Dolby B reduction. It works by boosting the high frequencies during recording, then reducing them during playback, leaving hiss behind and less audive. If a cassette is recorded with Dolby B it should be played on a Dolby B cassette player for the most accurate sound reproduction, but can still be played on non-Dolby hardware with acceptable results. Most prerecorded cassettes used Dolby B. See Dolby C.
Dolby C: Noise reduction system developed by Dolby Labs, used primarily on cassette tapes and successor to Dolby B. Dolby C offers more noise effective noise reduction and better high frequency response than Dolby B. Few prerecorded cassettes were made using Dolby C, so the bulk of Dolby C cassettes are home recordings. Cassettes recorded with Dolby C should be played on a Dolby C cassette player for the most accurate sound reproduction. Sound quality may be unacceptable when played on non-Dolby equipment, though using Dolby B will improve performance vs. using no Dolby at all. See Dolby B.
Dolby HX Pro: Dolby home recording technology developed in conjunction with Bang & Olufsen of Denmark, Dolby HX Pro improves and extends the high frequency response of cassette recordings. HX stands for High-frequency eXtension. See Dolby B, Dolby C.
Dolby Pro-Logic: Matrix surround system with a left front, right front, center, and surround channel. The left and right surround channel played exactly the same material, making this a 4 channel system. The rear channels are not full-range and can only reproduce a limited amount of frequencies. See Matrix Surround.
Dolby Pro-Logic II: Matrix surround system with a left front, right front, center, and separate left and right surround channels. The left and right surround channels are derived from a single Pro-Logic surround channel. The Pro-Logic II circuit compares the front left and right channels with the surround channel and using an algorythym creates full-range left and right surround channels playing different material, making this a 5 channel system. The surround effects and sound quality is greatly improved compared to Dolby Pro-Logic. This system can also be used with stereo music to create surround sound. See Matrix Surround.
Dolby Digital: Discrete surround sound system with 5 channels: left front, center, right front, left surround, right surround, and an LFE channel. Dolby Digital uses lossy compression and is used in DVDs and HDTV broadcasts. See 5.1, LFE, Lossy Compression.
Dolby Digital Plus: Higher quality version of Dolby Digital, using higher bitrates and improved compression to deliver better sound quality. Dolby Digital Plus is a discrete surround sound system that supports up to thirteen channels, though typically it uses five channels: left front, center, right front, left surround, right surround, and an LFE channel. Dolby Digital uses lossy compression and is used on HD DVDs and Blu-ray Discs. . See 5.1, Dolby Digital, LFE, Lossy Compression.
Dolby Laboratories: Developer of Dolby noise reduction and surround sound formats.
Dolby TrueHD: Dolby TrueHD is a discrete surround sound system with 5 channels: left front, center, right front, left surround, right surround, and an LFE channel. Dolby TrueHD uses losses compression so no quality is lost compared to the original master tapes, for the best possible sound quality. Dolby TrueHD is used on HD DVDs and Blu-ray Discs. See 5.1, LFE, Lossless Compression.
DRM: Digital Rights Management. Systems used to prevent piracy while allowing users to use their media in legal methods. Occasionally companies overstep and consumer rights are infringed. See Piracy, Rootkit Fiasco.
DTS: Surround sound format used in both the home video and commercial theater marketplace. DTS competes with Dolby Digital in both segments. The DTS system uses lossy compression but uses a different encoding method and higher bitrates than Dolby Digital. Many enthusiasts consider DTS to have better sound quality than Dolby Digital, as do some film directors. Steven Spielberg is a strong proponent of DTS and selected it for films such as Jurassic Park. See Dolby Digital, Lossy Compression.
DTS (manufacturer): Digital Theater Systems, developer of the dts surround-sound formats. DTS is sometimes described incorrectly as Digital Theater Sound or Digital Theater Surround.
DTS-HD High Resolution Audio: Improved DTS surround sound format using higher bitrates and improved encoding to deliver better sound quality than standard DTS. DTS-HD High Resolution Audio uses lossy compression and is analagous to Dolby Digital Plus from Dolby. DTS-HD High Resolution Audio is used on Blu-ray Discs. See DTS, Dolby Digital, Dolby Digital Plus.
DTS-HD Master Audio: DTS surround sound format that uses lossless compression and high bitrates to deliver sound quality identical to the studio master. DTS-HD Master Audio is analagous to Dolby TrueHD from Dolby, but has better technical specifications so potential sound quality is theoretically superior. DTS-HD Master Audio is found on Blu-ray Discs. See Dolby TrueHD, Lossless Compression.
DTS Neo:6: Matrix surround sound format from DTS. Neo: 6 delivers up to 6.1 channels of full-range surround sound from a stereo or matrix-surround encoded source. It competes with Dolby Pro-Logic II from Dolby. See Dolby Pro-Logic II, Matrix Surround.
DTV: Acronym for Digital Television. See ATSC, HDTV.
DTV Converter Box: Television tuner box for converting digital televison stations to an analog output. Converter boxes lack digital outputs with high-definition resolutions as they are intended to be used solely for with analog TVs. Converter boxes will be necessary for any analog TV wishing to receive television programming via antenna after the digital TV changeover in 2009. The converter box is connected to an antenna and an analog or RF connection is made from the box to the TV. The box then receives the digital transmissions, decodes them into an analog signal and then sends them to the television for display.
DV: Acronym for Digital Video. Also used as a file extension for digital video files saved on a computer.
DVD: Home videodisc format for NTSC standard, with 480 lines of resolution stored as MPEG-2 and Dolby Digital or dts sound. Though the material is stored on the disc digitally, DVDs conform to the NTSC and PAL analog television standards. DVDs hold 4.7GB (single-layer disc) or 9.4 GB (double-layer disc.) Most movies released on DVD are double-layer discs. The acronym originally stood for Digital Video Disc but was changed to Digital Versatile Disc to reflect its use for data storage applications. The latter fact is typically unknown by the general public. DVD was developed primarily by Toshiba and is managed by the DVD Forum. See Dolby Digital, dts, MPEG-2, DVD Forum.
DVD-A: High-resolution audio version of DVD. DVD-A discs can have much better sound quality than CDs, but a player that supports DVD-A is needed to play them and a good sound system is needed to take advantage of the improved sound quality. SACD was launched as a competitor to DVD-A and the resulting confusion probably played a part in relegating both products to niche status. See SACD.
DVD-R: Recordable DVD with a single layer and 4.7 GB capacity.
DVD-R DL: Recordable DVD with two layers and 9.4 GB capacity.
DVD-RW: Recordable DVD with a single layer and 4.7 GB capacity. DVD-RW discs can be erased and re-recorded.
DVD-RAM: DV- Randon Access Memory. DVD format used primarily in camcorders and data storage applications, it records data in a way that is optimal for data storage and retrieval. DVD-RAM is now uncommon and did not achieve widespread popularity.
DVD+R: Recordable DVD+ with a single layer and 4.7 GB capacity. This format was launched by Sony and Philips and is not an “official” DVD format recognized by the DVD Forum.
DVD+R DL: Recordable DVD+ with two layers and 9.4 GB capacity. This format was launched by Sony and Philips and is not an “official” DVD format recognized by the DVD Forum.
DVD+RW: Recordable DVD+ with a single layer and 4.7 GB capacity. DVD+RW discs can be erased and re-recorded. This format was launched by Sony and Philips and is not an “official” DVD format recognized by the DVD Forum.
DVD+RW: Recordable DVD+ with a two layers and 9.4 GB capacity. DVD+RW discs can be erased and re-recorded. This format was launched by Sony and Philips and is not an “official” DVD format recognized by the DVD Forum.
DVD Forum: Entity responsible for standards, development and marketing of the DVD format. See DVD.
DVD Region Coding: Commercially-produced DVDs and DVD players usually have a region code associated with them. This allows studios to control their content and prevent piracy. A Region 1 DVD will not play on a Region 2 DVD player, for example. General listing of DVD Regions: Region 1: Canada, USA, Bermuda, US Territories. Region 2: European Union. Region 3: Southeast Asia. Region 4: Australia, New Zealand, Caribbean, Mexico. Region 5: African nations. Region 6: People’s Republic of China. Region 7: Reserved for future use. Region 8: International.
DVI: Digital Video Interface, a connection used with computers and digital televisions. DVI connections provide the highest possible video quality (comparable to HDMI) but do not carry audio signals. See HDMI.
Dynamic Headroom: See Dynamic Power.
Dynamic Power: The ability of an amplifier to temporarily deliver more than its rated power for brief periods of time. For example, an amplifier may have a continuous power rating of 100 watts per channel but can temporarily increase its power to 150 watts for dynamic peaks such as an explosion or an orchestral crescendo. Sometimes dynamic power is called dynamic headroom and is rated in dB. To increase volume 3 dB power must be doubled. A 50 watt amplifier with 3 dB of headroom can double its power to 100 watts. A 50 watts amplifier with 6 dB of headroom can quadruple its power to 200 watts: 50 watts increased 3 dB= 100watts, 100 watts increased another 3 dB= 200 watts.
Dynamic Range (digital imaging): Range of tones from light to dark that a camera or sensor is capable of reproducing. High dynamic range is very desirable and leads to greater detail in both shadows and highlights. Generally speaking, the bigger the image sensor, the better the dynamic range capabilities. The larger image sensor is one reason digital SLRs typically have much better dynamic range than compact cameras.
Dynamic Range Control: A Dynamic Range Control setting is usually found on audio/video receivers and DVD players. It is sometimes called “Dialogue Enhancer” or “Midnight Mode.” The control is used to reduce dynamic range, makinge dialogue more audible at normal listening levels and reducing the volume of loud passages such as explosions so they are not overpowering.
