Chrominance
The color component of a video signal that includes information about hue (shade) and saturation (intensity).

Coaxial digital
Some DVRs include a digital audio output for sending the Dolby Digital or DTS bitstream to a compatible receiver. Coaxial digital inputs and outputs use standard RCA-type jacks, but the cable itself is specially designed to handle the much wider frequency bandwidth of digital signals.

Component video
A video connection which splits the video signal into three parts — one for brightness (luminance) and two for color (chrominance). Component video connections provide greater color accuracy than S-video or composite.

Composite video
A video connection in which the brightness (luminance) and color (chrominance) portions of the signal are combined. A DVR's standard RCA-type video jack provides a composite video signal.

Copy protection
A system for preventing the unauthorized reproduction of copyrighted media like movies or music. The DVD format includes both digital and analog forms of copy protection; the VHS format uses analog copy protection. You will most likely not be able to copy commercial DVDs or commercial VHS tapes to your DVR's hard drive.

Digital-to-analog converter (DAC)
An electronic circuit that converts digital information into a continuous analog signal.

DIRECTV®
DIRECTV is a popular satellite TV provider, offering over 225 channels of TV shows, movies, and sports, as well as dozens of music channels from XM Satellite Radio. For more information, check out our article on DIRECTV.

Dolby® Digital
Dolby Digital provides a bitstream of digital data consisting of up to six discrete channels (front left/right, center, surround left/right, and subwoofer). With full Dolby Digital 5.1 surround sound, the five main channels are full-bandwidth and the "low-frequency effects" subwoofer channel is dedicated to deep bass. See Surround Sound Formats for more info.

Dolby Digital EX
Dolby Digital EX is based on standard Dolby Digital technology (see above), but includes an extra "back surround" channel, making it a "6.1" format. This sixth channel is encoded as a matrixed signal within the standard left and right surround channels, and is reproduced by an additional one or two surround speakers.

Dolby Pro Logic® (also Dolby Surround)
Pro Logic processing can be found on almost all home theater receivers. It delivers 4-channel playback of Dolby Surround-encoded stereo sources (primarily VHS tapes and stereo TV broadcasts). Pro Logic includes a center channel for on-screen sound; front left and right channels for sound that moves with the action; and a limited-bandwidth mono surround channel sent to the left and right surround speakers to provide ambience and sound effects.

Dolby Pro Logic II
A big improvement of the original Dolby Pro Logic processing, Pro Logic II gives Dolby Surround-encoded sources a three-dimensionality that approaches the realism of Dolby Digital soundtracks. Pro Logic II transforms any Surround or stereo source — including music — into full 5.1-channel sound. This includes full-bandwidth stereo surround channels and a subwoofer channel.

Dolby Pro Logic IIx
The newest addition to the Pro Logic family was designed with today's 7-channel receivers in mind. Pro Logic IIx processing can transform Dolby Surround and stereo sources into enveloping 7.1-channel sound, complete with four full-bandwidth surround channels. (When used with 6-channel receivers, Pro Logic IIx yields 6.1 surround sound.)

DTS® (Digital Theater Systems)
Like Dolby Digital (see above) DTS provides up to 5.1 channels of digital audio. Most home theater receivers include decoding for DTS.

DVD-R/RW, DVD-RAM, DVD+R/RW
See recordable DVD.

DVD recorder
DVD recorders play DVD movies and record on blank DVD discs. While it's not possible to record copy-protected material, you can record TV shows, home movies, and other unprotected material. Some DVRs have built-in DVD recorders for easy, convenient archiving. See our DVD recorder shopping guide for more info.

DVI (Digital Visual Interface)
A multi-pin computer-style output included on a few HD-capable DVRs. DVI provides a high-resolution digital video signal to HD-compatible TVs with a corresponding connector. This digital video signal is encrypted with High-bandwidth Digital Content Protection (HDCP) to prevent recording of copy-protected material.

DVR (Digital Video Recorder)
Also known as a personal video recorder (PVR) or hard disk video recorder. DVRs store recordings on a large hard drive, and most let you pause and replay live television. When used with an electronic program guide service, you can find and record shows automatically.

Electronic program guide (EPG)
Provides an on-screen listing of available channels and program data for an extended time period, usually 1-2 weeks. Examples of program guides include subscription services like TiVo® and free guides like TV Guide On Screen®.

Hard disk video recorder
See DVR.

Hard drive
A hard drive (or "hard disk drive") is the large sealed drive built right into your DVR, just like a computer. It stores the programs you record. A larger hard drive means that you can save more hours of TV and that you'll have the space to record more shows at higher quality.

HDCP (High-Bandwidth Digital Content Protection)
HDCP encryption is used with high-resolution signals over DVI and HDMI connections to prevent unauthorized duplication of copyrighted material.

HDMI (High-Definition Media Interface)
This connection can be found on some HD-capable DVRs. Similar to DVI (but using smaller connectors), the multi-pin HDMI interface transfers uncompressed digital video with HDCP copy protection. Unlike DVI, HDMI is also capable of transmitting multichannel audio. With the addition of an adapter, HDMI is backward-compatible with most current DVI connections (video only).

HDTV (High-Definition Television)
A small but growing number of DVRs are able to record and play back HDTV. Often mistakenly used as a generic description of all digital television, HDTV specifically refers to the highest-resolution formats of the 18 total DTV formats. True HDTV is generally considered to be 1,080-line interlaced (1080i) or 720-line progressive (720p). See our article about HDTV for more info.

IEEE 1394 (also FireWire or i.LINK®)
IEEE 1394 can be found on some DVRs, often on the front panel for easy access with a compatible digital camcorder. This all-in-one, high-speed digital interface is used for the transmission of digital audio/video data. Some DVRs also use IEEE 1394 to transfer high-definition audio and video information to and from an HD-capable TV with a compatible connection.

IR blaster
A device that enables a DVD recorder or DVR to control your cable box or satellite receiver by sending signals that mimic those of a remote control. An IR blaster looks like a regular cable with two distinctly different ends. One end plugs into the back of a compatible DVD recorder or DVR. The other end is the IR emitter. It sits in front of the cable box/satellite receiver's IR sensor, which is located on the front-panel. IR blasters make for easier unattended timer recordings, since the DVD recorder/DVR can tune the set-top box to the right channel at the right time.

Luminance
The brightness or black-and-white component of a color video signal. Determines the level of picture detail.

Optical digital (Toslink)
Some DVRs include a digital audio output for sending the Dolby Digital or DTS bitstream to a compatible receiver. Toslink jacks and connectors usually come with protective caps which need to be removed before connections are made.

Personal Video Recorder (PVR)
See DVR.

Recordable DVD
Recordable DVDs can be broken up into two basic categories: those that can only be recorded once (write-once) and those that can be erased and re-recorded numerous times (rewriteable). Both types are useful for recording and storing different kinds of material — write-once is great for shows you want to keep forever, while rewriteable is perfect for shows you only want to store temporarily.

• Write-once: DVD-R, DVD+R
• Rewriteable: DVD-RW, DVD+RW, DVD-RAM

See our DVD recorder shopping guide for more info.

Recording quality
Most DVRs allow you to record at four or more "speeds" or levels of quality. Better quality (faster record speed) takes up more hard drive space; lower quality (slower record speed) takes up less hard drive space. There is always a balance between quantity and quality.

RF (radio frequency) or 75-ohm coaxial
This kind of connection is commonly used for bringing signals from antennas and other sources outside the home to components with a tuner, such as cable boxes, TVs, some DVRs, etc. A 75-ohm coaxial cable carries video and audio information simultaneously.

S-video
This video connection carries the chrominance (color) and luminance (brightness) portions of the video signal in separate streams, for improved color accuracy and reduced distortion. S-video provides a sharper picture than composite video, but is not as good as component video.

TiVo®
A subscription service that popularized DVRs. Includes a 14-day program guide, WishList™ (search and record), Season Pass™ (record whole seasons of a program), Home Media networking features, and more.

TiVo Series2™
The second generation of TiVo boxes, first available in 2002. Series2 boxes support free Home Media networking features. Also, Series2 boxes that don't have a built-in DVD recorder support TiVoToGo™, which lets you save your TV recordings to your desktop or laptop PC.

TV Guide On Screen®
A free service included with the purchase of some DVRs. Includes an 8-day program guide, handy searching functions, and smart recording features.

VCR Plus+®
A few DVRs include VCR Plus+ for easy timer recording. Simply enter the show's "PlusCode"® (found beside its title in most TV listings) and the DVR is automatically set for the channel, date, and time.

Windows® XP Media Center
A version of the popular XP operating system which boasts DVR functionality and a host of other A/V integration features. New Digital Entertainment Centers with Media Center software feature a built-in over-the-air HD tuner and can record in HD. All Media Center components include a 14-day program guide, live TV control, home media networking capabilities, and more.