Resource Center: How to Speak A/V
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Entries starting with: hard-disk drive: A digital data storage/retrieval device, found in computers and a variety of home and portable music and video gear, that uses a rigid, rapidly rotating disk coated with a magnetic recording surface. Thanks to the rapid rotation rate, the read/write head(s) float on a cushion of air very near the disk’s surface, allowing almost instantaneous cueing to any desired location without touching the surface. hard-disk recorder (HDR): A device using the immense data capacity of a hard-disk drive to store audio or A/V material in digital form. Video-oriented HDRs — usually called “digital video recorders” (DVRs) and sometimes “personal video recorders” (PVRs) — usually have versatile options for unattended recording and playback that can let you skip commercials or watch a program from the beginning while it’s still being recorded. harmonic distortion: In audio, spurious output signals found at frequencies that are “harmonics” — whole-number multiples — of the frequency of the input signal. Harmonic distortion is hard to hear on reproduced music unless it is very high (above 1% or more). See distortion, total harmonic distortion (THD). HDCD (High Definition Compatible Digital): An audio recording system for CDs, developed by Pacific Microsonics and now owned by Microsoft, that’s said to provide greater bandwidth and dynamic range than standard CDs on an HDCD-capable player. HDCP (High-bandwidth Digital Content Protection): A copy-protection scheme developed by Intel specifically to prevent digital programming transmitted across a DVI (Digital Visual Interface) connection from being copied; now also incorporated into HDMI (High Definition Multimedia Interface) connections. HD DVD: A high-capacity disc format approved by the DVD Forum for carrying high-definition video programs. The sandwiched disc structure resembles that of ordinary DVDs, but blue lasers instead of red are used to obtain high data density. HD DVD discs and players are slated for introduction in late 2005. HDMI (High Definition Multimedia Interface): An enhanced version of DVI that adds stereo and multichannel digital audio as well as signals for integrated remote control and infrared (IR) repeater functions on a single cable with a 19-pin connector that’s significantly smaller than a DVI connector. HDMI incorporates the HDCP copy-prevention scheme. HDTV monitor: A TV set that can display high-definition images when connected to an outboard HDTV tuner; see EDTV monitor. HDTV set: An HDTV display that has a built-in high-definition tuner. HDTV tuner: A digital TV tuner/decoder that can receive high-definition programs broadcast over the air, and possibly from a satellite receiver or cable service as well, and then decode the signals for display on an HDTV monitor. HDV: A new high-definition camcorder format consisting of specifications for recording and playing back high-def video using MiniDV tape cassettes, developed by JVC, Canon, Sharp, and Sony. head drum: A rotating cylinder inside a VCR or camcorder around which the tape is wrapped; two or more heads are mounted on the head drum for video recording and playback, hi-fi audio recording and playback, and erasure; see flying erase head. headphones: A pair of miniature speakers that fit over the ears; “open-air” headphones do not block outside sound or keep sound from leaking out; “circumaural” (around-the-ear) phones may do both. Even tinier headphones that fit inside the listener’s ears are called “earbuds” or “earphones.” headroom: The difference between the signal level at any moment and the maximum level an audio device can handle without clipping or other significant distortion; expressed in decibels (dB). hertz (Hz): The standard unit of frequency, representing cycles per second, or changes away from a basic state and back again. In audio, the basic state is defined as either ordinary air pressure (without sound) or its electrical equivalent: a constant-level (DC) signal, often 0 volts, or ground. For a sound in the audible range, the higher the frequency in hertz, the higher the pitch. In video, frequency usually relates to horizontal luminance resolution; the higher the frequency, the finer the detail and the higher the resolution. A kilohertz (kHz) is a thousand hertz, a megahertz (MHz) a million hertz, and a gigahertz (GHz) a billion hertz. hi-fi: High fidelity, used to refer to an audio system that can reproduce recorded sound with substantial fidelity to the original. VHS Hi-Fi is an audio recording system for VCRs. high-definition TV (HDTV): A specific subset of the digital TV standard that features increased horizontal and vertical resolution, choice of interlaced or progressive scan, and widescreen images; see enhanced-definition TV and standard-definition TV. high-pass filter: A circuit, as in a speaker’s crossover network, that progressively attenuates signals below its cutoff frequency, passing those above to, say, a tweeter; see filter and low-pass filter. home network: A system in which at least one computer is linked with A/V and other devices via wires or wireless means so that digital audio or video files don’t have to reside on the device that plays them. HomePlug: A standard for sending network data over a home’s electrical wiring. HomePNA: A standard for sending network data over a home’s telephone wiring without disrupting normal telephone service. home theater system: A collection of audio and video components designed and configured to reproduce a movie theater-like experience at home. A home theater is generally expected to include a TV screen of reasonable size and a surround sound audio system. horizontal luminance resolution: Measured in lines, this is the most common parameter for characterizing the reproduction of fine detail in video. (Do not confuse these “lines” with scan lines). hotspotting: A drop in brightness or a color shift that may occur when the image on a rear-projection TV or from a front projector is viewed from an off-center seating position; often caused by the use of a high-gain screen surface to increase picture brightness. H.264 (MPEG-4 Part 10): A very efficient, MPEG-4-based standard for encoding and decoding video, originally intended for low-bit-rate applications like cellphones and video over Internet but now a candidate for video encoding on high-definition DVDs. hue: A color’s position in the visible spectrum from red to blue, or its gradation of tint; the professional name for a video monitor’s tint control. Abbreviations |
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