|
Print-through
Print-through is a generally undesirable effect that arises in the use of magnetic tape for storing analog information, in particular music, caused by contact transfer of signal patterns from one layer of tape to another as it sits wound concentrically on a reel. Explanation Print-through is a category of noise caused by contact transfer of signal patterns from one layer of tape to another after it is wound onto a reel. Print-through can take two forms: # thermo-remanent magnetization induced by temperature, and # anhysteretic magnetization caused by an external magnetic field. The former is unstable over time and can be easily erased by rewinding a tape and letting it sit so that the patterns formed by the contact of upper and lower layers begin to erase each other and form new patterns with the repositioning of upper/lower layers after rewinding. This type of contact printing begins immediately after a recording and increases over time at a rate dependent on the temperature ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency-modulation
Frequency modulation (FM) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The technology is used in telecommunications, radio broadcasting, signal processing, and computing. In analog frequency modulation, such as radio broadcasting, of an audio signal representing voice or music, the instantaneous frequency deviation, i.e. the difference between the frequency of the carrier and its center frequency, has a functional relation to the modulating signal amplitude. Digital data can be encoded and transmitted with a type of frequency modulation known as frequency-shift keying (FSK), in which the instantaneous frequency of the carrier is shifted among a set of frequencies. The frequencies may represent digits, such as '0' and '1'. FSK is widely used in computer modems, such as fax modems, telephone caller ID systems, garage door openers, and other low-frequency transmissions. Radioteletype also uses FSK. Frequency modulation is wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Tape
Magnetic tape is a medium for magnetic storage made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany in 1928, based on the earlier magnetic wire recording from Denmark. Devices that use magnetic tape could with relative ease record and playback audio, visual, and binary computer data. Magnetic tape revolutionized sound recording and reproduction and broadcasting. It allowed radio, which had always been broadcast live, to be recorded for later or repeated airing. Since the early 1950s, magnetic tape has been used with computers to store large quantities of data and is still used for backup purposes. Magnetic tape begins to degrade after 10–20 years and therefore is not an ideal medium for long-term archival storage. Durability While good for short-term use, magnetic tape is highly prone to disintegration. Depending on the environment, this process may begin after 10–20 years. Over time, magnetic tape made in the 197 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type B Videotape
1–inch type B VTR (designated Type B by SMPTE) is a reel-to-reel analog recording video tape format developed by the Bosch Fernseh division of Bosch in Germany in 1976. The magnetic tape format became the broadcasting standard in continental Europe, but adoption was limited in the United States and United Kingdom, where the Type C videotape VTR met with greater success. Details The tape speed allowed 96 minutes on a large reel (later 120 minutes), and used 2 record/playback (R/P) heads on the drum rotating at 9,000 RPM with a 190-degree wrap around a very small head drum, recording 52 video lines per head segment. A single video frame was recorded across 6 tracks in the tape. The format only allowed for play, rewind and fast forward. Video is recorded on an FM signal with a bandwidth of 5.5 MHz. Three longitudinal audio tracks are recorded on the tape as well: two audio and one Linear timecode (LTC) track. BCN 50 VTRs were used at the 1980 Summer Olympics in Moscow. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microphonics
Microphonics, microphony, or microphonism describes the phenomenon wherein certain components in electronic devices transform mechanical vibrations into an undesired electrical signal (noise). The term comes from analogy with a microphone, which is intentionally designed to convert vibrations to electrical signals. Description When electronic equipment was built using vacuum tubes, microphonics were often a serious design problem. The charged elements in the vacuum tubes can mechanically vibrate, changing the distance between the elements, producing charge flows in and out of the tube in a manner identical to a capacitor microphone. A system sufficiently susceptible to microphonics could experience audio feedback, and make noises if jarred or bumped. To minimize these effects, some vacuum tubes were made with thicker internal insulating plates and more supports, and tube-socket assemblies were sometimes shock-mounted by means of small rubber grommets placed in the screw holes to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audio Spill
Spill (also known as bleed and leakage) is the occurrence in sound recording (particularly in close miking) and live sound mixing whereby sound is picked up by a microphone from a source other than that which is intended. Spill is usually seen as a problem, and various steps are taken to avoid it or reduce it. In some styles of music, such as orchestral music, jazz, and blues, it is more likely to be accepted or even seen as desirable. Occurrence Spill occurs when sound is detected by a microphone not intended to pick it up (for example, the vocals being detected by the microphone for the guitar). Spill is often undesirable in popular music recording, as the combined signals during the mix process can cause phase cancellation and may cause difficulty in processing individual tracks. It also causes difficulty in overdubbing, where the spill from the sound being replaced may still be audible on other channels. For sound reinforcement in live shows, mic bleed can make it hard for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forward Echo
In telecommunications, a forward echo is the propagation of a signal reflection in the same direction as the original signal and consisting of energy reflected back by one discontinuity and then forward again by another discontinuity. Forward echoes can be supported by reflections caused by splices or other discontinuities in the transmission medium (e.g. optical fiber, twisted pair, or coaxial tube). In metallic lines, they may be supported by impedance mismatches between the source or load and the characteristic impedance The characteristic impedance or surge impedance (usually written Z0) of a uniform transmission line is the ratio of the amplitudes of voltage and current of a single wave propagating along the line; that is, a wave travelling in one direction in ... of the transmission medium. They may cause attenuation distortion. See also * Pre-echo References Telecommunications engineering Telephony {{telephony-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Post-echo
In audio signal processing, pre-echo, sometimes called a '' forward echo'', (not to be confused with reverse echo) is a digital audio compression artifact where a sound is heard before it occurs (hence the name). It is most noticeable in impulsive sounds from percussion instruments such as castanets or cymbals. It occurs in transform-based audio compression algorithms – typically based on the modified discrete cosine transform (MDCT) – such as MP3, MPEG-4 AAC, and Vorbis, and is due to quantization noise being spread over the entire transform-window of the codec. Cause The psychoacoustic component of the effect is that one hears only the echo preceding the transient, not the one following – because this latter is drowned out by the transient. Formally, forward temporal masking is much stronger than backwards temporal masking, hence one hears a pre-echo, but no post-echo. Mitigation In an effort to avoid pre-echo artifacts, many sound processing systems use filters ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pre-echo
In audio signal processing, pre-echo, sometimes called a ''forward echo'', (not to be confused with reverse echo) is a digital audio compression artifact where a sound is heard before it occurs (hence the name). It is most noticeable in impulsive sounds from percussion instruments such as castanets or cymbals. It occurs in transform-based audio compression algorithms – typically based on the modified discrete cosine transform (MDCT) – such as MP3, MPEG-4 AAC, and Vorbis, and is due to quantization noise being spread over the entire transform-window of the codec. Cause The psychoacoustic component of the effect is that one hears only the echo preceding the transient, not the one following – because this latter is drowned out by the transient. Formally, forward temporal masking is much stronger than backwards temporal masking, hence one hears a pre-echo, but no post-echo. Mitigation In an effort to avoid pre-echo artifacts, many sound processing systems use filters where ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Type C Videotape
1–inch Type C (designated Type C by SMPTE) is a professional reel-to-reel analog recording helical scan videotape format co-developed and introduced by Ampex and Sony in 1976. It became the replacement in the professional video and broadcast television industries for the then-incumbent 2–inch quadruplex videotape (2–inch Quad for short) open-reel format. Additionally, it replaced the unsuccessful type A format, also invented by Ampex, and, primarily in mainland Europe, it supplemented the type B format, invented by the Fernseh division of Bosch, but it was replaced by type C format also there. Technical detail Compared to Quad, Type C had a smaller size, comparative ease of operation, and slightly higher video quality. 1–inch Type C is capable of "trick-play" functions such as still, shuttle, and variable-speed playback, including slow motion. 2–inch quadruplex videotape machines lacked these capabilities, due to the segmented manner in which it re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sine Wave
A sine wave, sinusoidal wave, or just sinusoid is a curve, mathematical curve defined in terms of the ''sine'' trigonometric function, of which it is the graph of a function, graph. It is a type of continuous wave and also a Smoothness, smooth periodic function. It occurs often in mathematics, as well as in physics, engineering, signal processing and many other fields. Formulation Its most basic form as a function of time (''t'') is: y(t) = A\sin(2 \pi f t + \varphi) = A\sin(\omega t + \varphi) where: * ''A'', ''amplitude'', the peak deviation of the function from zero. * ''f'', ''frequency, ordinary frequency'', the ''Real number, number'' of oscillations (cycles) that occur each second of time. * ''ω'' = 2''f'', ''angular frequency'', the rate of change of the function argument in units of radians per second. * \varphi, ''phase (waves), phase'', specifies (in radians) where in its cycle the oscillation is at ''t'' = 0. When \varphi is non-zero, the entire waveform appears to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
D-2 (video)
D-2 is a professional digital videocassette format created by Ampex and introduced in 1988 at the NAB Show as a composite video alternative to the component video D-1 format. It garnered Ampex a technical Emmy in 1989. Like D-1, D-2 stores uncompressed digital video on a tape cassette; however, it stores a composite video signal, rather than component video as with D-1. While component video is superior for advanced editing, especially when chroma key effects are used, composite video was more compatible with most analog facilities existing at the time. History Ampex created the first D-2 video machine, the ACR-225 commercial spot player working with Sony, who had done some early research into composite digital video, as a cost-effective solution for TV broadcasters with large investments in composite analog infrastructure such as video routers and switchers, since it could be inserted into existing analog broadcast facilities without extensive redesign or modifications. Thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
