NextLevel Glossary Home > Support > Glossary ASPI ASPI, the Advanced SCSI Programming Interface provides an API originated by Adaptec which standardizes communication on a computer bus between a SCSI host adapter on the one hand and SCSI (and ATAPI) peripherals on the other. Auto gain control Automatic gain control (AGC) is an adaptive system found in many electronic devices. The average output signal level is fed back to adjust the gain to an appropriate level for a range of input signal levels. For example, without AGC the sound emitted from an AM radio receiver would vary to an extreme extent from a weak to a strong signal; the AGC effectively reduces the volume if the signal is strong and raises it when it is weaker. AGC algorithms often use a PID controller where the P term is driven by the error between expected and actual output amplitude. Attack Attack is the parameter that sets the speed at which an envelope or dynamics processor starts. Buffer Buffers are often used in conjunction with I/O to hardware, such as disk drives, sending or receiving data to or from a network, or playing sound on a speaker. A line to a rollercoaster in an amusement park shares many similarities. People who ride the coaster come in at an unknown and often variable pace, but the roller coaster will be able to load people in bursts (as a coaster arrives and is loaded). The queue area acts as a buffer: a temporary space where those wishing to ride wait until the ride is available. Buffers are usually used in a FIFO (first in, first out) method, outputting data in the order it arrived. Band pass filter Band pass filter allows only the band of frequencies surrounding the cutoff frequency to pass through unaffected. Chorus Chorus is an effect in which multiple copies of a signal are played together slightly out of time to create a shimmering effect. CODEC An acronym for compression decompression. Codecs are installable Windows components which can be used to compress the size of a media file during save and to decompress the file during playback. Compressor A dynamics processor that reduces the level of any signal exceeding a specified threshold volume. Delay In its general sense, delay refers to a lapse of time. In audio, delay is an audio effect which records an input signal to an audio storage medium, and then plays it back after a period of time. The delayed signal may either be played back multiple times, or played back into the recording again, to create the sound of a repeating, decaying echo. Delay In its general sense, delay refers to a lapse of time. In audio, delay is an audio effect which records an input signal to an audio storage medium, and then plays it back after a period of time. The delayed signal may either be played back multiple times, or played back into the recording again, to create the sound of a repeating, decaying echo. DTMF Dual-tone multi-frequency (DTMF) signaling is used for telephone signaling over the line in the voice-frequency band to the call switching center. The version of DTMF used for telephone tone dialing is known by the trademarked term Touch-Tone (canceled March 13, 1984), and is standardized by ITU-T Recommendation Q.23. It is also known in the UK as MF4. Other multi-frequency systems are used for signaling internal to the telephone network. EQ (Equalization) Equalization, equalisation or EQ is the process of using passive or active electronic elements or digital algorithms for the purpose of altering (originally flattening) the frequency response characteristics of a system. Amplitude equalization is usually meant when it is stated without qualification but any frequency dependent response characteristic is capable of having equalization applied. Most notably there is phase and time-delay equalizations. There is also spatial directivity equalization. Expander Expander is a device or computer algorithm that reduces the level of a signal when it falls below a specified threshold in order to exaggerate its dynamic range. Flanger Flanger is an audio effect that occurs when two identical signals are mixed together, but with one signal time-delayed by a small and gradually changing amount, usually smaller than 20 milliseconds. This produces a swept comb filter effect: peaks and notches are produced in the resultant frequency spectrum, related to each other in a linear harmonic series. Varying the time delay causes these to sweep up and down the frequency spectrum. Part of the output signal is usually fed back to the input (a "re-circulating delay line"), producing a resonance effect which further enhances the intensity of the peaks and troughs. The phase of the fed-back signal is sometimes inverted, producing another variation on the flanging sound. Fade In / Fade Out Fade In is an effect that changes level over time increasing in amplitude from silence. Fade Out is an effect that changes audio level over time falling gradually to silence. Expander is a device or computer algorithm that reduces the level of a signal when it falls below a specified threshold in order to exaggerate its dynamic range. Filter Filter is a device or computer algorithm that removes specified frequencies from a signal. High pass filters High pass filters allow all frequencies higher than the cutoff frequency to pass through unaffected. Locator Locator is a bookmark for a time location. Notching Filter Notch or Notching Filter is filter wherein a selected frequency and a specified number of frequencies above and below it -- called a "band" -- are affected. OPC OPC is a function of a CD or DVD writer. It checks the proper writing power and reflection of the media in use, calculating the optimum laser power and adjusting it for writing the particular session. More sophisticated is Active OPC or Running OPC. Active OPC monitors writing power and reflection of the media in use, calculating the optimum laser power and adjusting it in real-time, which, in theory, should result in a better quality burn. Phaser A phaser is an audio signal processing technique used to filter a signal by creating a series of peaks and troughs in the frequency spectrum. The position of the peaks and troughs is typically modulated so that they vary over time, creating a sweeping effect. For this purpose, phasers usually include a low frequency oscillator. Synchronization Synchronization or Sync is the coordination of timing between audio and/or video devices. White noise White noise is an audio signal that contains noise at the same level at all frequencies. SPTI SPTI is SCSI Pass-Through Interface, it can help SCSI send order to application. It's based on Windows NT and Windows 2000.