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Entries found for search: coding

audio coding mode : A parameter in Dolby Digital surround-sound format which refers to the number of channels and their location in for form F/R, where F is the number of front channels and R is the number of rear channels. For example, 5-channel surround is called 3/2 mode, stereo is 2/0, and mono is designated 1/0.

coding : The process of altering the form of a signal, such as from analog to digital. Or, the coding may be used to allow a transformation of the signal not possible in its original form such as in noise reduction. Or, coding may be used to take advantage of effects inherent in the coding process itself, such as in PCM which allows recording and playback with low noise. The complementary stage to coding is decoding, a process which attempts to reconstruct the original signal, i.e., from digital back to analog for use with loudspeakers. See codec.

encoding : (1) The process of converting the already sampled, numerical voltage of the analog input into binary numbers and assembling these with any location and error-related data generated elsewhere into complete digital words, usually of 16 bits. See analog-to-digital converter. (2) The application of any type of processing to a signal before recording which will later be removed by complementary processing during playback. Most NR systems are good examples of the encoding/decoding process. See stretched.

free encoding : An extension of spaced microphone recording techniques, systems which create pseudo-stereo from a mono source will also generate a strong surround signal, and stereo-width controls can be used to manage the balance between frontal and surround channels. Increasing stereo width also increases the level of the surround channel, whereas decreasing width reduces the surround content. This is because a surround decoder will automatically send anything which is of a similar level, but opposite polarity between left and right channels, straight to the surround output. Artificial reverberation, for example, is automatically spread across L, S, and R. See LCRS.

sub-band coding : A type of the split-band coding process, where the incoming audio signal is split into a number of independent frequency sub-bands, and the accuracy of the quantization is varied in each band according to the input signal energy. Critical regions of the audio spectrum can, therefore, be coded more accurately, with quantizing energy being biased toward the high-sensitivity, low-frequency regions. High-energy regions are also coded more accurately than in PCM techniques, yielding a lower coding noise platform. See transform coding.

split-band coding : A transform encoding/decoding technique where the signal is split into a number of independent bands, used to take advantage of the spectral redundancies within the audio spectrum. A type of split-band encoding is sub-band coding.

Scheiber matrix encoding/decod : The algorithm used in Dolby Stereo optical process to produce quadraphonic LCRS(left/center/right/surround) sound from two channels. In this process, common in-phase information would bleed into the center channel, while the surround channel would receive out-of-phase material. See SVA.

perceptual coding : Any audio compression scheme that deletes audio frequencies that are masked by other, more dominant frequencies, and thus are not perceived by the listener. See split-band coding, transform coding, temporal masking, MPEG, PASC, ATRAC, and AC3.

transform coding : Used in Dolby AC-2 and MPEG codecs, whereby an input signal is analyzed within the frequency domain as a series of narrow bands,; e.g., an AC-2 encoder/decoder uses 256 narrow bands. Frequency-masked bands whose information is inaudible because of sustained tones or transients will be ignored by such systems, thereby enabling the compression algorithm to concentrate its bit allocation on those bands which contain subjectively relevant information. In addition, transform-based systems use a system of predefined waveform patterns from an established "wavelook-up" tablelibrary of sound models and send only the identity code to the decoder to "resynthesize" the closest-fit library model. As opposed to, for example, ADPCM.

decoding : (1) In signal processing, restoring a signal to its original state by reprocessing the signal in a complementary manner, e.g., a NR systemís re-expansion of the signal during playback. (2) In digital recording, the entire process converting the encoded data stream back into an analog signal, including the process of error correction, i.e., digital-to-analog conversion.

DP5xx encoding : A family (DP521/DP522/DP523/DP524) of 2-channel codecs used for point-to-point and point-to-multipoint signal distribution: ISDN, Switched-56, T1 or DS-3 networks; recording/post-production studio interconnection with or without video; and voice-over and other applications. AC-2 and AC-3 perceptual coding algorithms are supported to provide audio transfers at a total data rate between 56 kBps and 384 kBps. With AC-3, single-channel, two-channel, and composite stereo algorithms are supported.

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