companding


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companding

[kəm′pand·iŋ]
(electronics)
A process in which compression is followed by expansion; often used for noise reduction in equipment, in which case compression is applied before noise exposure and expansion after exposure.

companding

(1) In the analog world, a method for improving audio reproduction by altering the dynamic range of the signals. On outgoing transmission, it raises the amplitude of weak signals and lowers the amplitude of strong signals. On incoming transmission, it restores the signal to its original form. Such techniques are used in dbx and Dolby noise reduction, AM, FM and SSB radio as well as in voice and musical instrument amplification to reduce feedback. See codec.

(2) In the digital world, a compression technique used in pulse code modulation (PCM). It reduces the number of bits used to represent digital voice samples in the loudest parts of the conversation. See mu-Law, A-Law and codec.
References in periodicals archive ?
[18.] Yuan Jiang, "New companding transform for PAPR reduction in OFDM", IEEE Commun Letters, vol.14, no.4, pp.
For the coefficient z satisfying [absolute value of z] [greater than or equal to] T(p, q), the companding error e between z and z' is given by
Fig.4 CCDF for DWT/DCT with 64DAPSK/64QAM for no companding, companding and exponential signals In figure 4, the continuous line graphs represent the complementary cumulative distribution (CCDF) vs.
The efficiency of the proposed algorithm is compared to the scalar companding system based on the G.711 standard [4].
This unit is called companding transform (CT), which will be addressed in the next section in detail.
Companding schemes offer the advantages of low implementation complexity and capability of efficiently trading between PAPR and BER.
The aim of this study is to gain the advantages of KHN circuit structure, log-domain characteristics and companding idea listed above.
On the other hand, clipping and companding are low in complexity but cause significant signal distortion, that results in degraded error performance and spectral regrowth.
Motorised Unit,Sampling & Reconstruction ,Delta, Adaptive Delta and Delta Sigma Modulation/ Demodulation ,Data Formatting and Carrier Modulation/ Transmitter ,Data Reformatting & Carrier Demodulation Receiver,Error Detection and Correction-Cyclic Code,PCM Generation & Demodulation using CODEC Chip,4-Channel TDM-PCM Transmitter and Receiver,Digital Companding A-Law and o-Law,Understanding Noise Generator and its applications,PAM, PPM, PWM and Line
determining the codebook, is often based on companding technique by which non-uniform quantization is achieved by compression of the input signal x using a compressor with a non-linear characteristic c(*), then by the quantization of the compressed signal c(x) applying uniform quantizer and finally by expanding the quantized values of the compressed signal using a non-linear inverse compression characteristics [c.sup.-1](*).
The signal distortion algorithm limits the OFDM signal below a given threshold by nonlinear distortion and includes: signal clipping [7] and companding transformation [8].
In (9)-(10) parameter tmax denotes the maximal amplitude of the optimal companding quantizer for the unit variance and its values, depending on the number of quantization levels, can be find in [12].

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