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Speech and Channel Coding for North American TDMA Cellular Systems
Published in Jerry D. Gibson, The Communications Handbook, 2018
The IS-54 standard employs a vector-sum excited linear prediction (VSELP) coding technique. It represents a specific formulation of the much larger class of code-excited linear prediction (CELP) coders [2] that have proved effective in recent years for the coding of speech at moderate rates in the range 4-16 kb/s. VSELP provides reconstructed speech with a quality that is comparable to that available with frequency modulation and analog transmission over the AMPS system. The coding rate employed is 7.95 kb/s. Each of the six slots per frame carry 260 b of speech and channel coding information for a gross information rate of 13 kb/s. The 260 b correspond to 20 ms of real time speech, transmitted as a single burst.
Source Coding for Audio and Speech Signals
Published in Rajeshree Raut, Ranjit Sawant, Shriraghavan Madbushi, Cognitive Radio, 2020
Rajeshree Raut, Ranjit Sawant, Shriraghavan Madbushi
CELP coders are capable of producing good quality speech at around 4.8 Kbps. Below this, they suffer from distortion introduced by coarse quantization of model parameters due to limited number of bits. Also, the frame-by-frame analysis coupled with the high processing demands introduces delay that can degrade quality of conversation and introduce difficulties in related speech processing components, such as echo cancelling.
Digital Coding of Speech
Published in John Holmes, Wendy Holmes, Speech Synthesis and Recognition, 2002
In comparison with the other intermediate-rate systems described in this section, CELP coders usually offer better performance at the cost of greater computational complexity. Improvements in the technology of signal processing chips, and the general increase in available computational power, have made complexity less important than before, and CELP coders now dominate in the field of mobile telephony and in related application areas.
A SILK Adaptive Steganographic Scheme Based on Minimizing Distortion in Pitch Domain
Published in IETE Technical Review, 2021
Yanzhen Ren, Shan Zhong, Weiping Tu, Hanyi Yang, Lina Wang
With the emergency of the above steganographic algorithms, steganalytic schemes for CELP speech coding parameters were gradually proposed. For LPC parameters, the distribution characteristics of codebook and phonemes were, respectively, used in [18,19] to achieve steganalysis methods. For pitch period, based on the correlation characteristics of adjacent frames, the steganalysis algorithm proposed in [20] constructed a steganalytic network model using the codebook index; according to the short-term relative stability of pitch lags in voiced speech, Ren et al. [21] proposed a steganalysis algorithm based on the second-order difference of pitch lags. For excitation signal, in [22], a steganalysis algorithm was proposed based on the correlation between secret message and positions of non-zero pulses by taking advantage of the randomness of selecting non-zero pulses in fixed codebook searching process; Miao et al. [23] took the Markov transition matrix of pulse position, corresponding conditional entropy and joint entropy as characteristics for steganalysis; Ren et al. [24] found that the probability of the same pulse position in a track increases obviously after steganography, which can be taken as the characteristics of steganalysis algorithm.