Journal ArticleDOI
Predictive Coding of Speech at Low Bit Rates
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TLDR
A new class of speech coders are described which allow one to realize the precise optimum noise spectrum which is crucial to achieving very low bit rates, but also represent the important first step in bridging the gap between waveform coders and vocoders without suffering from their limitations.Abstract:
Predictive coding is a promising approach for speech coding. In this paper, we review the recent work on adaptive predictive coding of speech signals, with particular emphasis on achieving high speech quality at low bit rates (less than 10 kbits/s). Efficient prediction of the redundant structure in speech signals is obviously important for proper functioning of a predictive coder. It is equally important to ensure that the distortion in the coded speech signal be perceptually small. The subjective loudness of quantization noise depends both on the short-time spectrum of the noise and its relation to the short-time spectrum of the Speech signal. The noise in the formant regions is partially masked by the speech signal itself. This masking of quantization noise by speech signal allows one to use low bit rates while maintaining high speech quality. This paper will present generalizations of predictive coding for minimizing subjective distortion in the reconstructed speech signal at the receiver. The quantizer in predictive coders quantizes its input on a sample-by-sample basis. Such sample-by-sample (instantaneous) quantization creates difficulty in realizing an arbitrary noise spectrum, particularly at low bit rates. We will describe a new class of speech coders in this paper which could be considered to be a generalization of the predictive coder. These new coders not only allow one to realize the precise optimum noise spectrum which is crucial to achieving very low bit rates, but also represent the important first step in bridging the gap between waveform coders and vocoders without suffering from their limitations.read more
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DissertationDOI
Optimization of Coding of AR Sources for Transmission Across Channels with Loss
TL;DR: A new algorithm for optimization of predictive coding of AR sources for transmission across channels with loss is proposed and it is proved that employing fixed-lag smoothing at the decoder is guaranteed to reduce the estimated source signal mean squared error under mild constraints on the encoder filter coefficients.
Sllloothing the Evolution of the Spectral Par8.lIleters in Speech Coders
TL;DR: The objective of this thesis is to improve the modelling of speech signal within the constraints of a low bit rate coder by modifying the traditional linear prediction analysis in such way that the fluctuations of the LP coefficients are reduced, while the pitch pulse shape evolves slowly.
Journal ArticleDOI
On the Performance of Speech Waveform Coders with Noise Spectral Shaping
Hwang Soo Lee,Chong Un +1 more
TL;DR: Simulation results show that the performance improvement of these waveform coders with spectral shaping is about 0.5-3 dB over the systems without noise shaping, which yields subjectively more pleasing and intelligible sound than those without it.
Journal ArticleDOI
Encoder reverberations in adaptive predictive coding
TL;DR: Describing functions are used to model the nonlinear quantizer effects of coarsely quantized difference signals found primarily in adaptive predictive coding (APC) systems, and adaptive order prediction is introduced, analyzed, and offered as a method for increasing the robustness of APC encoders.
References
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Journal ArticleDOI
Speech analysis and synthesis by linear prediction of the speech wave.
B. S. Atal,Suzanne L. Hanauer +1 more
TL;DR: Application of this method for efficient transmission and storage of speech signals as well as procedures for determining other speechcharacteristics, such as formant frequencies and bandwidths, the spectral envelope, and the autocorrelation function, are discussed.
Journal ArticleDOI
Predictive coding--I
TL;DR: Part II will give the mathematical criterion for the best predictor for use in the predictive coding of particular messages, will give examples of such messages, and will show that the error term which is transmitted in predictive coding may always be coded efficiently.
Journal ArticleDOI
Optimizing digital speech coders by exploiting masking properties of the human ear
TL;DR: New results of masking and loudness reduction of noise are reported and the design principles of speech coding systems exploiting auditory masking are described.
Journal ArticleDOI
Predictive coding of speech signals and subjective error criteria
TL;DR: Improved speech quality is obtained by efficient removal of formant and pitch-related redundant structure of speech before quantizing, and by effective masking of the quantizer noise by the speech signal.
Journal ArticleDOI
Adaptive predictive coding of speech signals
Bishnu S. Atal,M. R. Schroeder +1 more
TL;DR: Preliminary studies suggest that the binary difference signal and the predictor parameters together can be transmitted at approximately 10 kilobits/second which is several times less than the bit rate required for log-PCM encoding with comparable speech quality.