CCITT has recommended two types of PCM primary multiplex system as a standard for international use. One is a 24-channel PCM system which has been widely introduced in Japan, North American countries and many others. ...
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CCITT has recommended two types of PCM primary multiplex system as a standard for international use. One is a 24-channel PCM system which has been widely introduced in Japan, North American countries and many others. The other is a 30-channel PCM system used in European countries. The development of a new 30-channel PCM system meeting CCITT recommendation which uses the latest techniques and wide experience in the PCM field is reported.
An adaptive differential-pulse-code-modulation method (ADPCM) for transmission of bandlimited analog signals is proposed. The ADPCM-method requires lower data rates than pulse-code-modulation (PCM) or differential-pul...
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An adaptive differential-pulse-code-modulation method (ADPCM) for transmission of bandlimited analog signals is proposed. The ADPCM-method requires lower data rates than pulse-code-modulation (PCM) or differential-pulse-code-modulation methods. If the bandlimited analog signal is quantized with m bit (this is equivalent to 2**m different signal levels) and if the maximum difference of two adjacent samples is plus or minus 2**i, one obtains data rates of D//P//C//M equals m multiplied by (times) f//a (f//a: sample frequency), D//D//P//C//M equals (i plus 1 multiplied by (times) f//a less than equivalent to D//P//C//M if m less than i, D//A//D//P//C//M equals 1? f//a//a equals (i minus 1? f//a less than D//D//P//C//M less than D//P//C//M (assumption: i greater than equivalent to 2).
An adaptive differential-pulse-code-modulation method (ADPCM) for transmission of bandlimited analog signals is proposed. The ADPCM-method requires lower data rates than pulse-code-modulation (PCM) or differential-pul...
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An adaptive differential-pulse-code-modulation method (ADPCM) for transmission of bandlimited analog signals is proposed. The ADPCM-method requires lower data rates than pulse-code-modulation (PCM) or differential-pulse-code-modulation methods. If the bandlimited analog signal is quantized with m bit (this is equivalent to 2**m different signal levels) and if the maximum difference of two adjacent samples is plus or minus 2**i, one obtains data rates of D//P//C//M equals m multiplied by (times) f//a (f//a: sample frequency), D//D//P//C//M equals (i plus 1 multiplied by (times) f//a less than equivalent to D//P//C//M if m less than i, D//A//D//P//C//M equals 1? f//a//a equals (i minus 1? f//a less than D//D//P//C//M less than D//P//C//M (assumption: i greater than equivalent to 2).
The paper is concerned with the receiver of an ADPCM-system, especially with the computation of the predictor coefficients and with the problem of receiver stability. The relationship between receiver stability and po...
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The paper is concerned with the receiver of an ADPCM-system, especially with the computation of the predictor coefficients and with the problem of receiver stability. The relationship between receiver stability and positive definiteness of the Toeplitz matrix from which the predictor coefficients are computed is pointed out. It is shown how simple tests can be incorporated into the process of computing the predictor coefficients. It is proved that the receiver derived this way is indeed stable.
In earlier investigations, it has been found that, at low bit rates, the dithered quantisation of speech samples in pulse-codemodulation (p.c.m.) is perceptually pleasing but is less intelligible than normal fixed-le...
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In earlier investigations, it has been found that, at low bit rates, the dithered quantisation of speech samples in pulse-codemodulation (p.c.m.) is perceptually pleasing but is less intelligible than normal fixed-level quantised p.c.m. Also, it has been suggested that a possible cause of the reduced intelligibility of the dithered p.c.m. is the effect that the dithering has on the zero crossings of the speech signal. This paper reports on an investigation into this suggestion. A number of methods of dithered quantisation are considered in which the zero crossings of the speech signal are preserved, and the results of intelligibility tests carried out to compare the various methods of dithering are presented. The statistical analysis of the results shows that, for 3, 4 and 5 bits per sample quantisation, two of the methods of dithered quantisation are significantly more intelligible than normal, correspondingly low-bit-rate p.c.m., and the advantage is better than 1 bit per sample.
Quantizing error in a PCM system for color television can lead to subcarrier phase and gain errors in a decoded color signal. These errors depend upon the signal/noise ratio at the encoder input, and crosscorrelation ...
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Quantizing error in a PCM system for color television can lead to subcarrier phase and gain errors in a decoded color signal. These errors depend upon the signal/noise ratio at the encoder input, and crosscorrelation techniques are applied to a digital computer model of an encoder-decoder system to evaluate this dependence.
The C. C. I. T. T. recommendations specify a well defined lower limit to the signal-to-quantizing-noise ratio of a P. C. M. transmission system, complete with both transmit and receive terminals. The purpose of this p...
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The C. C. I. T. T. recommendations specify a well defined lower limit to the signal-to-quantizing-noise ratio of a P. C. M. transmission system, complete with both transmit and receive terminals. The purpose of this paper is to analyse the possibility of giving convenient performance specifications for the transmitter (encoder) and the receiver (decoder), separately, in order to guarantee that the above mentioned recommendations are fulfilled for any transmitter-receiver pair.
Some quantizing and coding algorithms for differential pulse code modulation (DPCM) are analyzed and evaluated in terms of data statistics generated on the digital television communication system (DITEC) developed at ...
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Some quantizing and coding algorithms for differential pulse code modulation (DPCM) are analyzed and evaluated in terms of data statistics generated on the digital television communication system (DITEC) developed at COMSAT Laboratories. A DPCM encoder for monochrome television signals using entropy coding and selective prediction is proposed. Simulations of this encoder show that, at a transmission rate of 4. 5 bits/picture element (pel), there is no perceptible degradation between the original and the reconstructed pictures. A transmission buffer of 4,000 bits has been found adequate to accommodate the digitized signal.
Distortion effects of finite sampling rates on real nonbandlimited signals are usually ignored when considering the snr as a figure of merit. In this paper simple bounds to the snr of a PCM system with signal distorti...
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Distortion effects of finite sampling rates on real nonbandlimited signals are usually ignored when considering the snr as a figure of merit. In this paper simple bounds to the snr of a PCM system with signal distortion are derived. Given the snr that is required and the amount of distortion that can be tolerated, the sampling rate can approximately be found, provided that the signal statistics at the input is known. Some simple examples are presented for illustration.
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