Adaptive prediction filter using block floating point format and

Details Adaptive prediction filter using block floating point format and Adaptive prediction filter using block floating point format and

1995-01-05

1998-05-12

MacDonald, Allen R.

Boots, shoes, and leggings

364745, 36472419, G06F 738

Patent

active

057519021

DESCRIPTION:

BRIEF SUMMARY
RELATED APPLICATION

This application is related to concurrently filed copending application Ser. No. 08/362,513, of the same inventor, Attorney Docket No. PHD 93-066. Such related application pertains to a linear predictive coder or decoder wherein recursive recomputations of prediction coefficients are performed more accurately and without increasing the complexity of the required calculations. The present application relates to a linear predictive coder or decoder wherein the number of recursive recomputations which must be repeated when an overflow occurs is minimized by only performing such repeated recomputations starting with the prediction coefficient at which the overflow occurred. That is feasible because the values of the previously recomputed coefficients will correspond to the values that would be obtained if they were again recomputed using a revised block floating point format.


BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a transmission system comprising a coder for coding a signal, a transmitter for transmitting the coded signal to a receiver, which includes a decoder for decoding the coded signal, and an adaptive prediction filter.
The invention likewise relates to a terminal unit, a coder, a decoder and an adaptive prediction filter.
2. Description of the Related Art
Such a transmission system can be assembled, for example, without difficulty from the document (I) "Draft text for Annex A of G.728 16 Kbits Fixed Point Specification", Temporary Document 41(P), CCIT Study Group 15, Geneva, 7-17 Sept. 1993, which corresponds to no longer available Doc. AH. 93-D.3, CCITT Study Group XV, London, Mar. 29-30, 1993; and from the document (II) CCITT Recommendation G.728, "Coding of speech signals at 16 kbit/s using low-delay code excited linear prediction, Geneva 1992". The transmission systems can always be used when multiple use is to be made of a given transmission capacity. The coding reduces the bit rate of a signal and thereby makes it possible, for example, to hold four telephone conversations simultaneously over one 64 kbit/s transmission channel.
The multiple use of a given transmission capacity has very much importance in radio channels, as will be readily understood if one considers the rising number of subscribers of mobile radio systems. Also the storage capacity of a memory with an arbitrary storage medium can be used to considerably more advantage when bit rate reducing coders and appropriate decoders are used, because less storage space is necessary for storing an information signal. filter. The computation is performed segment by segment using sample values of an auxiliary signal which may be an (electric) audio signal or a speech signal, for example, coming from a person. Alternatively, it is possible for the auxiliary signal to be a synthetic audio or speech signal as produced in a coder which operates according to the principle of "analysis by synthesis". A linear correlation between a predicted sampling value (prediction value) of the auxiliary signal and previous sampling values of this signal is realised with prediction coefficients. The prediction coefficients are determined so that the sum of the squares of all the errors computed for a segment of sampling values assumes a minimum value. An error is here meant to be understood as the difference between a sampling value and its predicted value. More accurate descriptions will be given hereinbelow. signal by a synthesis filter. This synthetic audio signal is subtracted from an audio signal to be coded and the difference is used for optimizing selection of the excited signal.
The computation of the prediction coefficients calls for correlation coefficients which are derived from the sampling values of the synthetic audio signal. The computation of the prediction coefficients on the basis of the correlation coefficients calls for much circuitry and cost. To reduce this circuitry and cost the prediction coefficients are computed recursively. To begin with, a first reflection coefficient is co

REFERENCES:
patent: 3842250 (1974-10-01), Anderson
patent: 4520491 (1985-05-01), Raulin et al.
patent: 5025404 (1991-06-01), Janssen et al.
patent: 5142656 (1992-08-01), Fielder et al.
Draft text for Annex A of G.728-16 kbit/s Fixed Point Specification, Temporary Doc. 41(P), CCIT Study Group 15, Geneva, 7-17 Sep. 1993, pp. 1-18.
CCIT Recommendation G. 728, Coding of Speech Signals At 16 kbit/s Using Low-Delay Code Excited Linear Prediction, Geneva 1992.

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