Excavating
Patent
1993-04-26
1995-10-03
Envall, Jr., Roy N.
Excavating
381 46, G10L 300, G10L 500
Patent
active
054558336
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for the detection of errors, respectively perceptible disturbances, in the transmission of frequency-coded digital signals and, in particular, audio signals transmitted in blocks by a transmitter to a receiver.
STATE OF THE ART
Processes in which, by way of illustration, audio signals are transmitted frequency-coded are general state of the art. PCT publications WO 88/001811 and WO 89/08357 are cited, only by way of example. Moreover, explicitly these publications are to be referred to with regard to the explanation of any terms not made more apparent herein.
The processes described in these publications utilize a suited imaging technique, such as filter banks, fast Fourier transformation (FFT), DCT, MDCT, etc., for coding signals and, in particular, audio signals digitally with respect to frequency.
If the transmission of the data is faulty, i.e. if individual or several consecutive frequency coefficients contain an error due to disturbances, disturbances will occur in the receiver following "inverse transformation in this period", in the case of audio signals manifested by blubbering, gurgling, etc.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a process for the detection of errors, i.e. of perceptible disturbances, by a transmission of frequency-coded digital signals and, in particular, audio signals transmitted in blocks by a transmitter to a receiver, which operates in a simple manner and yet is subjectively relatively free of disturbances.
A solution to this object according to the present invention is set forth in claim 1 hereto. Further improvements to the present invention are the subject of the subclaims.
An element of the present invention is that from the frequency coefficients of earlier and, if need be, future blocks, a decision function is formed, on the basis of which it is determined whether or not an error occurred during the transmission. The term "error" means that a decision is made by comparing earlier and, if need be, future frequency coeffients whether or not a perceptible, i.e. by way of illustration, in the case of audio signals an audible disturbance is occurring following inverse transformation. If it is determined that a frequency coefficient contains an error, i.e. leads to a perceptible disturbance, it will not be utilized for the evaluation of subsequent blocks.
According to claim 2, other frequency coefficients may also be employed for the decision function. In particular, they may be frequency coefficients having a lower ordinal number, i.e. belonging to lower frequencies, than the frequency coefficients of the checked frequency coefficient (claim 3).
Furthermore, according to claim 4, it is preferable if only frequency coefficients of earlier blocks are used for the decision function. This obviates relatively time-consuming intermediate storage of the transmitted frequency coefficients in the receiver.
According to claims 5 and 6, functions F(i,k) formed by taking maximum value, averaging or other linear combinations of coefficients of adjacent blocks may be employed as decision functions.
According to claim 5, a symmetrical frequency interval which, on the one hand, permits particularly good error detection but in which, on the other hand, "unchecked higher" frequency coefficients are utilized is employed.
In any event, the invented process permits certain detection of errors, i.e. of perceptible distubances, without requiring the transmission of supplementary information in addition to the transmission of frequency coefficients. As correction occurs with utilization of temporally and/or frequency adjacent transformed values, the invented process can be applied in all types of imaging technology and independent of any specific internal set-up of the transmission system. It may, by way of illustration, be used in the detection of audible disturbances, by way of illustration, in the transmission of digital radio broadcasting in which a "data reduction process" is employed or also
REFERENCES:
patent: 4245248 (1981-06-01), Netravali et al.
patent: 4656514 (1987-04-01), Wilkinson et al.
patent: 4907277 (1990-03-01), Callens et al.
Robert Mitchell ("Channel Error Recovery for Transform Image Coding", IEEE, vol. COM 29, No. 12, Dec. 1981).
Herre Jurgen
Seitzer Dieter
Envall Jr. Roy N.
Fraunhofer Gesellschaft zur Forschung e.V.
Moise Emmanuel
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