Electrical audio signal processing systems and devices – Binaural and stereophonic – Broadcast or multiplex stereo
Patent
1997-07-21
1999-07-20
Chang, Vivian
Electrical audio signal processing systems and devices
Binaural and stereophonic
Broadcast or multiplex stereo
H04H 500
Patent
active
059265531
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
According to a first aspect, the present application refers to a method for measuring the conservation of stereophonic audio signals when employing a processing technique or a coding technique on stereophonic signals.
According to a further aspect, the present invention refers to a method for identifying jointly processed or coded stereophonic audio signals.
DESCRIPTION OF THE PRIOR ART
For the purposes of data reduction, techniques for the joint stereo coding of stereophonic audio signals are being used increasingly in the case of very high compression factors. A known coding technique of this type is the so-called "intensity stereo technique". When employing the intensity stereo technique, audible distortions may occur in the stereo acoustic pattern. It is therefore of interest to make it possible to detect such distortions by means of measurement. It is also of interest to establish whether a coded and then decoded signal was coded using a joint stereo coding technique.
From the prior, non-prepublished German patent application P 43 31 376.0-31, a method for determining the type of coding to be chosen for coding at least two signals is known, in which a transformation of signals into the frequency domain is performed and, on the basis of spectral values, a similarity measure is determined, on the basis of which the type of coding to be chosen is specified. Here, one of the signals in a coding type which is used if a high similarity measure is detected and which is e.g. the intensity stereo coding, is first coded and then decoded to create a coding-error-afflicted signal. Both this signal and the original signal, which is not afflicted with the coding error, are transformed into the frequency domain. Spectral values of the respective corresponding channels, e.g. of the left or e.g. of the right channel in the case of a twin-channel stereo signal, of mutually corresponding subbands both of the transformed coding-error-afflicted signal and of the transformed coding-error-free signal are compared with one another employing a masked hearing threshold, where the masked hearing threshold is determined by psychoacoustic calculations. This comparison of the spectral values of the respective corresponding channels forms the basis for the determination of a similarity measure, on the basis of which the coding type to be chosen is specified.
A known measurement method for the hearing-related evaluation of distortions in the stereo acoustic pattern is the so-called NMR method, which is known from the following prepublication: K. Brandenburg, T. Sporer: "`NMR` and `masking flag`: Evaluation of Quality using Perceptual Criteria", Proc. of the 11th International AES Conference on Audio Test and Measurement, Portland 1992 pp. 169-179. However, it is not possible to record the stereophonic acoustic pattern with a method of this kind.
Furthermore, with the known methods described above it is not possible to determine whether the coding technique used is a joint stereo coding one.
From WO-A-8908357 a method for the quantitative real-time recording of the audibility of disturbances in the coding of audio signals is known, in which a processed audio signal which is to be compared, obtained e.g. by coding and subsequent decoding, is correlated with the original signal in order to establish the signal delay of a system processing the signal, whereupon the difference of the signals for comparison is formed in the time domain, taking into account the ascertained signal delay time. The spectral composition both of the original signal and also of the difference signal is then formed. From the spectral composition of the original signal, the masked hearing threshold of the human ear is determined and compared with the spectral composition of the difference signal. The spectral regions of the difference signal which exceed the masked hearing threshold serve for the quantitative recording of the audibility of disturbances in the signal processing.
SUMMARY OF THE INVENTION
It is an object of the present i
REFERENCES:
K. Brandenburg and T. Sporer: "NMR" and "Masking Flag": Evaluation of Quay Using Perceptual Proceedings of AES 11th International Conference, pp. 169-179, Jan. 1992.
Brandenburg Karlheinz
Herre Jurgen
Keyhl Michael
Schmidmer Christian
Seitzer Dieter
Chang Vivian
Fraunhofer-Gesellschaft zur Forderung der Angewandten Forschung
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