Process for transmitting and/or storing digital signals of multi

Details Process for transmitting and/or storing digital signals of multi Process for transmitting and/or storing digital signals of multi

1995-05-02

1998-01-06

Chin, Stephen

Pulse or digital communications

Systems using alternating or pulsating current

Plural channels for transmission of a single pulse train

H04B 166

Patent

active

057063095

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a process for transmitting and/or storing digital signals of multiple channels according to the introductory part of claim 1.
2. Description of Related Art
Process in which digital signals, in particular audio signals, are transmitted frequency-coded are known, by way of illustration, from the PCT publications WO 88/01811 and WO 89/08357.
For one-channel and two-channel transmission, the standardization committee, Moving Pictures Experts Group (MPEG), of the International Standardization Organization (ISO) set the standard ISO-11172-3 for coding and the to-be-transmitted bit stream of audio signals.
Psychoacoustic models which permit reducing the amount of to-be-transmitted data while exploiting the properties of human hearing with minimal quality loss are used in the mentioned coding process.
For explanation of all terms not made more apparent herein reference is explicitly made to the publications and the standard.
In further developing international standards, work is presently being done, among other things, in reducing the data in multi-channel transmission. The scientific publication "MUSICAM-Surround: A Universal Multi-Channel Coding System Compatible with ISO 11172-3", 93rd AES convention, 1992, San Francisco, proposes a process for transmitting of up to 5 channels. By way of illustration, two stereo channels and one center channel as well as two side channels (3/2 stereophony) or two stereo channels and three commentary channels can be transmitted.
Further data reduction is achieved in that parts of the stereo signals, which are insignificant with regard to spatial perception, are transmitted in only one channel. In addition transmitted are scale factors, which represent a measure of the intensity of the signals conducted from the mono-channel to the corresponding loudspeakers. With this process, artefacts with lower audio pleasure are generated especially in the lower frequency range.
In addition to this, it has been proposed to reduce the to-be-transmitted amount of data by not determining a so-called intra-channel masking threshold for each channel for the coding, but rather by providing a common threshold for all the channels, taking into consideration the intra-channel masking effect. However, the use of a common masking threshold results in that interfering coding noises may be perceptible in the vicinity of a loudspeaker.


SUMMARY OF THE INVENTION

The object of the present invention is to provide a process for transmitting and/or storing digital signals of multiple channels permitting further reduction of the amount of to-be-transmitted data and resulting in no subjectively perceptible disturbance of transmitted signals.
This object is solved by a process with the features of claim 1.
According to the present invention, the signals of the different channels are first converted into spectral values. Subsequently, using the spectral values of the corresponding segments of the different channels it is determined in which channels similar spectral portions occur.
Investigated is whether in combining the segments from the different channels, the interferences caused by the joint coding are below the audibility threshold or if artefacts are generated. If no artefacts are expected, combination is permitted. In this manner, the K input channels are imaged in segments on the spectral data channels (transmitted spectral channels). The more different the original input channels are, the more different spectral data channels have to be used in order to transmit the signal information. If, in an extreme case, all the channels in a segment are practically the same, a single spectral data channel may suffice, in particular for the upper part of the spectrum. The amplitudes of the spectral segments can be controlled by means of the respective scale factors.
The number of NTSC (number of transmitted spectral channels) of the required spectral data channels is variable and may be less than or at most the same number K o

REFERENCES:
patent: 4170719 (1979-10-01), Fujimura
patent: 5371544 (1994-12-01), Jacquin et al.
patent: 5400433 (1995-03-01), Davis et al.

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