Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Reexamination Certificate
2001-07-19
2004-02-10
McFadden, Susan (Department: 2655)
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
C375S240030, C375S240110, C381S023000
Reexamination Certificate
active
06691086
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a digital transmission system for transmitting a wide-band digital signal having a transmitter and a receiver, the digital transmission system transmitting a wide-band digital audio signal comprising at least a first and a second audio signal component via a transmission medium, the transmitter comprising an encoder having analysis filter means for filtering the signal components so as to obtain a number of n sub-signals for each of the at least two signal components, data reducing means for carrying out a data reduction step on the n sub-signals of each of the at least two signal components, and transmission means for transmitting data-reduced sub-signals via the transmission medium, and the receiver comprising receiving means for receiving the data-reduced sub-signals, data expansion means for carrying out a data expansion step on the received data-reduced sub-signals so as to obtain non-data-reduced replicas of the sub-signals, and a decoder having synthesis filter means for combining the replicas of the sub-signals for each of the at least two signal components so as to obtain a replica of the at least first and second signal components.
The invention further relates to a transmitter and a receiver in the transmission system, and to a record carrier obtained by means of the transmitter being in the form of a device for recording a signal on a record carrier.
2. Description of the Related Art
A transmission system of the type defined in the opening paragraphs is known from the article “The Critical Band Coder Digital Encoding of Speech signals based on the Percentual requirements of the Auditory System” by M. E. Krasner, in Proc. IEEE ICASSP 80, Vol. 1, pp.327-331, Apr. 9-11, 1980. This article relates to a transmission system in which the transmitter employs a sub-band coding system and the receiver employs a corresponding sub-band decoding system, but the invention is not limited to such a coding system, as will become apparent hereinafter.
In the system known from this publication, the speech signal band is divided into a plurality of sub-bands having bandwidths approximately corresponding to the bandwidths of the critical bands of the human ear in the respective frequency ranges (cf. FIG. 2 in the article of Krasner). This division has been selected because, on the ground of psycho-acoustic experiments, it is foreseeable that the quantization noise in such a sub-band will be masked to an optimum extent by the signals in this sub-band if, in the quantization, allowance is made for the noise-masking curve of the human ear (this curve giving the threshold value for noise masking in a critical band by a single tone in the center of the critical band, cf. FIG. 3 in the article by Krasner).
It should, however, be noted that the invention is not restricted to an encoding into sub-band signals. It is equally well possible to apply transform coding in the encoder, a transform coding being described in the publication “Low bit-rate coding of high-quality audio signals. An introduction to the MASCAM system” by G. Theile et al., in EBU Technical Review, No. 230 (August 1988).
In the case of a high-quality digital music signal, which, in conformity with the Compact Disc Standard, is represented by 16 bits per signal sample in the case of a sample frequency of 1/T=44.1 kHz, it is found that with a suitably selected bandwidth and a suitably selected quantization for the respective sub-bands, the use of this known sub-band coding system yields quantized output signals of the coder which can be represented by an average number of approximately 2.5 bits per signal sample, the quality of the replica of the music signal not differing perceptibly from that of the original music signal in substantially all passages of substantially all kinds of music signals.
The sub-bands need not necessarily correspond to the bandwidths of the critical bands of the human ear. Alternatively, the sub-bands may have other bandwidths, for example, they may all have the same bandwidth, provided that allowance is made for this in determining the masking threshold.
SUMMARY OF THE INVENTION
It is an object of the invention to further improve the transmission characteristics of the transmission system.
This object is achieved in the digital transmission system described in the opening paragraphs, characterized in that the transmitter is further adapted to transmit at least a first auxiliary digital signal component, the transmitter comprising means for generating a composite transmission signal comprising frames, a frame including a first frame portion comprising synchronization information, a second frame portion comprising a block of data of the data-reduced sub-signals and a third frame portion located after the second frame portion in said frame, said third frame portion comprising a block of data of the auxiliary digital signal, and the receiver further comprising derivation means for deriving said at least one auxiliary digital signal component from third frame portions in frames of the composite transmission signal received.
The invention is based on the recognition that data reducing the first and second digital audio signal components results in space becoming available on the transmission medium, this space can then be used for transmitting at least one auxiliary signal component.
The transmission system may be further characterized in that the transmitter comprises control signal generator means for generating a signal type control signal indicating the type of said at least one auxiliary digital signal component, the transmitter further being adapted to transmit said signal type control signal, and the receiver further comprising detection means for detecting said signal type control signal, the derivation means being adapted to derive, in response to said signal type control signal, said at least one auxiliary digital signal component from the signal received. This enables the receiver to retrieve the auxiliary signal component of a specific type from the transmission signal received.
The transmission system may be further characterized in that the transmitter comprises control signal generator means for generating a signal presence control signal indicating the presence or absence of said at last one auxiliary digital signal component, the transmitter further being adapted to transmit said signal presence control signal, and the receiver further comprising detection means for detecting said signal type control signal, the derivation means being adapted to derive, in response to said signal presence control signal, said at last one auxiliary digital signal component from the signal received.
This enables the transmission of packets of auxiliary information in only those frames of the transmission signal that have sufficient space to store these packets in them. The receiver is now capable of identifying those frames so that the retrieval of the auxiliary signal component can be realized.
The auxiliary signal component can also be split into sub-signals or sub-band signals prior to encoding into the transmission signal. In the case of an encoding into a sub-band signal, allocation information and scale factor information corresponding to time equivalent signal blocks of the auxiliary signal component should be transmitted as well.
The auxiliary signal component can be an additional audio signal component, such as a surround sound signal component.
It is a further object of the invention to provide a number of steps for the transmission system, in particular, a very specific choice for the format with which the digital wide-band signal, after conversion into the second digital signal, can be transmitted via the transmission medium, in such away that a flexible and highly versatile transmission system is obtained. This is to be understood to mean that the transmitter should be capable of converting wide-band digital signals of different formats (these formats differing, inter alia, with respect to the sample frequency F
Dehery Yves-Francois
Lokhoff Gerardus C. P.
Stoll Gunther Josef
Goodman Edward W.
Koninklijke Philips Electronics , N.V.
McFadden Susan
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