Digital adaptive transformation coding method

• US 5,742,735 A
• Filed: 08/25/1994
• Issued: 04/21/1998
• Est. Priority Date: 10/06/1987
• Status: Expired due to Term

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Popp, Harald, Brandenburg, Karl Heinz, Eberlein, Ernst, Seitzer, Dieter, Gerhauser, Heinz, Schott, Hartmut
• Primary Examiner(s): MacDonald, Allen R.
• Assistant Examiner(s): Chawan, Vijay B.
• Application Number:
  US08/295,484
• Time in Patent Office: 1,335 Days
• Field of Search: 381/29-40, 375/122, 395/2.1-2.39
• US Class Current: 704/229
• CPC Class Codes: G10H 1/0041 in coded form
• CPC Class Codes: G10H 2250/235 Fourier transform; Discrete Fourier Transform [DFT]; Fast Fourier Transform [FFT]
• CPC Class Codes: G10H 7/02 in which amplitudes at successive sample points of a tone waveform are stored in one or more memories
• CPC Class Codes: G10L 19/0208 Subband vocoders
• CPC Class Codes: H04B 1/667 using a division in frequency subbands for TV signals H04N19/63

Abstract

A digital adaptive transformation coding method for the transmission and/ortorage of audio signals, specifically music signals, wherein N scanned values of the audio signal are transformed into M spectral coefficients, and the coefficients are split up into frequency groups, quantized and then coded. The quantized maximum value of each frequency group is used to define the coarse variation of the spectrum. The same number of bits is assigned to all values in a frequency group. The bits are assigned to the individual frequency groups as a function of the quantized maximum value present in the particular frequency group. A multi-signal processor system is disclosed which is specifically designed for implementation of this method.

Claims

1. Digital adaptive transformation coding method for the transmission and/or storage of audio signals, specifically music signals, wherein N scanned values of the audio signal are transformed into M spectral coefficients, wherein N and M are non zero integers, which are subdivided into frequency groups and then quantitized and coded, characterized in that:

a quantitized maximum value of the spectral coefficients of each frequency group is used to define the coarse variation of the spectrum;

the same number of bits is assigned to all spectrum values of a frequency group, wherein the number of bits depend on the quantitized maximum value of the respective spectral coefficient;

the number of bits assigned to each frequency group being adjusted to insure a minimum number of bits to each frequency group such that, in view of psycho-acoustic aspects, quantification noise is masked for that frequency group; and

if available after the preceding step, any additional number of bits are assigned to the individual frequency groups in correspondence to the quantitized maximum value occurring in the particular frequency group.

2. Method according to claim 1, characterized in that a logarithmic value of the maximum value of each frequency group is subjected to linear quantization.

3. Method according to claim 2, characterized in that the quantization takes place by multiplication and comparison against a stored table.

4. Method according to claim 1, characterized in that the N scanned values are transformed into M spectral values by means of DFT, DCT or TDAC methods.

5. Multi-signal processor system, specifically for the transmission and/or storage of audio signals, specifically music signals, wherein N scanned values of the audio signal are transformed into M spectral coefficients, wherein N and M are non zero integers, which are subdivided into frequency groups and then quantitized and coded, characterized in that a quantitized maximum value of the spectral coefficients of each frequency group is used to define the coarse variation of the spectrum, that the same number of bits is assigned to all spectrum values of a frequency group, wherein the number of bits depend on the quantitized maximum value of the respective spectral coefficient, that the number of bits assigned to each frequency group being adjusted to insure a minimum number of bits to each frequency group such that, in view of psycho-acoustic aspects, quantification noise is masked for that frequency group, and that if available after the preceding step, any additional number of bits are assigned to the individual frequency groups in correspondence to the quantitized maximum value occurring in the particular frequency group, comprising several digital signal-processing modules (M1 . . . M4) which process a data flow, e.g. a flow of digitized audio signals, and a location communication channel which handles the data communication between two adjacent modules (M1 . . . M4), characterized in that additionally at least one global communication channel is provided via which system observation, system control, parameter adaptation and/or global data communication are realized.

6. Multi-signal processor system according to claim 5, characterized in that two global communication channels are provided whereof the first one is a low-speed communication channel handling the system control and the parameter adaptation while the second one is a high-speed communication channel for data communication.

7. Multi-signal processor system according to claim 6, characterized in that a communication controller (KL) is provided which controls randomized data communication via the high-speed global communication channel.

8. Multi-signal processor system according to claim 7, characterized in that the communication controller (KL) operates as a local communication node.

9. Multi-signal processor system according to claim 7, characterized in that the communication controller (KL) controls data distribution via the high-speed global communication channel as a function of data and/or an algorithm.

10. Multi-signal processor system according to claim 6, characterized in that the high-speed global communication channel has precedence over the low-speed global communication channel in terms of priority.