JP3269690B2 - Sound field control processing circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound field control processing circuit for an audio compression signal used in a digital recording device such as a digital compact cassette (DCC) or a digital communication device such as a digital telephone.

[0002]

2. Description of the Related Art As a conventional technique, there is a method of obtaining a desired sound field effect by creating a certain sound field by performing a convolution operation on a music source by using a digital signal processor (DSP) for an impulse response. FIG. 3 is a block diagram of a conventional sound field processing circuit, which includes a compact disk (CD) and a digital audio tape recorder (DA).
A digital audio signal from a digital source 50 such as T) is input to a digital signal processor 51.

A sound field mode selection unit 53 receives data of a sound field mode such as a concert hall or a stadium extracted from a sound field impulse response, and a sound field parameter setting unit 54 according to the sound field mode based on the impulse response. Was
The sound field parameters indicated by the initial delay time te and the reverberation time tr as shown in FIG. 4 are input (in this case, two types of time parameters are used for simplification).

The initial delay time te of the sound field parameter is set to a maximum adjustment range of 200 msec, the reverberation time tr is set to 50 sec, and the set values obtained by dividing the unit equally (5 msec, 0.2 sec) are sequentially changed. Make the settings for FIG. 4 shows a case where the sound field mode data is for a concert hall, but it differs depending on the type of sound field such as a stadium or a live house.

[0005] The convolution of these sound field parameters into the digital source 50 is performed by an IIR (Infinite Impulse) constituting a digital signal processor 51 shown in FIG.
Response) filter group. In the digital signal processor 51, under the control of the CPU 52, the multiplier 70, the delay element 71, and the adder 72 in the number of IIR digital filters corresponding to the set band have the characteristic of the filter coefficient of each multiplier 70 set by the sound field parameter. Then, the input digital source 50 is recursively corrected and output via the D / A converter 55 and the amplifier 56, a predetermined sound field is generated, and a reproduction sound of a target acoustic effect is obtained. .

[0006]

However, in such a conventional technique, in order to correct the sound field by the convolution processing of the digital filter configuration, the number of band divisions is extremely increased, and a large number of digital filters are provided so that each band is provided. Therefore, there is a problem that the circuit configuration becomes large-scale, complicated and expensive.

The present invention has been made in view of the above problems, and corresponds to the audio compression system of a digital compact cassette tape recorder. By compressing sound field coefficients, the hardware scale in convolution processing can be reduced. It is an object to provide a sound field control processing circuit.

[0008]

In order to achieve the above object, the present invention provides a sound field control processing circuit for reproducing a signal on a magnetic tape recorded using a precision adaptive sub-band coding method. Data reproduced and demodulated based on the format according to the precision adaptive sub-band coding scheme, sound field parameters based on the impulse response, and a sound field control coefficient bit-compressed corresponding to the divided band of the PASC format;
A bit variable accumulator that performs a convolution operation of the sound field control coefficient on the reproduced and demodulated data, a control unit that controls the convolution operation, and a signal that has been subjected to the convolution operation in the method described above. And a decoder for decoding.

[0009]

With the above configuration, the sound field control coefficient storage unit stores sound field control coefficients that have been subjected to signal processing and bit compression in accordance with the precise adaptive sub-band coding method of the sound field, The control unit receives the sample data from the frame of the demodulated signal input to the bit variable accumulator according to the above method.
Detects the slot, sends the sound field control coefficient data to the bit variable accumulator while controlling the timing, performs convolution by filter processing, and outputs it to the decoder. The sound field control processing becomes possible.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a precision adaptive subband coding scheme which is constituted by a digital filter or the like.
g, PASC) is a bit variable accumulator that demodulates a signal formatted in accordance with the sound field control coefficient and demodulates the signal into a digital audio signal. Is a decoder that outputs to the subsequent DAC.

Reference numeral 3 denotes a sound field control coefficient storage unit for storing a sound field control coefficient obtained by compressing a sound field parameter based on an impulse response in accordance with a divided band of the PASC format, and 4 denotes a sound field control coefficient for the reproduced PASC signal. The control unit includes a CPU that controls the process of the variable bit accumulator 1 to be convolved. Reference numeral 5 denotes a reproduction coupling unit for performing 10-8 demodulation as a demodulation process of a signal read from a digital audio cassette tape.

Next, the operation will be described. The PASC signal reproduced by the reproducing head from the digital audio cassette tape is demodulated 10-8 and applied to the bit variable accumulator 1. On the other hand, the sound field control coefficient storage unit 3 stores PA
A sound field control coefficient of a parameter subjected to compression processing corresponding to SC is stored.

FIG. 2 is a diagram schematically showing a sound field control coefficient. FIG. 2A shows an impulse response at a fixed time interval in a sound field such as a concert hall, and FIG.
A sound field control coefficient which is divided into 32 bands in the SC format processing, divided into 12 data processing units in the same band, divided, and then subjected to masking compression processing of PASC and compression corresponding to variable bit allocation processing is schematically shown. Is shown. This is equivalent to the sound field mode and the sound field parameter of the conventional example. Therefore, in the concert hall mode of the conventional method, the sound field parameters are all divided into 40 points during the initial delay time te0 to 200 msec. Compared to the linear method, which is a field parameter set point, the set number of sound field coefficients is compressed and reduced to 1/4 or less.

The compressed sound field control coefficient is convolved with the PASC signal in the bit variable accumulator 1 under the control of the control unit 4, and the timing is controlled by the control unit 4, and the PASC format 384 is used. In synchronism with data, one frame, the sample data of slots 11 to 96 is processed by the IIR filter of bit variable accumulator 1 (same type as FIG. 5 shown in the conventional example) or the FIR filter for the corresponding slot data. Convolution processing is performed, and if overflow occurs in the bit processing, it is rounded off by rounding or the like, and the same number of output bits as the number of output bits are output.

The PASC signal bit to which the sound field coefficient has been added is decoded by the decoder 2 to become a digital audio signal, which is reproduced by the DAC to obtain a reproduced sound having a desired sound field effect. In addition, various sound fields can be added by changing the coefficients of the sound field control coefficient storage unit 3.

As described above, in the present embodiment, the sound field coefficient based on the sound field impulse response is subjected to PASC-compatible compression processing to reduce the parameter set points, reduce the bit operation, and convert the PASC signal into a PASC signal by the bit variable accumulator. Since convolution processing is used, in the case of the conventional example, a large number of filter circuits were required to perform high-precision correction, but highly accurate sound field control became possible with a greatly reduced number of filters. Therefore, the scale of the hardware can be reduced by the reduction in the number of operations.

[0017]

As described above, according to the present invention,
A sound field control coefficient storage unit that stores a sound field control coefficient obtained by PASC compression of a sound field coefficient based on an impulse response, a bit variable accumulator that convolves a sound field control coefficient with a reproduced and demodulated PASC signal, and a convolution process And a decoder for decoding the convoluted PASC signal, so that there is an effect that the sound field control processing can be performed with a small number of data calculations.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a diagram schematically showing a sound field control coefficient shown in FIG.

FIG. 3 is a block diagram of a conventional sound field processing circuit.

FIG. 4 is a diagram showing conventional sound field parameters.

FIG. 5 is a filter circuit of the digital signal processor of FIG. 3;

[Explanation of symbols]

 1 bit variable accumulator 2 decoder 3 sound field control coefficient storage unit 4 control unit 5 demodulation coupling unit

Continuation of the front page (58) Fields investigated (Int.Cl. ⁷ , DB name) G10K 15/12 G11B 20/10 301 H03H 17/02 H03H 21/00 H04B 14/04 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A sound field control processing circuit for reproducing a signal recorded on a magnetic tape using a precision adaptive sub-band coding method, wherein the sound field control processing circuit reproduces and demodulates the signal based on the format according to the precision adaptive sub-band coding method. Data and impulse response
The sound field parameters correspond to the divided bands of the PASC format.
A bit variable accumulator that performs convolution operation processing of the sound field control coefficient on the reproduced and demodulated data, and a control unit that controls the convolution operation processing And a decoder for decoding the signal subjected to the convolution operation processing in the above-mentioned method.