JP3045828B2 - Phase information compression device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase information compression apparatus for digital information processing of audio signals in broadcasting and digital media (CD, DAT, etc.).

[0002]

SUMMARY OF THE INVENTION The present invention relates to a technique for compressing phase information by using the auditory characteristic that human sound perception is ambiguous with respect to phase information. , FFT (Fast Fourier Transform)
After analysis, the phase component and the amplitude component are separated, and the phase component is subjected to phase unwrapping processing to remove the linear phase component, approximated by a spline function. Only the components are transmitted. As a result, it is possible to compress the phase information in a range that cannot be perceived in terms of audibility, and perform D / A conversion on the phase information in a decoder portion, thereby reproducing an acoustic signal with the same quality as the original sound.

[0003]

2. Description of the Related Art No such technique has been developed.

[0004]

Conventionally, the waveform of an input audio signal is cut out by a short-time window, separated into a phase component and an amplitude component by FFT analysis, and when this phase component is simply compressed, it is reproduced by zero phase conversion or the like. There was a problem that sound deteriorated.

It is an object of the present invention to solve the above-mentioned problems and to provide a phase information compression apparatus capable of obtaining a reproduced sound having the same quality as the original sound even if the phase component of the original sound is largely compressed.

[0006]

Therefore, the present invention provides a phase component extracting means for extracting a phase component from an input audio signal, a phase unwrapping means for performing a phase unwrapping process on the phase component extracted by the phase component extracting means, Linear phase component removing means for removing a linear phase component from the phase component processed by the phase unwrapping processing means, and data of a plurality of points in the phase component after the linear phase component has been removed by the linear phase component removing means Spline function approximation means for approximating the phase component after the removal of the linear phase component with a spline function based on the difference between the phase component after the removal of the linear phase component and the approximate phase component approximated by the spline function. A residual component computing means for computing as a residual component, and residual component data obtained by the residual component computing means and Characterized in that and means for outputting the data at a plurality of points for the line function approximation.

[0007]

According to the above arrangement, the phase component can be largely compressed while maintaining the same quality as the original sound.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings. FIG. 1 is a block diagram of a phase information compression device according to the present invention.

An analog / digital (A / D) conversion circuit 1 converts an analog input audio signal into a digital signal at a conversion bit number of 16 bits and a sampling frequency of 48 kHz. Reference numeral 2 denotes an FFT analysis circuit, which first cuts out the input audio signal A / D-converted by the A / D conversion circuit 1 through a cutout window of 1024 sample points (for about 22 ms), performs FFT analysis, and performs phase components (FIG. 2). ) And the amplitude component.

Reference numeral 3 denotes a phase unwrap circuit which receives a phase component from the FFT analysis circuit 2 and adds a phase rotation to a portion where the phase component is rotated by π or more, that is, adds a phase unwrap. 3 (A shows the phase component subjected to phase unwrapping in FIG. 3. The vertical axis of the figure indicates the phase (140π to −140π). In this range, the linear phase component corresponding to the group delay component is mainly used. A minute phase component as shown in FIG. 4 described later is superimposed on the linear phase component). Reference numeral 4 denotes a linear phase removing circuit which removes a linear phase component corresponding to a group delay component from the output of the phase unwrapping circuit 3 to generate a minute phase component (see FIG. 4).
Get. Reference numeral 5 denotes a spline function approximation circuit, which approximates a minute phase component with a spline function based on data (16 bits each) of eight representative points obtained from the minute phase component from the linear phase approximation circuit 4 (FIG. 5). FIG.
B denotes a minute phase component (same as in FIG. 4), and C denotes a phase component approximated by a spline function.

Reference numeral 6 denotes a residual component operation circuit which calculates a difference between a minute phase component from the linear phase removal circuit 5 and an approximate phase component from the spline function approximation circuit 5 as a residual component (D in FIG. 6). And C is the same as C in FIG. 5). A bit amount distribution circuit 7 determines, for example, a 512-point bit distribution according to the residual amount in the output of the residual component operation circuit 6 (for example, 8 bits are allocated to the maximum residual amount).

As described above, the spline function approximation circuit 5
The phase of the input sound signal is obtained by using the 8-point data (16 bits at each point) required for the approximation of the spline function and the data from the bit amount distribution circuit 7 in which the number of bits at each point is smaller than the 8-point bit number. The information is significantly compressed and expressed and output to the transmission circuit 8. Less than,
The same process is repeated by shifting the cutout section in the FFT analysis circuit 2 by １ ／. As a result, the phase information can be compressed in a range that cannot be perceived in terms of hearing.

[0013]

As described above, according to the present invention, the phase component can be greatly compressed while maintaining the same quality as the original sound.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing phase components obtained by FFT analysis.

FIG. 3 is a diagram showing phase components subjected to phase unwrapping.

FIG. 4 is a diagram showing a phase component from which a linear phase component has been removed.

FIG. 5 is a diagram illustrating a phase component from which a linear phase component is removed and a phase component approximated by a spline function.

FIG. 6 is a diagram illustrating a residual component.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 A / D conversion circuit 2 FFT analysis circuit 3 Phase unwrapping circuit 4 Linear phase elimination circuit 5 Spline function approximation circuit 6 Residual component operation circuit 7 Bit amount distribution circuit 8 Transmission circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03M 7/30

Claims (1)

(57) [Claims] 1. A phase component extracting unit for extracting a phase component from an input audio signal, a phase unwrapping unit for performing a phase unwrapping process on a phase component extracted by the phase component extracting unit, and a phase unwrapping unit. Linear phase component removing means for removing a linear phase component from the phase component, and removing the linear phase component based on data at a plurality of points among the phase components after the linear phase component has been removed by the linear phase component removing means. A spline function approximating means for approximating the phase component of the above with a spline function, and a residual calculating a difference between the phase component after the linear phase component is removed and the approximate phase component approximated by the spline function as a residual component Component operation means, and residual component data obtained by the residual component operation means and a plurality of points for approximating the spline function. Means for outputting data.