JPH09243680A - Spectrum analyzer and graphic equalizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a constitution by taking out a scale factor with amplitude information applied for each predetermined sub-band from an MPEG audio signal for storage and displaying the amplitude information for each sub band. SOLUTION: An MPEG audio signal generator SG outputs an MPEG signal, and a scale factor take-out part 10 takes out a scale factor from the MPEG audio signal. A multiplexer 20 distributes the scale factor into 34 for each sub-band. The distributed scale factor is stored in each of registers R1 to R34, and amplitude information corresponding to the stored scale factor is displayed by display devices LED 1 to LED 34. Thus even if frequency resolution is raised, registers only may be added, and since the registers are not so large, a circuit size may not be large with its structure simple.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a spectrum analyzer and a graphic equalizer.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a conventional spectrum analyzer SA2.

The spectrum analyzer SA2 detects frequency components such as audio signals for each predetermined frequency band,
The level is displayed, and n band pass filters BPF1 to BPFn and n power calculators PC1 to PC are provided.
n and n display devices LED1 to LEDn.

That is, the bandpass filters BPF1 to BPF1
Each of the PFn passes a signal in a predetermined frequency band, the power calculators PC1 to PCn calculate the power of each output signal of the bandpass filters BPF1 to BPFn for each frequency, and the calculated power values are respectively calculated. , Are displayed on the display devices LED1 to LEDn.

FIG. 5 shows a conventional graphic equalizer G.
It is a block diagram which shows E2.

The graphic equalizer GE2 adjusts frequency characteristics of audio signals and the like, and has n band pass filters BPF1 to BPFn, n variable gain amplifiers VGA1 to VGAn, and a mixer M.

That is, the bandpass filters BPF1 to BPF
The level of each output signal of PFn is set to the variable gain amplifier VG.
A1 to VGAn are used to attenuate and amplify, respectively, the output signals of the variable gain amplifiers VGA1 to VGAn are mixed by the mixer M, and the mixed signals are output as audio from a speaker.

[0008]

By the way, the bandpass filters BPF1 to BPF used in the above-mentioned conventional example.
Since n is composed of an analog circuit in which a coil and a capacitor are combined, a delay occurs between the input signal and the output signal of the bandpass filter, and the delay time changes depending on the frequency (the phase changes). . Therefore, the conventional spectrum analyzer SA2 and graphic equalizer GE2 using the bandpass filter have a problem that the delay time changes depending on the frequency.

In addition, the conventional spectrum analyzer SA
In 2, the number of bandpass filters and the number of power calculators are determined according to the frequency resolution, and the higher the frequency resolution, the greater the number of bandpass filters and the number of power calculators and the circuit scale. There is a problem of getting bigger.

Further, the conventional graphic equalizer G
In E2, the number of bandpass filters and the number of variable gain amplifiers are determined according to the frequency resolution, and the higher the frequency resolution, the larger the number of bandpass filters and the number of variable gain amplifiers, and the circuit scale. There is a problem of getting bigger.

An object of the present invention is to provide a spectrum analyzer having a simple structure.

Another object of the present invention is to provide a graphic equalizer having no phase distortion and a simple structure.

[0013]

According to the first aspect of the present invention,
Scale factor extraction means for extracting from the MPEG audio signal a scale factor having a data structure to which amplitude information is given for each predetermined sub-band, a register for storing the scale factor for each sub-band, and storage in this register It is a spectrum analyzer having a display device for displaying the amplitude information being displayed for each sub-band.

According to a second aspect of the present invention, scale factor extracting means for extracting a scale factor having a data structure to which amplitude information is added for each predetermined subband from an MPEG audio signal, and the scale factor for the subband. A plurality of registers for each sub-band, a plurality of adding means for adding the gain designated by the input unit for each sub-band as an addition value for each sub-band of the scale factor, and the scale factor in the adding means. Is a graphic equalizer having a plurality of decoders for decoding the values added for each subband and a mixer for mixing the output values of the plurality of decoders.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a spectrum analyzer SA1 which is a first embodiment of the present invention.

The spectrum analyzer SA1 is an MPE
G audio signal generator SG, scale factor extraction unit 10, multiplexer 20, register R1,
R2, ..., R34 and display device LED1, LED
2, ..., and LED 34.

The scale factor extracting section 10 extracts the scale factor from the MPEG audio signal, and the scale factor has a data structure in which amplitude information is given to each predetermined subband. The number of subbands in the above embodiment is 34.

The multiplexer 20 divides the scale factor into 34 for each subband. Register R
1, R2, ..., R34 are registers that store the scale factors distributed by the multiplexer 20 into each subband. Display device LED
1, LED2, ..., LED34 are registers R1 and R
2, ..., Amplitude information corresponding to each scale factor stored in R34 is displayed. Although the register is connected to the display device in FIG. 1, a display control device is actually provided between the register and the display device, and the display control device is omitted in FIG. There is.

Next, the data structure of MPEG audio in the above embodiment will be described.

One frame of an MPEG audio bit stream is processed by AAU (Audio Access Un).
It is referred to as it (audio decoding unit)), and MPEG audio is composed of a large number of AAUs. This AA
One of U is the minimum unit that can be independently decoded into an audio signal. The AAU is composed of a header 32 bits, an error check 16 bits, MPEG audio data, and ancillary data.

FIG. 2 is a diagram showing an MPEG audio data frame.

The MPEG audio data frame of the MPEG audio signal comprises allocation, scale factor, and sample. The scale factor is divided into 34 frequency bands to be reproduced, and one divided sub-band. Amplitude information is given for each.

Next, the operation of the spectrum analyzer SA1 will be described.

The MPEG audio signal generator SG is MP
An EG audio signal is output, a scale factor extraction unit 10 extracts the scale factor from the MPEG audio signal, a multiplexer 20 distributes the scale factor into 34 subbands, and the distributed scale factors are respectively registered. R1, R2,
..., R34 stores. Then, the registers R1 and R
2, ..., The amplitude information corresponding to each scale factor stored in R34 is displayed on the display device LEDs 1, L, respectively.
ED2, ..., LED 34 displays.

In the spectrum analyzer SA1 of the above embodiment, even if the frequency resolution is increased, it is sufficient to increase the number of registers. Even if the number of registers is increased in this way,
Since the register itself is not so large, it is not necessary to increase the bandpass filter and the variable gain amplifier as in the conventional example, and the circuit scale does not become larger than the conventional example,
The spectrum analyzer SA1 has a simple structure.

FIG. 3 is a diagram showing a graphic equalizer GE1 according to a second embodiment of the present invention.

The graphic equalizer GE1 is an MPE
G audio signal generator SG, scale factor extraction unit 10, multiplexers 20, 50, key input unit 30, registers Ra1, Ra2, ..., Ra34.
, Adders A1, A2, ..., A34, and decoder D
1, D2, ..., D34 and registers Rb1, Rb2,
.., Rb 34, a sample extracting unit 40, and a mixer M.

The key input section 30 includes subbands f1 and f.
The gain is designated with the key for every 2, ..., F34. The adders A1, A2, ..., A34 add the gain designated by the input unit 30 for each sub-band as an addition value to the scale factor for each sub-band.

The sample extracting section 40 is a means for extracting a sample from an MPEG audio signal. Decoders D1, D2, ..., D34 sample the samples (registers Rb1, Rb) extracted by the sample extracting unit 40 according to the value added for each subband of the scale factor.
2, ..., Samples stored in Rb34) are decoded for each subband. Mixer M
Is for mixing the output values of a plurality of decoders D1, D2, ..., D34.

Next, the operation of the graphic equalizer GE1 will be described.

First, by operating the keys of the key input unit 30, the gain is designated for each of the sub-bands f1, f2, ..., F34. On the other hand, the MPEG audio signal generator SG outputs an MPEG audio signal, and this MPEG
Scale factor extraction unit 10 from audio signal
Takes out the scale factor and
Distributes the scale factor to each sub-band 34, and the distributed scale factor is respectively registered in the register R.
a1, Ra2, ..., Ra34 are stored.

Adders A1, A2, ..., A34 using the gain designated by the input unit 30 for each sub-band as an addition value.
Is added to the scale factor for each subband, and the registers Rb1, Rb2, ... Are added in accordance with the added value.
Decoders D1, D2, ..., D34 respectively decode the samples stored in Rb34, and mixer M mixes the output values of a plurality of decoders D1, D2 ,. The audio signal is output by the speaker.

Since the graphic equalizer GE1 of the above embodiment does not use a bandpass filter,
There is no delay time, and thus there is no change in the delay time with frequency, that is, there is no phase distortion.

Further, in the graphic equalizer GE1 of the above embodiment, even if the frequency resolution is increased, it is sufficient to increase the number of registers. Even if the number of registers is increased in this way, the number of registers itself is not so large. It is not necessary to increase the bandpass filter and the power calculator as in the example, and the circuit scale does not become larger than the conventional example,
The graphic equalizer GE1 has a simple structure.

[0035]

According to the invention described in claim 1, there is an effect that the structure of the spectrum analyzer is simple.

According to the second aspect of the invention, there is an effect that the phase of the graphic equalizer is not distorted and the configuration is simple.

[Brief description of drawings]

FIG. 1 is a block diagram showing a spectrum analyzer SA1 which is a first embodiment of the present invention.

FIG. 2 is a diagram showing an MPEG audio data frame.

FIG. 3 is a block diagram showing a graphic equalizer GE1 according to a second embodiment of the present invention.

FIG. 4 is a block diagram showing a conventional spectrum analyzer SA2.

FIG. 5 is a block diagram showing a conventional graphic equalizer GE2.

[Explanation of symbols]

 SG ... MPEG audio signal generator, 10 ... Scale factor extracting unit, 20, 50 ... Multiplexer, 30 ... Key input unit, 40 ... Sample extracting unit, Ra1 to Ra34, Rb1 to Rb34 ... Register, LED1 to LED34 ... Display device, A1 to A34 ... Adder, D1 to D34 ... Decoder, M ... Mixer.

Claims (2)

[Claims] 1. A scale factor having a data structure in which amplitude information is given to each predetermined subband is MP
A scale factor extracting means for extracting from the EG audio signal; a register for storing the scale factor for each subband; and a display device for displaying the amplitude information stored in this register for each subband. A spectrum analyzer characterized by. 2. A scale factor having a data structure in which amplitude information is given to each predetermined subband is MP
Scale factor extracting means for extracting from the EG audio signal; a plurality of registers for storing the scale factor for each of the subbands; a gain designated by an input unit for each of the subbands as an addition value, and the sub of the scale factor A plurality of adding means for adding for each band; a sample extracting means for extracting a sample from the MPEG audio signal; and; from the MPEG audio signal according to the value added by the adding means for each subband of the scale factor A graphic equalizer, comprising: a plurality of decoders for decoding the taken-out samples for each subband; and a mixer for mixing output values of the plurality of decoders.