JP2574521B2 - Bass emphasis method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bass enhancement method for a music signal, and more particularly, to a bass enhancement method that does not cause a phase rotation or an unnecessary increase in gain in a middle frequency range.

<Prior Art> In an audio device, a bass boost circuit for increasing a low-frequency gain is provided in order to emphasize a low tone of a music signal. Such a conventional bass boost circuit is composed of a resistor and a capacitor, and emphasizes and outputs the low frequency of an input analog audio signal.

<Problems to be Solved by the Invention> However, in the conventional bass boost circuit, the gain is raised to an unnecessary middle tone range, or phase rotation (phase delay) is caused, thereby causing deterioration of sound quality.

In view of the above, it is an object of the present invention to provide a bass enhancement method that does not raise the phase around or the midrange.

<Means for Solving the Problem> According to the present invention, a first filter processing means for extracting a low-frequency component of a music signal and a rectangular wave signal based on a positive or negative result of the first filter processing are provided. Square wave generation processing means to generate, frequency division processing means to divide the square wave signal by 1 / N, fetch the first filter processing result at a predetermined sampling period, and calculate the average value of the absolute value of the latest M sampling An envelope generation processing means for multiplying the result of the envelope generation processing by the 1 / N frequency-divided output; a second filter processing means for cutting high-frequency components included in the multiplication result; This is achieved by adding processing means for adding the filter processing result to the original music signal.

<Operation> The first filter processing means extracts a low-frequency component of the music signal, the rectangular wave generation processing means generates a rectangular wave signal based on the positive or negative of the first filter processing result, and the frequency division processing means generates the rectangular wave signal. Divide the signal by 1 / N. The envelope generation processing means takes in the first filter processing result at a predetermined sampling period, calculates the average value of the absolute values of the latest M samplings, and outputs the average value. The multiplication processing means multiplies the result of the envelope generation processing by the 1 / N frequency-divided output, the second filtering processing means cuts high-frequency components included in the multiplication result, and the adding processing means uses the second filtering processing result as an original. In addition to the music signal, this emphasizes low frequencies.

In this way, to keep the source music signal intact,
It is possible to eliminate gain rise around the phase and in the midrange.

<Embodiment> FIG. 1 shows a DSP for realizing a bass enhancement method according to the present invention.
(Digital Signal Processor) signal flow diagram, FIG. 2 is a waveform diagram of each part in the signal flow.

In FIG. 1, reference numeral 10 denotes a digital input terminal (DIN) to which a digital music signal SND is input, and reference numeral 11 denotes a first component for extracting a low-frequency component of the music signal SND, for example, a signal component LSW of 100 Hz or less.
, A filter processing unit 12 is a first filter processing result
A rectangular wave generation processing unit that generates a 100 Hz rectangular wave signal RTS based on the sign (sine) of a signal component (100 Hz sine wave) LSW of 100 Hz or less, and 13 converts the 100 Hz rectangular wave signal RTS to 1 / N (for example, 1/2).
And outputs a 50 Hz rectangular wave HRTS having a positive peak of +1 and a negative peak of -1.

14 takes in the first filter processing result LSW at a predetermined sampling cycle, and obtains the latest M samplings (for example, 30
An envelope generation unit that sequentially calculates the average value of the absolute values of the sampling values) and outputs an envelope value (EVL). 15 is a multiplication processing unit that multiplies the envelope value EVL by a 50 Hz rectangular wave HRTS, and 16 is a smooth 50 Hz signal component LSD that cuts even harmonic components of 50 Hz included in the multiplication result DTR.
Is a second filter processing unit that outputs. The second filter processing unit 16 performs an FIR type low-pass filter operation to remove even harmonic components (100 Hz, 200 Hz,...)
This makes it possible to output a steep signal having no group delay.

17, 18 are level adjustment processing units, 19 is an addition processing unit that adds the second filter processing result LSD to the original music signal SND, 20
Is a digital audio signal output terminal (DOUT).

According to the bass enhancement method of the present invention, (1) the low-frequency component (for example, 100 Hz or less) LSW of the music signal SND is extracted by the first filter processing unit 11, and (2) the square wave generation processing unit 12 (3) The frequency division processing unit 13 generates the 100 Hz rectangular wave signal RTS based on the sign, and
2) Divide the frequency to generate a 50 Hz rectangular wave signal HRTS with a peak ± 1.

(4) In parallel with the above, the envelope generation unit 14 takes in the first filter processing result LSW at a predetermined sampling cycle, sequentially calculates and outputs the average value (EVL) of the absolute values of the latest 30 samplings.

(5) The multiplication unit 15 multiplies the average value EVL output from the envelope generation unit 14 by the 50 Hz rectangular wave HRTS, and outputs a low-frequency component signal of 50 Hz or less.

(6) Next, the second filter processing unit 16 calculates the multiplication result DT
(7) The addition processing unit 19 adds the 50 Hz signal LSD obtained by removing the even-order harmonic component to the original music signal SND, and
Emphasize bass below Hz.

As described above, according to the present invention, the bass can be emphasized without modifying the source music signal, and the gain around the phase of the music signal and in the midrange can be eliminated.

The reason why the first filter processing unit 11 extracts the signal component of 100 Hz or less is that 50 Hz included in the music signal SND is included.
This is because the following signal components are small, and signal components of 100 Hz or less are easier to create.

In the above, the description has been made assuming that the low range below 50 Hz is emphasized, but the present invention is not limited to such a case.

Further, in the above description, when emphasizing 50 Hz or less, a component of 100 Hz or less is extracted and frequency-divided by 1/2, but a component of 200 Hz or less may be extracted and frequency-divided by 1/4.

<Effects of the Invention> As described above, according to the present invention, a low-frequency component (for example, 10
Low-frequency component of 0 Hz or less), and generates a rectangular wave signal based on the sign of the signal.
The frequency is divided to output a low-frequency (50 Hz) rectangular wave. In parallel with these, the low-frequency component of the music signal is fetched at a predetermined sampling period, and the average value of the absolute values of the latest M samplings is calculated. Multiplying the average value by the 1 / N frequency-divided output to output a low-frequency component (low-frequency component of 50 Hz or less), cut a high-frequency component included in the multiplication result, and add the result to the original music signal. , Because it is configured to emphasize low frequencies below a predetermined frequency (50 Hz), it is possible to emphasize components below a predetermined frequency without modifying the source music signal, and to adjust the gain around the phase and in the midrange. Lifting can be eliminated.

[Brief description of the drawings]

FIG. 1 is a signal flow diagram of a DSP for realizing the bass enhancement method according to the present invention, and FIG. 2 is a waveform diagram of each part in the signal flow diagram. 10 Digital input terminal (DIN) 11 First filter processing unit 12 Rectangular wave generation processing unit 13 Frequency division processing unit 14 Envelope generation processing unit 15 Multiplication processing unit 16 2 filter processing section 19: addition processing section 20: audio signal output terminal (DOUT)

Claims (1)

(57) [Claims] In a bass emphasis method for emphasizing bass by adding a low frequency component of a music signal, a first filter processing for extracting a low frequency component of the music signal, and a positive or negative result of the first filter processing are provided. Square wave generation processing to generate a square wave signal, frequency division processing to divide the square wave signal by 1 / N, the first filter processing result is taken in at a predetermined sampling cycle, and the average value of the absolute values of the latest M samplings An envelope generation process for calculating and outputting the result of the multiplication, a multiplication process for multiplying the result of the envelope generation process by the 1 / N frequency-divided output, a second filter process for cutting high-frequency components included in the multiplication result, and a second filter A bass enhancement method having an addition process of adding a processing result to an original music signal.