JPH01185010A - Envelope detecting circuit for digital signal processing unit - Google Patents

Abstract

PURPOSE:To facilitate a coefficient change and to prevent the loss of the energy sense of an input signal by using a fixed attack coefficient, executing a peak detection at the time of the attack of the input signal, calculating a recovery coefficient from an effective value detecting value and executing an envelope detection at the time of a recovery. CONSTITUTION:By a digital signal processing unit, the attack time of the input signal to be digitally converted is operated by a fixed attack coefficient (ta), and the peak detection is executed. For a recovery time, a recovery coefficient (tr) is operated from a value to effective-value-detect the input signal, and the envelope detection is executed by executing successive selections by means of the optimum recovery coefficient (tr) based on the result. Consequently, an (rms) detection is digitally executed. Thus, a detection output to reflect the energy of the input signal can be obtained, and simultaneously, a detecting means 18 can be easily obtained.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Field of industrial application B. Outline of the invention C. Prior art D. Problem to be solved by the invention E. Means for solving the problem (Fig. 1) F. Effect G. Example H. Effect of the invention A. Industrial application FIELD OF THE INVENTION The present invention relates to an amplifier detection circuit for use in a digital signal processing apparatus for digitally processing a dynamic range of an A-TE signal converted into a digital signal.

B. Summary of the Invention The present invention provides an envelope detection circuit for a digital signal processing device that digitally controls the dynamic range of an input signal. Peak detection is performed using the attack coefficient, and during recovery, the recovery coefficient is calculated from the effective value detection value, and ζen/LI-p detection is performed using the J recovery coefficient. The aim was to obtain something that would not impair the sense of energy.

C. Conventional technology In order to control the dynamic range of an audio signal, a dynamic range controller (hereinafter referred to as LIRC) has been known that uses analog technology to compress and expand the dynamic range to kk degrees. ing. FIG. 6A shows, for example, a DRC that prevents over-cuffing during recording and functions as a transmitter, and input terminal '! The audio signal manually input to ``1'' is output to the output terminal ``1'' through the multiplier circuit (11) constituting the transformer element 1, but the output 1d of the multiplier circuit (1) is output to the control system (2 This configuration does not require any additional time for the control system (2), but due to the delay in the control system (2), an excessively high level signal is output to the output terminal 'I'2. There is a drawback that overshoot occurs because the gain cannot be reduced until the audio signal is input to the input terminal T1 as shown in FIG. 6B. If we adopt a control method using an input signal in which the control signal is supplied to the control system (2) and the multiplier circuit tll is controlled by the control signal of the control system (2), the dyna (7 range) Although it is possible to adjust the characteristics accurately, it is necessary to precisely specify the control system (2).Although not shown in the figure, this control system (2) includes an analog-configured envelope detection circuit. This envelope detection method includes a peak detection method and an effective value (rms
s) detection method is known, and FIG. 7A shows a peak detection circuit diagram. When a tone burst signal as shown in FIG. 7B is supplied to the input terminal T3, the buffer (4(.

The attack time, recovery time, and hold time of the tone burst signal amplified and rectified through the rectifying element CD are determined by a time constant circuit including a resistor 1ft, R2, and a capacitor cl. These ports have a great influence on the distortion rate of L)RC and the quality of noise masking. Attack time, recovery time, etc. & amounts are IE
In definitions such as C, the value at which the initial 6 dB overshoot converges within 2 dB after a temperature signal such as a tone burst wave is applied is defined as the actuating time, and similarly the recovery time (release time or decay time) (
^ is also output...tti is recommended until the value increases to within 2 dB of the convergence value. In the peak detection circuit shown in Figure 7A, the resistor 'aRt and capacitor C are shown in Figure 7C.
1 determines the actuation time, and the recovery time is determined by the capacitor c1 and resistor R2. For this reason, the time constant is determined regardless of the level of the input signal, which has the disadvantage of affecting the RC distortion rate and noise masking, resulting in unnatural processing results of dynamic level control.

In order to eliminate such drawbacks, a peak detection circuit has also been proposed in which the time constant of the recovery time is changed according to the level of the input signal. This configuration is shown in FIGS. 8A and 9. The raw silk path shown in the upper row of FIGS. 8A and 9 constitutes the same peak detection circuit as that of FIG. 7A, and therefore is given the same reference numeral and redundant explanation will be omitted. The tone burst signal supplied to the input terminals '1' and 3 of Fig. 8A and Fig. 9A is input to the buffer (4) and also inputted to the buffer (5), where it is rectified by the rectifier CDL and sent to the comparator 16).
The signal is supplied to the inverting input terminal or non-inverting input terminal of the differential amplifiers (6a) and (6b) forming the differential amplifiers (6a) and (6b). Shyness increase l1
The reference voltage divided by the resistors R4 and Hs is supplied to the inverting input terminal or non-inverting input terminal of the transformer III (6a) (6b), and the difference V11*width transformer (6υ), (6b
) is connected to the base of the transistor Rx for the switch. The collector of the transistor 'l' Rt is connected to the midpoint of the series connection of the resistors R2 and Ra, and the emitter and one end of the resistor R are grounded. When the tone burst signals shown in Fig. 8B and Fig. 9B are input to the input terminals '1 and 3, the peak detection circuit shown in Fig. 8 contains many low-frequency components in the input signal. This method is effective in cases where the recovery time is reduced by lSc. That is, as shown in the output waveform of Fig. 8C, the tanoff time is determined by the time constants Rs and Ct of the main thread path, and the recovery time is determined by the reference level TL of the comparator (6). During this period, the switching transistor ``l''p1 is in the off state and discharges with a time constant determined by the time constant circuit (/1 + R2 + R3, but when the voltage falls below the reference level ``l'', the switching transistor ``rR1'' is turned off by the resistor P5R.
3 is shunted, and thereafter the time constant circuit discharges with a time constant determined by C1+R2.

The peak detection circuit shown in the ninth picture is effective when the input signal contains a pulse-like western component.

That is, as shown in the output waveform diagram in Figure 9C, the attack time is determined by the time constant 01.Rt of the main thread path, but the recovery time is determined by the time constant 01.Rt of the main thread path, while the recovery time is determined by the time constant 01. is switching transistor '1' H
Since l is in the "on" state so as to shunt resistors 1 to 3, it is discharged by the time constant of time constant circuits C1 and R2, but when it falls below the reference level 'l' L, the switching transistor ' After l' l(t is in the "off" state, it will be discharged with a time constant determined by cl.R1.Ry of the time constant circuit.

This kind of peak detection circuit's boyfriend ＼ru
Even if the recovery time is configured to be variable, the output waveform signal does not become a detection circuit that reflects the energy amount of the input signal, so there is a problem that various aural complaints remain.

In order to solve such problems, r rn of the input signal
Effective value detection lL as shown in Fig. 10, based on the s value and adding time constants for °r tank and recovery! l path has been proposed. The circuit shown in Figure 1O is the same as the one shown in Figure 7 except for the °ζ effective value detection circuit (7), so 1iJ-
Press the general/number (-J?).Fruit J4ti detection circuit (7)
is constructed as shown in FIG. 10B or 10C. In the case of Figure 10 B, human power (iT No. X squared 13
It has an iJ arithmetic circuit (7a), and input signal The configuration is such that a signal of /T=π is extracted as the signal y. In the case of Figure 1C, there is a squaring circuit (7a) that squares the input signal X, and this 231! /JJ arithmetic circuit (7a
), let 1￥I-x be X', and take the logarithm of this.
A logarithmic circuit (7d) with Iogx' and this Iogx"
An integration filter (7b) that integrates /logx
' It is composed of division circuit II (7e) in which dt is 1/2.

D Problems to be Solved by the Invention In the envelope detection circuit of a conventional analog DRC, when an effective value detection circuit is used, a square calculation circuit (
7aJ, a square root circuit (7c), a logarithm circuit (7d), and a division circuit (7e)W, which require analog calculation circuits, making the circuit complex. High precision is required for the control system (2) shown in Figure 6B.

If quotient stability is required, the device configuration of the effective value detection circuit becomes extremely commercially expensive. Historically, due to the principle of RMS detection, an integral filter ('/b) is used, which has poor response to transient signals (especially at the time of attack).1) When RC is used as a limiter (compression that increases the dynamic range) There are many problems with this. Furthermore, when the delay circuit (3) of the main yarn path shown in FIG. 6B is configured in an analog manner, there is a problem that the delay circuit (3) of the main yarn path becomes too large.

In view of the above-mentioned problems, the present invention provides an envelope detection circuit for a digital signal processing device that processes an input signal digitally, allows easy coefficient changes, and can reflect the energy feeling of the input signal in No. 46. The purpose is ().

Ha! Means for Solving the Problems The configuration of the present invention, an example of which is shown in FIG. Then, the digital signal processing device performs peak detection using this human power (during the attack of No. In this embodiment, envelope detection (I2) is performed.

F Function The envelope detection circuit for digital signal processing of the present invention uses a digital signal processing device to set the attack time of a digitally converted input signal to a fixed attack coefficient t8.
Peak detection is performed by calculating the input signal, and the recovery time is determined by calculating the recovery coefficient [
Calculate r and select the optimal recovery coefficient based on the result [Since envelope detection is performed by continuously selecting r, rms detection is performed digitally, and a detection output that reflects the energy of the input signal is obtained. 11 detection means can be easily obtained.

Embodiment 1 An embodiment of an envelope detection circuit for a digital signal processing device according to the present invention will be described with reference to FIGS. 1 to 5. FIG. 2 shows a dynamic range controller using the envelope detection circuit for digital signal processing of the present invention.
It shows the overall genealogy of I-Ra. In FIG. 2, a digital delay circuit (
3) and a multiplier circuit (1a) to output terminals '1 and 2. This upper thread path delay circuit (3) has a time delay due to the attack time etc. generated in the envelope detection circuit (10) of the control system path, which will be described later, and the gain control signal generated by the control system thread does not pass through the upper thread path. Because this causes a delay with respect to the flowing signal, this delay causes an overshoot in the processing of the compressor, limiter, etc., causing a delay in the raw silk path. Circuit (3) is inserted to prevent these causes.

In the control system Itoro, the input signal supplied to the human-powered machine 1 is envelope-detected by a digital envelope detection circuit (10), and this envelope detection signal is processed by a digital logarithm circuit (11). Against ft! It is converted into a digital gain control signal and supplied to a digital gain control signal generation circuit (12), which generates a gain control signal from the logarithmically converted envelope detection signal. This generated gain-side Th1fh signal is output as a logarithmic output signal, so it is converted into a linear gain control signal by passing through the next stage digital inverse lawful number circuit (13). The gain control signal is supplied to an integrating digital filter (14). This gain control signal is based on the logarithmic circuit (11) and the antilogarithmic circuit (11) based on the word length.
3) This is an LPF for smoothing the drastic changes that occur when performing a wide range of 1 number processing such as l, P.
The gain side θII fR smoothed by F is applied to the multiplier circuit (l
multiplied by a).

Gain 11i11θII (W generation circuit (12
) will be described in more detail in FIGS. 3A and 3B. Now, if we take the linear input signal r and the linear output signal y', then in the gain control signal generation circuit (12), X' = 201
og x'-...1llY' =
201og y'...+2). For X', Y', Y' = ax' + b...(
3), the gain G is y' G = 201og = 20 log y' -1
ag x'X' If we substitute equations (1) and (2) here, we get G=Y'-X', and if we substitute equation ('A) here, we get G= (ax'
+b)-x' = a) ('+b-x' = (a-1) x' 4-b -・14
It becomes 1.

Compression ratio Cr to start one operation at 4f1CL11 or more per minute
When considering the pressure 1ill''a, the relationship between human output is Y'
=Cr -X' +CLh (1- to r)...
151, compression ratio -1/3, threshold CLb = -20
Figure 3A shows an example of neo when expressed as dB. Therefore +31.
+41 formula, profit 11G is G= (Cr 1)X' +Cth(1-Cr)
” (Cr l) (X'-CLh)
...1(il.Here, if 5=Cr-1...171, the gain G is G-(Cr-1) (CLh to X-)-Cs ・(X
CLh) ...181. That is, a control signal with a gain G is generated by processing the equation (8) on the input signal X' which has been logarithmized by a logarithm circuit after envelope detection. In this example, only in the case of compression characteristics, there is also a function in charge of equation ('l) in the case of limiters, expander noise gates, etc., and this processing is utilized by the f4#ifi control signal generation circuit (12). Every time you do it.

Figure 1 shows a 1st @ system diagram when the envelope detection circuit (10) in Figure 2 is configured using a digital signal processing device. All waves that make up the envelope detection t-S! tkH
& (17) and is also supplied to the square calculation means (19) of the recovery coefficient detection path (16).

First, the recovery coefficient detection thread path (16) will be explained.

In the square calculation means (19), in order to calculate the recovery coefficient '1'r using r m a, the output signal y2 is calculated by supplying the digital input signal x1? 2 (n
l = x t'tnl...(
9) is performed. Here, n represents the n-th sampling human output signal, and the output signal y2 of the square calculation means (!9) is supplied to the first-order recursive digital filter (20) as human power (14"+x2). This digital filter (20) The human output signals x2 and y3 have a multiplication coefficient of t
8ν, y 3 (nl= Lav (X2 tnl
-y3(n--1))+y3(n
l)...(10) is performed and functions as L)'l.'. 7 in this case. -1
indicates the amount of delay of one sample value after Z-transformation. The output signal y3 of the digital filter (20) is supplied to the next stage square root calculation means (21) as X number of people's moons, and the output signal y
4 is y 4 h li -, no xl (n)
・ ・ ・
(11) is calculated and becomes y 4111) r I
n S value is calculated.

Next, the output signal y4, which is the r fil S value of the first stage of square root calculation (21), is manually inputted to the recovery coefficient calculation means (22) through manual power No. 15 X→ (y<=X4). In the recovery coefficient calculating means (22), the recovery coefficient tr is determined using, for example, a -order function.

In this example, as shown in Figure 4 A and H, the linear function curve <2:D
(24) 0) Use iS1ki trs and intercept trc.

In the case of Fig. 4, S<0, and in the case of Fig. 4 B, tri>
0, with the recovery coefficient tr on the vertical axis and r on the horizontal axis.
Take the value of the output signal y4, which is the m s value, and calculate y 4 (
The recovery coefficient Lr is continuously determined according to the nlO value. That is, as the recovery coefficient tr, tr-trs-y
4 tnl+Lrc ...(12) is calculated and the recovery coefficient tr of the envelope detection means (18) is calculated.
The signal is supplied to the envelope detection means (18) so as to change the signal. On the other hand, in the envelope detection system 1/3 (15), the input signal x1 inputted to the full-wave rectifier (17) is full-wave rectified, and the output signal y51nl is y5(1re-IXI1n)l
HHH (13
), and this output signal y s +Ill is sent to the enprobe detection means (18) as the output signal y s −
XS) is manually inputted and output as an output signal y6, but when Xs(mouth 1>yc (n-1)), ys
(n)-ta (XS (n)-ys (n-1)
)+y6 (n l)... (
14) However, ta determines the attack time as the attack coefficient of the digital filter. Also, when x61n)≦ye(n-1), YG 1nl-tr-)I'G(n-1)
Envelope detection is performed by determining the recovery time as (15).

Although the processing described above was expressed using a breakaway thread, in order to make it easier to understand, it will be replaced with a continuous value system and will be explained using the waveform diagram in FIG.

Figure 5A shows the full-wave rectification means (17) and the square calculation means (19).
) Tone burst-like human power supplied to Xtll
) through the digital filter (20) and square root calculation means (21). The output signal y4, which is set to 1 value, changes as shown in FIG. 5 (HO). , this output signal 74
11), the recovery coefficient ゛1゛r is a linear function (
23) and (24) change as shown in FIG. 5 C1E depending on whether the threshold trs is smaller or larger than zero. For this reason, the waveform subjected to envelope detection by the envelope detection circuit 19 (1B) becomes as shown in Figure 5, F. That is, x of the input signal inputted to the envelope detection means (18)
When x5 (Ll>yctLl, that is, when the input signal rises), as shown in FIG. time is 1
When the sequence trs of the following function (23) is trs<0, the successive recovery coefficient values tr shown in FIG. The output signal yt, (t) changes as shown in the fifth diagram. In this case, the response is a pulsed input signal. In addition, the recovery time of the falling edge is the fifth when the linear function (24) Lrs is trs>0.
The continuous recovery coefficients Lr shown in FIG. 5E are sequentially supplied to the envelope detection means (18), and the output signal 7 b ttl changes as shown in FIG. In this case, the response of the input signal with many low frequency components is passed through.

As described above, the envelope detection circuit for a digital signal processing device of this example performs peak detection of t6 at the time of attack at the rising edge of the input signal, accurately and quickly follows the input signal waveform, and at the time of recovery at the falling edge By using the recovery coefficient tr calculated directly from the mS value,
After this detection, the dynamometer <Ivy level control I->
Envelope detection through roll processing (since it can generate the i signal, it reflects the energy sweetness of the input signal r ffl 3
! Since detection is performed and it can be configured with a digital signal processing device, the envelope detection circuit can be configured at low cost and with a high 11i degree, and the recovery coefficient can be easily changed.

In the above embodiment, it is a linear function (23).

Although the recovery coefficient was calculated using (24), various modifications are possible without departing from the gist of the present invention, such as storing quadratic function curve values in memory.

11 Effects of the Invention According to the present invention, the recovery coefficient can be changed extremely easily since the digital signal processing device is used to perform digital processing. Since RMS detection is used as the detection method, the sense of energy of the input signal can be reflected in the detected output, which solves the auditory problem during dynamic range control, and since the hardware is only a digital signal processing device. It has the effect of being able to be constructed with high precision and at low cost.

[Brief explanation of the drawing]

Fig. 1 is a tm functional system diagram showing an embodiment of the envelope detection circuit for a digital processor No. 4 according to the present invention, Fig. 2 is a system diagram for performing dynamic range controller compression and expansion, and Fig. 3 is the gain control number generation 1 in Figure 1! Figure 4 is a diagram for determining the recovery coefficient, Figure 5 is a waveform diagram showing the operation explanation of Figure 1 in analog form, and Figure 6 is the conventional diagram. Figure 7 is a conventional peak detection circuit and its input/output waveform diagram, Figure 8 is a conventional recovery time switching circuit and its input/output waveform diagram,
FIG. 9 shows another example of switching circuit Vδ similar to FIG. 6.
FIG. 10 is a system diagram of a conventional effective value detection circuit. (la) is a multiplication circuit, (3) is a delay circuit, (1o) is an envelope detection circuit, (12) is a gain control signal generation circuit, (17) is a full-wave rectification means, (18) is an envelope detection means, ( 19) is a square calculation means, (2o) is a digital filter, (21) is a square root calculation means, and (22) is a recovery coefficient calculation means. Between Matsukuma Shokumori - λh ifugome (dB) A - λ power signal <When O, 0' ゎ, 5>., 2, Asahikawa + fl of the stimulant section Fig. 5 Fig. 6 Beef 3N C circuit and mute input/output Ura form 1 Fig. 7 Secondary glue cover 1-Time Tpp Maru OY# Kojiiri Tomoe j
Le Punishment 1fi Figure 8 4 Nori Shiba 9 Im tat Expenses 01 Bodhisattva Attendance; l ia W ;7! j II
R' In Figure 10

Claims (1)

[Claims] In an envelope detection circuit for a digital signal processing device for digitally controlling the dynamic range of an input signal, the digital signal processing device uses a fixed attack coefficient when attacking the input signal. What is claimed is: 1. An envelope detection circuit for a digital signal processing device, characterized in that: at the time of recovery, a recovery coefficient is calculated from an effective value detected value, and envelope detection is performed using the recovery coefficient.