EP0776144B1 - Signal modification circuit - Google Patents

Description

The invention relates to an electronic circuit for modifying a first and second signal, which are either available individually or in connection with other signals are available. Such circuits are known to have certain effects of to amplify or weaken information contained in the signals. On The application is, for example, a contour amplifier for signals with optical Signals are linked and by a raster scan or by a variety are formed by sensors. For signals that are linked to sound waves, there is Similar applications ranging from very low frequencies to far into the ultrasound range reach into it. With these signals, seismic signals can, too high-frequency signals in the ultrasonic range, such as in the Material testing are used. The is included normal audio area dealing with audible signals. In the simplest case the modification circuit is based on stereo signals according to one of the standardized stereo coding methods, which a left and a right signal in coded form as sum and Transfer differential signal. By means of the known modification circuits electronically change the so-called stereo base, which makes the two the effect of the associated loudspeakers as it were. The change effects can also affect more elaborate playback systems with more than two speakers and / or more than two signals related to a surround sound convey that can be changed by the modification circuit.

US 5,420,929 is the closest prior art to a signal modification circuit described for stereo signals. From a left and a right signal the direction-independent lowers are reduced with the help of filters Frequency components and the possibly direction-dependent higher ones Frequency components separated, the direction-independent or directional signal components as "coherent" or "non-coherent" Signal components are referred to. To avoid an "acoustic Loches "in the middle between two speakers that are relatively far apart From about 300 Hz, the filtered signals become pseudo-coherence signals formed, the two speakers additive to the existing signal components are supplied and thus a larger mono signal component to pretend. This can hide the "acoustic hole" in the middle. The The pseudo-coherence signals are formed by means of delay stages in the Signal paths for signal ranges above 300 Hz Delay stages take the resulting phase of the delayed signals with them increasing signal frequency steeply, so that frequency ranges with Multiple phases of +/- 180 ° and 360 ° and the intermediate areas each other alternate. Due to the steep phase response, the coherence and the Non-coherence property of the respective signal components for dense successive frequency ranges of the signal as it were "blurred" and thereby ineffective for the directional location.

From US 5,136,650, for example, a complex circuit arrangement for Sound signals known, in which six spatially distributed speakers controlled individually are initially based on only two signals. By a Effect control simulates a spatial sound that was not originally available.

From the magazine "Elrad", 1994, Issue 7, pages 76 to 81 is under the title "Effect showmanship" describes how, with electronic means, the stereo base in usual Stereo signals broadened and finally a spatial effect using a surround matrix can be achieved. Three basic circuits are presented, each for certain signal properties are optimal. As the circuits changed Cannot follow signal properties, their use is problematic because it is in these cases it is possible that the effect control deteriorated to an overall Leads auditory impression.

The object of the invention is a circuit arrangement for modification specify at least two signals that simply match the respective signal properties can be adjusted.

The solution to the problem results from the features of claim 1.

Fig. 1

zeigt eine erste bekannte Modifikationsschaltung,

Fig. 2

zeigt eine zweite bekannte Modifikationsschaltung,

Fig. 3

zeigte eine dritte bekannte Modifikationsschaltung,

Fig. 4

zeigt ein erstes Ausführungsbeispiel der Erfindung und

Fig. 5

zeigt ein weiteres Ausführungsbeispiel der Erfindung.

The invention and advantageous embodiments are now explained in more detail with reference to the figures in the drawing:

Fig. 1

shows a first known modification circuit,

Fig. 2

shows a second known modification circuit,

Fig. 3

showed a third known modification circuit,

Fig. 4

shows a first embodiment of the invention and

Fig. 5

shows a further embodiment of the invention.

The known modification circuits from FIGS. 1 to 3 are located, for example in the article cited in Elrad 1994, volume 7, pages 76 to 81. Each circuit shows an input for a left signal L and another input for a Right signal R on. Accordingly, each modification circuit has an output for a modified left signal L 'and another output a modified Right signal R 'on. Each circuit also includes first and second Combination device Kl, K2, in which different signal components with each other be combined, usually added or subtracted, to finally the modified To form output signal L 'or R'. These modified signals are then each fed at least one speaker, not shown, these not too tight may stand side by side. It is known that only then a directional impression is recognizable when the two signals L, R and L ', R' differ from each other. The greater the difference, the greater the discernment that finally it goes that the sound sources subjectively located by the listener as it were move apart. The individual modification circuits are used to Magnification of the stereo base increases the differences in the individual signals and in contrast, the common signal component is reduced. The common signal component is usually referred to as a mono signal and the difference as a difference signal. As is known, these two components play in the transmission of the stereo multiplex signal an essential role. The mono component in itself sounds good. The However, the difference is not attributable to an actual audible signal and sounds alone very uncomfortable.

Filter circuits are included in all of the circuits of FIGS. 1 to 5. For However, audio signals can be assumed that the lower ones are usually Frequency components up to a few 100 Hz are available as mono signals and Directional dependency only affects the overlying frequency components. Here you wear the fact that low frequencies from the human ear do not follow Directions can be resolved. The individual signal components that the legal and Affect the left signal are thus high-pass filtered signals, so that the in Filter circuits operating in the forward direction are realized by high-pass filters HP. The respective contribution of the individual signal components to the modification is by Multiplier M and weighting factors controlled, the negative, the positive and the Amount after may be greater than 1. In reality they move Weighting factors in relatively narrow areas, because otherwise the effects generated are unified cause a false sound impression. In Figures 2 and 3 there is only one Multiplier M, which effects the weighting by means of a supplied signal k. In Fig. 1 there are two multipliers M, both with the weighting factor k are controlled.

1. Das ursprüngliche erste und zweite Signal L bzw. R sind einander entgegengesetzt gleich: R = - L . Das bedeutet, daß das Summensignal (= Monosignal (R + L)) den Wert Null hat und das Differenzsignal (L - R) seinen Maximalwert erreicht.

2. Das ursprüngliche erste und zweite Signal L bzw. R sind einander gleich: R = L . Das bedeutet, daß das Summensignal (= Monosignal (R + L)) seinen Maximalwert erreicht und das Differenzsignal ( L - R) den Wert Null aufweist.

3. Eines der ursprünglichen Signale L bzw. R hat den Wert Null: z.B. R = 0. Das bedeutet, daß das Summensignal (L + R) und das Differenzsignal (L - R) dem Betrag nach gleich sind. Das Summensignal (R + L) täuscht bei der Modifikation gegebenenfalls ein unspezifisches Signal (Monosignal) vor, das bei einer unzweckmäßigen Schaltung das Modifikationsergebnis stört. Mit diesen extrem einseitigen Signalen L und R = 0 läßt sich anschaulich darstellen, inwieweit Signalkomponenten bei der jeweiligen Modifikationsschaltung in den falschen Signalzweig eingekoppelt werden.

The considerations on which the individual circuits of FIGS. 1 to 3 are based are described below. The following frequency diagrams show how the modifications then affect the individual modified signals using the following characteristic signal contents:

1. The original first and second signals L and R are mutually the same: R = - L. This means that the sum signal (= mono signal (R + L)) has the value zero and the difference signal (L - R) reaches its maximum value.

2. The original first and second signals L and R are equal to each other: R = L. This means that the sum signal (= mono signal (R + L)) reaches its maximum value and the difference signal (L - R) has the value zero.

3. One of the original signals L or R has the value zero: for example R = 0. This means that the sum signal (L + R) and the difference signal (L - R) are equal in amount. The sum signal (R + L) may simulate an unspecific signal (mono signal) during the modification, which interferes with the result of the modification in the event of an inappropriate switching. With these extremely one-sided signals L and R = 0, it can be clearly illustrated to what extent signal components are coupled into the wrong signal branch in the respective modification circuit.

In any case, the aim is that the frequency response should be as possible after the modification stays straight because otherwise the sound will be distorted. The volume impression should not changed overall.

In the known circuit arrangement of FIG. 1, the directional impression is amplified by subtracting part of the first and second signals L and R, which is determined by the weighting factor k and a high-pass filter HP, from the other signal R and L, respectively becomes. The frequency diagram on the left shows that this modification is ideal if either only a first signal L or only a second signal R is present. The associated frequency response L ' with R = 0 runs flat in this case. Signals that have a higher sum component L + R (i.e. R is approximately equal to L) appear to be lowered at higher frequencies. Contrary signals R = - L are raised at higher frequencies. Signals with a higher mono component thus sound dull and signals with a higher differential component are highlighted unpleasantly at high frequencies.

The known circuit example of Fig. 2 reinforces the directional impression by the first and second signal L and R signal components with the same signal component, that is Signals with a high sum of L + R, are subtracted, whereby the Differences in the first and second signals are more pronounced. From the The frequency diagram shown here shows that this is optimal for a mixed signal is a significant sum of R + L and additionally a highlighted or heavily lowered signal source, e.g. R = 0. This corresponds to Audio signals from a one-sided sound source and a high proportion of mono signals.

In the known circuit arrangement of FIG. 3, a differential signal L-R is finally formed from the first and second signals L and R by means of a subtractor sb and a signal component is formed therefrom by means of a high-pass filter HP and a weighting stage M, which component adds to the first signal L. and subtracted from the second signal R. The difference between the first and second signals is increased by the addition and subtraction of the difference value, so that the modified signals L ' , R ' have an amplified directional effect at the output and thus enlarge the stereo base.

The adjacent frequency diagram shows that the circuit of FIG. 3 for unspecific signals or mono signals with R = L have an ideal frequency response. For different signals, i.e. in the borderline case the same opposite signals R = - L, however, the frequency response is very unfavorable. These signals are at higher Frequencies raised up to 10 dB and therefore distort the sound impression.

The invention teaches that a general circuit with which all variants can be realized can be accomplished by including further signal components in the respective modification, the influence of which is controlled by associated weighting factors. The individual signal components are also combined by means of combination devices, ie added or subtracted, in order finally to obtain a modified first and second signal L ' or R ' again.

4 is a first embodiment of the modification circuit according to the Invention shown in which each modified signal by three signal components is formed. To make any modifications, each signal component should individually by means of a filter circuit and a weighting factor can be changed. The exemplary embodiment according to FIG. 4 already provides one Simplification is because two signal components s2, s3 and s5, s6 have only one Filter circuit F2 or F4 are performed.

A signal source q delivers a first and a second signal L, R at its output Signal source q is not specified, it can also be, for example Represent multiple signal source with parallel outputs, the first and second Signal is to be assigned to neighboring signals. For the better overview the exemplary embodiments are limited to stereo signals, the first signal L a left signal and the second signal R corresponds to a right signal. The In these cases, signal source q contains a decoder for stereo multiplex signals.

In the circuit according to FIG. 4, the first signal L is fed to an input of a first combination device K1 by means of a first filter F1 and a first weighting device with a multiplier M1 as the first signal component s1. The associated weighting factor g is supplied to the first multiplier M1 as a data value or corresponds to a fixed position shift. The first signal L is also fed to the input of a second filter F2 and forms, by means of a second weighting device, a sixth signal component s6 which is fed to a second combination device K2, at the output of which the second modified signal R 'can be tapped. The weighting in the second weighting device effects a second multiplier M2, the weighting input of which is supplied with a second weighting factor k. After the second weighting device, the signal is passed through a third weighting device and reaches the first combination device K1 as second signal component s2. The weighting in the third weighting device effects a third multiplier M3, the weighting input of which is supplied with a third weighting factor α. In parallel to the first, second and sixth signal components s1, s2, s6 which are formed from the first signal L, a fourth, fifth and third signal component s4, s5, s3 are formed from the second signal R. A third or fourth filter F3, F4 corresponds to the first or the second filter F1, F2. The first, second and third multipliers M1, M2, M3 correspond to a fourth, fifth and a sixth multiplier M4, M5, M6, to which the first, second and third weighting factors g, k and α are supplied. The third and sixth signal components s3, s6 are routed to a subtrahead input of the first and second combination devices K1, K2. The subtrahend inputs can be avoided if the associated weighting factors are changed in the sign.

5 shows another embodiment of the invention, the circuit of Fig. 4 in a simplified form. The circuit also contains Control devices, b1, b2, r and control devices st for regulation and / or specification the weighting factors. The embodiment of the circuit of FIG. 5 is still geared more towards processing audio signals than the more general one Circuit of Fig.4. The signal source q delivers L, R as first and second signals Left and right signal. The first and fourth signal components s1, s4 are neither filtered or weighted but correspond directly to the first and second signal L or R. Using a high pass filter HP and weighting by the second Weighting factor k becomes the sixth signal component s6 from the first signal L. formed, which is fed to the subtrahend of the second combination device K2 is. In the same way, using a high-pass filter HP and the like Weighting factor k formed from the second signal R the third signal component s3, which is fed to the subtrahend of the first combination device K1. The second weighting factor k is controlled by the control device st, which thus the The amount of the desired effect and thus the stereo base width is influenced. There like already indicated the directional dependency for conventional stereo signals only in middle and upper frequency range are used to form the second, third, fifth and sixth signal components s2, s3, s5, s6 high-pass filter HP used, the cutoff frequency is greater than 300 Hz and typically at 700 Hz lies. From the frequency diagrams of Fig. 1 to Fig. 3 it can be seen that the Cutoff frequency the range of signal increases or decreases is changed, which affects the hearing impression with mixed signals. From the high-pass filtered first or second signal becomes the second or fifth Signal component s2, s5 formed by the signal by means of the third Weighting factor α is changed in size. About the value of the third Weighting factor α can now not only the properties of the known Set circuits from Fig. 1 to Fig. 3, but also any intermediate stages, which enables an optimal signal adaptation.

The frequency diagram m of FIG. 1 is set with a weighting factor α = 0, which provides an optimal modification for stereo signals, in which one of the two Components L, R has the value 0. With a weighting factor α, which is approximately between 0.4 and 0, 5, a frequency response is set which corresponds to the frequency response of FIG. 2 corresponds and is optimal for mixed signals. If necessary, the third Weighting factor α also be negative to increase the signal for unspecific signals to reduce in the upper frequency range. Finally, using a weighting factor α = 1 the frequency response of Fig. 3 is set for pure mono signals or signals high mono signal component is ideal.

The third weighting factor α can be set in different ways. Either as a fixed value via the control device st - in FIG. 5 this is by a Dashed connection shown. The third weighting factor α can also are adaptively controlled by the signal properties themselves, for example by means of a first evaluation device b1 determined from the left and right signals L, R. become. In the simplest case, the mono or Difference signal component determined. Using individual filters with which the Individuals can reproduce physiological hearing sensitivity Frequency ranges are treated separately or specially weighted. This matches with an adaptive control of the weighting factor α, which is shown by the dashed line in FIG Line at the output of the first evaluation device b1 is shown schematically.

If a corresponding evaluation is also carried out on the modified output signals L ' , R ' by means of a second evaluation device b2, the outputs of the first and second evaluation devices b1, b2 can be connected to a control device r, the output of which controls the level of the weighting factors. By comparing the input and output signals of the modification circuit, the control device r can be used, in particular, to ensure that the volume impression does not change during the modification, regardless of the respective effect control. If the control device r is to take into account the volume impression in the entire frequency range or in individual frequency ranges, then the first and second evaluation devices b1, b2 must determine, among other things, performance-related data from the signals at the input and output of the modification circuit. In the exemplary embodiment of FIG. 5, the output of the control device r controls the third weighting factor α.

Of course, a combination of the evaluation and control devices is also possible 5 with the modification circuit of FIG. 4 is conceivable. Here can be about the first Weighting factor g the proportion of the first and second signals L, R can be controlled. The first and third filters F1, F3 can be connected through or each one Allpass can be realized. The time equalizations required for digital circuits are as usual not shown in the individual circuit examples. It will be again noted that the invention and the associated embodiments are not limited to the processing of stereo signals, but that the adaptive effects control is beneficial for many other signals.

Claims (8)

1. A circuit for modifying a first signal (L) and a second signal (R) which are provided by a signal source (q), the circuit including devices (F1 to F4, M1 to M6) comprising filters (F1 to F4) and weighting devices (M1 to M6) for forming first to sixth signal components (s1 to s6) from the first and second signals, the signal components separating the first and second signals (L, R) essentially into originally common and originally different signal components, which are combined into a modified first signal (L') and a modified second signal (R') by means of a first combining device (K1) and a second combining device (K2), respectively,

   the first and second signal components (s1, s2), which are associated with the first signal (L), and the third signal component (s3), which is associated with the second signal (R), are coupled to the first combining device, whose output provides the first modified signal (L'),

   the fourth and fifth signal components (s4, s5) which are associated with the second signal (R), and the sixth signal component (s6), which is associated with the first signal (L), are coupled to the second combining device (K2), whose output provides the second modified signal (R'),

   characterized in that
   at least one of the signal components (s1 to s6) is inverted in its effect with respect to the original signal characteristic on the first or second modified signals (L', R') as either the first and second combining devices (K1, K2) have a negative signal input for this at least one signal component (s1 to s6) or the associated weighting device (M1 to M6) has a negative signal input or a negative weighting input for this at least one signal component (s1 to s6).
2. A circuit as claimed in claim 1, characterized by the following features:

   The first signal component (s1) is formed from the first signal (L) by means of a first filter (F1) and a first multiplier (M1), which applies a first weighting factor (g);

   the sixth signal component (s6) is formed from the first signal (L) by means of a second filter (F2) and a second multiplier (M2), which applies a second weighting factor (k);

   the fourth signal component (s4) is formed from the second signal (R) by means of a third filter (F3) and a fourth multiplier (M4), which applies the first weighting factor (g);

   the third signal component (s3) is formed from the second signal (R) by means of a fourth filter (F4) and a fifth multiplier (M5), which applies the second weighting factor (k);

   the second signal component (s2) is formed from the sixth signal component (s6) by means of a third multiplier (M3), which applies a third weighting factor (α);

   the fifth signal component (s5) is formed from the third signal component (s3) by means of a sixth multiplier (M6), which applies the third weighting factor (α); and

   the respective values of the weighting factors (g, k, α) are either preset by a control device (st) or adjusted via evaluating devices (b1, b2).
3. A circuit as claimed in claim 1 or 2, characterized in that at least one of the weighting factors (g, k, α) is controlled by means of a first evaluating device (b1), to which the first and second signals (L, R) are applied.
4. A circuit as claimed in claim 1 or 2, characterized in that a first evaluating device (b1) is supplied with the first and second signals (L, R), and a second evaluating device (b2) is supplied with the modified first and modified second signals (L', R'), and that the circuit further comprises a regulating device (r) which is coupled to the first and second evaluating devices (b1, b2) and which is designed to control at least one of the weighting factors (g, k, α).
5. A circuit as claimed in claim 2, characterized in that the second and fourth filters (F2, F4) are highpass filters, and that by means of the second weighting factor (k) from the second and fifth multipliers, the respective stereo effect is variable.
6. A circuit as claimed in any one of claims 1 to 5, characterized in that the first signal component (s1) corresponds to the first signal (L), and the fourth signal component (s4) to the second signal (R).
7. A circuit as claimed in claim 4, characterized in that the regulating device (r) is designed to influence the value of the third weighting factor (α).
8. A circuit as claimed in claim 4 or 7, characterized in that in the first and second evaluating devices (b1, b2), power levels in individual frequency ranges are determined, and that the regulating device (r) is designed to process respective equal frequency ranges.

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