JP2007274442A - Sound level controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound level controller ensuring excellent response characteristic without generation of irregular sound. <P>SOLUTION: The sound level controller includes a multiplier for providing an output by multiplying a gain coefficient to an input digital audio signal, and a gain coefficient processing unit for changing the gain coefficient of this multiplier on the basis of an external gain instructing signal. This sound level controller further includes a monotonous decreasing/increasing detecting unit for detecting a monotonous decreasing and increasing point through comparison of a plurality of continuous data points of the input digital audio signal. The gain coefficient processing unit sends an output to the multiplier by increasing or attenuating the number of gain coefficients as much as the predetermined gain adjusting width, in the manner that sound level amplitude does not change for that of one preceding data point when the gain adjustment has been conducted at the point that has been detected as the monotonous reducing point or increasing point. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a volume adjusting device that adjusts a reproduction volume by digital signal processing in volume adjustment of a television or audio.

  Conventionally, various devices have been proposed as volume control devices that adjust the playback volume by digital signal processing. When the volume is adjusted, if the gain is changed in the middle of the waveform of the audio signal, the waveform becomes discontinuous at that point, causing abnormal noise. For example, as shown in FIG. 4A, if the gain is changed to a small value in the middle of a sinusoidal waveform, the waveform becomes discontinuous at that point (a state in which the volume level has changed) and is distorted. Waveform, which causes abnormal noise. Therefore, in general, when performing volume adjustment, the zero cross of the audio signal is detected to avoid abnormal noise during adjustment, and the gain is changed at this zero cross point to achieve volume adjustment that does not generate abnormal noise. Was.

As described above, there are many conventional techniques for adjusting the sound volume by detecting the zero cross, for example, a gain variable device described in Patent Document 1. Although the gain variable device described in Patent Document 1 performs gain adjustment by detecting zero crossing, there is a problem that responsiveness becomes dull when gain conversion is performed only at the time of zero cross detection. Timeout time is set from the lower limit frequency of the band, and this timeout time is defined as the zero cross interval when assuming the sine wave of the lower limit frequency, and gain adjustment is performed at the timing when the zero cross is detected or the timeout time elapses. Is.
JP 09-298431 A

  In this patent document 1, the time-out time is set to ensure the responsiveness at the time of volume adjustment. However, since processing is performed assuming that the time-out time elapses as zero crossing, basically only zero crossing is performed. This is the same as the process. This process has a problem that the gain adjustment range per step becomes large and the adjustment may cause abnormal noise. For example, as shown in FIG. 5A, when the gain is increased with a large adjustment width at the zero cross point, the adjustment point feels abnormal noise even though the waveform itself maintains continuity. There is a problem.

  In this way, changing the gain in the middle of the waveform causes abnormal noise as shown in FIG. 4A. Therefore, by detecting the zero crossing and performing gain adjustment, waveform distortion can be prevented and abnormal noise can be detected. However, for example, when the input signal is 20 Hz, a standby time of 25 ms is required, which causes a problem in responsiveness. Further, even when the gain is changed at the time of zero crossing, if the gain is increased with a large adjustment range, there is a problem that abnormal noise as shown in FIG.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a volume control device that does not generate abnormal noise while ensuring responsiveness.

  Claim 1 of the present invention is a multiplier that multiplies an input digital audio signal by a gain coefficient and outputs the signal, and a gain coefficient processing unit that changes the gain coefficient of the multiplier based on an external gain instruction signal A volume adjustment apparatus comprising: a monotonic decrease / increase detecting unit that compares a plurality of consecutive data points of an input digital audio signal to detect a monotonic decrease point and a monotone increase point; The gain that is set in advance so that the magnitude relationship of the volume level does not vary with the previous data point when gain adjustment is performed at the point detected as the monotonic decrease point or the monotone increase point. The volume adjusting device is characterized in that the gain coefficient is increased or attenuated by an adjustment width and output to a multiplier.

  According to a second aspect of the present invention, a multiplier that multiplies an input digital audio signal by a gain coefficient and outputs the signal, and a gain coefficient processing unit that changes the gain coefficient of the multiplier based on an external gain instruction signal A monotonic decrease / increase detecting unit for detecting a monotonic decrease point and a monotone increase point by comparing a plurality of consecutive data points of an input digital audio signal, and an input digital A zero cross detection unit is provided for detecting a zero cross point by comparing two consecutive data of an audio signal, and the gain coefficient processing unit gains a gain at the point detected as the monotone decrease point, the monotone increase point, or the zero cross point. When the adjustment is performed, the gain coefficient is increased or attenuated by a preset gain adjustment width so that the magnitude relation of the volume level does not fluctuate with the previous data point, and is output to the multiplier. A volume control apparatus according to claim Rukoto.

  According to a third aspect of the present invention, a multiplier that multiplies an input digital audio signal by a gain coefficient and outputs the signal, and a gain coefficient processing unit that changes the gain coefficient of the multiplier based on a gain instruction signal from the outside. A monotonic decrease / increase detecting unit for detecting a monotonic decrease point and a monotone increase point by comparing a plurality of consecutive data points of an input digital audio signal, and an input digital A zero cross detection unit is provided for detecting a zero cross point by comparing two consecutive data of an audio signal, and the gain coefficient processing unit performs gain adjustment at the point detected as the monotone decrease point or the monotone increase point. The gain coefficient is increased or attenuated by a preset gain adjustment width so that the magnitude relation of the volume level does not change with the previous data point, and is output to the multiplier. A sound volume characterized by increasing or attenuating the gain coefficient with a gain adjustment range larger than the gain adjustment range in the case of the monotonic decrease point or the monotone increase point at the point detected as the locross point. It is an adjustment device.

  According to a fourth aspect of the present invention, in addition to the first to third aspects, the monotonic decrease / increase detection unit is a second point when data of three consecutive points of the input digital audio signal is gradually decreasing. Even if the gain is increased by a preset gain adjustment width, a point that does not become larger than the previous data point is detected as a monotonically decreasing point, and the data of three consecutive points of the input digital audio signal are gradually The second point in the case of increasing is that a point which does not become smaller than the previous data point even if the gain is reduced by a preset gain adjustment width is detected as a monotonically increasing point. It is the volume control apparatus characterized.

  According to the first aspect of the present invention, when the gain adjustment is performed at the point detected as the monotonic decrease point or the monotonic increase point, the magnitude relationship of the volume level does not vary with the previous data point. Since the gain coefficient is increased or attenuated by a preset gain adjustment width and output to the multiplier, gain adjustment can be started even in the middle of the waveform, so that responsiveness is ensured. If the gain adjustment range at this point is small so that the magnitude relation of the volume level does not change with the previous data point (for example, ± 0.1 dB), the waveform after gain adjustment is distorted This will not cause abnormal noise.

  According to the invention described in claim 2, when the gain adjustment is performed at the point detected as the monotonic decrease point, the monotone increase point, or the zero cross point, there is a volume level relationship with the previous data point. Since the gain coefficient is increased or attenuated by a preset gain adjustment width so as not to fluctuate and output to the multiplier, gain adjustment can be started even in the middle of the waveform to ensure responsiveness, Also, if the gain adjustment range at each point is small so that the magnitude relationship of the volume level does not change with the previous data point (for example, ± 0.1 dB), the waveform after gain adjustment is distorted. It will not cause abnormal noise. Also, gain adjustment is possible at the zero cross point.

  According to the invention described in claim 3, when the gain adjustment is performed at the point detected as the monotonic decrease point or the monotonic increase point, the magnitude relationship of the volume level does not change with the previous data point. The gain coefficient is increased or attenuated by a preset gain adjustment width and output to the multiplier, and the gain adjustment width in the case of the monotonic decrease point or the monotone increase point at the point detected as the zero cross point. Since the gain coefficient is increased or attenuated with a larger gain adjustment width and output to the multiplier, the gain adjustment can be started even in the middle of the waveform, so that responsiveness is ensured. If the gain adjustment range is small so that the volume level does not change with the previous data point (eg, ± 0.1 dB), the waveform after gain adjustment will be distorted. Does not cause abnormal noise. In addition, at the zero cross point, gain adjustment with higher responsiveness is possible by adjusting the gain adjustment range (for example, ± 1.0 dB) larger than the gain adjustment range at the monotonic decrease point and the monotone increase point. .

  According to a fourth aspect of the present invention, the monotonic decrease / increase detection unit is a second point when the data of three consecutive points of the input digital audio signal is gradually decreasing and has a preset gain. Even when the gain is increased by the adjustment width, a point that does not become larger than the previous data point is detected as a monotonic decrease point, and 2 in the case where the data at three consecutive points of the input digital audio signal are gradually increased. Even if the gain is reduced by a preset gain adjustment width, a point that does not become smaller than the previous data point is detected as a monotonically increasing point. Only points where the waveform does not change suddenly can be detected, and abnormal noise can be prevented.

A volume control apparatus according to the present invention includes a multiplier that multiplies an input digital audio signal by a gain coefficient and outputs the signal, and a gain coefficient processing unit that changes the gain coefficient of the multiplier based on an external gain instruction signal A volume adjustment apparatus comprising: a monotonic decrease / increase detecting unit that compares a plurality of consecutive data points of an input digital audio signal to detect a monotonic decrease point and a monotone increase point; The gain that is set in advance so that the magnitude relationship of the volume level does not vary with the previous data point when gain adjustment is performed at the point detected as the monotonic decrease point or the monotone increase point. The gain coefficient is increased or attenuated by an adjustment width and output to the multiplier. Further, the monotonous decrease / increase detection unit includes data of three consecutive points of the input digital audio signal. The second point in the case of a gradual decrease, even if the gain is increased by a preset gain adjustment width, the point that does not become larger than the previous data point is detected as a monotonic decrease point, and the input digital This is the second point when the data at three consecutive points in the audio signal is gradually increasing, and even if the gain is reduced by a preset gain adjustment width, it does not become smaller than the previous data point. Is detected as a monotonically increasing point.
Embodiments will be described below with reference to the drawings.

  A configuration of a volume control device 10 according to the present invention will be described with reference to FIG. In FIG. 1, an analog audio signal input from a sound source 11 is converted to a digital signal by an A / D converter 12 and input to a DSP (digital signal processor) 13. In the DSP 13, the gain of the signal is changed, and then converted into an analog signal by the D / A converter 14, and then output to the speaker 17 through the low-pass filter 15 and the amplifier 16. Further, a signal for instructing a gain change from the gain indicator 18 is input to the control unit 19, and a gain instruction signal is sent from the control unit 19 to the DSP 13. The control unit 19 controls the entire DSP 13 and includes, for example, a microcomputer.

  The DSP 13 includes a monotonic decrease / increase detection unit 20, a gain coefficient processing unit 21, and a multiplier 22. The monotone decrease / increase detection unit 20 is for detecting a monotone decrease point and a monotone increase point of the input signal, and outputs the detection result to the gain coefficient processing unit 21. The gain coefficient processing unit 21 performs a process of changing the gain coefficient of the multiplier 22 at the timing when the monotonous decrease point and the monotone increase point are detected. The multiplier 22 multiplies the input signal by a gain coefficient and then outputs it to the D / A converter 14.

The monotonic decrease / increase detection unit 20 compares the size of three consecutive sampling data of the digital audio signal output from the A / D converter 12 and also relates to the magnitude level of the volume level even if the gain adjustment is performed. It is checked whether or not the condition for not changing is satisfied, and a data point satisfying the condition of the monotonically decreasing point or the monotonically increasing point is detected. Specifically, assuming that three consecutive sampling data are A, B, and C in the order of input, it can be said that if A>B> C, it is a monotonic decrease point, and if A <B <C, it is a monotone increase point. In order to prevent the waveform relationship from being distorted later and the volume level relationship from the previous data point to fluctuate, the condition that the magnitude relationship does not change even if each gain adjustment of ± 0.1 dB is performed. Append. That is, assuming that the coefficient corresponding to the gain adjustment of ± 0.1 dB is k, the point B is detected as a monotone decreasing point or a monotone increasing point only when the following conditions are satisfied.
Monotone decreasing point: A>B> C and A−B × (1 + k)> 0 (1)
Monotonically increasing point: A <B <C and B × (1-k) −A> 0 (2)

  The above condition (1) is that if the three data are monotonically decreasing, even if the gain adjustment of +0.1 dB (multiplication of (1 + k)) is performed on the data at point B, the data at point A before The point B is detected as a monotonically decreasing point only when it does not increase, and the condition (2) above assumes that when the three data are monotonically increasing, the gain adjustment is −0.1 dB for the data at the B point. The point B is detected as a monotonically increasing point only when (multiplication of (1-k)) is not made smaller than the data of the previous point A. When a monotonic decrease point or a monotone increase point is detected in this way, it is output to the subsequent gain coefficient processing unit 21.

  The gain coefficient processing unit 21 performs a process of changing the gain coefficient of the multiplier 22 at the timing when the monotonous decrease point or the monotone increase point is detected. First, when a signal instructing a gain change from the gain indicator 18 is input to the control unit 19 and a gain instruction signal is sent from the control unit 19 to the gain coefficient processing unit 21, the gain coefficient processing unit 21 gives an instruction. The gain conversion amount is held (for example, stored in a lookup table). When a detection signal of a monotone decrease point or a monotone increase point is input from the monotone decrease / increase detection unit 20, the gain is increased or decreased by a preset gain change amount, for example, a change amount of 0.1 dB. In this way, the gain is increased or decreased by 0.1 dB each time a monotonic decrease point or a monotone increase point is detected, and the gain coefficient of the multiplier 22 is changed each time. Then, when the gain conversion amount instructed from the gain indicator 18 is reached, the change of the gain coefficient is finished.

  The multiplier 22 multiplies the digital audio signal output from the A / D converter 12 by the gain coefficient set by the gain coefficient processing unit 21 and outputs the result to the D / A converter 14 at the subsequent stage. To do. The gain coefficient of the multiplier 22 is rewritten by the gain coefficient processing unit 21, and the multiplication process is performed while maintaining the same gain coefficient until rewriting, and after the rewriting, the gain coefficient is multiplied by holding a new gain coefficient. Process.

Next, the operation of the volume control device 10 of the present invention shown in FIG. 1 will be described.
When the user adjusts the volume using the gain indicator 18, a gain instruction signal is sent from the control unit 19 to the gain coefficient processing unit 21. For example, if the user performs an operation of −5 dB, this is stored in the gain coefficient processing unit 21. The gain coefficient processing unit 21 outputs the gain coefficient attenuated by 0.1 dB to the multiplier 22 at the timing when the detection signal of the monotonic decrease point or the monotone increase point from the monotone decrease / increase detection unit 20 is input. In this way, the gain is decreased by 0.1 dB each time a monotonic decrease point or monotonic increase point is detected, and the gain coefficient is changed when the total reaches -5 dB by performing -0.1 dB processing at 50 locations. Exit. Similarly, when the gain is increased, processing is performed in increments of 0.1 dB.

  FIG. 4B is a waveform diagram showing the case where the volume is adjusted according to the present invention. As can be seen from FIG. 4B, gain adjustment is performed while maintaining the continuity of the waveform (a state in which the magnitude relationship of the volume level is maintained) by gradually attenuating the gain from the start of the gain change. I can do it. The data point for gain adjustment is a monotone decrease point or a monotone increase point that satisfies the above condition (1) or (2) in the monotonic decrease / increase detection unit 20, so that the waveform does not change even if the gain adjustment process is performed. There is no discontinuity (a state in which the magnitude relation of the sound volume level fluctuates). Here, FIGS. 4A and 4B show the same amount of gain attenuation, but in FIG. 4A, the waveform is discontinuous because it is suddenly attenuated at one location, resulting in abnormal noise. However, in (b), since it is attenuated little by little, the waveform is maintained and no abnormal noise is caused.

  In FIG. 4, the same gain adjustment width is set within the half wavelength of the sine wave for easy comparison. However, when the adjustment is actually performed by 0.1 dB, the processing is not necessarily finished within the half wavelength. It is possible for processing to continue across several waveforms. That is, as shown in FIG. 5B, the gain gradually increases. For this reason, in the example of FIG. 5A, abnormal noise has been generated by converting the gain with a large adjustment width at the time of zero crossing. However, in the present invention, as shown in FIG. 5B, the gain is gradually increased. Does not cause abnormal noise. Of course, the same applies to the case of reducing the gain.

  As described above, in the volume adjusting device 10 according to the present invention, in order to solve the problem of responsiveness when performing gain adjustment only at the time of the conventional zero crossing and the problem of abnormal noise due to a sudden gain change, The gain adjustment is started, and at this time, a monotone decrease point or a monotone increase point where the magnitude relationship of the volume level does not change with the previous data point even if the gain adjustment is performed is detected. Since the gain adjustment is performed little by little (for example, ± 0.1 dB), both the abnormal noise due to the discontinuity of the waveform and the abnormal noise due to a sudden gain change are generated while ensuring responsiveness. It became possible to achieve no volume adjustment.

  In the first embodiment, the monotone decrease / increase detection unit 20 detects the monotone decrease point or the monotone increase point and performs gain adjustment at this point. However, the present invention is not limited to this. Absent. For example, as shown in FIG. 2, a zero cross detection unit 23 may be provided to perform gain adjustment even during zero crossing. In FIG. 2, the same components as those in FIG.

The zero cross detection unit 23 detects whether or not the point is a zero cross using two consecutive sampling data of the digital audio signal output from the A / D converter 12. Specifically, two consecutive sampling data are set as A and B in the order of input, and point B when these products are 0 or less is detected as a zero cross point.
Zero cross point: A × B ≦ 0 (3)
That is, when the point B is at the zero level or when the zero level is crossed between ABs, it is detected as a zero cross point, so that the zero cross point has a width.

  The detection result of the zero cross detection unit 23 is input to the OR circuit 24 together with the detection result of the monotonic decrease / increase detection unit 20, and the output of the OR circuit 24 is input to the gain coefficient processing unit 21. With such a configuration, it is possible to detect the zero cross point in addition to the monotonous decrease point and the monotone increase point, and to adjust the gain.

  In the second embodiment, the gain adjustment is performed without distinguishing the monotonic decrease point, the monotone increase point, and the zero cross point by using the OR circuit 24. However, the gain adjustment is performed with different adjustment amounts by distinguishing these. It may be. In this case, as shown in FIG. 3, the detection result of the monotonic decrease / increase detection unit 20 and the detection result of the zero-cross detection unit 23 are respectively input to the gain coefficient processing unit 25, and the gain coefficient processing unit 25 Gain adjustment is performed with different adjustment amounts by distinguishing signals.

  In the gain coefficient processing unit 25, for example, in the case of the detection result from the monotonic decrease / increase detection unit 20, as in the case of the first embodiment, the adjustment is performed by 0.1 dB, and the zero cross detection unit 23 In the case of the detection result, the adjustment range is larger than the monotonic decrease point and the monotone increase point, and the adjustment range is within a range that does not cause abnormal noise, for example, 1.0 dB. With such a configuration, it is possible to adjust the volume with higher responsiveness while preventing the generation of abnormal noise.

  In the above embodiment, the gain adjustment is started even in the middle of the waveform. At this time, even if the gain adjustment is performed, the monotonous decrease point where the magnitude relationship of the volume level does not vary with the previous data point or Although a monotonically increasing point is detected and gain adjustment of ± 0.1 dB is performed at that point, this ± 0.1 dB is merely an example, and the present invention is not limited to this. For example, it may be ± 0.05 dB or ± 0.2 dB, and can be set as appropriate. In such a case, the above-described formulas (1) and (2) that are detection conditions for a monotonic decrease point or a monotone increase point The value of the constant k in) needs to be adjusted accordingly.

It is a block diagram showing the structure of the volume control apparatus by Example 1 of this invention. It is a block diagram showing the structure of the volume control apparatus by Example 2 of this invention. It is a block diagram showing the structure of the volume control apparatus by Example 3 of this invention. (A) is a waveform diagram showing a state of causing abnormal noise by changing the gain in the middle of the waveform, (b) is a state of changing the gain in the middle of the waveform by the method according to the present invention. FIG. (A) is a waveform diagram showing how abnormal noise is generated by converting gain with a large adjustment width at zero crossing, and (b) shows how gain is changed by the method according to the present invention. It is a waveform diagram.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Volume control apparatus, 11 ... Sound source, 12 ... A / D converter, 13 ... DSP, 14 ... D / A converter, 15 ... LPF, 16 ... Amplifier, 17 ... Speaker, 18 ... Gain indicator, 19 ... Control unit, 20 ... monotonic decrease / increase detection unit, 21 ... gain coefficient processing unit, 22 ... multiplier, 23 ... zero-cross detection unit, 24 ... OR circuit, 25 ... gain coefficient processing unit.

Claims (4)

  A volume control device comprising a multiplier that multiplies an input digital audio signal by a gain coefficient and outputs the gain, and a gain coefficient processing unit that changes the gain coefficient of the multiplier based on an external gain instruction signal A monotonic decrease / increase detection unit that detects a monotonic decrease point and a monotonic increase point by comparing a plurality of continuous data points of the input digital audio signal, and the gain coefficient processing unit includes the monotonic decrease point or The gain coefficient is increased by a preset gain adjustment width so that the magnitude relationship of the volume level does not fluctuate with the previous data point when gain adjustment is performed at the point detected as a monotonically increasing point. Alternatively, a volume adjusting device that attenuates and outputs to a multiplier.   A volume control device comprising a multiplier that multiplies an input digital audio signal by a gain coefficient and outputs the gain, and a gain coefficient processing unit that changes the gain coefficient of the multiplier based on an external gain instruction signal A monotonic decrease / increase detecting unit for detecting a monotonic decrease point and a monotone increase point by comparing a plurality of continuous data points of the input digital audio signal, and two continuous points of the input digital audio signal A zero-cross detection unit for comparing data and detecting a zero-cross point is provided, and the gain coefficient processing unit is provided when gain adjustment is performed at a point detected as the monotonic decrease point, monotone increase point, or zero-cross point. The gain coefficient is increased or attenuated by a preset gain adjustment width so as not to change the magnitude relation of the volume level with the previous data point, and output to the multiplier Amount adjusting device.   A volume control device comprising a multiplier that multiplies an input digital audio signal by a gain coefficient and outputs the gain, and a gain coefficient processing unit that changes the gain coefficient of the multiplier based on an external gain instruction signal A monotonic decrease / increase detecting unit for detecting a monotonic decrease point and a monotone increase point by comparing a plurality of continuous data points of the input digital audio signal, and two continuous points of the input digital audio signal A zero cross detection unit for comparing data and detecting a zero cross point is provided, and the gain coefficient processing unit detects the previous data when gain adjustment is performed at the point detected as the monotonic decrease point or the monotone increase point. The gain coefficient is increased or attenuated by a preset gain adjustment width so that the magnitude relation of the volume level does not change between the points and output to the multiplier, and the zero cross point is detected. In point, volume control device and outputting said at large gain adjustment width than the gain adjustment width when monotonically decreasing point or monotonically increasing point increase or attenuate the gain factor in the multiplier.   The monotonic decrease / increase detection unit is the second point when the data of three consecutive points of the input digital audio signal is gradually decreasing, and even if the gain is increased by a preset gain adjustment width, A point that does not become larger than the previous data point is detected as a monotonically decreasing point, and is a second point when the data of three consecutive points of the input digital audio signal is gradually increasing, and is a preset gain. 4. The volume adjusting apparatus according to claim 1, wherein a point that does not become smaller than the previous data point even if the gain is reduced by the adjustment width is detected as a monotonically increasing point.

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