JP5558276B2 - Audio processing device - Google Patents

Description

  The present invention relates to an audio processing apparatus suitable for use in an audio adjustment console that processes and adjusts audio signals in, for example, a broadcast studio and a recording studio.

  In broadcast studios, recording studios, etc., an audio adjustment console generally called a mixer is installed for adjusting the volume and sound quality of an input audio signal. The audio adjustment console inputs an audio signal from a microphone or an audio source, and performs various adjustments and processes such as level adjustment, sound effect, sound image localization, and mixing to create desired audio data.

  In this audio adjustment console, an audio processing device is used that performs audio processing and volume adjustment as described above by applying digital processing to an input analog signal. The performance of the analog signal input unit of this audio processing device is determined by the analog amplifier circuit and the AD conversion circuit. For example, the noise level depends on the performance of the operational amplifier and AD conversion circuit to be used. Further, since the input signal is digitally processed, headroom is taken into consideration for the signal processed by the analog signal input unit.

  This headroom refers to the margin between the maximum signal level that can be recorded by the device and the peak of the sound actually processed, that is, the level difference from the reference level until the circuit is saturated and the waveform is clipped. . If there is not enough headroom, distortion will occur at the peak of the sound, and if too much headroom is taken, the S / N ratio will decrease. Especially when the signal is processed digitally, if there is not enough headroom, even if the signal waveform saturates, the clip that is not distorted gently, but the peak of the signal is cut out digitally. Since this causes a large distortion, how to take headroom is important.

  For example, in a live broadcast or variety program, even if an unexpectedly high sound pressure level is input from a microphone, the headroom at the analog signal input section prevents the output waveform from being hard clipped and distorted audio output. Is preferably, for example, (20 + α) dB. α is a positive real number, for example, 6. Therefore, in the prior art, an analog amplifier circuit is set so that the reference level after AD conversion becomes − (20 + α) dBFS, and then gain adjustment of + α dB is performed by digital signal processing, so that a general digital audio signal It was said that it was adjusted to the reference level of −20 dBFS.

  Note that dBFS is a unit of the magnitude of a digital signal, and FS is full scale, which is the maximum value that can be digitally expressed. 0 dBFS is the maximum digital value, and all signals exceeding this value are hard clipped. The magnitude of the signal is expressed in dB, and a normal signal is expressed as a negative value.

  A conventional speech processing apparatus 10 will be described with reference to FIG. The voice processing apparatus 10 includes a plurality of voice processing systems 11 to 1n. Each of the sound processing systems 11 to 1n includes a plurality of analog amplification circuits 21 to 2n for inputting sound signals, AD conversion circuits 31 to 34n connected to the analog amplification circuits 21 to 2n, and AD conversion circuits 31 to 31n. Have digital signal processing circuits 41 to 4n connected to each other.

  In the audio processing device 10, when an analog signal is input to the analog amplifier circuits 21 to 2n, the analog signal is amplified by the analog amplifier circuits 21 to 2n based on a predetermined headroom 20 + αdB. The analog signal amplified from the analog amplifier circuit 21 is input to the AD conversion circuits 31 to 3n, and the AD conversion circuit 31 converts the analog signal into a digital signal.

  The digital signal processing circuits 41 to 4n adjust the gain of the digital signal from the AD conversion circuits 31 to 34n. This gain adjustment is to perform + α dB digital signal processing on − (20 + α) dBFS which is an output level from the AD conversion circuits 31 to 3n. By this signal processing, for example, a general reference level of a digital audio signal can be set to −20 dBFS.

  Such a prior art is known as Patent Document 1. In Patent Document 1, in a remote head amplifier with an AD conversion circuit, when a line whose headroom is set to (20 + α) dB is connected, a signal processing unit controls data carried together with the digital audio signal. It is disclosed. In this control, the reference level is adjusted to −20 dBFS by increasing the + α dB gain and compressing the headroom to 20 dB with a digital limiter.

Japanese Patent Laid-Open No. 10-51254

  Such digital signal processing of the prior art has a problem that it is difficult to maintain a good S / N characteristic because the noise component is amplified simultaneously with the audio signal at the time of gain amplification of + αdBFS.

For example, when a gain adjustment of +6 dB is performed on a −26 dBFS signal output from the AD conversion circuit to set the digital audio signal level to −20 dBFS, the noise level is also amplified by +6 dB. This +6 dB is equivalent to amplifying the sound pressure by about twice, and the noise is about twice. Even in the invention described in Patent Document 1, the problem of the S / N characteristic is not solved.

  The present invention has been proposed to solve the above-described problems of the prior art, even when a large headroom is set in the analog amplifier circuit and the output level is adjusted in the digital processing circuit. Another object of the present invention is to provide an audio processing device capable of improving the S / N characteristic of an output signal from a digital processing circuit.

  The present invention relates to a plurality of analog amplifier circuits composed of individual analog amplifier circuits that individually amplify a plurality of input analog signals based on a predetermined headroom, and analog signals output from the individual analog amplifier circuits. A plurality of AD conversion circuits comprising individual AD conversion circuits that convert digital signals of predetermined output levels corresponding to the predetermined headroom, and digital signals of the predetermined output levels output from the individual AD conversion circuits In the audio processing device for audio adjustment console, comprising: a plurality of individual digital signal processing circuits each of which outputs a signal as a digital signal obtained by individually adjusting the gain to an output level of a general reference of the digital audio signal. Distribute individual analog signals to the individual analog amplifier circuit and one or more other analog amplifier circuits A plurality of distribution switches for switching, a plurality of changeover switches for switching the output of a predetermined output level of two or more from a digital signal processing circuit, and the switched two of the distribution signals. A digital signal addition / processing circuit that inputs, adds, adjusts the gain as necessary, and outputs a digital signal having a general reference output level, by inputting the outputs of the predetermined output levels described above; And

  Further, the present invention is characterized in that the signal level of the predetermined headroom and the signal level by gain adjustment in the digital signal addition / processing circuit are freely set.

  Further, the present invention is characterized in that the digital signal addition / processing circuit makes an error determination when each of the two or more predetermined output levels is not substantially the same or within a predetermined threshold.

  According to the present invention, when there is an unused audio processing system, the signal of the audio processing system in use is distributed to the unused audio processing system, and after each audio processing is performed in each distributed system, With a simple configuration of adding and outputting the signals of each system, it is possible to improve the S / N characteristics when the output level is adjusted in the digital processing circuit for an analog signal in which a large headroom is set. .

It is a block diagram explaining the structure of the audio processing apparatus which concerns on embodiment of this invention. It is a flowchart explaining operation | movement of the audio processing apparatus which concerns on embodiment of this invention. It is a block diagram explaining the structure of the conventional audio processing apparatus.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. In addition, about the part same as a prior art, the same code | symbol is attached | subjected and demonstrated.

[Configuration of the embodiment]
As shown in FIG. 1, the speech processing apparatus 10 of this embodiment includes a plurality of speech processing systems 11 to 1n. Each of the sound processing systems 11 to 1n includes analog amplifier circuits 21 to 2n, AD conversion circuits 31 to 3n, and digital signal processing circuits 41 to 4n, respectively.

From the first audio processing system 11 to the input side of the analog amplifier circuits 21 to 2n-1 of the (n-1) th audio processing system 1n-1, the audio signal input to the first audio processing system 11 is second To distribution lines 50 having distributors 51 to 5n-1 that distribute to the nth sound processing systems 12 to 1n. Distribution switches 62 to 6n are provided in front of the analog amplifier circuits 22 to 2n in the second to nth audio processing systems 12 to 1n, and the two terminals on the input side of the distribution switches 62 to 6n are connected to each system. The sound source (normal position) is distributed to the distribution wiring 50 (distribution position).

  The distribution switches 62 to 6n distribute a signal input to one audio processing system to other audio processing systems. For example, an analog signal input to the first analog amplifier circuit 21 is This switch distributes the analog amplification circuits 22 to 2n of the second to n-th sound processing systems 12 to 1n.

  Changeover switches 71 to 7n are provided in the subsequent stage of the AD conversion circuits 31 to 3n in the respective sound processing systems 11 to 1n. Two terminals on the output side of the changeover switches 71 to 7n are connected to the digital signal processing circuits 41 to 4n (normal position) of the own system and the addition / processing circuit 40 (distribution position) of the distributed digital signal, respectively. ing.

  The digital signal addition / processing circuit 40 includes an error determination unit that determines whether or not the digital signals output from any two or more audio processing systems of the AD conversion circuits 31 to 3n are the same, and each audio processing system The signal adding unit for adding the digital signals from and the gain adjusting unit for adjusting the gain of the added signal.

  It is also possible to provide a signal addition unit and an addition processing unit that perform gain adjustment on the signals of each system before addition and then add the signals of each system. In addition, the digital addition / processing circuit 40 may include a processing processing unit that applies various acoustic effects to the audio signal, like the digital processing circuits 41 to 4n.

  The audio device 10 is provided with a control device 80 for controlling the respective units. The control device 80 includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and the like. For example, the control device 80 executes a program stored in the ROM and controls each unit of the sound processing device 10.

More specifically, the control device 80 includes the following units.
(1) An input line setting unit 81 for operating the distribution switches 62 to 6n.
(2) An analog gain setting unit 82 that sets the gain of each of the analog amplifier circuits 21 to 2n.
(3) An output destination setting unit 83 for operating the changeover switches 71 to 7n.
(4) An addition / processing circuit control unit 84 that controls error determination, gain adjustment, and addition processing of the digital signal addition / processing circuit 40.
(5) A digital gain setting unit 85 for setting the gain of the digital signal processing circuits 41 to 4n of each audio processing system.

  Connected to the control device 80 are a display unit 86 for status (whether or not an error is displayed) constituted by LEDs and the like, and an external controller 87 provided in the sound adjustment console. The external controller 87 is provided with an input line state display part 87a and input means 87b for setting an input line.

[Operation of the embodiment]
FIG. 2 is a flowchart for explaining the operation of the speech processing apparatus according to the embodiment of the present invention. The operation of the speech processing apparatus 10 according to this embodiment will be described with reference to FIGS. 1 and 2.

  The speech processing apparatus 10 of this embodiment is generally used in the normal mode in step S10. Here, the normal mode is a case where a high sound pressure level that is not predicted by an analog input from a sound source such as a microphone is not input from the microphone, and the analog amplifier circuit 21 does not require a large headroom, or a plurality of modes. This is adopted when a sound source is connected to all of the provided voice processing systems 11 to 1n and there is no free voice processing system.

  Therefore, in this normal mode, when a large headroom is not required for the input signal, the output from the AD conversion circuit is set to −20 dBF. In addition, in the audio processing systems 11 to 1n, for a sound source with an input of an unpredictable high sound pressure level such as a microphone of a live broadcast or a variety program, the output of the AD conversion circuit is set to −26 dBFS as in the conventional technology. Then, amplification processing of +6 dB is performed in the subsequent digital signal processing circuits 41 to 4n.

  In this normal mode, the distribution switches 62 to 6n and the changeover switches 71 to 7n provided in each of the sound processing systems 11 to 1n are connected to analog signals provided to the respective processing systems. It is set to the normal position (the position of each switch in FIG. 1) that flows only to the amplifier circuits 21 to 2n, the AD conversion circuits 31 to 3n, and the digital signal processing circuits 41 to 4n.

  In a state where the normal mode is set as described above, if any of the sound processing systems 11 to 1n is vacant and it is necessary to connect a sound source that requires a large headroom, the sound processing is performed. The device 10 is set to the distribution mode. That is, in step S11, an instruction to change the operation mode to the distribution mode is given. This instruction is given by the user operating the input means 87b of the external controller 87 provided in the control device 80.

  Next, in step S12, the input line is changed, the analog gain is changed, and the like. For example, if the analog amplifier circuit 22 is empty, the input line setting unit 81 of the control device 80 switches the distribution switch 62 to the distribution position, and the first audio processing is connected to a sound source that requires a large headroom. A part of the analog signal input to the analog amplifier circuit 21 of the system 11 is distributed to the analog amplifier circuit 22 of the second sound processing system 12.

  Similarly, the input line setting unit 81 switches the changeover switches 71 and 72 connected to the first and second audio processing systems 11 and 12 to the distribution position on the digital signal addition / processing circuit 50 side. The completion of the input line setting is sent to the input line setting unit 81 as a setting state notification and displayed on the display unit 87a of the external controller 87.

  At the same time, the analog gain setting unit 92 of the control device 80 changes the analog gain of the analog amplifier circuits 21 and 22 to which the distributed signal is input, for example, changes the headroom from 20 dB to 26 dB.

  As a result, the audio signal input to the audio processing system 11 is divided into two by the distributor 99 to the first and second audio processing systems 11 and 12, and these two distributed signals are analog amplifier circuits of each system. Amplified by 21 and 22, then converted into a digital signal by AD conversion circuits 31 and 32, and input to a digital signal addition / processing circuit 40.

  Next, in step S13, an error determination is performed on the two systems of signals input to the digital signal addition / processing circuit 40. In this error determination, an error determination unit provided in the digital signal addition / processing circuit 40 compares two input digital signals to determine whether or not they are the same. In this case, the identity of the two systems of digital signals can be determined by a method such as comparing the frequency components of both signals.

  A plurality of digital signals input to the digital signal addition / processing circuit 40 are basically the same, but may not be the same due to a malfunction of each circuit or switch. When a plurality of such non-identical signals are added, the original analog signal input to the audio processing device 10 is different. In that case, since it is preferable to maintain the normal mode without switching to the distribution mode, the error determination unit determines the signal identity.

  When the error determination unit determines that the digital signals are the same (step S14: Yes), the process proceeds to step S15, and the distribution switch 62 and the changeover switches 71 and 72 maintain the distribution position. As a result, digital signal outputs from the AD conversion circuits 31 and 32 are input to the digital signal addition / processing circuit 40, and these digital signals are added. Further, the gain of the added digital signal is adjusted as necessary.

  For example, the headroom of the digital signals output from the AD conversion circuits 31 and 32 is 26 dB, respectively. These digital signals are the same, and when they are added, the digital signals are doubled. If the input to output ratio is twice, the dB is about 6.02, and the digital signal amplified to -26 dBFS is about -19.98 dBFS. This is a value close to −20 dBFS, which is the output level of the general reference. When outputting at the output level of the general reference, the output can be performed without adjusting the gain.

  The output level from the AD conversion circuits 31 and 32 can be set without being limited to −26 dBFS. For example, when set to −28 dBFS, these digital signals are approximately − by the addition processing in the addition / processing circuit 40. An output level of 22 dBFS is required, and a level adjustment of about +2 dBFS is required to obtain a general reference output level.

  As described above, when the identity of the signals of the respective systems input to the addition / processing circuit 40 is confirmed, the transition to the distribution mode is completed assuming that there is no error (step S16).

  On the other hand, when these digital signals are not determined to be the same in step S14 (step S14: No), the process proceeds to step S17. That is, when the addition / processing circuit 40 determines an error, the information is sent to the control device 80, and the control device 80 displays this state on the status display unit 86 as an error. If it is determined that there is an error, the distribution mode cannot be set. Therefore, the control device 80 can determine the distribution switches 62 to 6n and the changeover switches 71 to 7n according to commands from the input line setting unit 81 and the output destination setting unit 83. To the normal side.

  At the same time, the control device 81 sets the analog gain of each of the analog amplifier circuits 21 to 2n to the value in the normal mode according to a command from the analog gain setting unit 82. In this way, the audio signal input to the first audio processing system 11 is input to the analog amplifier circuit 21 with the same sound pressure without being distributed, and returns to the normal mode (step S18).

[Effect of the embodiment]
The set value of the headroom in the analog amplifier circuit 21 exemplified in the embodiment is 26 dB. In this case, if the noise generated in the analog amplifier circuit 21 is α1, and the noise generated in the AD converter circuit 31 is β1, the noise input to the digital signal processing circuit 41 in the normal mode is (α1 + β1). . Note that the noise in the analog amplifier circuit and the noise in the AD converter circuit cannot be calculated by simple addition, but are expressed as (α1 + β1) for convenience. When the digital signal processing circuit 41 adjusts the gain of +6 dB, the noise becomes (2α1 + 2β1). As described in the prior art, this noise is approximately doubled by this gain adjustment.

  On the other hand, when the analog input is distributed to the analog amplifier circuits 21 and 22, the setting value of each headroom is 26 dB, and the noise generated in the analog amplifier circuits 21 and 22 is α1 / 2 and α2 / 2, respectively. . The noises generated in the AD conversion circuits 31 and 32 are β1 / 2 and β2 / 2, respectively. The reason why these noises are different is that the characteristics of each circuit are different, and the reason why the noises are ½ is that the analog input signals are distributed.

  In this case, the noise input to the digital signal addition / processing circuit 40 becomes (α1 / 2 + β1 / 2) and (α2 / 2 + β2 / 2) by the addition processing, and further, 6 dB of the addition / processing circuit 40. When the output level of the digital signal becomes about −20 dBFS by the amplification process, the noise becomes 2 (α1 / 2 + β1 / 2 + α2 / 2 + β2 / 2) = (α1 + β1 + α2 + β2) by this amplification process.

  Comparing the noise in the normal mode (2α1 + 2β1) and the noise in the distribution mode (α1 + β1 + α2 + β2), the noise in the distribution mode (α1 + β1 + α2 + β2) is smaller. This is because the noise components (noise phases) generated in the noises α1, β1, α2, and β2 are different, and the noise synthesis peak of these noises is smaller than the noise synthesis peak of the noises 2α1 and 2β1.

  Thus, in this embodiment, since the same audio signal is input to the analog amplifier circuit 21 and the analog amplifier circuit 22, the output audio of the AD conversion circuit 31 input to the adder by digital signal processing. The signal and the output audio signal of the AD conversion circuit 32 are the same. Therefore, since the level of the audio signal is +6 dB by the addition by the digital signal processing, in order to keep the reference level of the digital signal processing circuit 1 at −20 dBFS, the gains are respectively set to −6 dB by the analog amplifier circuits 21 and 22 in advance. deep.

  That is, the output levels of the analog amplifier circuits 21 and 22 are −26 dBFS, respectively, and the headroom of the analog amplifier circuits 21 and 22 is 26 dB. On the other hand, since the signal noise components of the AD conversion circuits 31 and 32 input to the digital signal addition / processing unit 40 are not the same, the noise components are not amplified here. In this way, only necessary audio signal components are amplified by +6 dB and unnecessary noise components are not amplified, and 26 dB of headroom can be secured in the analog amplifier circuit without sacrificing S / N characteristics. become.

  As described above, according to the present embodiment, an input signal is distributed to an analog amplifier circuit of an unused audio processing system, and after the analog amplification or AD conversion processing is performed on the distributed signal, the distributed signal is added. By applying digital processing, it is possible to improve S / N characteristics and headroom.

[Other Embodiments]
The present invention is not limited to the above-described embodiments, and includes other embodiments as follows.

(1) In the above example, the analog input is divided into two. However, if there are more unused audio processing systems, the headroom of the analog amplifier circuit can be increased by increasing the number of distributions to three distributions and four distributions. Can be secured.

(2) When not much headroom is required, the S / N characteristics should be improved by adjusting the gain setting of the analog amplifier circuit and the distribution of the gain setting of the amplifier by digital signal processing. Is also possible.

(3) The error determination unit is also equipped with a function that can set a threshold value (a value indicating the degree of identity of each system to be compared) for determining whether or not there is an error. To make correct error judgments.

(4) The analog signal distribution of the audio processing device uses a switch, but is not limited to this, and for example, a distribution transformer may be used. The switch may be provided in the middle stage of the analog amplifier circuit.

(5) The voice processing device according to the embodiment is processed by a control signal from an external controller provided in the control device 80, but is not limited thereto, for example, a configuration in which the voice processing device has a control unit. It may be.

(6) In the above embodiment, the audio signal input to the analog amplifier circuit 21 is targeted for distribution. However, the present invention is not limited to this. For example, the analog signal input to the analog amplifier circuits 22, 23, 24 is distributed. It may be a target. It is also possible to provide a plurality of combinations of the voice processing systems on the distribution side and the distributed side in a voice processing apparatus having a large number of voice processing systems.

DESCRIPTION OF SYMBOLS 10 ... Audio processing apparatus, 11-1n ... Audio processing system, 21-2n ... Analog amplifier circuit, 31-3n ... AD converter circuit, 40 ... Digital signal addition / processing circuit, 41-4n ... Digital signal processing circuit, 50 ... distribution wiring, 51-5n-1 ... distributor, 62-6n ... distribution switch, 71-7n ... switch, 80 ... control device, 81 ... input line setting unit, 82 ... analog amplification factor setting unit, 83 ... Output destination setting unit, 84... Addition / processing circuit control unit, 85... Digital gain setting unit, 86. Status display unit, 87... External controller, 87 a. means.

Claims (3)

A plurality of sound processing systems for connecting sound sources to be processed are provided, and each sound processing system has an analog amplifier circuit that amplifies an analog signal input based on a predetermined headroom, and is output from the analog amplifier circuit. In an audio processing apparatus provided with an AD conversion circuit that converts an analog signal into a digital signal and a digital signal processing circuit that amplifies the digital signal output from the AD conversion circuit,
A distributor that distributes an analog signal input to the voice processing system in use to an analog amplifier circuit of the voice processing system in use, and an analog amplifier circuit of another unused voice processing system;
It has an addition / processing circuit for converting the distributed analog signal of each voice processing system into a digital signal in each AD conversion circuit and adding the converted digital signal of each voice processing system to perform digital processing. A voice processing device. Provided in front of the analog amplifier circuit in each audio processing system is a distribution switch that switches between an analog signal from a sound source connected to each audio processing system and an analog signal from the distributor,
At the subsequent stage of the AD conversion circuit in each sound processing system, a digital signal output from the AD conversion circuit and a changeover switch for switching between the digital processing circuit provided in each sound processing system and the addition / processing circuit are provided. The speech processing apparatus according to claim 1.   3. The digital signal addition / processing circuit according to claim 1, wherein when the distributed digital signals of the respective audio processing systems are not the same or within a predetermined threshold value, error determination is performed. 4. Audio processing device.