JP6626397B2 - Sound image quantization device, sound image inverse quantization device, operation method of sound image quantization device, operation method of sound image inverse quantization device, and computer program - Google Patents

Description

  The present invention relates to a technique for reducing a calculation load of a gain when a sound image is formed in a space.

  2. Description of the Related Art Conventionally, in public viewing and concerts, audio, music, and the like are reproduced from a plurality of speakers installed in a screening venue. In recent years, efforts have been made to realize more realistic sound reproduction by forming a virtual sound source (sound image) in a screening space.

  According to the method disclosed in Non-Patent Document 1, the position of the sound image perceived by the audience can be controlled by defining the position of the sound image in the virtual space in the screening hall and adjusting the volume of the speaker according to the position of the sound image. .

  Patent Document 1 relates to a sound reproduction technology for creating a virtual sound source in a screening space, and realizes a telephone conference with a high sense of reality by giving a pseudo sound image to voice transmitted from a telephone conference partner. I do.

  In Patent Literature 1, a position at which a sound image is localized for each point of a communication partner is fixed in advance, and sound image localization can be realized with a small amount of computation using a gain included in a speech code transmitted from the communication partner. There is a problem that cannot be moved flexibly.

  On the other hand, in the technology disclosed in Non-Patent Document 2, there is a limit to the resolution of the sound image position that can be perceived by humans. Can not be distinguished.

JP 2011-182141 A

Ville Pulkki, "Virtual Sound Source Positioning Using Vector Base Amplitude Panning," J. Audio Engineering Society, Vol. 45, No. 6, 1997, June. G. Kearney, Enda Bates, Frank Boland and Dermot Furlong, ”A Comparative Study of the Performance of Spatialization Techniques for a Distributed Audience in a Concert Hall Environment,” in Proc. Of 31th International Conference of the Audio Engineering Society, June 2007.

  The method of Non-Patent Document 1 can be realized with a relatively simple device configuration as a sound reproduction technique having a sound image localization effect. However, when the number of sound images increases or the sound images move, the gain given to the speaker each time is increased. Since recalculation is required, there is a problem that the calculation load increases.

  Also, the method described in Patent Document 1 can perform sound image localization with a small amount of computation, but since it is a technology based on two-channel stereo, there is a problem in supporting sound image localization for multi-channel sound.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a technique for reducing a calculation load of a gain when a sound image is formed in a space.

  In order to solve the above problem, a sound image quantization device according to a first aspect of the present invention includes a direction vector storage unit that stores a plurality of direction vectors and a direction vector corresponding to a direction of a sound source direction vector from an observation point to a sound image. A sound source direction quantization unit that obtains from the direction vector storage unit, a distance storage unit that stores a plurality of distances, and a sound source distance quantization unit that obtains a distance corresponding to the norm of the sound source direction vector from the distance storage unit. It is characterized by having.

  A sound image dequantization device according to a second aspect of the present invention includes a panning gain storage unit that stores a panning gain in association with each of a plurality of directions, and a direction of a sound source direction vector from an observation point to a sound image. A panning gain determination unit that obtains a panning gain corresponding to the distance from the panning gain storage unit, a distance attenuation gain storage unit that stores a distance attenuation gain in association with each of a plurality of distances, and a norm of the sound source direction vector. And a sound source distance inverse quantization unit that acquires a distance attenuation gain according to the norm from the distance attenuation gain storage unit.

  A third operation method of the sound image quantization apparatus according to the present invention comprises the steps of: obtaining a direction vector corresponding to a direction of a sound source direction vector from an observation point to a sound image from a direction vector storage unit; Obtaining the distance to be performed from the distance storage unit.

  The operation method of the sound image dequantization device according to a fourth aspect of the present invention includes: acquiring a direction of a sound source direction vector from an observation point to a sound image; and acquiring a panning gain corresponding to the direction from a panning gain storage unit; Acquiring a norm of the sound source direction vector, and acquiring a distance attenuation gain according to the norm from a distance attenuation gain storage unit.

  A computer program according to a fifth aspect of the present invention is a computer program for causing a computer to function as a sound image quantization device or a sound image inverse quantization device.

  ADVANTAGE OF THE INVENTION According to this invention, the calculation load of the gain at the time of forming a sound image in space can be reduced.

FIG. 2 is a system configuration diagram of the first embodiment. FIG. 3 is a diagram illustrating a relationship between a sound source direction vector and a sound image position. It is a figure showing an example of a direction vector. FIG. 4 is a diagram illustrating a specific example of a direction vector stored in a direction vector storage unit 12. FIG. 4 is a diagram illustrating an example of a distance stored in a distance storage unit 14. FIG. 3 is a diagram illustrating an example of a panning gain stored in a panning gain storage unit 21. FIG. 4 is a diagram illustrating an example of a distance attenuation gain stored in a distance attenuation gain storage unit 23. FIG. 3 is a diagram illustrating a relationship between each gain (panning gain, distance attenuation gain) and a channel. It is a system configuration diagram of Embodiment 2. 9 is a flowchart illustrating a processing flow according to the second embodiment. FIG. 3 is a diagram illustrating a positional relationship between a real sound source (sound image) and an imaginary sound source. It is a detailed flowchart of step S7. FIG. 9 is a waveform diagram of an acoustic signal generated in the second embodiment. FIG. 9 is a diagram illustrating evaluation results of performance of the technology of the present embodiment, showing evaluation results when the direction of a sound image is fixed (Experiment 1). FIG. 9 is a diagram illustrating evaluation results of performance of the technology of the present embodiment, showing evaluation results when the direction of a sound image is changed (Experiment 2).

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present embodiment discloses, for example, a sound reproduction technique having an effect of creating a virtual sound source in a screening space.

  As described in Non-Patent Document 2, there is a limit to the accuracy of a sound image position that can be distinguished by humans. Therefore, in the embodiment, the position and direction in which the sound image is localized are quantized in advance in space, and when the sound image is present at each position, the gain of the speaker to be given to each channel is set in advance, and the sound image quantized for each sound source is set. The sound source position is encoded using an index corresponding to the position or direction.

  At the time of reproduction, since the gain of the speaker when reproducing the corresponding sound source can be uniquely specified based on the above-mentioned index, a sound image localization effect can be given to a large number of sound sources with a very low calculation load.

  Hereinafter, the embodiment will be described in detail by dividing into Embodiments 1 and 2.

[Embodiment 1]
The first embodiment is an example of the most basic configuration for performing sound image control using reverberation, and FIG. 1 shows a system configuration.

  The system according to the first embodiment has a configuration including a sound image quantization device 1, a sound image inverse quantization device 2, an audio reproduction device 3, and an audio device 4.

  The sound image quantization device 1 obtains, for example, the position of a sound image (virtual sound source) determined in advance by the content producers, and obtains the obtained sound image from an observation point such as a sitting position at a movie screening venue. And the distance from the observation point to the position of the sound image.

  The sound image inverse quantization device 2 receives the sound signal and assigns a gain to the sound signal based on the obtained direction and distance so that the sound image is actually formed at the position of the obtained sound image.

  The sound reproducing device 3 supplies the sound signal after the assignment to each speaker of the sound device 4, and each speaker of the sound device 4 reproduces sound corresponding to the sound signal. A sound image is actually formed at the position of the acquired sound image by the reproduced sound.

  The audio device 4 is, for example, a speaker of n (n is plural) channels (CH1 to CHn) arranged in the screening venue.

  The sound image quantization device 1 includes a sound image position calculation unit 11, a direction vector storage unit 12, a sound source direction quantization unit 13, a distance storage unit 14, and a sound source distance quantization unit 15.

  The sound image position calculation unit 11 obtains the position of the sound image determined in advance by the content producers, and based on the obtained position of the sound image and the position of the predetermined observation point, as shown in FIG. From the sound source to the sound image. The sound source direction vector includes, for example, an azimuth based on a predetermined horizontal direction (X axis), an elevation based on an XY plane, and a norm from the observation point to the sound image.

  Returning to FIG. 1, the direction vector storage unit 12 stores a plurality of direction vectors in advance. As the direction vector, a vector or the like obtained by uniformly dividing an azimuth angle (−180 degrees to +180 degrees) and an elevation angle (−90 degrees to +90 degrees) from the observation point can be used. For example, as shown in FIG. 3, four direction vectors V1 to V4 obtained by dividing the elevation angle into +45 degrees and the azimuth into -135 degrees, -45 degrees, +45 degrees, and +135 degrees are used. These direction vectors are stored in the direction vector storage unit 12.

  FIG. 4 is a diagram illustrating a specific example of the direction vector stored in the direction vector storage unit 12.

  In the above example, the direction vector storage unit 12 stores four direction vectors, and each direction vector is associated with a direction index v1 to v4 that uniquely indicates the direction vector. The direction vector includes an azimuth angle and an elevation angle with the same reference as the sound source direction vector.

  In practice, the direction vector obtained by dividing the quantization step of the azimuth and the elevation at a resolution of about 5 degrees or less is stored in the direction vector storage unit 12. That is, the direction vector storage unit 12 stores a sufficient number of direction vectors that can be quantized to the degree that sound images do not cause discontinuity.

  Returning to FIG. 1, the sound source direction quantization unit 13 acquires the sound source direction vector from the sound image position calculation unit 11, and quantizes the direction (azimuth and elevation) of the sound source direction vector. That is, a direction vector corresponding to the direction (azimuth and elevation) is acquired from the direction vector storage unit 12. Specifically, the sound source direction quantization unit 13 calculates the inner product of each direction vector stored in the direction vector storage unit 12 and the sound source direction vector, and calculates the inner product of all the direction vectors as a result of calculating the inner product of all the direction vectors. The direction index associated with the given direction vector is transmitted (output) to the sound image inverse quantization device 2.

  The distance storage unit 14 stores a plurality of distances determined in advance by, for example, learning.

  FIG. 5 is a diagram illustrating an example of the distance stored in the distance storage unit 14.

  The distance storage unit 14 stores a plurality of distances, and each distance is associated with a sound source distance index d1, d2, d3, d4,... Uniquely indicating the distance.

  Referring back to FIG. 1, the sound source distance quantization unit 15 acquires the sound source direction vector from the sound image position calculation unit 11 and quantizes the norm of the sound source direction vector using the distance storage unit 14. That is, the sound source distance quantization unit 15 acquires the distance corresponding to the norm from the distance storage unit 14. For example, the sound source distance quantization unit 15 calculates a difference between the norm and each distance, and transmits (outputs) a sound source distance index corresponding to the smallest difference to the sound image inverse quantization device 2.

  The sound image inverse quantization device 2 includes a panning gain storage unit 21, a panning gain determination unit 22, a distance attenuation gain storage unit 23, a sound source distance inverse quantization unit 24, and a gain adjustment unit 25.

  The sound image inverse quantization device 2 receives the direction index and the sound source distance index from the sound image quantization device 1.

  The panning gain determination unit 22 of the sound image inverse quantization device 2 obtains a direction index, obtains a panning gain corresponding to the direction index from the panning gain storage unit 21, and assigns the panning gain to each channel of the audio signal.

  FIG. 6 is a diagram illustrating an example of the panning gain stored in the panning gain storage unit 21.

  The panning gain storage unit 21 stores a panning gain in association with each of a plurality of directions. For example, the panning gain storage unit 21 stores the panning gain in association with each of the four direction indexes v1 to v4. Each panning gain includes a channel gain for each channel (CH1, CH2,..., CHn) of the audio signal. The panning gains associated with the respective direction indexes v1 to v4 are generally vectors having different channel gains (values) for each channel, but the same values may be included in the same vector.

  The panning gain determination unit 22 obtains the direction of the sound source direction vector from the observation point to the sound image, that is, the direction index, and obtains the obtained direction, that is, the panning gain corresponding to the direction index, from the panning gain storage unit 21. , And assigns each channel gain of panning gain to the corresponding channel.

  The sound source distance inverse quantization unit 24 assigns the distance attenuation gain corresponding to the sound source distance index to each channel to which each channel gain of the panning gain is assigned.

  FIG. 7 is a diagram illustrating an example of the distance attenuation gain stored in the distance attenuation gain storage unit 23.

  The distance attenuation gain storage unit 23 stores the distance attenuation gain in association with each of the plurality of distances. The distance attenuation gain is a scalar quantity. For example, each distance attenuation gain is associated with an individual sound source distance index d1, d2, d3, d4,. That is, each distance attenuation gain is substantially associated with a distance.

  Returning to FIG. 1, the sound source distance inverse quantization unit 24 acquires the sound source distance index, and assigns a delay (a delay corresponding to the scalar amount) corresponding to the sound source distance index to each channel to which each channel gain of the panning gain is assigned. , And the sound signal is delayed and added.

  Specifically, the sound source distance inverse quantization unit 24 obtains, from the distance attenuation gain storage unit 23, the distance attenuation gain associated with the same sound source distance index as the obtained sound source distance index, and obtains each channel gain of the panning gain. Is assigned a distance attenuation gain to each channel to which the sound signal is assigned, and the sound signal is delayed and added.

  The gain adjustment unit 25 assigns the gain (channel gain, distance attenuation gain) assigned to each channel to the audio signal (processes the audio signal), and transmits the audio signals for the number of channels after the allocation to the audio reproducing device 3. I do. The processing of the acoustic signal is performed, for example, in a buffer provided in the sound image inverse quantization device 2. That is, the audio signal is stored in the buffer, and a gain (channel gain, distance attenuation gain) is assigned (processed) to the audio signal in the buffer.

  The sound reproducing device 3 receives each sound signal, and transmits each sound signal to a speaker or the like of the corresponding channel of the sound device 4. Each speaker of the sound device 4 reproduces sound according to the received sound signal. By the reproduced sound, a sound image is actually formed at a desired position, that is, at the position of the input sound image.

  FIG. 8 is a diagram showing a relationship between each gain (panning gain, distance attenuation gain) and a channel.

  The sound signal (hereinafter, referred to as “original sound signal”) input to the sound image inverse quantization device 2 is amplified or attenuated by an amplification amount or an attenuation amount according to the channel gain of the channel CH1 acquired by the panning gain determination unit 22. Attenuated. Further, the amplified or attenuated sound signal is processed so that a delay is generated with a delay amount corresponding to the distance attenuation gain acquired by the sound source distance inverse quantization unit 24.

  In addition, the original sound signal is similarly amplified or attenuated by an amplification amount or an attenuation amount according to the channel gain of the channel CH2. Further, the amplified or attenuated sound signal is processed such that a delay occurs with a delay amount corresponding to the same distance attenuation gain.

  Similar processing is performed for the other channels.

  Thereby, the speaker of the channel CH1 reproduces the sound from the timing delayed with respect to the original sound signal, for example, by using the amplified sound signal of the original sound signal.

  Further, the speaker of the channel CH1 reproduces the sound from the same delayed timing as that of the channel CH1 using, for example, an amplified sound signal of the original sound signal.

  Further, the loudspeaker of the channel CHn reproduces the sound from the same delayed timing as the channels CH1 and CH2, for example, by using the sound signal in which the original sound signal is attenuated.

  The sound reproduced in this manner actually forms a sound image at the position of the input sound image.

(Modification of First Embodiment)
In the first embodiment, the sound source distance quantization unit 15 transmits the sound source distance index, and the sound source distance inverse quantization unit 24 reads out (dequantizes) the distance attenuation gain associated with the sound source distance index. However, the sound source distance inverse quantization unit 24 may be configured to calculate the distance attenuation gain from the norm of the sound source direction vector. For example, the sound image quantization device 1 does not include the distance storage unit 14 and the sound source distance quantization unit 15, and the sound image position calculation unit 11 transmits the norm of the sound source direction vector to the sound image inverse quantization device 2. The sound source distance inverse quantization unit 24 obtains the transmitted norm and calculates a distance attenuation gain according to the norm (for example, a distance attenuation gain according to the reciprocal of the norm). Other processes are the same as in the first embodiment.

  Alternatively, the sound image quantization device 1 may quantize the norm by scalar quantization or the like, and the sound source distance inverse quantization unit 24 may perform inverse quantization, thereby calculating a value corresponding to the norm.

  As described above, according to the first embodiment, the position and direction in which the sound image is localized are quantized and coded in advance in the space, so that the calculation load of the gain applied to the speaker when reproducing the sound source during reproduction is reduced. Can be reduced. That is, according to the first embodiment, the sound image quantization device 1 stores the direction vector storage unit 12 that stores a plurality of direction vectors and the direction vector corresponding to the direction of the sound source direction vector from the observation point to the sound image. A sound source direction quantization unit 13 obtained from the unit 12, a distance storage unit 14 storing a plurality of distances, and a sound source distance quantization unit 15 obtaining a distance corresponding to the norm of the sound source direction vector from the distance storage unit 14. Prepare.

  Further, each distance attenuation gain in the distance attenuation gain storage unit 23 is associated with an individual sound source distance index, and the sound source distance inverse quantization unit 24 acquires a sound source distance index corresponding to the norm of the sound source direction vector, and obtains the distance attenuation. From the gain storage unit 23, a distance attenuation gain associated with the same sound source distance index as the obtained sound source distance index is obtained.

  In addition, the sound image inverse quantization device 2 of the modification acquires a panning gain storage unit 21 that stores a panning gain in association with each of a plurality of directions, and a direction of a sound source direction vector from an observation point to a sound image. A panning gain determining unit 22 that obtains a panning gain corresponding to a direction from the panning gain storage unit 21; a distance attenuation gain storage unit 23 that stores a distance attenuation gain in association with each of a plurality of distances; And a sound source distance inverse quantization unit 24 that acquires a distance attenuation gain according to the norm from the distance attenuation gain storage unit 23.

Therefore, there is no need to calculate the panning gain and the distance attenuation gain one by one, and the calculation load can be reduced.
In addition, since the calculation load is small, a sound image can be quickly formed at the position of the input sound image, and the sound image can be quickly moved if another sound image position is input.

  Further, in the sound image quantization device 1, a step of obtaining a direction vector corresponding to the direction of the sound source direction vector from the observation point to the sound image from the direction vector storage unit 12, and a step of storing the distance corresponding to the norm of the sound source direction vector in the distance storage unit And obtaining from.

  The sound image inverse quantization device 2 obtains the direction of the sound source direction vector from the observation point to the sound image, obtains the panning gain corresponding to the direction from the panning gain storage unit 21, and obtains the norm of the sound source direction vector. And obtaining a distance attenuation gain according to the norm from the distance attenuation gain storage unit 23.

Therefore, there is no need to calculate the panning gain and the distance attenuation gain one by one, and the calculation load can be reduced.
In addition, since the calculation load is small, a sound image can be quickly formed at the position of the input sound image, and the sound image can be quickly moved if another sound image position is input.

[Embodiment 2]
In a second embodiment, an invention for generating a reflected sound from a wall surface will be disclosed.

  FIG. 9 is a system configuration diagram for performing sound image control using reflected sound from a wall surface in the second embodiment.

  In the second embodiment, a sound image quantization device 1a further including the imaginary sound source generation unit 16 is used for the sound image quantization device 1 of the first embodiment.

  Here, it is assumed that the sound image inverse quantization device 2 has a buffer for storing an acoustic signal for each channel.

  When generating an audio signal, the buffer stores, as an input signal, an audio signal accumulated for a time corresponding to one frame such as 20 mS, for example. Alternatively, an audio signal obtained by encoding and decoding using a codec is used as an audio waveform, and after applying a panning gain and a distance attenuation gain, the buffer of each channel is stored in a buffer of each channel according to a delay time corresponding to the distance attenuation gain. Then, a superposition addition process is performed. Then, this inverse quantization operation is repeated by the number of sound sources (to be described in detail later), and an audio signal to be reproduced from each speaker is output.

  The details will be described below.

  FIG. 10 is a flowchart illustrating a flow of a process according to the second embodiment.

  First, the sound image inverse quantization device 2 initializes the buffer (S1).

  Next, the imaginary sound source generation unit 16 acquires, for example, the position of the sound image determined in advance by the content creators, and calculates the position of the imaginary sound source when the sound source is arranged at the position of the sound image from the position of the sound image and the observation point. Is calculated, and the acquired position of the sound image and the calculated position of the imaginary sound source are output to the sound image position calculation unit 11 (S3).

  In step S3, the imaginary sound source generation unit 16 arranges a real sound source (such as a speaker) at the position of the sound image as shown in FIG. That is, the position of the imaginary sound source is calculated. The imaginary sound source generation unit 16 further calculates the position of the mirror image of the imaginary sound source as the imaginary sound source. Although the imaginary sound source can be generated indefinitely, the imaginary sound source generation unit 16 may calculate the position of the imaginary sound source included in a range not exceeding a predetermined threshold.

  Next, the sound image position calculation unit 11 calculates the sound source direction vector from the position of the sound image as in the first embodiment, and also generates a sound source direction vector from the observation point to the imaginary sound source (for the sound image) for each imaginary sound source. A “imaginary sound source direction vector” is calculated separately from the sound source direction vector calculated from the position (S5). Hereinafter, the sound source direction vector calculated from the position of the sound image is referred to as the “real sound source direction vector” to be distinguished from the “imaginary sound source direction vector”.

  In step S5, the sound source direction quantization unit 13 acquires a direction vector corresponding to the direction of the real sound source direction vector and a direction vector corresponding to the direction of each imaginary sound source direction vector from the direction vector storage unit 12, and sets the sound source distance. The quantization unit 15 acquires the distance corresponding to the norm of the real sound source direction vector and the distance corresponding to the norm of each imaginary sound source direction vector from the distance storage unit 14. In practice, a direction index corresponding to the direction vector and a sound source distance index corresponding to the distance are acquired.

  In other words, the directional index and the sound source distance index are acquired not only for the real sound source direction vector but also for each imaginary sound source direction vector, as in the first embodiment.

  Next, the sound image inverse quantization device 2 inversely quantizes the index for each sound source, and outputs a panning gain and a distance attenuation gain (delay time) to be assigned to each channel. That is, the sound image inverse quantization device 2 receives the directional index and the sound source distance index from the sound image quantization device 1, and provides the loudspeaker of each channel of the audio device 4 in the buffer based on the directional index and the sound source distance index. An audio signal for one frame is generated and transmitted to the audio reproducing device 3 (S7).

  That is, the gain adjuster 25 assigns the gain (channel gain, distance attenuation gain) assigned to each channel to the audio signal (processes the audio signal), and assigns the audio signals of the number of channels after the assignment to the audio reproducing device 3. (S7).

  Next, it is determined whether or not there is a next frame in the sound signal (S9). If there is a next frame (S9: YES), the process returns to step S7 and there is no next frame (input of the sound signal is not performed). If (end) (S9: NO), the process ends.

  FIG. 12 is a detailed flowchart of step S7.

  The panning gain determination unit 22 obtains the direction index obtained from the real sound source direction vector and each virtual sound source direction vector, and the sound source distance inverse quantization unit 24 obtains the direction index obtained from the real sound source direction vector and each virtual sound source direction vector. The sound source distance index is acquired (S71).

  Next, the panning gain determination unit 22 inversely quantizes the directional index obtained from the actual sound source direction vector, that is, acquires the panning gain associated with the directional index from the panning gain storage unit 21 (S73).

  Next, the sound source distance inverse quantization unit 24 inversely quantizes the sound source distance index obtained from the actual sound source direction vector, that is, obtains the distance attenuation gain associated with the sound source distance index from the distance attenuation gain storage unit 23. (S75).

  Next, the panning gain determination unit 22 assigns each channel gain of the acquired panning gain to each channel, and the sound source distance inverse quantization unit 24 assigns the acquired distance to each channel to which each channel gain of the panning gain is assigned. A damping gain is assigned and superimposed and added (S77).

  Next, whether or not the allocation of all sound sources is completed, that is, whether or not the allocation of panning gain and distance attenuation gain obtained from the direction index and the sound source distance index has been completed for all of the real sound source direction vector and each of the virtual sound source direction vectors. Is determined (S79).

  If NO is determined in the step S79, the process returns to the step S73, and thereafter, the imaginary sound source direction vectors are set one by one, and the directional index and the sound source distance index obtained from the target imaginary sound source direction vector are set to the real sound source direction. As with the direction index and the sound source distance index obtained from the direction vector, acquisition of panning gain (S73), acquisition of distance attenuation gain (S75), and allocation of gain (S77) are performed.

  If YES is determined in the step S79, the process is terminated.

  In step S7 in FIG. 10, the gain adjustment unit 25 assigns, for each channel, an index obtained from the real sound source direction vector, an allocation based on the processed sound signal and the index obtained from each imaginary sound source direction vector, and Are synthesized. Then, the gain adjustment unit 25 transmits the synthesized audio signal to the audio reproduction device 3 for each channel.

  FIG. 13 is a waveform diagram of the acoustic signal generated in the second embodiment.

  In the first frame of the acoustic signals of the channels CH1 to CHn, although the peaks are different, the waveforms for generating the actual sound source (sound image) appear from the same timing. The peak corresponds to the channel gain by applying the channel gain obtained from the actual sound source direction vector. The timing is in accordance with the distance attenuation gain by applying the distance attenuation gain obtained from the actual sound source direction vector.

  With a delay from this timing, a waveform for generating the imaginary sound source closest to the observation point (illustrated as a waveform of the imaginary sound source 1 in the figure) appears in each channel, although the peak is different. The peak corresponds to the channel gain by applying the channel gain obtained from the imaginary sound source direction vector corresponding to the imaginary sound source 1. The appearance timing is in accordance with the distance attenuation gain by applying the distance attenuation gain obtained from the virtual sound source direction vector.

  Delayed from this timing, a waveform for generating a virtual sound source second closest to the observation point (illustrated as a waveform of virtual sound source 2 in the figure) appears in each channel, although the peak is different. The peak corresponds to the channel gain by applying the channel gain obtained from the imaginary sound source direction vector corresponding to the imaginary sound source 2. The appearance timing is in accordance with the distance attenuation gain by applying the distance attenuation gain obtained from the virtual sound source direction vector.

  Thus, a first frame is generated in which a waveform for generating a real sound source (sound image) and a waveform for generating each imaginary sound source are synthesized.

  Similarly, a waveform for generating a real sound source (sound image) and a waveform for generating each imaginary sound source are synthesized in the second and subsequent frames.

  In the second embodiment, the reflected sound from the wall surface can be generated by the waveform corresponding to the imaginary sound source, that is, reverberation can be generated. In this case, it is necessary to calculate the panning gain and the distance attenuation gain one by one. And the calculation load can be reduced.

  As described above, according to the second embodiment, the sound image quantization device 1 includes the imaginary sound source generation unit 16 that calculates the position of the imaginary sound source when the sound source is arranged at the position of the sound image. Obtains a direction vector corresponding to the direction of the imaginary sound source direction vector from the observation point to the imaginary sound source from the direction vector storage unit 12, and the sound source distance quantization unit 15 calculates the distance corresponding to the norm of the imaginary sound source direction vector as the distance. Obtained from the storage unit 14.

  Therefore, reflected sound and reverberation from the wall surface can be generated, and in this case, there is no need to calculate the panning gain and the distance attenuation gain one by one, and the calculation load can be reduced.

  Next, in order to evaluate the performance of the technology of the present embodiment, a quality evaluation test was performed on a general subject, and an experimental method and evaluation results will be described.

(experimental method)
A sound sample that can be heard from a specific direction was created using the conventional technology described in Non-Patent Document 1 and the technology of the present embodiment. In making the sample, white noise was generated, and a sample was created by applying the gains generated using the conventional technology and the technology of the present embodiment to the noise. The length of the sample was 8 seconds for each of the conventional technique and the technique of the present embodiment.

  The sound presented from 24 randomly selected general subjects from the outside of the sample to 32 external subjects was compared with the prior art and asked, "Is the direction of the sound source unchanged?" Not answered ".

  When the technology of the present embodiment was used, samples were created by changing the quantization steps to 2, 4, 8, 12, and 45 degrees, and the number of answers was counted for each quantization step.

  In Experiment 1, a sample in which the direction of the sound source was fixed was presented to the subject, and in Experiment 2, a sample in which the direction of the sound source changed (the sound image rotates around the subject) was presented. The speed of the change in the direction of the sound source in Experiment 2 was set to 5 stages (1/4, 1/2, 1, 2 and 3 turns around the subject in 8 seconds).

(Evaluation results)
The results when the direction of the sound image is fixed (Experiment 1) and when the direction of the sound image is changed (Experiment 2) are shown in FIGS. 14 and 15, respectively.

  The graph shows the average value of the number of responses per trial (bar graph) and the 95% confidence interval.

  When the direction of the sound source was fixed (Experiment 1), no significant difference could be confirmed even when the quantization step was set to 12 degrees as compared with the case where the quantization step was set to 2 degrees. On the other hand, in the case where the direction of the sound source changes (Experiment 2), it was confirmed that the perception of the sound image was significantly deteriorated when the quantization step was larger than 4 degrees. From the above results, it was confirmed that even if the quantization step was thinned to about 4 degrees, the amount of calculation could be reduced without deteriorating the quality of the generated sound image.

  In the embodiment, a movie screening venue is taken as an example of the space, but another closed space (for example, a gymnasium) or an open space (for example, an outdoor stadium) may be used. In the second embodiment, the above-mentioned gymnasium or indoor entertainment venue can be used.

  Further, a computer program for causing a computer to function as the sound image quantizing device or the sound image dequantizing device according to the first or second embodiment is computer-readable such as a semiconductor memory, a magnetic disk, an optical disk, a magneto-optical disk, and a magnetic tape. It can be recorded on a simple recording medium and transmitted through a communication network such as the Internet to be widely distributed.

  As described above, the embodiments of the present invention have been described. However, it should not be understood that the description and drawings forming part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art.

Reference Signs List 1, 1a Sound image quantizer 2 Sound image inverse quantizer 3 Sound reproducing device 4 Sound device 11 Sound image position calculating unit 12 Direction vector storage unit 13 Sound source direction quantization unit 14 Distance storage unit 15 Sound source distance quantization unit 16 Imaginary sound source generation Unit 21 panning gain storage unit 22 panning gain determination unit 23 distance attenuation gain storage unit 24 sound source distance inverse quantization unit 25 gain adjustment units CH1, CH2,..., CHn channels v1, v2, v3, v4 direction indexes d1, d2, d3 , D4, ... sound source distance index

Claims (7)

A direction vector storage unit for storing a plurality of direction vectors,
A sound source direction quantization unit that obtains a direction vector corresponding to the direction of the sound source direction vector from the observation point to the sound image from the direction vector storage unit,
A distance storage unit for storing a plurality of distances;
A sound source distance quantization unit that obtains a distance corresponding to the norm of the sound source direction vector from the distance storage unit ,
An imaginary sound source generation unit that calculates the position of an imaginary sound source when a sound source is arranged at the position of the sound image,
The sound source direction quantization unit,
Obtain a direction vector corresponding to the direction of the imaginary sound source direction vector from the observation point to the imaginary sound source from the directional vector storage unit,
The sound source distance quantization unit,
A sound image quantization device , wherein a distance corresponding to a norm of the imaginary sound source direction vector is obtained from the distance storage unit . A panning gain storage unit that stores a panning gain in association with each of a plurality of directions;
Obtain the direction of the sound source direction vector from the observation point to the sound image, a panning gain determination unit that obtains a panning gain corresponding to the direction from the panning gain storage unit,
A distance attenuation gain storage unit that stores a distance attenuation gain in association with each of the plurality of distances;
A sound source distance inverse quantization unit that acquires a norm of the sound source direction vector, and acquires a distance attenuation gain according to the norm from the distance attenuation gain storage unit .
The panning gain determination unit acquires a direction of an imaginary sound source direction vector from the observation point to an imaginary sound source when a sound source is arranged at the position of the sound image, and stores a panning gain corresponding to the direction in the panning gain storage unit. Obtained from
The sound image inverse quantization device, wherein the sound source distance inverse quantization unit acquires a norm of the imaginary sound source direction vector, and acquires a distance attenuation gain according to the norm from the distance attenuation gain storage unit . Each distance attenuation gain of the distance attenuation gain storage unit is associated with an individual sound source distance index,
The sound source distance inverse quantization unit,
Acquiring a sound source distance index corresponding to the norm of the sound source direction vector, and acquiring a distance attenuation gain associated with the same sound source distance index as the acquired sound source distance index from the distance attenuation gain storage unit. 3. The sound image inverse quantization apparatus according to claim 2, wherein Calculating the position of the imaginary sound source when the sound source is arranged at the position of the sound image;
Obtaining a direction vector from the direction vector storage unit from the observation point corresponds to the direction of the sound source direction vector to said sound image,
Obtaining a distance corresponding to the norm of the sound source direction vector from a distance storage unit ;
Obtaining a direction vector corresponding to the direction of the imaginary sound source direction vector from the observation point to the imaginary sound source from the directional vector storage unit;
Obtaining a distance corresponding to the norm of the imaginary sound source direction vector from the distance storage unit . Acquiring the direction of the sound source direction vector from the observation point to the sound image, and acquiring a panning gain corresponding to the direction from a panning gain storage unit;
Acquiring a norm of the sound source direction vector, and acquiring a distance attenuation gain according to the norm from a distance attenuation gain storage unit;
From the observation point, obtain the direction of the imaginary sound source direction vector up to the imaginary sound source when a sound source is placed at the position of the sound image, and obtain a panning gain corresponding to the direction from the panning gain storage unit.
Acquiring the norm of the imaginary sound source direction vector, and acquiring a distance attenuation gain according to the norm from the distance attenuation gain storage unit . Each distance attenuation gain of the distance attenuation gain storage unit is associated with an individual sound source distance index,
Get the sound source distance index corresponding to the norm, claim wherein the attenuation gain storage unit, and acquires the acquired the sound source distance index and attenuation gain associated with the same sound source distance index was 5 An operation method of the sound image inverse quantization device according to the above description. Computer program for causing a computer to function as a sound image inverse quantization apparatus of the sound image quantization apparatus or claim 2, wherein according to claim 1, wherein.

Images