Date processing system, decoding device and data processing method

Abstract

To provide a data processing system, a decoding device, and a data processing method that reduce noise contained in an approach warning sound corresponding to decoded data.SOLUTION: An encoding device 20 encodes multiple pieces of digital data using ADPCM or linear prediction to generate multiple pieces of encoded data. The encoding device 20 determines an upper frequency limit fa at which the sound pressure is equal to or greater than a threshold Sa in the frequency characteristics of sound pressure. The encoding device 20 determines filter coefficients 1 to 5 for a low-pass filter having the upper frequency limit fa as its cutoff frequency. A decoding device 30 corrects the decoded data by filtering the multiple pieces of decoded data using a low-pass filter based on the filter coefficients 1 to 5, thereby suppressing the inclusion of noise in the approach alarm sound corresponding to the decoded data.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a data processing system, a decoding apparatus, and a data processing method.

Background Art

[0002] Conventionally, in a data processing system, there has been proposed a method of compressing digital data by encoding digital data corresponding to sound using linear prediction to generate encoded data (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described data processing system, digital data can be compressed by encoding digital data using linear prediction to generate encoded data.

[0005] However, according to the study by the present inventors, it has been found that white noise is mixed into the encoded data generated by encoding using linear prediction in order to compress digital data.

[0006] Therefore, when the encoded data is decoded to generate decoded data, if the sound corresponding to the decoded data is output from the speaker, the sound output from the speaker includes noise.

[0007] For this reason, the sound quality of the output sound of the speaker deteriorates due to the noise. Therefore, depending on the frequency characteristics of the sound source, the noise may become prominent, which may give a sense of discomfort to the person listening to the output sound of the speaker.

[0008] Such problems occur not only in the encoding process using linear prediction, but also in the encoding process using ADPCM or the like.

[0009] In view of the above points, an object of the present disclosure is to provide a data processing system, a decoding device, and a data processing method that suppress a deterioration in sound quality.

Means for Solving the Problems

[0010] According to one aspect of the present disclosure, A data processing system including an encoding device (20) that encodes a plurality of digital data corresponding to sounds to generate a plurality of encoded data, and a decoding device (30) that decodes the plurality of encoded data to generate a plurality of decoded data, The encoding device includes An encoding processing unit (S100) that encodes a plurality of digital data using ADPCM or linear prediction to generate a plurality of encoded data, A filter calculation unit (S120, S120A) that obtains filter information for filtering a plurality of decoded data based on the plurality of encoded data, The decoding device includes A decoding processing unit (S200) that decodes the plurality of encoded data generated by the encoding processing unit to generate a plurality of decoded data, A filter processing unit (S230, S230A) that corrects the plurality of decoded data by filtering the plurality of decoded data with a filter based on the filter information, and suppresses noise from being included in the sounds corresponding to the plurality of decoded data, A sound output unit (S240, S240A) that outputs sounds corresponding to the plurality of decoded data corrected by the filter processing unit.

[0011] Therefore, since a plurality of decoded data are corrected by the filter processing unit, noise included in the sound corresponding to the plurality of decoded data can be reduced. For this reason, it is possible to provide a data processing system that suppresses a deterioration in the sound quality of the sound output by the sound output unit.

[0012] According to one aspect of the present disclosure, the plurality of encoded data are generated using ADPCM or linear prediction. For this reason, as data related to sound, compared with the case of using data in PCM format, the amount of data processed by the decoding device can be reduced, so that data compression can be achieved.

[0013] On the other hand, although filter information is added as data related to sound in addition to the plurality of encoded data, the amount of data of the filter information is at most several bytes. For this reason, the data compression by encoding is not impaired due to the addition of the filter information. Thereby, a significant decrease in the data compression rate can be suppressed.

[0014] According to another aspect of the present disclosure, an encoding processing unit (S100) that encodes a plurality of digital data corresponding to sound using ADPCM or linear prediction to generate a plurality of encoded data, and a plurality of encoded data are filtered based on the plurality of encoded data. A decoding device applied to a data processing system (10) including an encoding device (20) having a filter calculation unit (S120, S120A) for obtaining filter information for filtering a plurality of decoded data, a decoding processing unit (S200) that decodes the plurality of encoded data generated by the encoding processing unit to generate a plurality of decoded data; a filter processing unit (S230, S230A) that corrects a plurality of decoded data by filtering the plurality of decoded data based on the filter information to suppress noise from being included in the sound corresponding to the plurality of decoded data; and a sound output unit (S240, S240A) that outputs a sound corresponding to the plurality of decoded data corrected by the filter processing unit.

[0015] Therefore, since a plurality of decoded data is corrected by the filter processing unit, noise included in the sound corresponding to the plurality of decoded data can be reduced. For this reason, it is possible to provide a decoding apparatus that suppresses deterioration in the sound quality of the sound output by the sound output unit.

[0016] According to another aspect of the present disclosure, similar to the data processing system described above, since a plurality of encoded data is generated using ADPCM or linear prediction, data compression can be achieved. On the other hand, although filter information is added in addition to the plurality of encoded data as data related to sound, the addition of the filter information does not impair the data compression by encoding. Thereby, a significant decrease in the data compression rate can be suppressed.

[0017] According to still another aspect of the present disclosure, in a data processing method, an encoding device (20) encodes a plurality of digital data corresponding to sound using ADPCM or linear prediction to generate a plurality of encoded data; the encoding device obtains filter information for filtering a plurality of decoded data based on the plurality of encoded data; a decoding device (30) decodes the plurality of encoded data generated by the encoding device to generate a plurality of decoded data; the decoding device filters the plurality of decoded data by a filter based on the filter information, thereby correcting the plurality of decoded data and suppressing the inclusion of noise in the sound corresponding to the plurality of decoded data; and the decoding device outputs a sound corresponding to the plurality of corrected decoded data.

[0018] Therefore, since a plurality of decoded data is corrected by the filter processing unit, noise included in the sound corresponding to the plurality of decoded data can be reduced. For this reason, it is possible to provide a data processing method that suppresses deterioration in the sound quality of the sound output by the sound output unit.

[0019] According to yet another aspect of the present disclosure, similar to the data processing system described above, a plurality of encoded data is generated using ADPCM or linear prediction, so that data compression can be achieved. On the other hand, as data related to sound, although filter information is added in addition to the plurality of encoded data, the addition of the filter information does not impair the data compression by encoding. Thereby, a significant decrease in the data compression rate can be suppressed.

[0020] Note that the reference numerals in parentheses attached to each component etc. show an example of the correspondence relationship between the component etc. and the specific components etc. described in the embodiments described later.

Brief Description of Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following respective embodiments, parts that are identical or equivalent to each other are denoted by the same reference numerals in the drawings in order to simplify the description.

[0023] (First Embodiment) Hereinafter, the data processing system 10 of the first embodiment of the present disclosure will be described with reference to FIG. 1. As shown in FIG. 1, the data processing system 10 of the present embodiment includes an encoder 20 and a decoder 30.

[0024] The encoder 20 is a jig for manufacturing the decoder 30 and is arranged in a manufacturing factory or the like. The encoder 20 is composed of a microcomputer 21 and a memory 22. The microcomputer 21 executes an encoding process according to a computer program pre-recorded in the memory 22.

[0025] The microcomputer 21 encodes a plurality of digital data input from an external device along with the execution of the encoding process to generate a plurality of encoded data. The plurality of digital data are digital signals indicating the sound source of the approaching notification sound.

[0026] A plurality of digital data are each generated by sampling an analog signal, which is a sound source of an approaching notification sound, at a predetermined sampling period. The approaching notification sound is a notification sound for notifying people around the vehicle, etc., that the vehicle speed of the vehicle equipped with the decoding device 30 is approaching at a relatively low speed. Examples of the vehicle include an electric vehicle equipped with a driving motor, such as a hybrid vehicle or an electric vehicle.

[0027] When the microcomputer 21 of the present embodiment encodes a plurality of digital data, well-known ADPCM or linear prediction is used. ADPCM is an abbreviation of adaptive differential pulse code modulation, which is the English notation of adaptive differential pulse code modulation.

[0028] The microcomputer 21 outputs to the decoding device 30 output data obtained by adding filter coefficients 1 to 5, a filter availability flag, etc., based on the frequency characteristics of the approaching notification sound corresponding to the plurality of encoded data, to the header of the plurality of encoded data.

[0029] The memory 22 is a recording medium composed of a semiconductor memory such as a RAM or a non-volatile memory. In addition to the computer program of the microcomputer 21, a plurality of digital data are recorded in the memory 22.

[0030] As shown in FIG. 1, the decoding device 30 of the present embodiment includes a microcomputer 31 and a memory 32. The microcomputer 31 executes an encoding process according to a computer program recorded in advance in the memory 32.

[0031] The microcomputer 31 decodes a plurality of digital data input from the encoding device 20 with the execution of the decoding process to generate a plurality of decoded data. The microcomputer 31 filters the plurality of decoded data using filter coefficients 1 to 5 and outputs a PWM signal corresponding to the filtered decoded data to the speaker 40.

[0032] The memory 32 is a recording medium composed of a semiconductor memory such as a RAM or a non-volatile memory. The memory 32 stores a plurality of encoded data, filter coefficients 1 to 5, and a filter availability flag, in addition to a computer program by the microcomputer 31.

[0033] The speaker 40 is a sound output device that outputs an approaching notification sound corresponding to a PWM signal output from the microcomputer 31 toward people around the vehicle. Next, the details of the encoding process of the microcomputer 21 of the encoding device 20 will be described with reference to FIGS. 2, 3, and 4.

[0034] FIG. 2 is a flowchart showing the details of the encoding process by the microcomputer 21. The microcomputer 21 executes the encoding process according to the flowchart of FIG. 2. The encoding process is executed, for example, when the encoding device 20 is activated by an operation by an operator or the like.

[0035] First, in step S100, the microcomputer 21, as an encoding processing unit, acquires a plurality of digital data indicating the sound source of the approaching notification sound from an external device, and encodes each of the acquired plurality of digital data to generate a plurality of encoded data.

[0036] Here, when the microcomputer 21 encodes each of the plurality of digital data, white noise is mixed into the approaching notification sound corresponding to the plurality of encoded data. Therefore, when the approaching notification sound corresponding to the encoded data is output from the speaker 40, it may give a sense of discomfort to pedestrians or the like around the vehicle.

[0037] In contrast, in the present embodiment, the microcomputer 21 obtains filter coefficients 1 to 5 of a low-pass filter for suppressing noise from being included in the approach notification sound corresponding to a plurality of encoded data in steps S110 and S120. The filter coefficients 1 to 5 are filter information for setting the expression of Equation 1 to the transfer function of the low-pass filter.

[0038] First, in step S110, the microcomputer 21 analyzes the frequency characteristics of the approach notification sound corresponding to a plurality of encoded data as a frequency analysis unit. The microcomputer 21 obtains an upper limit value fa of the frequency of a component regarded as important among the approach notification sounds corresponding to the plurality of encoded data based on the analysis result of the analyzed frequency characteristics. Hereinafter, the upper limit value fa of the frequency of a component regarded as important among the approach notification sounds is simply referred to as the frequency upper limit value fa.

[0039] Specifically, the microcomputer 21 obtains a sound pressure frequency characteristic indicating the relationship between the sound pressure and the frequency of the approach notification sound corresponding to a plurality of encoded data, and obtains the frequency upper limit value fa based on the obtained sound pressure frequency characteristic.

[0040] The microcomputer 21 of the present embodiment obtains, as the frequency upper limit value fa, the upper limit value of the frequency at which the sound pressure, which is the pressure of the approach notification sound corresponding to a plurality of encoded data, becomes equal to or higher than the threshold value Sa in the sound pressure frequency characteristic.

[0041] The frequency upper limit value fa is used as the cut-off frequency of the low-pass filter. In the present embodiment, in the sound pressure frequency characteristic of FIG. 3, the frequency range fw in which the sound pressure is equal to or higher than the threshold value Sa is the frequency range of the component regarded as important described above.

[0042] Next, in step S120, the microcomputer 21 obtains filter coefficients 1 to 5 of the transfer function of the filter shown in Equation 1 based on the frequency upper limit value fa as a filter calculation unit. The filter coefficients 1 to 5 are used to set the transfer function shown in Equation 1 to the transfer function of the low-pass filter.

[0043]

Number

[0044] Therefore, n, n - 1, and n - 2 indicate the order in which digital data is generated by x and y in steps S200, S230, and S230A. n, n - 1, and n - 2 are integers representing past digital data in x and y, with smaller values representing older data.

[0045] x(n) is the decoded data generated in the n - th step S200. x(n - 1) is the decoded data generated in the (n - 1)-th step S200. x(n - 2) is the decoded data generated in the (n - 2)-th step S200.

[0046] y(n) is the decoded data after the filtering process generated in the n - th steps S230 and S230A. y(n - 1) is the decoded data after the filtering process generated in the (n - 1)-th steps S230 and S230A. y(n - 2) is the decoded data after the filtering process generated in the (n - 2)-th steps S230 and S230A.

[0047] Filter coefficient 1 is the coefficient (b0 / a0) of x(n) in Equation 1. Filter coefficient 2 is the coefficient (b1 / a0) of x(n - 1) in Equation 1. Filter coefficient 3 is the coefficient (b2 / a0) of x(n - 2) in Equation 1. Filter coefficient 4 is the coefficient (a1 / a0) of y(n - 1) in Equation 1.

[0048] Filter coefficient 5 is the coefficient (a2 / a0) of y(n - 2) in Equation 1. ω a is the angular frequency corresponding to the upper frequency limit value fa, and ωa is obtained by multiplying the upper frequency limit value fa by 2π. b0 is ω a is obtained by substituting ω into the following Equation 2.

[0049]

Equation

[0050]

Equation

[0051]

Equation

[0052]

Equation

[0053]

Equation

[0054]

Equation

[0055] Next, as shown in FIG. 4, in step S130, the microcomputer 21 generates output data in which filter coefficients 1 to 5 and a filter availability flag are added to the header of a plurality of encoded data.

[0056] Since b0 and b2 have the same value, filter coefficients 1 and 3 have the same value. Therefore, filter coefficients 1, 2, 4, 5 or filter coefficients 2, 3, 4, 5 are added to the header of the actual plurality of encoded data.

[0057] Here, the filter availability flag is a flag for setting whether or not to perform filtering processing using filter coefficients 1 to 5 on the microcomputer 31 of the decoding device 30.

[0058] Next, in step S140, the microcomputer 21 outputs the output data to the memory 32 through the microcomputer 31 of the decoding device 30 as a digital data output unit. As a result, in the memory 32, a plurality of encoded data, filter coefficients 1, 2, 4, 5, and the filter availability flag can be recorded.

[0059] Next, details of the decoding process by the microcomputer 31 of the decoding device 30 will be described with reference to FIG. 5. FIG. 5 is a flowchart showing details of the decoding process by the microcomputer 31. The microcomputer 21 executes the decoding process according to the flowchart of FIG. 5. This is executed when the vehicle speed is below a predetermined speed while the vehicle equipped with the decoding device 30 is running.

[0060] First, in step S200, the microcomputer 31 reads a plurality of encoded data from the memory 32 as a decoding processing unit and decodes the read plurality of encoded data. As a result, the microcomputer 31 can generate decoded data x(n), x(n - 1), x(n - 2) ··· x(1).

[0061] Next, in step S210, the microcomputer 31 reads the filter availability flag from the memory 32, and determines whether filtering processing should be performed on a plurality of decoded data based on the read filter availability flag.

[0062] If it is set in the filter availability flag that filtering processing should be performed on a plurality of decoded data, the microcomputer 31 determines YES, assuming that filtering processing should be performed on the plurality of decoded data.

[0063] Next, in step S220, the microcomputer 31 reads filter coefficients 1 to 5 from the memory 32 to prepare for filtering processing.

[0064] Next, in step S230, as a filter processing unit, the microcomputer 31 substitutes the read filter coefficients 1 to 5 into Equation 1 to obtain the transfer function of the low-pass filter.

[0065] In step S230 above, the microcomputer 31 sequentially performs filtering processing on the decoded data x(n), x(n-1), x(n-2), x(n-3) ···, x(3), x(2), x(1) using the obtained transfer function.

[0066] Thereby, the microcomputer 31 performs filtering processing for each of the decoded data generated in step S200 described above to obtain the filtered decoded data y(n), y(n-1), y(n-2) ···, y(3), y(2), y(1).

[0067] Specifically, the microcomputer 31 generates the filtered decoded data y(n) by substituting the decoded data x(n), x(n-1), x(n-2) and the decoded data y(n-1), y(n-2) into the transfer function of the low-pass filter.

[0068] For example, the microcomputer 31 generates the decoded data y(3) after the filtering process by substituting the decoded data x(3), x(2), x(1) and the decoded data y(2), y(1) into the transfer function of the low-pass filter.

[0069] Next, in step S240, the microcomputer 31 outputs a PWM signal to the speaker 40 as the sound output unit based on the decoded data y(n), y(n - 1), y(n - 2) ······ y(1) after the filtering process. The PWM signal is a signal indicating the approach notification sound.

[0070] Therefore, the speaker 40 outputs the approach notification sound based on the PWM signal toward the people around the automobile. PWM is an abbreviation for Pulse Width Modulation.

[0071] Note that when it is set in the filter availability flag that filtering should not be performed on a plurality of decoded data, the microcomputer 31 determines NO, assuming that filtering should not be performed on the plurality of decoded data.

[0072] In this case, in step S250, the microcomputer 31 outputs a PWM signal corresponding to the decoded data acquired in the above step 200 to the speaker 40. Therefore, the microcomputer 31 outputs a PWM signal to the speaker 40 based on the decoded data on which the filtering process has not been performed. Thereby, the speaker 40 outputs the approach notification sound based on the PWM signal toward the people around the automobile.

[0073] According to the present embodiment described above, the data processing system 10 includes an encoding device 20 and a decoding device 30. The encoding device 20 encodes a plurality of digital data corresponding to a sound source to generate a plurality of encoded data.

[0074] The decoding device 30 decodes a plurality of encoded data respectively to generate a plurality of decoded data. The microcomputer 21 includes step S100 of encoding a plurality of digital data using ADPCM or linear prediction to generate a plurality of encoded data.

[0075] The microcomputer 21 includes step S110 of obtaining an upper limit value fa of a frequency (i.e., a frequency upper limit value fa) at which the sound pressure is equal to or higher than a threshold value Sa in a sound pressure-frequency characteristic indicating the relationship between the sound pressure and the frequency corresponding to the plurality of encoded data. The frequency upper limit value fa is the upper limit value of the frequency of a component regarded as important among the approaching sound notifications corresponding to the plurality of encoded data.

[0076] The microcomputer 21 includes step S120 of obtaining filter coefficients 1 to 5 of a low-pass filter having the frequency upper limit value fa as a cut-off frequency. The microcomputer 31 decodes the plurality of encoded data generated in step S100 to generate a plurality of decoded data.

[0077] The microcomputer 31 includes step S230 of filtering the plurality of decoded data by a low-pass filter based on the filter coefficients 1 to 5 to correct the decoded data and suppress the inclusion of noise in the approaching sound notification corresponding to the decoded data.

[0078] The microcomputer 31 includes step 240 of outputting a PWM signal corresponding to the decoded data corrected in step S230 to the speaker 40 to output an approaching sound notification corresponding to the PWM signal from the speaker 40.

[0079] Therefore, it is possible to reduce the noise included in the approaching sound notification corresponding to the decoded data output from the speaker 40. Accordingly, it is possible to provide a data processing system, a decoding device, and a data processing method that suppress a deterioration in the sound quality of the output sound from the speaker 40.

[0080] Accordingly, it is possible to suppress giving discomfort to pedestrians and the like around the vehicle due to noise included in the approaching notification sound output from the speaker 40. According to the present embodiment configured as described above, the following operational effects (a), (b), (c), (d), and (e) can be obtained.

[0081] (a) The plurality of encoded data in the present embodiment are generated by encoding using ADPCM or linear prediction. Therefore, as data related to sound, compared with the case of using data in PCM format, the amount of data related to sound processed by the decoding device 30 can be reduced, so that data compression can be achieved.

[0082] On the other hand, although filter information is added in addition to the encoded data as data related to sound, the amount of data of the filter information is at most several bytes. Therefore, due to the addition of the filter information, the data compression by encoding is not impaired. Thereby, a significant decrease in the data compression rate can be suppressed. Along with this, a significant increase in the storage capacity of the memory 32 can be suppressed.

[0083] (b) The microcomputer 21 outputs a plurality of decoded data to the decoding device 30 and records them in the memory 32. Therefore, the microcomputer 31 can smoothly decode the plurality of encoded data by reading the plurality of encoded data from the memory 32.

[0084] (c) The microcomputer 21 outputs the filter coefficients 1 to 5 to the decoding device 30 and records them in the memory 32. Therefore, the microcomputer 31 can smoothly perform filtering processing on the plurality of decoded data based on the filter coefficients 1 to 5 by reading the filter coefficients 1 to 5 from the memory 32.

[0085] (d) The microcomputer 31 obtains filter coefficients 1 to 5 based on the upper frequency limit value fa calculated in step S110. Among the sounds corresponding to the decoded data, the components with frequencies higher than the upper frequency limit value fa are regarded as high-frequency components.

[0086] The microcomputer 31 corrects a plurality of decoded data by filtering using filter coefficients 1 to 5, and suppresses the inclusion of high-frequency components in the approaching notification sound corresponding to the plurality of decoded data. Therefore, among the approaching notification sounds corresponding to the plurality of decoded data, the noise with a frequency higher than the upper frequency limit value fa can be reduced.

[0087] (e) The microcomputer 31 sets the upper limit value of the frequency at which the sound pressure becomes equal to or higher than the threshold value Sa in the sound pressure-frequency characteristic indicating the relationship between the sound pressure and the frequency of the approaching notification sound corresponding to the plurality of encoded data as the upper frequency limit value fa. Therefore, the microcomputer 31 can accurately obtain the upper frequency limit value fa.

[0088] (Second Embodiment) In the first embodiment described above, an example in which the decoding device 30 filters a plurality of decoded data by a low-pass filter to suppress the inclusion of noise in the approaching notification sound corresponding to the plurality of decoded data has been described.

[0089] However, instead of this, the second embodiment in which the decoding device 30 filters a plurality of decoded data by a high-pass filter to suppress the inclusion of noise in the approaching notification sound corresponding to the plurality of decoded data will be described with reference to FIGS. 6, 7, and 8.

[0090] This embodiment and the first embodiment mainly differ in the encoding process by the encoding device 20 and the decoding process by the decoding device 30. Hereinafter, the encoding process by the encoding device 20 and the decoding process by the decoding device 30 will be described.

[0091] First, the details of the encoding process of the encoding device 20 will be described with reference to FIG. 6. FIG. 6 is a flowchart showing the details of the encoding process by the microcomputer 21. In the flowchart of FIG. 6, in FIG. 2, the same reference numerals indicate the same steps, and the description thereof will be omitted. The microcomputer 21 executes the encoding process according to the flowchart of FIG. 6 in place of FIG. 2.

[0092] First, in step S100, the microcomputer 21, as an encoding processing unit, encodes each of the plurality of digital data acquired from an external device in the same manner as in the first embodiment to generate a plurality of encoded data.

[0093] In steps S110A and S120A, the microcomputer 21 obtains filter coefficients 1 to 5 of the transfer function of the filter of Equation 1 in order to suppress noise from being included in the approach notification sound corresponding to the plurality of encoded data.

[0094] In step S110A, the microcomputer 21 analyzes the frequency characteristics of the approach notification sound corresponding to the plurality of encoded data as a frequency analysis unit. Based on the analysis result of the analyzed frequency characteristics, the microcomputer 21 obtains a lower limit value fb of the frequency of the components regarded as important among the approach notification sounds corresponding to the plurality of encoded data. Hereinafter, the lower limit value fb of the frequency of the components regarded as important will be simply referred to as the frequency lower limit value fb.

[0095] Specifically, the microcomputer 21 obtains a sound pressure frequency characteristic indicating the relationship between the sound pressure and the frequency of the approach notification sound corresponding to the plurality of encoded data, and obtains the frequency lower limit value fb based on the obtained sound pressure frequency characteristic.

[0096] The microcomputer 21 of the present embodiment obtains, as the frequency lower limit value fb, the lower limit value of the frequency at which the sound pressure, which is the pressure of the approach notification sound corresponding to the plurality of encoded data, becomes equal to or higher than the threshold value Sa in the sound pressure frequency characteristic.

[0097] The lower frequency limit fb is used as the cut-off frequency of the high-pass filter. In the present embodiment, in the sound pressure frequency characteristics of FIG. 8, the frequency at which the sound pressure is equal to or higher than the threshold value Sa is the frequency of the component regarded as important as described above.

[0098] Next, in step S120A, the microcomputer 21, as a filter calculation unit, obtains filter coefficients 1 to 5 of the transfer function of the filter shown in Equation 1 based on the lower frequency limit fb. The filter coefficients 1 to 5 are set to set the transfer function shown in Equation 1 as the transfer function of the high-pass filter.

[0099] The lower frequency limit fb is used as the cut-off frequency of the high-pass filter. The filter coefficients 1 to 5 are set by b0, b1, b2, a0, and a1, a2 in the same manner as in the first embodiment. ω b is the angular frequency corresponding to the lower frequency limit fb, and ω b is obtained by multiplying the lower frequency limit fb by 2π.

[0100] b0 of the present embodiment is obtained by substituting ω b into the following Equation 8.

[0101]

Equation

[0102]

Equation

[0103]

Equation

[0104]

Number

[0105]

Number

[0106]

Number

[0107] Next, in substantially the same manner as in the first embodiment, in step S130A, the microcomputer 21 generates output data in which the filter coefficients 1 to 5 and the filter availability flag are added to the header of a plurality of encoded data.

[0108] Next, in substantially the same manner as in the first embodiment, in step S140A, the microcomputer 21 outputs the output data to the memory 32 through the microcomputer 31 of the decoding device 30 as a digital data output unit. As a result, in the memory 32, a plurality of encoded data, filter coefficients 1, 2, 4, 5, and the filter availability flag can be recorded.

[0109] Next, the details of the decoding process by the microcomputer 31 of the decoding device 30 will be described with reference to FIG. 7. FIG. 7 is a flowchart showing the details of the decoding process by the microcomputer 31. The microcomputer 21 executes the decoding process according to the flowchart of FIG. 7 which replaces FIG. 5.

[0110] First, in step S200, the microcomputer 31 reads a plurality of encoded data from the memory 32. In step S200 above, as a decoding process, the microcomputer 31 decodes the read plurality of encoded data to generate decoded data x(n), x(n - 1), x(n - 2) ··· x(1).

[0111] Next, in step S210, the microcomputer 31 reads a filter availability flag from the memory 32, and determines whether or not to perform filtering on the plurality of decoded data based on the read filter availability flag.

[0112] If the filter availability flag is set to indicate that filtering should be performed on the plurality of decoded data, the microcomputer 31 determines YES, assuming that filtering should be performed on the plurality of decoded data.

[0113] Accordingly, in step S220A, the microcomputer 31 reads filter coefficients 1 to 5 from the memory 32.

[0114] Next, in step S230A, the microcomputer 31 substitutes the read filter coefficients 1 to 5 into Equation 1 to obtain the transfer function of the high-pass filter. As a filter processing unit, the microcomputer 31 sequentially performs filtering processing on the decoded data x(n), x(n - 1), x(n - 2) ··· x(1) using the obtained transfer function.

[0115] Thereby, the microcomputer 31 performs filtering processing for each of the decoded data generated in step S200 described above to obtain decoded data y(n), y(n - 1), y(n - 2) ··· y(1).

[0116] Specifically, the microcomputer 31 generates the decoded data y(n) after filtering by substituting the decoded data x(n), x(n-1), x(n-2) and the decoded data y(n-1), y(n-2) into the transfer function of the high-pass filter.

[0117] For example, the microcomputer 31 generates the decoded data y(3) after filtering by substituting the decoded data x(3), x(2), x(1) and the decoded data y(2), y(1) into the transfer function of the high-pass filter.

[0118] Next, in step S240A, the microcomputer 31 outputs a PWM signal to the speaker 40 as the sound output unit based on the decoded data y(n), y(n-1), y(n-2) ··· y(1) after filtering. The PWM signal is a signal indicating an approach notification sound. Therefore, the speaker 40 outputs the approach notification sound based on the PWM signal to the people around the vehicle.

[0119] If it is set in the filter availability flag that filtering should not be performed on a plurality of decoded data, the microcomputer 31 determines NO, assuming that filtering should not be performed on the plurality of decoded data.

[0120] In this case, in step S250, the microcomputer 31 outputs a PWM signal to the speaker 40 based on the decoded data obtained in the above step 200. Therefore, the speaker 40 outputs the approach notification sound corresponding to the PWM signal to the people around the vehicle.

[0121] According to the present embodiment described above, in the data processing system 10, the microcomputer 21 includes step S100 of encoding a plurality of digital data corresponding to an approach notification sound using ADPCM or linear prediction to generate a plurality of encoded data.

[0122] The microcomputer 21 includes a step S110A of obtaining a lower limit value fb of a frequency (i.e., a frequency lower limit value fb) at which the sound pressure is equal to or higher than a threshold value Sa in a sound pressure-frequency characteristic indicating the relationship between the sound pressure and the frequency corresponding to a plurality of encoded data.

[0123] The microcomputer 21 includes a step S120A of obtaining filter coefficients 1 to 5 of a high-pass filter having the lower limit value fb of the frequency obtained in step S110A as a cut-off frequency.

[0124] The microcomputer 31 includes a step S200A of decoding a plurality of encoded data generated by the encoding device 20 to generate a plurality of decoded data. The decoding device 30 includes a step S230A of correcting the plurality of decoded data by performing a filtering process on the plurality of decoded data using a high-pass filter based on filter coefficients 1 to 5.

[0125] The microcomputer 31 includes a step 240A of outputting a PWM signal corresponding to the decoded data corrected in step S230A to the speaker 40 and causing the speaker 40 to output a proximity notification sound corresponding to the PWM signal.

[0126] Thereby, in the proximity notification sound output from the speaker 40 based on the plurality of decoded data thus corrected, noise can be reduced. Thereby, it is possible to provide a data processing system, a decoding device, and a data processing method that suppress a deterioration in the sound quality of the output sound from the speaker 40.

[0127] Accordingly, it is possible to suppress giving a sense of discomfort to pedestrians or the like around the vehicle due to the noise included in the proximity notification sound output from the speaker 40. According to the present embodiment configured as described above, the following operational effects (f), (g), and (h) can be obtained.

[0128] (f) In the memory 32 of this embodiment, in addition to a plurality of encoded data, filter coefficients 1 to 5 and a filter availability flag are recorded. Therefore, similar to the first embodiment, it is possible to suppress a decrease in the compression rate of the data recorded in the memory 32. Along with this, it is possible to suppress an increase in the storage capacity of the memory 32.

[0129] (g) In step S110A, the microcomputer 21 obtains the lower limit value fb of the frequency, that is, the frequency lower limit value fb, at which the sound pressure is equal to or higher than the threshold value Sa in the sound pressure-frequency characteristic indicating the relationship between the sound pressure and the frequency corresponding to a plurality of encoded data.

[0130] The microcomputer 31 obtains filter coefficients 1 to 5 based on the frequency lower limit value fb calculated in step S110A. Among the approaching notification sounds corresponding to the decoded data, the components having a frequency lower than the frequency lower limit value fb are regarded as bass components.

[0131] The microcomputer 31 corrects a plurality of decoded data by filtering using filter coefficients 1 to 5, and suppresses the inclusion of bass components in the approaching notification sounds corresponding to the plurality of decoded data. Therefore, it is possible to suppress the inclusion of noise having a frequency lower than the frequency lower limit value fb in the approaching notification sounds corresponding to the plurality of decoded data.

[0132] (h) In the sound pressure-frequency characteristic indicating the relationship between the sound pressure and the frequency of the approaching notification sounds corresponding to a plurality of encoded data, the microcomputer 31 sets the lower limit value fb of the frequency at which the sound pressure is equal to or higher than the threshold value Sa as the lower limit value of the frequency regarded as important as described above. Therefore, the microcomputer 31 can obtain the frequency lower limit value fb favorably.

[0133] (Other Embodiments) (1) In the above-described first embodiment, an example in which filtering processing is performed on a plurality of decoded data by a low-pass filter having a frequency upper limit value fa as a cut-off frequency has been described. In the above-described second embodiment, an example in which filtering processing is performed on a plurality of decoded data by a high-pass filter having a frequency lower limit value fb as a cut-off frequency has been described.

[0134] However, instead of this, filtering processing may be performed on a plurality of decoded data by a band-pass filter having a frequency upper limit value fa and a lower limit value fb as cut-off frequencies, respectively.

[0135] Thereby, the decoding device 30 can correct a plurality of decoded data and reduce high-frequency component noise and low-frequency component noise in the proximity notification sound corresponding to the plurality of decoded data.

[0136] In this case, the microcomputer 21 of the encoding device 20 calculates the frequency upper limit value fa in the first embodiment and the frequency lower limit value fb in the second embodiment as the encoding process is executed.

[0137] The microcomputer 21 outputs the frequency upper limit value fa and the lower limit value fb to the decoding device 30 together with the headers of a plurality of encoded data as the encoding process is executed. The microcomputer 31 of the decoding device 30 performs filtering processing on a plurality of decoded data by a band-pass filter based on the frequency upper limit value fa and the lower limit value fb output from the microcomputer 21.

[0138] (2) In the above-described first embodiment and the second embodiment, an example using a filter availability flag for setting whether or not to perform filtering processing using filter coefficients 1 to 5 on a plurality of decoded data has been described.

[0139] Not limited to this, a filter availability flag may be used to specify a filter to be used among a low-pass filter, a high-pass filter, and a band-pass filter, and to instruct the decoding device 30 to perform filtering processing using this filter.

[0140] (3) In the above-described first embodiment and second embodiment, an example in which the microcomputer 31 outputs a PWM signal based on a plurality of decoded data to the speaker 40 has been described. However, instead of this, a plurality of decoded data may be converted into an analog signal, and this converted analog signal may be output to the speaker 40 to output an approach notification sound from the speaker 40.

[0141] (4) In the above-described first embodiment, an example in which the above-described upper frequency limit value fa is calculated based on a frequency characteristic indicating the relationship between the sound pressure and frequency of the approach notification sound corresponding to a plurality of encoded data has been described.

[0142] However, instead of this, the above-described upper frequency limit value fa may be calculated based on a frequency characteristic indicating the relationship between the sound intensity and frequency in the approach notification sound corresponding to a plurality of encoded data. In this case, the microcomputer 21 sets the upper limit value of the frequency at which the sound intensity is equal to or greater than the threshold value in the frequency characteristic indicating the relationship between the sound intensity and frequency as the above-described upper frequency limit value fa.

[0143] (5) In the above-described second embodiment, an example in which the above-described lower frequency limit value fb is calculated based on a frequency characteristic indicating the relationship between the sound pressure and frequency of the approach notification sound corresponding to a plurality of encoded data has been described.

[0144] However, instead of this, the above-described lower frequency limit value fb may be calculated based on a frequency characteristic indicating the relationship between the sound intensity and frequency in the approach notification sound corresponding to a plurality of encoded data. In this case, the microcomputer 21 sets the lower limit value of the frequency at which the sound intensity is equal to or greater than the threshold value in the frequency characteristic indicating the relationship between the sound intensity and frequency as the above-described lower frequency limit value fb.

[0145] (6) In the above-described first and second embodiments, an example in which the speaker 40 is used as the sound output device that outputs the approach notification sound has been described. However, instead of this, a sound output device other than the speaker 40 may be used as the sound output device that outputs the approach notification sound.

[0146] (7) In the above-described first and second embodiments, an example in which the decoding device 30 is mounted on an automobile has been described. However, instead of this, the decoding device 30 may be mounted on various devices other than an automobile (for example, an audio device, an information terminal, etc.).

[0147] (8) In the above-described first and second embodiments, an example in which the approach notification sound is used as the sound corresponding to the digital data has been described. However, instead of this, a sound other than the approach notification sound (for example, music) may be used as the sound corresponding to the digital data.

[0148] (9) In the above-described first and second embodiments, an example in which the microcomputer 21 outputs a plurality of encoded data, filter coefficients 1 to 5, etc. to the decoding device 30 and records a plurality of encoded data, filter coefficients 1 to 5, etc. in the memory 32 has been described.

[0149] However, instead of this, the microcomputer 21 may directly record a plurality of encoded data, filter coefficients 1 to 5, etc. in the memory 32 as a plurality of encoded data, filter coefficients 1 to 5, etc.

[0150] In this case, in the manufacturing process of the decoding device 30, the memory 32 in which a plurality of encoded data, filter coefficients 1 to 5, etc. are pre-recorded is prepared, and the prepared memory 32 is incorporated into the decoding device 30.

[0151] (10) In the above-described first embodiment, the microcomputer 21 obtained the frequency upper limit value fa based on the frequency characteristics indicating the relationship between the sound pressure and the frequency. In the second embodiment, the microcomputer 21 obtained the frequency lower limit value fb based on the frequency characteristics indicating the relationship between the sound pressure and the frequency.

[0152] However, in the above first embodiment, the microcomputer 21 may use a predetermined value as the upper frequency limit value fa. In the above second embodiment, the microcomputer 21 may use a predetermined value as the lower frequency limit value fb.

[0153] (11) In the above first embodiment and second embodiment, an example in which a recording medium made of a semiconductor memory is used as the memories 32 and 22 has been described. However, alternatively, a recording medium made of a magnetic medium may be used as the memories 32 and 22.

[0154] (12) Note that the present disclosure is not limited to the above-described embodiments, and can be appropriately modified within the scope described in the claims. Also, the above embodiments are not unrelated to each other, and can be appropriately combined except in cases where the combination is clearly impossible. Also, in the above embodiments, the elements constituting the embodiments are not necessarily essential, except in cases where it is explicitly stated that they are essential and cases where they are considered to be clearly essential in principle. Also, in the above embodiments, when numerical values such as the number, numerical value, quantity, and range of the components of the embodiments are mentioned, they are not limited to the specific number, except in cases where it is explicitly stated that they are essential and cases where they are clearly limited to a specific number in principle. Also, in the above embodiments, when referring to the shape, positional relationship, etc. of the components, etc., they are not limited to the specific shape, positional relationship, etc., except in cases where it is explicitly stated and cases where they are clearly limited to a specific shape, positional relationship, etc. in principle.

Explanation of Reference Numerals

[0155] 10 Data processing system 20 Encoding device 21 Microcomputer 22 Memory 30 Decoding device 31 Microcomputer 32 Memory 40 Speaker

Claims

1. A data processing system comprising an encoding device (20) that encodes a plurality of digital data corresponding to sounds to generate a plurality of encoded data, and a decoding device (30) that decodes the plurality of encoded data to generate a plurality of decoded data, wherein the encoding device comprises an encoding processing unit (S100) that encodes the plurality of digital data using ADPCM or linear prediction to generate the plurality of encoded data, and a filter calculation unit (S120, S120A) that obtains filter information for filtering the plurality of decoded data based on the plurality of encoded data, and the decoding device comprises a decoding processing unit (S200) that decodes the plurality of encoded data generated by the encoding processing unit to generate the plurality of decoded data, a filter processing unit (S230, S230A) that filters the plurality of decoded data by a filter based on the filter information to correct the plurality of decoded data and suppress noise from being included in the sound corresponding to the plurality of decoded data, and a sound output unit (S240, S240A) that outputs the sound corresponding to the plurality of decoded data corrected by the filter processing unit. A data processing system comprising the above components.

2. The decoding device comprises a recording medium (32) on which the plurality of encoded data generated by the encoding processing unit and the filter information obtained by the filter calculation unit are recorded, the decoding processing unit decodes the plurality of encoded data recorded on the recording medium to generate the plurality of decoded data, and the filter processing unit filters the plurality of decoded data based on the filter information recorded on the recording medium. The data processing system according to claim 1.

3. A decoding device applied to a data processing system (10) comprising an encoding device (20) having an encoding processing unit (S100) that encodes a plurality of digital data corresponding to sounds using ADPCM or linear prediction to generate a plurality of encoded data, and a filter calculation unit (S120, S120A) that obtains filter information for filtering a plurality of decoded data based on the plurality of encoded data, the decoding device comprising a decoding processing unit (S200) that decodes the plurality of encoded data generated by the encoding processing unit to generate the plurality of decoded data, A filter processing unit (S230, S230A) that corrects the plurality of decoded data by filtering the plurality of decoded data based on the filter information to suppress noise from being included in the sound corresponding to the plurality of decoded data; A sound output unit (S240, S240A) that outputs the sound corresponding to the plurality of decoded data corrected by the filter processing unit; A decoding apparatus comprising:

4. A recording medium (32) in which a plurality of encoded data generated by the encoding processing unit and filter information obtained by the filter calculation unit are recorded; The decoding processing unit decodes the plurality of encoded data recorded on the recording medium to generate the plurality of decoded data; The decoding apparatus according to claim 3, wherein the filter processing unit filters the plurality of decoded data based on the filter information recorded on the recording medium.

5. The encoding apparatus includes a frequency analysis unit (S110) that obtains an upper limit value (fa) of the frequency of a component regarded as important among the sounds corresponding to the plurality of encoded data based on the plurality of encoded data; The filter calculation unit obtains the filter information based on the upper limit value of the frequency; When components having a frequency higher than the upper limit value of the frequency are regarded as high-frequency components among the sounds corresponding to the plurality of decoded data, The decoding apparatus according to claim 3, wherein the filter processing unit corrects the plurality of decoded data to suppress noise from being included in the sound corresponding to the plurality of decoded data, and suppresses the high-frequency components from being included in the sound corresponding to the plurality of decoded data.

6. The frequency analysis unit obtains a frequency characteristic indicating the relationship between the sound pressure, which is the pressure of the sound corresponding to the plurality of encoded data, and the frequency, and in the obtained frequency characteristic, sets the upper limit value of the frequency at which the sound pressure is equal to or higher than a threshold value (Sa) as the upper limit value of the frequency of the component regarded as important. The decoding apparatus according to claim 5.

7. The encoding apparatus includes a frequency analysis unit (S110A) that obtains a lower limit value (fb) of the frequency of a component regarded as important among the sounds corresponding to the plurality of encoded data based on the plurality of encoded data; The filter calculation unit obtains the filter information based on the lower limit value of the frequency; Among the sounds corresponding to the plurality of decoded data, when a component having a frequency lower than the lower limit value of the frequency is defined as a bass component, The decoding apparatus according to claim 3, wherein the filter processing unit corrects the plurality of decoded data in order to suppress noise from being included in the sound corresponding to the plurality of decoded data, and suppresses the bass component from being included in the sound corresponding to the plurality of decoded data.

8. The frequency analysis unit obtains a frequency characteristic indicating the relationship between the sound pressure, which is the pressure of the sound corresponding to the plurality of encoded data, and the frequency, and in the obtained frequency characteristic, the lower limit value of the frequency at which the sound pressure is equal to or higher than a threshold value (Sa) is set as the lower limit value of the frequency of the component regarded as important. The decoding apparatus according to claim 7.

9. An encoding apparatus (20) encodes a plurality of digital data corresponding to a sound using ADPCM or linear prediction to generate a plurality of encoded data, The encoding apparatus obtains filter information for filtering a plurality of decoded data based on the plurality of encoded data, A decoding apparatus (30) decodes the plurality of encoded data generated by the encoding apparatus to generate the plurality of decoded data, The decoding apparatus filters the plurality of decoded data by a filter based on the filter information, thereby correcting the plurality of decoded data and suppressing noise from being included in the sound corresponding to the plurality of decoded data, The decoding apparatus outputs a sound corresponding to the plurality of corrected decoded data, A data processing method including.

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