Voice reproduction device and voice reproduction method

Abstract

To shorten time required for completion of processing to detect a peak of amplitude of voice of digital voice data.SOLUTION: A voice reproduction device includes: an A / D converter; a classification part for classifying a plurality of pieces of digital voice data into at least a first group and a second group; a first up-sampling part for up-sampling digital voice data classified into the first group; a second up-sampling part for up-sampling digital voice data classified into the second group; a peak detection part for detecting a peak of amplitude of voice when digital voice data after up-sampling by the first up-sampling part and digital voice data after up-sampling by the second up-sampling part are reproduced; and a specification part for specifying a gain coefficient for normalizing digital voice data based on the detected peak.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an audio playback device and an audio playback method for playing back audio.

Background Art

[0002] Various devices for playing back audio have been proposed. For example, in Patent Document 1, it is proposed to sample a playback pilot signal output by A / D conversion means and adjust the output of a digital filter so as to compensate for fluctuations in the fixed signal level of the sampled pilot signal.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When performing N-fold upsampling on A / D-converted digital audio data, it takes N times as long as equal-fold sampling. Since the process of detecting the peak of the amplitude of the audio in the digital audio data is a process performed after sampling the digital audio data, there is a problem that the time required to complete the process of detecting the peak becomes excessive when performing N-fold upsampling.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a signal generation device capable of shortening the time required to complete the process of detecting the peak of the amplitude of the audio in digital audio data when performing upsampling of the digital audio data.

Means for Solving the Problems

[0006] The audio playback device according to the first aspect of the present invention includes an A / D converter that converts analog audio data into digital audio data at predetermined time intervals, a classification unit that classifies a plurality of the digital audio data into at least a first group and a second group, a first upsampling unit that upsamples the digital audio data classified by the classification unit into the first group, a second upsampling unit that upsamples the digital audio data classified by the classification unit into the second group, a peak detection unit that detects the peak of the amplitude of the audio when reproducing both the digital audio data after upsampling by the first upsampling unit and the digital audio data after upsampling by the second upsampling unit, a specifying unit that specifies a gain coefficient for normalizing the digital audio data based on the detected peak, a normalization unit that normalizes the digital audio data with the gain coefficient specified by the specifying unit, and a playback unit that plays back the digital audio data normalized by the normalization unit.

[0007] The audio playback device further includes a first FIR filter that passes frequencies in a first band among the frequency components included in the digital audio data upsampled by the first upsampling unit, and a second FIR filter that passes frequencies in a second band among the frequency components included in the digital audio data upsampled by the second upsampling unit. The peak detection unit may detect the peak of the amplitude of the audio when reproducing both the digital audio data after passing through the first FIR filter and the digital audio data after passing through the second FIR filter.

[0008] The audio playback device further includes a storage control unit that stores digital audio data converted from analog audio data by the A / D converter in a storage unit, and a playback upsampling unit that upsamples a plurality of the digital audio data stored in the storage unit in the playback order. The classification unit classifies at least some of the plurality of digital audio data stored in the storage unit into the first group and the second group. The first upsampling unit and the second upsampling unit may start upsampling of the plurality of digital audio data stored in the storage unit in an order different from the playback order.

[0009] Before the first upsampling unit completes upsampling of the first digital audio data in the playback order among the plurality of digital audio data classified into the first group, the second upsampling unit may start upsampling of the first digital audio data in the playback order among the plurality of digital audio data classified into the second group.

[0010] The audio playback method according to the second aspect of the present invention includes steps of converting analog audio data into digital audio data at predetermined time intervals, classifying a plurality of the digital audio data into at least a first group and a second group, upsampling the digital audio data classified into the first group, upsampling the digital audio data classified into the second group, detecting a peak of the amplitude of the audio when playing back both the upsampled digital audio data classified into the first group and the upsampled digital audio data classified into the second group, specifying a gain coefficient for normalizing the digital audio data based on the detected peak, normalizing the digital audio data with the specified gain coefficient, and playing back the normalized digital audio data.

Advantages of the Invention

[0011] According to the present invention, it is possible to achieve the effect of shortening the time required to complete the process of detecting the peak of the amplitude of the voice in the digital voice data.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0013] [Configuration of Voice Playback Device] FIG. 1 shows the configuration of the voice playback device 100 of the present embodiment. The voice playback device 100 records voice data, for example, and plays back the recorded voice data in response to a user operation. When playing back the recorded voice data, the voice playback device 100 performs upsampling to convert the sampling frequency of the voice data to a higher sampling frequency. At this time, the voice playback device 100 performs upsampling on a plurality of digital voice data in parallel.

[0014] The audio playback device 100 detects the peak of the audio when playing back digital audio data based on a plurality of digital audio data obtained by parallel upsampling, and normalizes the digital audio data using the gain coefficient determined based on the detected peak. The audio playback device 100 plays back the normalized digital audio data. Since the audio playback device 100 performs upsampling on a plurality of digital audio data in parallel, the time required for playing back the digital audio data can be shortened.

[0015] The audio playback device 100 includes an A / D converter 1, a storage unit 2, and a control unit 3. The control unit 3 includes a memory control unit 31, a classification unit 32, upsampling units 33-1 to 33-N, an upsampling unit 34, FIR filters 35-1 to 35-N, an FIR filter 36, a peak detection unit 37, a specifying unit 38, a normalization unit 39, and a playback unit 40.

[0016] The A / D converter 1 converts analog audio data into digital audio data at predetermined time intervals. The predetermined time is determined according to, for example, the period of the clock signal supplied to the A / D converter 1. The A / D converter 1 converts the analog audio data input to a microphone (not shown) into digital audio data. The A / D converter 1 may convert the analog audio data acquired from an external device (not shown) by wireless communication or the like into digital audio data. The A / D converter 1 inputs the converted digital audio data to the memory control unit 31.

[0017] The storage unit 2 includes storage media such as a ROM (Read Only Memory), a RAM (Random Access Memory), and a hard disk. The storage unit 2 stores the program executed by the control unit 3. The storage unit 2 stores the gain coefficient for normalizing the digital audio data. The control unit 3 is, for example, a processor.

[0018] By executing the program stored in the storage unit 2, the control unit 3 functions as a storage control unit 31, a classification unit 32, a plurality of upsampling units 33-1 to 33-N and 34, a plurality of FIR filters 35-1 to 35-N and 36, a peak detection unit 37, a specifying unit 38, a normalization unit 39, and a playback unit 40. Each functional block included in the control unit 3 operates in synchronization with the same clock signal.

[0019] The storage control unit 31 stores various types of information in the storage unit 2. The storage control unit 31 stores the digital audio data converted from the analog audio data by the A / D converter 1 in the storage unit 2.

[0020] The classification unit 32 classifies a plurality of digital audio data into at least a first group and a second group. The classification unit 32 classifies at least a part of the plurality of digital audio data stored in the storage unit 2 into at least a first group and a second group. In the example of FIG. 1, the classification unit 32 classifies the digital audio data stored in the storage unit 2 into a first group to an Nth group. These groupings are for determining which of the upsampling units 33-1 to 33-N will perform upsampling.

[0021] The plurality of upsampling units 33-1 to 33-N and 34 convert the sampling frequency of the digital audio data stored in the storage unit 2. The plurality of upsampling units 33-1 to 33-N and 34 perform upsampling to convert the sampling frequency of the digital audio data to a sampling frequency higher than the sampling frequency when the A / D converter 1 converts the analog audio data into digital audio data.

[0022] The plurality of upsampling units 33-1 to 33-N and 34 convert the sampling frequency of the digital audio data so that it becomes a sampling frequency four times the sampling frequency when the A / D converter 1 converts analog audio data into digital audio data (hereinafter, also referred to as quadruple upsampling). The plurality of upsampling units 33-1 to 33-N and 34 may perform upsampling by a factor of 2, 6, or 8.

[0023] The upsampling unit 33-1 (corresponding to the first upsampling unit) upsamples the digital audio data classified into the first group by the classification unit 32. The upsampling unit 33-2 (corresponding to the second upsampling unit) upsamples the digital audio data classified into the second group by the classification unit 32. Similarly, the upsampling unit 33-k (k = 1, 2, ···, N) upsamples the digital audio data classified into the k-th group by the classification unit 32.

[0024] The upsampling units 33-1 to 33-N perform upsampling of a plurality of digital audio data in parallel. The upsampling unit 33-1 and the upsampling unit 33-2 start the upsampling of the plurality of digital audio data stored in the storage unit 2 in an order different from the playback order in order to quickly perform processes such as peak detection by the peak detection unit 37 after upsampling.

[0025] For example, the upsampling unit 33-1 and the upsampling unit 33-2 start the upcycling of the digital audio data one by one for each group first, and repeat the process of starting the upcycling of the remaining digital audio data one by one for each group to start the upsampling of the digital audio data. Since the upsampling units 33-1 to 33-N upsample the digital audio data in such an order, the efficiency when upsampling a plurality of digital audio data in parallel can be further improved.

[0026] Figures 2 and 3 show an example of the order of start of upsampling by a plurality of upsampling units 33-1 to 33-4 and 34. In the examples of FIGS. 2 and 3, the audio playback device 100 includes a total of five upsampling units, namely, upsampling units 33-1 to 33-4 and upsampling unit 34. FIG. 2 shows the order of start of upsampling by the upsampling unit 34. The upsampling unit 34 upsamples a plurality of digital audio data stored in the storage unit 2 in the playback order. In the example of FIG. 2, upsampling is started in the order of the first digital audio data, the second digital audio data, ···, the sixteenth digital audio data.

[0027] FIG. 3 shows the order of start of upsampling by the upsampling units 33-1 to 33-4. The first digital audio data to the sixteenth digital audio data are shown in the order of earlier timing of starting upsampling by the upsampling units 33-1 to 33-4. As shown in the first row from the top in FIG. 3, the upsampling unit 33-1 first starts upsampling of the first digital audio data, which is the earliest in the playback order by the playback unit 40 among the first digital audio data to the fourth digital audio data classified into the first group by the classification unit 32.

[0028] Next, as shown in the second row from the top in FIG. 3, the upsampling unit 33-2 starts upsampling of the fifth digital audio data, which is the earliest in the playback order by the playback unit 40 among the fifth digital audio data to the eighth digital audio data classified into the second group by the classification unit 32. As shown in the third row from the top in FIG. 3, the upsampling unit 33-3 starts upsampling of the ninth digital audio data, which is the earliest in the playback order by the playback unit 40 among the ninth digital audio data to the twelfth digital audio data classified into the third group by the classification unit 32.

[0029] As shown in the fourth row from the top in FIG. 3, the upsampling unit 33-4 starts upsampling the 13th digital audio data, which is the digital audio data with the earliest playback order among the 13th to 16th digital audio data classified by the classification unit 32 into the fourth group, by the playback unit 40. As shown in the fifth row from the top in FIG. 3, the upsampling unit 33-1 starts upsampling the 2nd digital audio data, which is the digital audio data with the earliest playback order among the remaining 2nd to 4th digital audio data in the first group, by the playback unit 40.

[0030] The upsampling units 33-1 to 33-4 start upsampling one by one in advance for each group of digital audio data, and then repeat the process of starting upsampling one by one for each group of the remaining digital audio data. In this way, the upsampling units 33-1 to 33-4 can upsample a plurality of digital audio data in parallel.

[0031] [Time chart showing the state of upsampling by the audio playback device] As described above, the upsampling units 33-1 to 33-N upsample a plurality of digital audio data in parallel. At this time, before the upsampling unit 33-1 completes upsampling the first digital audio data in the playback order by the playback unit 40 among the plurality of digital audio data classified by the classification unit 32 into the first group, the upsampling unit 33-2 starts upsampling the first digital audio data in the playback order by the playback unit 40 among the plurality of digital audio data classified by the classification unit 32 into the second group.

[0032] FIG. 4 is a time chart showing the state of upsampling by the audio playback device 100. The horizontal axis in FIG. 4 indicates time. In the example of FIG. 4, the audio playback device 100 includes a total of five upsampling units, namely, the upsampling units 33-1 to 33-4 and 34, and the upsampling units 33-1 to 33-4 each perform 4-fold upsampling of digital audio data.

[0033] The "Clock" row in FIG. 4 shows the voltage change of the clock signal supplied to the upsampling units 33-1 to 33-4. The "Start Timing" row in FIG. 4 shows the timing at which the upsampling units 33-1 to 33-4 start upsampling the digital audio data stored in the storage unit 2. "D1" to "D16" in FIG. 4 are abbreviations indicating the first digital audio data to the sixteenth digital audio data in order. "Address 1" in FIG. 4 indicates that the write destination of the first digital audio data (D1 in FIG. 1) after upsampling is address 1 of the storage unit 2. "Address 2" in FIG. 4 indicates that the write destination of the second digital audio data (D2 in FIG. 1) after upsampling is address 1 of the storage unit 2.

[0034] The "First Group" row in FIG. 4 shows the timing at which the upsampling unit 33-1 up-samples the first digital audio data to the fourth digital audio data classified into the first group by the classification unit 32. The three "0"s arranged between "D1" and "D2" in the "First Group" row in FIG. 4 indicate that the upsampling process of the immediately preceding "D1" is continuing. The "Second Group" row in FIG. 4 shows the timing at which the upsampling unit 33-2 up-samples the fifth digital audio data to the eighth digital audio data classified into the second group.

[0035] As shown in FIG. 4, before the upsampling of the first digital audio data (D1 in FIG. 4) by the upsampling unit 33-1 is completed, the upsampling of the fifth digital audio data (D5 in FIG. 4) by the upsampling unit 33-2, the upsampling of the ninth digital audio data (D9 in FIG. 4) by the upsampling unit 33-3, and the upsampling of the thirteenth digital audio data (D13 in FIG. 4) by the upsampling unit 33-4 are started. In this way, since the plurality of upsampling units 33-1 to 33-2 perform upsampling of digital audio data in parallel, the time required for upsampling can be shortened.

[0036] [Filtering by FIR Filters 35-1 to 35-N and 36] Among the frequency components included in the digital audio data, the plurality of FIR filters 35-1 to 35-N and 36 in FIG. 1 pass signals having frequencies in a predetermined band. The plurality of FIR filters 35-1 to 35-N attenuate signals having frequencies outside the predetermined band among the frequency components included in the digital audio data. For example, the FIR filter 35-1 (corresponding to the first FIR filter) passes signals having frequencies in the first band among the frequency components included in the digital audio data upsampled by the upsampling unit 33-1. The first band is, for example, a frequency band within the audible range of humans. The FIR filter 35-1 attenuates frequencies other than those in the first band among the frequency components included in the digital audio data upsampled by the upsampling unit 33-1.

[0037] The FIR filter 35-2 (corresponding to the second FIR filter) passes signals having frequencies in the second band among the frequency components included in the digital audio data upsampled by the upsampling unit 33-2. The FIR filter 35-2 attenuates frequencies other than those in the second band among the frequency components included in the digital audio data upsampled by the upsampling unit 33-2. The second band is, for example, the same frequency band as the first band. The second band may be a frequency band different from the first band.

[0038] [Detection of Peak of Audio Amplitude] The peak detection unit 37 detects a value that becomes the peak of the audio amplitude when the reproduction unit 40 reproduces the digital audio data after upsampling by the upsampling units 33-1 to 33-N. For example, the peak detection unit 37 detects a value that becomes the peak of the audio amplitude when all of the digital audio data after upsampling by the upsampling units 33-1 to 33-N is reproduced.

[0039] The peak detection unit 37 may detect the peak of the amplitude of the audio when playing a part of the digital audio data among the digital audio data after upsampling by the upsampling units 33-1 to 33-N. For example, the peak detection unit 37 may detect the peak of the amplitude of the audio when playing both the digital audio data after upsampling by the upsampling unit 33-1 and the digital audio data after upsampling by the upsampling unit 33-2.

[0040] At this time, the peak detection unit 37 detects the peak of the amplitude of the audio when playing both the digital audio data after passing through the FIR filter 35-1 after upsampling and the digital audio data after passing through the FIR filter 35-2 after upsampling. The peak detection unit 37 may also detect the peak of the amplitude of the audio of the digital audio data on which filtering by the FIR filter 35-1 or the FIR filter 35-2 has not been performed.

[0041] [Specification of gain coefficient] The specifying unit 38 specifies a gain coefficient for normalizing the digital audio data based on the peak detected by the peak detection unit 37. For example, the specifying unit 38 specifies a gain coefficient that enables the playback unit 40 to appropriately play the digital audio data even near the timing when the peak detection unit 37 detects a peak. The specifying unit 38 stores the specified gain coefficient in the storage unit 2.

[0042] The upsampling unit 34 upsamples the digital audio data in the same manner as the upsampling units 33-1 to 33-N. The upsampling unit 34 (corresponding to the playback upsampling unit) reads out the plurality of digital audio data before upsampling corresponding to these plurality of digital audio data from the storage unit 2 after the specifying unit 38 specifies the gain coefficients for normalizing the plurality of digital audio data. The upsampling unit 34 upsamples the read plurality of digital audio data in the playback order.

[0043] The FIR filter 36 passes the frequencies in a predetermined band among the frequency components included in the digital audio data upsampled by the upsampling unit 34. The predetermined band is, for example, the same frequency band as the first band. The predetermined band may be a frequency band different from the first band. The FIR filter 36 attenuates the frequencies other than the predetermined band among the frequency components included in the digital audio data upsampled by the upsampling unit 34.

[0044] [Normalization of Audio Data] The normalization unit 39 normalizes the digital audio data with the gain coefficient specified by the specifying unit 38. First, the normalization unit 39 reads out the gain coefficient specified by the specifying unit 38 from the storage unit 2. The normalization unit 39 normalizes the digital audio data that has passed through the FIR filter 36 using the read gain coefficient.

[0045] [Reproduction of Audio Data] The reproduction unit 40 reproduces the digital audio data normalized by the normalization unit 39. For example, the reproduction unit 40 outputs the sound corresponding to the normalized digital audio data in the reproduction order (see FIG. 3) via a speaker (not shown) connected via a network. The reproduction unit 40 may output the sound corresponding to the normalized digital audio data in the reproduction order via a speaker (not shown) built in the audio reproduction device 100.

[0046] [Processing Procedure for Reproduction of Audio Data] FIG. 5 is a flowchart showing the processing procedure for reproduction of digital audio data by the audio reproduction device 100. The processing procedure in FIG. 5 starts, for example, when an operation receiving unit (not shown) receives an operation of a user instructing reproduction of sound from the audio reproduction device 100.

[0047] First, the A / D converter 1 converts the analog audio data into digital audio data (S101). The storage control unit 31 stores the digital audio data converted from the analog audio data by the A / D converter 1 in the storage unit 2.

[0048] The classification unit 32 classifies a plurality of digital audio data stored in the storage unit 2 into a first group to an Nth group (S102). A plurality of upsampling units 33-1 to 33-N upsample a plurality of digital audio data stored in the storage unit 2 (S103).

[0049] A plurality of FIR filters 35-1 to 35-N perform filter processing that allows signals of frequencies in a predetermined band among the frequency components included in the digital audio data to pass through and attenuates signals of frequencies outside the predetermined band (S104). The peak detection unit 37 detects a value that becomes the peak of the amplitude of the audio when the playback unit 40 plays back the digital audio data after upsampling by the upsampling units 33-1 to 33-N (S105).

[0050] The specifying unit 38 specifies a gain coefficient for normalizing the digital audio data based on the peak detected by the peak detection unit 37 (S106). After the specifying unit 38 specifies the gain coefficients for normalizing a plurality of digital audio data, the upsampling unit 34 reads out a plurality of digital audio data before upsampling corresponding to these plurality of digital audio data from the storage unit 2. The upsampling unit 34 upsamples the read plurality of digital audio data in the playback order (S107).

[0051] The FIR filter 36 performs filter processing that allows frequencies in a predetermined band among the frequency components included in the digital audio data upsampled by the upsampling unit 34 to pass through and attenuates frequencies outside the predetermined band (S108). The normalization unit 39 normalizes the digital audio data that has passed through the FIR filter 36 with the gain coefficient specified by the specifying unit 38 (S109). The playback unit 40 plays back the digital audio data normalized by the normalization unit 39 (S110), and the process ends.

[0052] [Effect of the audio playback device according to the present embodiment] According to the audio playback device 100 of the present embodiment, since the plurality of upsampling units 33-2 to 33-N upsample a plurality of digital audio data in parallel, the time required until the peak detection unit 37 detects the peak of the amplitude of the audio of the digital audio data can be shortened. As a result, the audio playback device 100 can shorten the time until the recorded audio data becomes playable.

[0053] As described above, the present invention has been described using embodiments. However, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist. For example, all or part of the device can be configured by functionally or physically dispersing and integrating it in an arbitrary unit. Also, new embodiments resulting from an arbitrary combination of a plurality of embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination have the effects of the original embodiments combined.

Explanation of Reference Numerals

[0054] 1 A / D converter 2 Storage unit 3 Control unit 31 Storage control unit 32 Classification unit 33-1 Upsampling unit 33-2 Upsampling unit 33-3 Upsampling unit 33-4 Upsampling unit 33-N Upsampling unit 34 Upsampling unit 35-1 FIR filter 35-2 FIR filter 35-N FIR filter 36 FIR filter 37 Peak detection unit 38 Identification unit 39 Normalization unit 40 Reproduction unit 100 Audio playback device

Claims

1. An A / D converter that converts analog audio data into digital audio data at predetermined time intervals, A classification unit that classifies a plurality of the digital audio data into at least a first group and a second group, A first upsampling unit that upsamples the digital audio data classified by the classification unit into the first group, A second upsampling unit that upsamples the digital audio data classified by the classification unit into the second group, A peak detection unit that detects a peak of the amplitude of the audio when reproducing both the digital audio data after upsampling by the first upsampling unit and the digital audio data after upsampling by the second upsampling unit, A specifying unit that specifies a gain coefficient for normalizing the digital audio data based on the detected peak, A normalization unit that normalizes the digital audio data with the gain coefficient specified by the specifying unit, A reproduction unit that reproduces the digital audio data normalized by the normalization unit, An audio reproduction device comprising the above.

2. A first FIR filter that passes frequencies in a first band among the frequency components included in the digital audio data upsampled by the first upsampling unit, A second FIR filter that passes frequencies in a second band among the frequency components included in the digital audio data upsampled by the second upsampling unit, further comprising, The peak detection unit detects a peak of the amplitude of the audio when reproducing both the digital audio data after passing through the first FIR filter and the digital audio data after passing through the second FIR filter, The audio reproduction device according to Claim 1.

3. A storage control unit that stores the digital audio data converted from analog audio data by the A / D converter in a storage unit, A reproduction upsampling unit that upsamples a plurality of the digital audio data stored in the storage unit in the order of reproduction, Further comprising, The classification unit classifies at least some of the digital audio data of the plurality of digital audio data stored in the storage unit into the first group and the second group, The first upsampling unit and the second upsampling unit start upsampling of the plurality of digital audio data stored in the storage unit in an order different from the playback order. The audio playback device according to claim 1 or 2.

4. Before the first upsampling unit completes upsampling of the first digital audio data in the playback order among the plurality of digital audio data classified into the first group, the second upsampling unit starts upsampling of the first digital audio data in the playback order among the plurality of digital audio data classified into the second group. The audio playback device according to claim 3.

5. A step of converting analog audio data into digital audio data at regular intervals; A step of classifying the plurality of digital audio data into at least a first group and a second group; A step of upsampling the digital audio data classified into the first group; A step of upsampling the digital audio data classified into the second group; A step of detecting a peak of the amplitude of the audio when playing back both the upsampled digital audio data classified into the first group and the upsampled digital audio data classified into the second group; A step of specifying a gain coefficient for normalizing the digital audio data based on the detected peak; A step of normalizing the digital audio data with the specified gain coefficient; A step of playing back the normalized digital audio data; An audio playback method comprising the steps.

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