Method and system for digitizing recorded audio

Abstract

This invention provides a method and system for digitizing record audio, which can produce reproduced sound with suppressed pitch fluctuations caused by eccentricity of the record. [Solution] The head unit of the player 1, which has an audio sensor unit and an image sensor unit, digitizes audio information from the audio sensor that scans the groove of a record on the turntable at a first sampling frequency and stores it in the storage unit. The image sensor obtains a first linear velocity, which is the actual linear velocity at the scanning position, based on the image of the groove scanned by the audio sensor, and obtains a second linear velocity, which is the average linear velocity, from the rotation speed of the turntable and the average scanning position in the radial direction. The first linear velocity and the second linear velocity are compared, and if the first linear velocity is greater than the second linear velocity, the reading sampling frequency of the audio information stored in the storage unit is made smaller than the first sampling frequency, and if the first linear velocity is smaller than the second linear velocity, the reading sampling frequency is made larger than the first sampling frequency.

Description

[Technical Field]

[0001] This invention relates to a method for digitizing recorded audio and a system for digitizing recorded audio. [Background technology]

[0002] If an analog audio record (hereinafter also referred to as a record) placed on a turntable is off-center, the linear velocity of the position where the record needle scans the groove on the record surface fluctuates with each rotation period, causing a problem where the pitch of the reproduced sound fluctuates. A technique for resolving this problem is described in Patent Document 1.

[0003] The technology described in Patent Document 1 is a record eccentricity detection device. This eccentricity detection device detects radial fluctuations in the scanning position of the record needle that scans the groove of a rotating record as tonearm deflection, and outputs a beat sound that physically fluctuates according to the amount of deflection. The user listens to this beat sound and manually adjusts the position of the record on the turntable to the position where the fluctuation of the beat sound is minimized. This is said to easily eliminate the eccentricity of the record. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-29049 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The technology described in Patent Document 1 requires time to correct the eccentricity as preparation, separate from the time it takes to play the record. Furthermore, because the eccentricity correction work is done manually, it is difficult to optimize the position of the record. In addition, since only the eccentricity due to the gap between the turntable spindle and the center hole of the record can be corrected, the eccentricity between the center hole and the sound groove that occurred during the record's manufacturing cannot be corrected. Therefore, it is desirable to resolve these problems so that pitch fluctuations caused by the eccentricity in the playback sound of the record are minimized.

[0006] Therefore, the object of the present invention is to provide a method for digitizing recorded audio and a system for digitizing recorded audio in order to obtain reproduced sound in which pitch fluctuations caused by eccentricity of the record are suppressed. [Means for solving the problem]

[0007] To solve the above-mentioned problems, one aspect of the present invention has the following steps 1) and 2), and configurations 3) and 4). 1) Audio information output from an audio sensor that scans the grooves of a record placed on a rotating turntable is digitized at a first sampling frequency and stored in a memory unit. Based on the image of the groove scanned by the sound sensor, a first linear velocity, which is the actual linear velocity at the scanning position of the sound sensor on the record, is obtained. A second linear velocity, which is the average linear velocity of the record at the scanning position of the audio sensor, is obtained from the rotational speed of the turntable and the average radial scanning position of the audio sensor. Comparing the first linear velocity and the second linear velocity, If the first linear velocity is greater than the second linear velocity, the audio information stored in the storage unit is read out at a second sampling frequency smaller than the first sampling frequency. If the first linear velocity is less than the second linear velocity, the audio information stored in the memory unit is read out at a third sampling frequency that is higher than the first sampling frequency. This is a method for digitizing audio from records. 2) Audio information output from an audio sensor that scans the grooves of a record placed on a rotating turntable is digitized at a predetermined sampling frequency and stored in a memory unit. The audio sensor is attached to the tonearm, and its horizontal rotation angle (first rotation angle) and vertical rotation angle (second rotation angle) are detected. Based on the first rotation angle, the second rotation angle, and the rotation speed of the turntable, the linear velocity at the scanning position of the record is acquired in real time as the third linear velocity. Based on the first average angle, which is the average value of the first rotation angle, and the average rotation speed, which is the average value of the rotation speed of the turntable, over a predetermined period, the average value of the linear velocity at the scanning position of the record is obtained as the fourth linear velocity. A readout sampling frequency is generated from the predetermined sampling frequency according to the ratio of the third linear velocity to the fourth linear velocity, and the audio information stored in the storage unit is read out from the storage unit at the readout sampling frequency and then converted to the predetermined sampling frequency. This is a method for digitizing audio from records. 3) A sound sensor that scans the grooves of a record and outputs audio information, An information processing device comprising: a storage unit for storing the audio information digitized at a first sampling frequency; a first linear velocity acquisition unit for acquiring a first linear velocity, which is the actual linear velocity at the scanning position of the audio sensor on the record, from an image of the sound groove; a second linear velocity acquisition unit for acquiring a second linear velocity, which is the average linear velocity, from the average scanning position in the radial direction of the audio sensor; and a read sampling frequency acquisition unit for comparing the first linear velocity and the second linear velocity and acquiring read sampling frequencies that are in a relative magnitude relationship with respect to the first sampling frequency, respectively, and reading the audio information stored in the storage unit at the read sampling frequency. This is a system for digitizing recorded audio, equipped with [specific features / features]. 4) A turntable on which a record is placed and rotates, A voice sensor that scans the sound groove of the record placed on the rotating turntable and outputs voice information; A tone arm to which the voice sensor is attached and that rotates around a predetermined axis; An image sensor that captures an image of the sound groove scanned by the voice sensor; An arm first angle detection sensor that detects the rotation angle of the tone arm to which the voice sensor is attached; An information processing device that processes the voice information; Comprising; The information processing device: A storage unit that stores the voice information from the voice sensor as digital information at a first sampling frequency; A first linear velocity acquisition unit that acquires a first linear velocity, which is the actual linear velocity at the scanning position of the voice sensor of the record, based on the image that has come in from the image sensor; A second linear velocity acquisition unit that acquires a second linear velocity, which is the average linear velocity at the scanning position of the voice sensor of the record, based on the rotation speed of the turntable and the rotation angle detected by the arm first angle detection sensor; A read sampling frequency acquisition unit that compares the first linear velocity and the second linear velocity and generates a second sampling frequency that has a magnitude relationship with respect to the first sampling frequency according to the magnitude relationship between the first linear velocity and the second linear velocity; Having; Reading out the voice information stored in the storage unit at the second sampling frequency; A digitalization system for record voice.

Effect of the Invention

[0008] According to one aspect of the present invention, an effect is obtained in that a reproduced sound with pitch fluctuations suppressed due to eccentricity of the record can be obtained.

Brief Description of the Drawings

[0009] [Figure 1]Figure 1 shows a record audio digitization system 91 according to an embodiment of the present invention. [Figure 2A] Figure 2A is a bottom view of the head section 123. [Figure 2B] Figure 2B is a side view of the head unit 123. [Figure 3] Figure 3 shows images captured by the image sensor unit 3 of the head unit 123, where Figure 3(a) is the image at time t1 and Figure 3(b) is the image at time t2. [Figure 4] Figure 4 is a block diagram showing the configuration of the record audio digitization system 91. [Figure 5] Figure 5 is a block diagram showing the configuration of the read sampling frequency acquisition unit 24 in the record audio digitization system 91. [Figure 6A] Figure 6A illustrates the warping of the record RC, with Figure 6A(a) showing a side view of the case without warping and Figure 6A(b) showing the case with warping. [Figure 6B] Figure 6B is a schematic diagram illustrating the acquisition of linear velocity in the case of warping. [Figure 7] Figure 7 is a block diagram showing the configuration of the record audio digitization system 91A. [Modes for carrying out the invention]

[0010] A record audio digitization system 91, which is one embodiment of the present invention, will be described with reference to Figures 1 to 5. Figure 1 is a diagram showing the record audio digitization system 91 according to an embodiment of the present invention. Figure 2A is a bottom view of the head unit 123. Figure 2B is a side view of the head unit 123. Figure 3 shows an image captured by the image sensor unit 3 provided in the head unit 123, where Figure 3(a) is the image at time t1 and Figure 3(b) is the image at time t2. Figure 4 is a block diagram showing the configuration of the record audio digitization system 91. Figure 5 is a block diagram showing the configuration of the read sampling frequency acquisition unit 24 in the record audio digitization system 91.

[0011] The record audio digitization system 91 described below is a system that converts sound fixed in the grooves of an analog record (hereinafter also referred to as record audio) into digital audio. As shown in Figure 1, the record audio digitization system 91 has a player 1 and an information processing device 2. The player 1 has a turntable 11, a spindle motor M, and a tonearm 12. The turntable 11 has a spindle 112 in the center and can hold an analog audio record (hereinafter referred to as record RC). The spindle motor M rotates the turntable 11 at a predetermined rotational speed under the control of the motor drive unit 26 of the information processing device 2 (see Figure 4). The record RC has a spindle hole in the center, and the spindle 112 is inserted through this hole and placed on the turntable 11.

[0012] The tonearm 12 comprises a pivot shaft 121, an arm section 122, a head section 123, and a first arm angle detection sensor 124. The pivot shaft 121 is to which the arm section 122 is fixed and is rotatable around the center C2 in Figure 1 (see arrow DR). The arm section 122 is a pipe member formed in a roughly S-shape or J-shape, with one end fixed to the pivot shaft 121. The head section 123 is attached to the end of the arm section 122 opposite to the pivot shaft 121. The tonearm 12 is also equipped with a first arm angle detection sensor 124 that detects the first rotation angle θa of the pivot shaft 121.

[0013] As shown in Figures 2A and 2B, the head unit 123 is fitted with an audio sensor unit 5 and an image sensor unit 3. The audio sensor unit 5 has an audio sensor 51. The audio sensor 51 is a so-called cartridge to which a cantilever having a record needle 51a is flexibly attached, and it converts the vibration of the record needle 51a into an electrical signal and outputs it as audio information J5 to the A / D conversion unit 25 of the information processing device 2 (see Figure 4).

[0014] The image sensor unit 3 is attached to the tip of the head unit 123 and includes an image sensor 31 and an illumination unit 32. The illumination unit 32 illuminates the vicinity of the contact position when the record needle 51a is in contact with the sound groove RCg of the record RC. The image sensor 31 captures multiple images of a predetermined area within the range illuminated by the illumination unit 32 on the surface of the record RC at predetermined time intervals and outputs them as image information J3 to the image processing unit 21 of the information processing device 2 (see Figure 4). The image processing unit 21 controls the operation of the illumination unit 32 and the image sensor 31.

[0015] As shown in Figure 1, the positions of the three centers C1 to C3 in the player 1 are set as follows when viewed from above the axis of the spindle 112. That is, center C1 is the center position of the spindle 112, center C2 is the rotation center position of the pivot shaft 121 of the tonearm 12, and center C3 is the position (scanning position) where the record needle 51a contacts and scans the surface of the record RC. Furthermore, the line segment connecting centers C1 and C2 is defined as side C12, the line segment connecting centers C2 and C3 is defined as side C23, and the line segment connecting centers C3 and C1 is defined as side R.

[0016] The lengths L and Lt of sides C12 and C23, respectively, are fixed lengths determined by the specifications of player 1. On the other hand, the length Lr of side R changes depending on the scanning position of the record needle 51a relative to the groove RCg. In accordance with the change in length Lr, the first rotation angle θa, which is the angle between sides C12 and C23, also changes. The arm first angle detection sensor 124 detects this first rotation angle θa and outputs it as first angle information J12 to the second linear velocity acquisition unit 23 of the information processing device 2 (see Figure 4).

[0017] As shown in Figure 4, the information processing device 2 is composed of an image processing unit 21, a first linear velocity acquisition unit 22, a second linear velocity acquisition unit 23, a read sampling frequency acquisition unit 24, an A / D conversion unit 25, a motor drive unit 26, a storage unit 27, a sampling rate converter 28, and a D / A conversion unit 29. Furthermore, as shown in Figure 5, the read sampling frequency acquisition unit 24 is composed of a WF calculation unit 241, a D / A conversion unit 242, a reference voltage generation unit 243, a first oscillator 244, a second oscillator 245, and a subtractor 246.

[0018] As shown in Figure 5, the first oscillator 244 outputs a master clock signal from output port 24P3 that is a constant multiple (e.g., 256fs) of the first sampling frequency fs, according to the reference voltage Vref from the reference voltage generation unit 243. The WF calculation unit 241 calculates and outputs the difference rate WF, as described later. The second oscillator 245 converts this difference rate WF (details described later) into a voltage Vwf using the D / A conversion unit 242. Based on the difference voltage between this voltage and the reference voltage Vref, it sets the sampling frequency corresponding to the difference rate WF as the read sampling frequency fsa, generates a constant multiple (e.g., 256fs) of this fsa, and outputs it from output port 24P4 as a read master clock signal.

[0019] The record audio digitization system 91, with the configuration described above, outputs analog playback sound from the output port 2P of the information processing device 2 by placing the record needle 51a on the sound groove RCg of the record RC, which is placed on the turntable 11 and rotates integrally with the turntable 11, and scanning it.

[0020] The record audio digitization system 91 has the above configuration and performs pitch correction of the reproduced sound to cancel out the effect of the eccentricity when the record RC placed on the turntable 11 is eccentric.

[0021] (Audio information J5) The audio sensor 51 converts vibrations generated in response to the undulation of the groove RCg by the record needle 51a scanning the groove RCg into an audio signal and sends it to the information processing device 2 as audio information J5 (see Figure 4). The audio information J5 is digitally converted by the A / D conversion unit 25 at a first sampling frequency fs (e.g., 44.1kHz, 48kHz, 96kHz, etc.) and stored as digital information in the storage unit 27. In the storage unit 27, the digitized audio information J5 is stored for a certain period of time. This period is, for example, approximately two rotations of the record RC, after which it is overwritten from the beginning.

[0022] (Image information J3) The image sensor 31, under the control of the image processing unit 21, continuously captures multiple images G1 of the record surface RC at minute predetermined time intervals, as shown in Figure 3(a), and outputs each image as image information J3 to the image processing unit 21. The predetermined time interval can be set according to the performance of the image sensor 31, but for example, if it is 120 to 480 FPS (Frames Per Second), it is approximately 2 to 8 msec. Since the image sensor 31 is positioned at the tip of the head unit 123, image G1 is an image of the record surface immediately after the record needle 51a has scanned it. Also, since image G1 is an image obtained by capturing the area illuminated by the illumination unit 32, it is an image without blur caused by a high-speed shutter even if the record surface is rotating. Image G1 includes multiple sound grooves RCg adjacent to the sound groove RCg1 scanned by the record needle 51a, with the central sound groove in the left-right direction. The actual distance GL along the sound groove RCg on the disc surface captured in image G1 is calculated based on the pixel pitch and number of pixels of the image sensor 31. The actual distance GL is known in advance according to the specifications and stored in the memory unit 27.

[0023] The image processing unit 21 extracts regions AR1 and AR2, in which the same portion of the sound groove RCg is captured, from multiple images, including image G1 captured at time t1 as shown in Figure 3(a) and image G2 captured at time t2, which is a small time interval Δt after time t1 as shown in Figure 3(b). Here, time Δt is set based on the rotation speed of the record RC so that at least the same region is included in images G1 and G2.

[0024] As shown in Figure 4, the spindle motor M rotates under the control of the motor drive unit 26. The spindle motor M is equipped with an encoder (not shown), which outputs the actual rotational speed of the spindle motor M as rotational speed information JM to the second linear speed acquisition unit 23 of the information processing device 2. In this direct drive system, the actual rotational speed of the spindle motor M matches the actual rotational speed of the turntable 11.

[0025] (1st linear velocity Va) The first linear velocity acquisition unit 22 determines the on-screen movement distance Δx between regions AR1 and AR2 shown in Figures 3(a) and 3(b). Next, from the ratio of the movement distance Δx to the actual distance GL stored in the storage unit 27, the actual movement distance Δxa, which is the actual movement distance of the sound groove RCg at time Δt, is determined, and the first linear velocity Va is determined. Va = Δxa / Δt ... (Equation 1) This is obtained and stored in the memory unit 27. The first linear velocity Va is the actual linear velocity at which the record needle 51a scans the groove RCa.

[0026] (Second linear velocity Vb) The arm first angle detection sensor 124 detects the first rotation angle θa of the support shaft portion 121 to which the arm portion 122 is fixed in real time and continuously outputs it as first angle information J12 to the second linear velocity acquisition unit 23. The second linear velocity acquisition unit 23 calculates the first average angle θav from the input first angle information J12, which is the average value of the first rotation angle θa, which fluctuates periodically in the case of eccentricity, over time tr, when the record RC completes one rotation. The second linear velocity acquisition unit 23 also calculates the average rotation speed Ev from the rotation speed information JM received from the spindle motor M, which is the average value of the rotation speed E of the spindle motor M over time tr.

[0027] In the following explanation, the unit of length will be (mm), the unit of rotations per minute will be (revolutions / minute), and the unit of angle will be (degrees).

[0028] The second linear velocity acquisition unit 23 determines the length Lr of side R from the lengths L and Lt of sides C12 and C23 respectively, and the first rotation angle θa, as follows: First, by the law of cosines, Lr=(L 2 +Lt 2 (-2 × L × Lt × cosθa) 1 / 2 ... (Formula 2) That is the case.

[0029] On the other hand, at the average rotational speed Ev of record RC, the second linear velocity Vb, which is the geometric linear velocity of the record needle 51a at the scanning position of the tonearm 12 at the first average angle θav, Vb=2πLrEv / 60... (Formula 3) Therefore, substituting (Equation 2) into Lr, Vb = [2πEv(L)] 2 +Lt 2 (-2 × L × Lt × cosθav) 1 / 2 ] / 60 (mm / sec)... (Formula 4) To obtain.

[0030] The second linear velocity Vb can be considered as the linear velocity at the scanning position of the record needle 51a when the record RC is rotating at a normal speed and there is no eccentricity. Therefore, when the record RC is not eccentric, the first linear velocity Va and the second linear velocity Vb are the same.

[0031] In contrast, if the record RC is eccentric, the scanning position of the record needle 51a repeatedly moves radially with a period of one rotation. Specifically, the scanning position fluctuates by repeatedly approaching and moving away from the spindle 112. When the scanning position fluctuates to approach the spindle 112, the travel distance Δx obtained from images G1 and G2 becomes smaller, so the first linear velocity Va becomes smaller than the second linear velocity Vb. Also, when the scanning position fluctuates to move away from the spindle 112, the travel distance Δx becomes larger, so the first linear velocity Va becomes larger than the second linear velocity Vb.

[0032] The pitch of the audio signal output from the audio sensor 51 is determined by the linear velocity of the record needle 51a at the scanning position relative to the groove RCg. Therefore, if the first linear velocity Va differs significantly from the second linear velocity Vb, the pitch of the reproduced sound will be higher or lower than the pitch that should be reproduced from the groove RCg. Furthermore, the magnitude of the difference between the second linear velocity Vb and the first linear velocity Va is reflected in the magnitude of the pitch shift of the reproduced sound.

[0033] The first linear velocity acquisition unit 22 and the second linear velocity acquisition unit 23 send the information of the first linear velocity Va and the second linear velocity Vb, which they have acquired as described above, to the read sampling frequency acquisition unit 24.

[0034] The WF calculation unit 241 of the readout sampling frequency acquisition unit 24 compares the first linear velocity Va and the second linear velocity Vb, and calculates the difference ratio WF, which is the ratio of the difference to the second linear velocity Vb, using (Equation 5). WF = (Va - Vb) / Vb ... (Equation 5) Next, the read sampling frequency fsa when reading the audio information J5 stored in the memory unit 27 is determined by (Equation 6). fsa = fs × (1 - WF) ... (Equation 6)

[0035] As shown in Figure 5, the read sampling frequency acquisition unit 24 inputs the difference between the reference voltage Vref from the reference voltage generation unit 243 and the voltage Vwf obtained by the D / A conversion unit 242 from the difference rate WF calculated by the WF calculation unit 241 to the second oscillator 245. In response, the second oscillator 245 generates a master clock signal [256fs(1-WF)] corresponding to the read sampling frequency fsa, and sequentially reads out the audio information J5 (audio data) between time t1 and time t2 from the audio information stored in the storage unit 27 at the read sampling frequency fsa corresponding to the difference rate WF.

[0036] Since the sampling frequency of the audio information J5 read out in this way is not a common sampling frequency (e.g., 44.1kHz, 48kHz, 96kHz, etc.), as shown in Figure 4, the sampling rate converter 28 converts it to a sampling frequency that a common D / A converter can input (e.g., 44.1kHz, 48kHz, 96kHz, etc.), and then the D / A conversion unit 29 converts it to analog audio and outputs it from output port 2P. Alternatively, it may be output as a digital audio signal without going through the D / A conversion unit 29. The sampling rate converter 28 is preferably an asynchronous sampling rate converter. Furthermore, regarding the sampling frequency after conversion by the sampling rate converter 28, a higher sampling frequency after conversion, and a multiple of the same series as the first sampling frequency, will result in less conversion error.

[0037] As described above, the method of digitizing record audio by the record audio digitization system 91 involves scanning the sound groove RCg of the record RC to acquire audio information J5, which is then stored in the storage unit 27 at a normal first sampling frequency fs. The stored audio information J5 is then read out at a read sampling frequency fsa corresponding to the actual first linear velocity Va during scanning of the record needle 51a, and then converted back to the normal first sampling frequency fs to produce the playback sound. This playback operation is performed in real time. Specifically, the first linear velocity Va and the second linear velocity Vb are compared, and if the first linear velocity Va is greater than the second linear velocity Vb, the audio information J5 stored in the storage unit 27 is read out at a second sampling frequency smaller than the first sampling frequency fs. If the first linear velocity Va is less than the second linear velocity Vb, the audio information J5 stored in the storage unit 27 is read out at a third sampling frequency larger than the first sampling frequency fs. This allows for good correction of pitch fluctuations that occur depending on the degree of eccentricity, even if the record RC is eccentric, resulting in reproduced audio with virtually no pitch fluctuations caused by the eccentricity.

[0038] In this method of digitizing recorded audio, the read sampling frequency acquisition unit 24 compares the first linear velocity Va and the second linear velocity Vb, and generates read sampling frequencies fsa that are in a relative magnitude relationship with respect to the first sampling frequency fs, according to the relative magnitude relationship between the first linear velocity Va and the second linear velocity Vb.

[0039] Furthermore, the record audio digitization system 91 acquires the actual first linear velocity Va during scanning of the record needle 51a from an image captured by the image sensor 31 of the sound groove RCg being scanned, enabling real-time, high-precision pitch fluctuation correction. The image sensor 31 may be mounted in a location other than the head unit 123, as long as it can capture images of the vicinity of the sound groove RCg of the record RC in contact with the record needle 51a.

[0040] The correction operation for pitch fluctuations caused by the eccentricity described above is performed in virtually real time. Therefore, the time of the audio information J5 that can be stored in the memory unit 27, that is, the playback time of the record RC that can be stored, is usually sufficient if it is equivalent to one rotation. If the storage area allocated to the audio information J5 in the memory unit 27 is small and reading is difficult, or if a considerable amount of time is required from storage to reading, the rotation speed of the spindle motor M may be intentionally reduced by the motor drive unit 26 compared to the generally accepted reference rotation speeds of 33 1 / 3 and 45 (revolutions / minute).

[0041] The embodiments of the present invention are not limited to the configurations described above, and may be modified without departing from the spirit of the invention.

[0042] (modified version) As a modified example of the record audio digitization system 91, the record audio digitization system 91A will be described with reference to Figures 6A, 6B, and 7. Figure 6A is a diagram illustrating the warping of the record RC, with Figure 6A(a) being a side view showing the case without warping and Figure 6A(b) showing the case with warping. Figure 6B is a schematic diagram illustrating the linear velocity when there is warping. Figure 7 is a block diagram showing the configuration of the record audio digitization system 91A.

[0043] The record audio digitization system 91A has a player 1A and an information processing device 2A, which correspond to the player 1 and information processing device 2 in the record audio digitization system 91, respectively. As shown in Figures 6A(a) and 6(b), player 1A differs from player 1 in that it is equipped with an arm second angle detection sensor 125 that detects the second rotation angle θb, which is the vertical rotation angle of the tonearm 12 around the horizontal axis CLH, in real time at the pivot shaft portion 121 of the tonearm 12, and does not have an image sensor portion 3. As shown in Figure 7, the arm second angle detection sensor 125 constantly sends the detected second rotation angle θb as second angle information J12A to the information processing device 2A.

[0044] Information processing device 2A differs from information processing device 2 in that the image processing unit 21 is omitted, and the first linear velocity acquisition unit 22 and the second linear velocity acquisition unit 23 are replaced with a linear velocity acquisition unit 23A.

[0045] The record audio digitization system 91A, which includes a player 1A and an information processing device 2A, suppresses pitch fluctuations of the reproduced sound caused by eccentricity and warping of the record RC as follows.

[0046] If the record RC is warped, the stylus 51a scanning the groove RCg moves up and down to follow the warp of the record surface, and the arm 122 rotates around the horizontal axis CLH of the support shaft 121 in conjunction with the up and down movement of the stylus 51a (see Figure 6A(b)). Specifically, as shown in Figure 6A(b), the stylus 51a scanning a single warped section RCs of the record RC placed on the turntable 11 which rotates as indicated by arrow DR6 first moves upward, and then moves downward. Therefore, even if the horizontal linear velocity of the scanning position is the same whether the record RC is warped or not, the scanning distance will be longer when the record is warped because the groove RCg, which serves as the scanning path, is inclined. Accordingly, the information processing device 2A performs the following process to suppress pitch fluctuations of the reproduced sound caused by the eccentricity and warping of the record RC.

[0047] First, as shown in Figure 7, the linear velocity acquisition unit 23A of the information processing device 2A is constantly input with first angle information J12, second angle information J12A, and rotation speed information JM. The first angle information J12 is the first rotation angle θa, which is the horizontal rotation angle of the tonearm 12 detected in real time by the arm first angle detection sensor 124. The second angle information J12A is the second rotation angle θb, which is the vertical rotation angle of the tonearm 12 detected in real time by the arm second angle detection sensor 125. The rotation speed information JM is the actual rotation speed of the turntable 11, which is constantly input from the encoder of the spindle motor M.

[0048] The linear velocity acquisition unit 23A acquires the third linear velocity Vc and the fourth linear velocity Vd from the first angle information J12, the second angle information J12A, and the rotational speed information JM as follows, and outputs them to the read sampling frequency acquisition unit 24A.

[0049] The third linear velocity Vc is the linear velocity that varies in real time at the scanning position of the stylus 51a, and is the linear velocity in which the influence of the eccentricity and warping of the record RC is reflected. On the other hand, the fourth linear velocity Vd is a fixed value determined by the second rotation angle θb geometrically obtained by calculation, and corresponds to the second linear velocity. Further, while the second linear velocity is a value considering the variation due to eccentricity, the fourth linear velocity is a value considering not only eccentricity but also the influence of warping, and is obtained as the average linear velocity at the time tr when the record RC rotates once, similar to the second linear velocity.

[0050] (The third linear velocity Vc) The linear velocity acquisition unit 23A first obtains the linear velocity VcH, which is the horizontal component caused by the eccentricity of the record RC in the actual linear velocity at the scanning position of the stylus 51a. Specifically, the linear velocity VcH is obtained in real time using (Equation 2), (Equation 3A), and (Equation 4A). (Equation 3A) and (Equation 4A) are obtained by replacing the first average angle θav with the first rotation angle θa and the average rotational speed Ev with the rotational speed E in (Equation 3) and (Equation 4). That is, (Equation 3A) is VcH = 2πLrE / 60 ··· (Equation 3A) and (Equation 4A) is obtained by substituting (Equation 2) into (Equation 3A), VcH = 〔2πE(L 2 + Lt 2 - 2×L×Lt×cosθa) 1 / 2 〕 / 60 (mm / sec) ··· (Equation 4A) That is.

[0051] The linear velocity acquisition unit 23A calculates the increase in scanning distance per unit time due to warping as follows. Figure 6B is a schematic diagram showing the height change of the record needle 51a scanning the warped sections RCs. Over the time Δt2 from time t11 to time t12, the scanning position of the record needle 51a rises from point P6a to point P6b. This rising distance, height H6, is the distance between point P6b and point P7, which is the projection position of point P6 onto the unwarped record surface.

[0052] In this case, the relationship between the ramp D6R, which is the actual scanning distance of the groove RCg, the horizontal scanning distance D6, and the height H6 is given by the Pythagorean theorem as follows (Equation 7). D6R 2 =D6 2 +H6 2 ...(Formula 5)

[0053] Here, the height H6 is determined by the length Lt of the side C23 between the centers C2 and C3 in Figure 1 and the second rotation angle θb shown in Figure 6A(b). H6=Lt×cosθb (Formula 8) It can be calculated using this method. Furthermore, since the distance D6 is the distance scanned during time Δt2 at the linear velocity VcH obtained by (Equation 4A), D6=VcH×Δt2 (Formula 9) It can be calculated using this method.

[0054] Therefore, substituting (Equation 9) and (Equation 8) into (Equation 5), D6R = [(VcH × Δt²)] 2 +(Lt×cosθb) 2 ] 1 / 2 ...(Formula 10) Therefore, the third-line velocity Vc (mm / sec) is, Vc = D6R / Δt² = [(VcH × Δt²)] 2 +(Lt×cosθb) 2 ] 1 / 2 / Δt2 ...(Formula 11) It is required as such.

[0055] (4th linear velocity Vd) The fourth linear velocity Vd is the linear velocity corresponding to the second linear velocity Vb described above, and is the average linear velocity over a predetermined period. That is, the linear velocity acquisition unit 23A determines the fourth linear velocity Vd as the average linear velocity of the third linear velocity Vc at time Δt2.

[0056] Specifically, the rotational speed E and first rotational angle θa in equations (4A), (8), (10), and (11) used to obtain the third linear velocity Vc are replaced with the average rotational speed Ev and first average angle θav, respectively, which are obtained as average values ​​over time Δt2. The second rotational angle θb is replaced with the minimum second rotational angle θbm, which is the minimum value over time Δt2. This is because the first rotational angle θa repeatedly fluctuates in positive and negative directions relative to the normal angle due to eccentricity, whereas the fluctuation of the second rotational angle θb due to warping only increases in a positive value relative to the normal angle.

[0057] The linear velocity acquisition unit 23A performs this variable substitution to obtain the fourth linear velocity Vd. Vd = [(VcH × Δt²)] 2 +(Lt×cosθbm) 2 ] 1 / 2 / Δt2 ...(Equation 12) The data is acquired and sent to the read sampling frequency acquisition unit 24A.

[0058] Next, the information processing device 2A will perform the following processing, in the same manner as the processing procedure in the information processing device 2. In other words, the readout sampling frequency acquisition unit 24A calculates the difference ratio WF2 for the input third linear velocity Vc and fourth linear velocity Vd using (Equation 13). WF2=(Vc−Vd) / Vd (Formula 13) Then, the read sampling frequency fsAa for reading the audio information J5 stored in the memory unit 27 is determined by (Equation 14). fsAa = fs × (1 - WF²) ... (Equation 14)

[0059] In Figure 5, the symbols for the read sampling frequency acquisition unit 24A are indicated in parentheses. As shown in Figure 5, the read sampling frequency acquisition unit 24A inputs the difference between the reference voltage Vref from the reference voltage generation unit 243 and the voltage Vwf2 obtained by the D / A conversion unit 242 by analog conversion of the difference rate WF2 obtained by the WF calculation unit 241 to the second oscillator 245. In response, the second oscillator 245 generates a master clock signal [256fs(1-WF2)] corresponding to the read sampling frequency fsAa, and sequentially reads out the audio information J5 (audio data) between time t1 and time t2 from the audio information stored in the storage unit 27 at the read sampling frequency fsAa corresponding to the difference rate WF2.

[0060] Since the sampling frequency of the read audio information J5 is not a common sampling frequency (e.g., 44.1kHz, 48kHz, 96kHz, etc.), as shown in Figure 4, the sampling rate converter 28 converts it to a sampling frequency that a common D / A converter can accept (e.g., 44.1kHz, 48kHz, 96kHz, etc.), and then the D / A conversion unit 29 converts it to analog audio and outputs it from output port 2P. Alternatively, it may be output as a digital audio signal without going through the D / A conversion unit 29.

[0061] In the method for obtaining the fourth linear velocity Vd, an example was explained in which the second rotation angle θb is replaced with the minimum second rotation angle θbm, which is the minimum value at time Δt2. However, if the curvature of the board surface is such that it protrudes on both sides, it is better to replace it with the second mean angle θbv, which is the average value at time Δt2.

[0062] As described above, the record audio digitization system 91A stores audio information J5 obtained by scanning the sound groove RCg of the record RC in the storage unit 27 at the normal first sampling frequency fs. Then, it performs a playback operation in real time in which it reads out the stored audio information J5 at a read sampling frequency fsAa corresponding to the actual first linear velocity Va when the record needle 51a is scanning, and converts it back to the first sampling frequency fs. As a result, even if the record RC is eccentric or warped, the pitch fluctuations that occur according to the degree of such eccentricity or warping are well corrected, and a playback sound is obtained in which pitch fluctuations caused by eccentricity or warping are substantially absent.

[0063] Furthermore, the record audio digitization system 91A obtains the actual third linear velocity Vc during scanning of the record needle 51a from the first rotation angle θa and the second rotation angle θb, which are the horizontal and vertical rotation angles of the arm at the scanning position, respectively. This enables real-time, high-precision pitch variation correction.

[0064] The audio sensor unit 5 is not limited to one in which the record needle 51a contacts and scans the sound groove RCg, but may also be one that scans the sound groove RCg non-contact using light and outputs an audio signal.

[0065] The record audio digitization system 91 may consist of a player 1 and an information processing device 2 as an integrated unit, or they may be separate units. If they are separate, the player 1 and the information processing device 2 may be separated, and signal transmission between them may be performed by wire or wireless connection. [Explanation of Symbols]

[0066] 1.1A Player 11 Turntable 112 spindles 12 Tonearms 121 Support shaft 122 Arm section 123 Head section 124 Arm 1st Angle Detection Sensor 125 Arm 2nd Angle Detection Sensor 2.2A Information Processing Device 21 Image Processing Unit 22 1st linear velocity acquisition section 23 2nd linear velocity acquisition section 23A Linear velocity acquisition section 24 Readout sampling frequency acquisition unit 24P3, 24P4 output ports 241 WF Calculation Section 242 D / A Conversion Section 243 Reference Voltage Generation Unit 244 First Oscillator 245 Second Oscillator 246 Subtractor 25 A / D conversion section 26 Motor drive unit 27 Memory section 28 Sampling Rate Converters 29 D / A Conversion Section 2P output port 3 Image sensor unit 31 Image Sensor 32 Lighting Section 5. Voice sensor unit 51 Voice Sensor 51a Record needle 91,91A Record Audio Digitization System AR1,AR2 area CLH horizontal axis C1,C2,C3 center C12, C23, R side D6,D6R,L6 distance E rotational speed EV Average rotational speed fs: Sampling frequency (first sampling frequency) fsa,fsAa Readout sampling frequency G1, G2 images GL actual distance H6 Height JM rotation speed information J12 1st angle information J12A 2nd angle information J3 Image Information J5 Audio Information L, Lt, Lr Length M Spindle Motor P6a,P6B,P7 points RC Records RCg,RCg1 Sound groove RCs (reinforced concrete) curved section t1,t2 time Va 1st linear velocity Vb 2nd linear velocity Vc 3rd linear velocity VcH linear velocity Vd 4th linear velocity Vref Reference Voltage VWF, VWF2 voltage WF difference rate θa First rotation angle θb Second rotation angle θbm Minimum second rotation angle θav 1st average angle θbv 2nd average angle Δt,Δt2,tr time Δx Travel distance Δxa Actual distance traveled

Claims

1. Audio information output from an audio sensor that scans the grooves of a record placed on a rotating turntable is digitized at a first sampling frequency and stored in a memory unit. Based on the image of the groove scanned by the sound sensor, a first linear velocity, which is the actual linear velocity at the scanning position of the sound sensor on the record, is obtained. A second linear velocity, which is the average linear velocity of the record at the scanning position of the audio sensor, is obtained from the rotational speed of the turntable and the average radial scanning position of the audio sensor. Comparing the first linear velocity and the second linear velocity, If the first linear velocity is greater than the second linear velocity, the audio information stored in the storage unit is read out at a second sampling frequency smaller than the first sampling frequency. If the first linear velocity is less than the second linear velocity, the audio information stored in the memory unit is read out at a third sampling frequency that is higher than the first sampling frequency. Methods for digitizing audio from records.

2. The first linear velocity is obtained based on multiple images of the sound groove scanned by the sound sensor, which are captured at predetermined time intervals. The second linear velocity is obtained based on the first average angle, which is the average value of the first rotation angle, which is the horizontal rotation angle of the tonearm to which the sound sensor is attached, over a predetermined period, and the average rotation speed, which is the average value of the rotation speed of the turntable. The method for digitizing the audio of a record according to claim 1.

3. Audio information output from an audio sensor that scans the grooves of a record placed on a rotating turntable is digitized at a predetermined sampling frequency and stored in a memory unit. The audio sensor is attached to the tonearm, and its horizontal rotation angle (first rotation angle) and vertical rotation angle (second rotation angle) are detected. Based on the first rotation angle, the second rotation angle, and the rotation speed of the turntable, the linear velocity at the scanning position of the record is acquired in real time as the third linear velocity. Based on the first average angle, which is the average value of the first rotation angle, and the average rotation speed, which is the average value of the rotation speed of the turntable, over a predetermined period, the average value of the linear velocity at the scanning position of the record is obtained as the fourth linear velocity. A readout sampling frequency is generated from the predetermined sampling frequency according to the ratio of the third linear velocity to the fourth linear velocity, and the audio information stored in the storage unit is read out from the storage unit at the readout sampling frequency and then converted to the predetermined sampling frequency. Methods for digitizing audio from records.

4. A sound sensor that scans the grooves of a record and outputs audio information, An information processing device comprising: a storage unit for storing the audio information digitized at a first sampling frequency; a first linear velocity acquisition unit for acquiring a first linear velocity, which is the actual linear velocity at the scanning position of the audio sensor on the record, from an image of the sound groove; a second linear velocity acquisition unit for acquiring a second linear velocity, which is the average linear velocity, from the average scanning position in the radial direction of the audio sensor; and a read sampling frequency acquisition unit for comparing the first linear velocity and the second linear velocity and acquiring read sampling frequencies that are in a relative magnitude relationship with respect to the first sampling frequency, respectively, and reading the audio information stored in the storage unit at the read sampling frequency. A system for digitizing recorded audio, equipped with [specific features / features].

5. A turntable on which a record is placed and rotates, A sound sensor that scans the grooves of the record placed on the rotating turntable and outputs audio information, A tonearm to which the aforementioned sound sensor is attached and which rotates around a predetermined axis, An image sensor that captures an image of the sound groove scanned by the aforementioned sound sensor, An arm first angle detection sensor that detects the rotation angle of the tonearm to which the sound sensor is attached, An information processing device for processing the aforementioned audio information, Equipped with, The aforementioned information processing device is A storage unit that stores the audio information from the audio sensor as digital information at a first sampling frequency, A first linear velocity acquisition unit acquires a first linear velocity, which is the actual linear velocity at the scanning position of the audio sensor of the record, based on the image received from the image sensor. A second linear velocity acquisition unit acquires a second linear velocity, which is the average linear velocity of the record at the scanning position of the audio sensor, based on the rotation speed of the turntable and the rotation angle detected by the first arm angle detection sensor. A read sampling frequency acquisition unit compares the first linear velocity and the second linear velocity and generates a second sampling frequency that is less than or equal to the first sampling frequency, according to the relative magnitudes of the first and second linear velocities. Having, The audio information stored in the memory unit is read out at the second sampling frequency. A system for digitizing the audio from records.

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