Audio signal processing apparatus and recording and/or reproducing apparatus for a tape-shaped recording medium

Abstract: A recording and/or reproducing apparatus for a tape-shaped recording medium (1) to record analog audio signals includes a recording and/or reproducing head (2), a detecting section (10), and a compensating section (11). The head (2) records on and/or reproduces from analog signals the tape-shaped recording medium (1). The detecting section (10) detects any fluctuation in the transporting speed of the tape-shaped recording medium (1) with respect to a rated transporting speed. The compensating section (11) modifies, on the basis of detection results from the detecting section (10), the analog signals, read out from or to be recorded on the tape-shaped recording medium (1) by the head (2), so as to compensate for the effect of any fluctuation in the transporting speed of the tape-shaped recording medium(1) with respect to the rated transporting speed before outputting these analog signals or supplying them to the head.

Description: BACKGROUND 1. Field of the Invention The present invention relates to a recording and reproducing apparatus for a tape-shaped recording medium and an audio signal processing apparatus. More particularly, the present invention relates to a recording and/or reproducing apparatus for a tape-shaped recording medium which is recorded an analog signal and an audio signal processing apparatus. 2. Background or the Invention There are various types of tape-shaped recording media, for example a compact tape cassette and a micro tape cassette, which are magnetically recorded analog audio signals. In recording and/or reproducing apparatuses for a tape-shaped recording medium such as the above-mentioned cassettes, various countermeasures have been taken against the deterioration in sound quality (unstableness in frequency) of the reproduced signals due to wow, flutter, that is, fluctuations in the tape speed. For example, in a tape player using a compact cassette, such fluctuations in tape speed have been restrained by increasing the weight of the flywheel, which is integral with the capstan, to thereby utilize the inertia thereof or providing a servo circuit to cope with the fluctuations in the speed of the capstan-drive motor, effecting a constant rotational speed control on the motor so that it may rotate at a constant rotational speed. However, none of these above-mentioned conventional systems has been capable of eliminating the wow, the flutter to a sufficient degree. For example, in the case of a mechanism in which torque is transmitted from the drive motor to the capstan through a belt, the high-frequency fluctuation components cannot be eliminated even by performing the above-mentioned constant rotational speed control on the drive motor with a servo circuit since the mechanism involves a time delay due to the use of the belt. Further, in cases where the reduction in the size and weight of the tape player is to be further promoted, an increase in the weight of the flywheel would constitute a serious obstacle to such a reduction. Thus, in many cases, that cannot be accepted. Moreover, an increase in the weight of the flywheel is to be considered disadvantageous from the viewpoint of so-called anti-rolling measures, which must be taken for the purpose of preventing irregularities in rotation due to the rolling of the player. JP-A-57027408 discloses a recording/reproducing system in which the effect of uneven tape travelling speed is eliminated by comparing the frequency corresponding to the travelling speed of a magnetic tape with a reference frequency. Thereby, the travelling speed of the magnetic tape is controlled. JP-A-6068548 discloses a reproducing apparatus in which dropout can be eliminated by providing an envelope detection circuit following up a tape running speed and a level fluctuation at time of reproduction. JP-A-3136413 discloses a recording/reproducing system in which a clock is correctly synchronously output with an input data even when a change in recording density due to tape speed fluctuation at write and read is accumulated by varying a level of a control voltage with the write state and the read state. However, none of these conventional systems has been capable of eliminating the wow and the flutter from reproduced signals to a sufficient degree for the reasons set out above. The object of the present invention is therefore to provide a recording and/or reproducing apparatus according to the preamble of claim 1 and an audio signal processing apparatus according to the preamble of claim 9, in which the wow and the flutter can be eliminated from the reproduced signals to a sufficient degree. This object is achieved by a recording and/or reproducing apparatus according to claim 1 and an audio signal processing apparatus according to claim 9. Further advantageous features are defined in the subclaims. According to the present invention, there is provided a recording and/or reproducing apparatus for a tape-shaped recording medium, the apparatus including a recording and/or reproducing head, a detecting section, and a compensating section. The recording and/or reproducing head records on and/or reproduces from analog signals the tape-shaped recording medium. The apparatus is characterised by the following features. The detecting section detects any fluctuation in the transporting speed of the tape-shaped recording medium with respect to a rated transporting speed. The compensating section modifies analog signals, read from or to be recorded on the tape-shaped recording medium by the head, so as to compensate for any fluctuation in the transporting speed of the tape-shaped recording medium with respect to the rated transporting speed on the basis of detection results from the detecting section before these analog signals are output or supplied to the recording and/or reproducing head. According to the present invention, there is further provided an audio signal processing apparatus including a clock pulse generating section, an A/D-converting section, a computing section, and a signal generating section. The A/D-converting section converts input analog signals into digital signals in accordance with clock pulses from the clock pulse generating section. The audio signal processing apparatus is characterised by the following features. The computing section computes any fluctuation in the transporting speed of a tape-shaped recording medium with respect to a reference transporting speed on the basis of the results of the detection of the actual transporting speed of the tape-shaped recording medium. The signal generating section converts the digital signals from the A/D-converting section into analog signals in which any fluctuation in the transporting speed of the tape-shaped recording medium with respect to the reference transporting speed has been compensated for on the basis of detection results from the computing section, and outputs the analog signals thus generated. In accordance with the present invention, the input/output timing of analog signals is controlled to vary in accordance with the results of the detection of the transporting speed of the tape-shaped recording medium, whereby it is possible to eliminate the wow components, the flutter components due to fluctuations in the transporting speed of the tape-shaped recording medium from the reproducing signals or the signals recorded on the recording medium. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing an essential part of a recording and/or reproducing apparatus according to a first embodiment of the present invention; Figs. 2A to 2D are diagrams illustrating the operation of the first embodiment; Fig. 3 is a block diagram showing a modulation of the first embodiment; Fig. 4 is a block diagram showing an essential part of a recording and/or reproducing apparatus according to a second embodiment of the present invention; Figs. 5A to 5D are diagrams illustrating the operation of the second embodiment; and Fig. 6 is a block diagram showing an essential part of a recording and/or reproducing apparatus according to a third embodiment of the present invention. DESCRIPTION OF THE INVENTION The construction of a recording and/or reproducing apparatus for a tape-shaped recording medium according to the present invention will now be described in detail with reference to the drawings. In the embodiments described below, a magnetic tape that is accommodated in a cassette, such as a compact tape cassette or a micro tape cassette, is adopted as an example of the tape-shaped recording medium. Fig. 1 is a block diagram showing an essential part of a recording and/or reproducing apparatus according to a first embodiment of the present invention. When recording or reproducing, the magnetic tape is transported or traveled at low tape speed in the forward or reverse direction by means of a capstan and pinch roller (not shown) of the recording and/reproducing apparatus. A reproducing head 2P is read out audio signals from a magnetic tape 1. A reproducing amplifier 3 is supplied the output signal form the reproducing head 2P. The output of the reproducing amplifier 3 is supplied to a digital signal processing section 11, which is composed of a DSP (digital signal processor), and the output of the digital signal processing section 11 is supplied to a power amplifier 4. A speaker unit 5 is supplied the output signals from the power amplifier 4 and converts the output signal form the power amplifier 4 into an audible sound and outputs the audible sound. A speed detector 10 detects a transporting speed or a traveling speed of the magnetic tape 1 and includes roller 10a and a rotary encoder 10b. The roller 10a is contacted to the magnetic tape 1 and rotated according to transportation of the magnetic tape 1. The rotary encoder 10b detects the rotation of the roller 10a. The rotary encoder 10b outputs pulses in accordance with the rotation of the roller 10a which is rotated by the transportation of the magnetic tape 1. Namely, the rotary encoder 10b outputs an information of transporting speed as a detecting result of the transporting speed of the magnetic tape 1. A reference numeral 12 indicates an A/D converter, a reference numeral 13 indicates a memory and a reference numeral 14 denotes a D/A converter. Analog audio signals output from the reproducing amplifier 3 are converted into digital data by the A/D converter 12, and the digital data are successively stored in the memory 13. Data read out from the memory 13 is converted into analog signals by the D/A converter 14, and the analog signals outputted from the D/a converter 14 are supplied to the power amplifier 4. The analog signals supplied to the power amplifier 4 are amplified by this power amplifier and supplied to the speaker unit 5. The speaker 5 converts the output signals supplied from the power amplifier 4 into an audible sound through electro-acoustic conversion before outputting them. The memory 13 is composed of a RAM or the like. Clock pulses CK 1 are used as sampling clock pulses for the A/D converter 12, and as write clock pulses for the memory 13. Clock pulses CK 2 are used as read clock pulses for the memory 13, and as sampling clock pulses for the D/A converter 14. A reference numeral 15 indicates a clock oscillator, and a reference numeral 16 indicates a clock control section. The clock control section 16 divides clock pulses from the clock oscillator 15 and generates the clock pulses CK 1 which are fixed frequency clock pulses. The clock pulses CK 1 is supplied to the A/D converter 12 and the memory 13. For example, the frequency of the clock pulses CK 1 is 100 KHz. The clock control section 16 also generates clock pulses CK 2 and supplies them to the memory 13 and the D/A converter 14. The frequency of the clock pulses CK 2 is not a fixed one. As stated below, this frequency is to be varied in accordance with the transporting speed of the magnetic tape 1. A reference numeral 17 indicates a frequency counter, and a reference numeral 18 indicates a controller. The frequency counter 17 is supplied the pulses outputted from the rotary encoder 10b and measures the pulse cycle of the supplied pulses. The controller 18 computes a frequency fluctuation coefficient k from the measured pulse cycle from the frequency counter 17 used a pulse cycle which is to be obtained when the magnetic tape 1 is transported or traveled at a rated transporting speed. The frequency fluctuation coefficient k is supplied to the clock control section 16. The controller 18 controls a writing operation of the digital data from the A/D converter 12 and a read-out operation of the stored data of the memory 13. Suppose the pulse cycle that is to be obtained as the output of the rotary encoder 10b when the magnetic tape 1 were transporting at a rated speed in a predetermined period of time t, which is between points in time t 0 and t 1 , is T 0 . Further, suppose the pulse cycle that is actually output from the rotary encoder 10b when the tape 1 is transporting and measured between the same period of time t, i.e., t 0 to t 1 , is T(t). If T(t) = T 0 , the magnetic tape 1 is to be considered transporting at the rated speed. In this case, T(t)/T 0 = k = 1 . In this condition, no fluctuations due to wow, flutter are to be found in the signals reproduced from the magnetic tape 1, nor do the signals recorded on the magnetic tape 1 include any fluctuation component due to wow, flutter. Next, a case in which there is a fluctuation in the tape transporting speed will be considered. In this case, T(t) ≠ T 0 , and if the value of T(t)/T 0 = k , k indicates a fluctuation with respect to a reference frequency, i.e., the frequency that would be obtained when the tape were transporting at the rated speed. That is, the value of k represents the ratio of the actual transporting speed of the tape to the rated transporting speed. When T(t) ≠ T 0 , fluctuation components due to wow, flutter are included in the signals reproduced from or recorded on the magnetic tape 1. Here, by way of example, the case in which audio signals are reproduced will be considered. Data that is subjected to sampling by the A/D converter 12 during the period t which is between the period time t 0 to t 1 , is again subjected to sampling when it is D/A-converted by the D/A converter 14. It is to be assumed that, if the cycle of this sampling is multiplied by 1/k, the data will be turned into signals that are free from any components due to fluctuations in the transporting speed of the magnetic tape 1. That is, the controller 18 keeps the value of the pulse cycle T 0 to be obtained when the tape is transporting at the rated speed, and performs the computation of the value of T(t)/T 0 = k each time the actual pulse cycle T(t) is obtained as the output of the rotary encoder 10b, which is measured during the period t, i.e., t 0 to t 1 . In this way, the cycle fluctuation coefficient k is calculated. The calculated cycle fluctuation coefficient k is supplied to the clock control section 16, which performs, on the basis of the cycle fluctuation coefficient k thus supplied, the calculation to obtain CK 2 = CK 1 /k with respect to the clock pulses CK 1 of a fixed frequency to thereby generate clock pulses CK 2 . These clock pulses CK 2 are supplied as reading-out clock pulses for the memory 13 and as sampling clock pulses for the D/A converter 14, whereby it is possible to obtain audio signals that are free the influence of wow and flutter as the output audio signals of the D/A converter 14. This operation will be schematically described with reference to Figs. 2A to 2D. When fixed clock pulses having a cycle T S1 as shown in Fig. 2A are used to A/D-convert audio signals input from the reproducing amplifier 3, pieces of data D 0 , D 1 , D 2 , D 3 , ···· are obtained, as shown in Fig. 2B. These pieces of data D 0 , D 1 , D 2 , D 3 , ···· are stored in the memory 13. Suppose the waveform shown in Fig. 2B is contracted along the dimension of time axis as compared to the waveform to be obtained when the tape is transporting at the rated speed because the transporting speed of the tape is higher than the rated transporting speed. Further, suppose the waveform as shown in Fig. 2C is the one to be obtained when the magnetic tape is transporting at the rated speed. In the clock controller 16, the clock pulses CK 2 , serving as reading clock pulses for the memory 13 and as sampling clock pulses for the D/A converter 14, are set so as to satisfy the equation: CK 2 = CK 1 /k , and have a cycle T S2 , as shown in Fig. 2D. As stated above, the cycle fluctuation coefficient k is a value calculated from the output of the rotary encoder 10b. The reading-out of data from the memory 13 and the D/A conversion at the D/A converter 14 are effected on the basis of the clock pulses CK 2 , whereby the output signal from the D/A converter 14 is a signal having the correct waveform as shown in Fig. 2C, i.e., an analog audio signal from which wow, flutter components have been eliminated. Thus, in the first embodiment of the present invention, the input/output timing of the digital signal processing section 11 is controlled in accordance with the output of the rotary encoder 10b, thereby making it possible to compensate for any fluctuation component due to wow, flutter in the signals reproduced from the magnetic tape 1, i.e., the reproduced analog signals. This audio signal processing method is also applicable to a recording circuit. Fig. 3 shows the essential part of a recording circuit to which the above processing is applied. In Fig. 3, a reference 2R indicates a recording head, a reference numeral 6 indicates a recording amplifier and a reference numeral 7 indicates an analog audio signal input terminal. The other components are formed in the same way as in Fig. 1, so a detailed description of them will be omitted here. In the circuit shown, analog audio signals to be recorded are inputted to the digital signal processing section 11 from the input terminal 7, and the output signals from the digital signal processing section 11 are supplied to the recording head 2R through the recording amplifier 6 before they are successively recorded on the magnetic tape 1 by the recording head 2R. The analog audio signals supplied from the input terminal 7 are naturally free from the influence of fluctuations in the transporting speed of the magnetic tape 1. They are correct signals the waveform of which is neither expanded nor contracted along the time axis dimension. However, if they were directly recorded on the magnetic tape 1, any fluctuation in the transporting speed of the magnetic tape 1 would cause the recorded audio signals to be deformed to exhibit a waveform correspondingly expanded or contracted along the time axis dimension. In view of this, as in the case of Fig. 1, the input analog audio signals are converted to digital data at the A/D converter 12 by using clock pulses CK 1 , and the digital data thus obtained is temporarily stored in the memory 13 before it is converted to analog signals at the D/A converter 14 by using clock pulses CK 2 . In the above recording system, when the transporting speed of the magnetic tape 1 decreases, the analog audio signals supplied to the recording head 2R will be ones that are expanded along the time axis dimension by an amount of time corresponding to the fluctuation in the transporting speed toward delay. Similarly, when the transporting speed of the magnetic tape 1 increases, the analog audio signals supplied to the recording head 2R will be ones that are compressed along the time axis dimension by an amount of time corresponding to the fluctuation in transporting speed toward advance. Thus, when considered in terms of their positional relationship with the magnetic tape 1, the recorded analog audio signals are neither expanded nor contracted along the time axis dimension in spite of the fluctuation in the transporting speed of the tape 1, and are recorded so as to exhibit the correct waveform. Thus, the above-described processing for reproducing is also applicable to recording, making it possible to effectively eliminate fluctuation components due to wow and flutter. Next, a recording and/or reproducing apparatus for a tape-shaped recording medium according to the second embodiment of the present invention will be described in detail with reference to Figs. 4 and 5. In Figs. 4 and 5, the components which are the same as those of Figs. 1 and 2 are indicated by the same reference numerals, and a detailed description of such components will be omitted here. In Fig. 4, a reference numeral 2 indicates a recording and reproducing head, and references SW 1 , SW 2 , and SW 3 indicate changeover switches that are connected to terminal R when recording is to be performed and to terminal P when signals recorded on the magnetic tape 1 are to be reproduced. The switching of the changeover switches SW 1 , SW 2 , SW 3 between recording and reproducing is effected by a system controller (not shown) of the recording and/or reproducing apparatus. When the switches SW 1 to SW 3 are connected to terminal P, the reproducing circuit is composed of the signal path which is from the recording and reproducing head 2 → the reproducing amplifier 3 → the digital signal processing section 21 → the power amplifier 4 → the speaker unit 5. When the switches SW 1 to SW 3 are connected to terminal R, the recording circuit is composed of the signal path which is from the input terminal 7 → the digital signal processing section 21 → the recording amplifier 6 → the recording and reproducing head 2. Like the first embodiment, the second embodiment described below is applicable not only to a reproducing apparatus but also to a recording apparatus. Here, it will be described as applied to a reproducing apparatus. The digital signal processing section 21 includes an A/D converter 22, an interpolation processing section 23, and a D/A converter 24. Analog audio signals outputted from the reproducing amplifier 3 are converted into digital data by the A/D converter 22, and processed by the interpolation processing section 23. The digital data which has undergone interpolation processing by the interpolation processing section 23 (described below) is converted into analog signals by the D/A converter 24, and supplied to the power amplifier 4. In the second embodiment, the sampling clock pulses supplied to the A/D converter 22 and the sampling clock pulses supplied to the D/A converter 24 are the same ones, which compose of clock pulses CK from a clock pulse generating section described below. A reference numeral 25 indicates a clock oscillator, and a reference numeral 26 indicates a clock pulse generating section. The clock pulse generating section 26 divides the clock pulses from the clock oscillator 25 and generates clock pulses CK as sampling clock pulses. The clock pulses CK are supplied to the A/D converter 22, the interpolation processing section 23 and D/A converter 24. A reference numeral 27 indicates a frequency counter for measuring the cycle of the pulses from the rotary encoder 10b, and a reference numeral 28 indicates a controller. Like the controller 18 of the first embodiment, the controller 28 computes the cycle fluctuation coefficient k from the measured actual pulse cycle T(t) by using the pulse cycle T 0 that is to be obtained when the magnetic tape 1 is transporting at the rated speed, and supplies this cycle fluctuation coefficient k to the interpolation processing section 23. An explanation of the cycle fluctuation coefficient k will be omitted here since it can be obtained in the same manner as in the first embodiment. As in the first embodiment, it is a value indicating a fluctuation in time with respect to a reference cycle. The operation of the second embodiment will be described with reference to Figs. 5A to 5D. When analog audio signals inputted from the reproducing amplifier 3 are digitized at the A/D converter 22 by using clock pulses CK having a cycle T SP , as shown in Fig. 5A, pieces of data D 0 , D 1 , D 2 , D 3 , ···· are obtained as shown in Fig. 5B. These pieces of data are supplied to the interpolation processing section 23. Suppose the waveform shown in Fig. 5B is one relatively contracted along the time axis dimension because of the transporting speed of the magnetic tape 1 being higher than the rated speed. Suppose, at the same time, the waveform of Fig. 5C is the one to be obtained when the transporting speed of the tape is the rated one. The interpolation processing section 23 generates the waveform of Fig. 5C by using the cycle fluctuation coefficient k, which is supplied from the controller 28. This processing performs in multiplying the data cycle by 1/k. However, if the pieces of data D 0 , D 1 , D 2 , D 3 , ···· were directly converted to analog signal by using the clock pulses CK, the waveform of the output analog audio signals would be restored to the one shown in Fig. 5B. In view of this, a data interpolation processing is performed on the waveform of Fig. 5C to thereby generate pieces of data D H0 , D H1 , D H2 , D H3 , ···· arranged in the cycle of the clock pulses CK. That is, the interpolation processing section 23 generates, for example, the piece of data D H1 , which corresponds to point a in Fig. 5C, on the basis of the pieces of data D 1 and D 2 . The pieces of data D H2 , D H3 , ···· are generated in the same manner through interpolation processing. This interpolation processing may consist, for example, in a linear interpolation or a change in sampling frequency through over sampling and down sampling. In the case of a linear interpolation, it can be effected with respect to the item of data D H2 , for example, through computation using the pieces of data D 1 and D 2 and the cycle fluctuation coefficient k. The pieces of data D H0 , D H1 , D H2 , D H3 , ····, generated as shown in Fig. 5D, are subjected to D/A conversion at the D/A converter 24 by using the clock pulses CK, whereby the output signals from the D/A converter 24 are signals having the correct waveform as shown in Fig. 5D, that is, analog audio signals from which wow, flutter components have been eliminated. Thus, with the second embodiment also, it is possible to eliminate wow components, flutter components from the reproduced signals by appropriately controlling the input/output timing of the digital signal processing section 11 on the basis of the output of the rotary encoder 10b. Further, also in the case of recording, in which the switches SW 1 to SW 3 are connected to R-terminal, analog audio signals are so recorded on the magnetic tape 1 that they exhibit the correct waveform with respect to the time axis due to the above-described processing executed by the digital signal processing section 11. Next, the third embodiment of the present invention will be described with reference to Fig. 6. According to the third embodiment, wow components, flutter components are cancelled through an analog signal processing. The third embodiment will also be described as applied to a recording and/or reproducing apparatus. In the drawing, the components which are common to the first and second embodiments are indicated by the same reference numerals, and a description of such components will be omitted. A recording and/or reproducing apparatus according to the third embodiment is formed by the rotary encoder 10b and a signal processing section 30. When the switches SW 1 to SW 3 are connected to P-terminal, the reproducing circuit is composed of the signal path which is from the recording and reproducing head 2 → the reproducing amplifier 3 → the signal processing section 30 → the power amplifier 4 → the speaker unit 5. When the switches SW 1 to SW 3 are connected to R-terminal, the recording circuit is composed of the signal path which is from the input terminal 7 → the signal processing section 30 → the recording amplifier 6 → the recording and reproducing head 2. The signal processing section 30 includes sample-and-hold circuits 31 and 32. In the reproducing operation, in which the switches SW 1 to SW 3 are connected to P-terminal, analog audio signals output from the reproducing amplifier 3 are supplied to the power amplifier 4 through the sample-and-hold circuits 31 and 32. The sample-and-hold circuit 31 is supplied with a fixed sampling cycle signal T S1 from a terminal 33. A reference numeral 34 indicates a frequency/voltage converting section, and reference numerals 35 and 36 indicate dividers. The frequency/voltage converting section 34 converts a pulse cycle T ENC from the rotary encoder 10b into a voltage value V ENC(t) . The divider 35 obtains through division a fixed value V0 ENC from the voltage value V ENC(t) supplied from the frequency/voltage converting section 34. Suppose the cycle of the output pulses to be obtained from the rotary encoder 10b when the magnetic tape 1 is transporting at a rated speed in a period of time t, which is between predetermined points in time t 0 to t 1 , is T0 ENC . The above pulse cycle T ENC(t) is the output of the rotary encoder 10b which is actually measured in the period t, i.e., t 0 to t 1 , during the transportation of the magnetic tape 1. Suppose the voltage value when the pulse cycle T ENC(t) = T0 ENC is V0 ENC . That is, the fixed value V0 ENC used in the division by the divider 35 is the value obtained when the magnetic tape 1 is transporting at the rated speed. The value of k, which is to be obtained through the calculation by the divider 35: V ENC(t) /V0 ENC = k , is the value of T ENC(t) /T0 ENC . That is, k is a value indicating a fluctuation in time with respect to a reference cycle when there is a fluctuation in the transporting speed of the magnetic tape 1. Thus, in the third embodiment, the cycle fluctuation constant k is calculated by the divider 35. Here, the reproduction of analog audio signals in this system will be considered. Signals which have undergone sampling at the sample-and-hold circuit 31 during the period of time t, i.e, t 0 to t 1 , are output through the sample-and-hold circuit 32, where multiplication by 1/k times is effected on the output from the sample-and-hold circuit 31, with the result that reproduced signals are free from fluctuation components due to the fluctuation in the tape transporting speed. The cycle fluctuation coefficient k, calculated by the divider 35, is supplied to the divider 36. The divider 36 is also supplied with a sampling cycle signal T S1 from the terminal 33. This divider 36, in which the division (T S1 /k) = T S2 is executed, generates a sampling cycle signal T S2 for the sample-and-hold circuit 32. Thus, in the third embodiment, the holding time T S2 of the sample-and-hold circuit 32, as compared to the holding time T S1 of the sample-and-hold circuit 31, is given as: T S2 = (T S1 /k) , thereby making it possible to eliminate wow and flutter from the reproduced signals. What has been described above also applies to recording operation, in which the switches SW 1 to SW 3 are connected to R-terminal. That is, due to the signal processing operation of the signal processing section 30, analog audio signals having a proper waveform with respect to the time axis dimension can be recorded on the magnetic tape 1. Apart from this, the third embodiment is advantageous in that it can be employed in an apparatus in which no digital circuit section is incorporated. It goes without saying that the present invention is not restricted to the above-described embodiments but allows various modifications without departing too much from the scope of the gist of the present invention. For example, while in the above-described embodiments the speed detector for detecting the transporting speed of the magnetic tape is formed by a roller adapted to rotate with the transporting of the magnetic tape and a rotary encoder for detecting the rotation of the roller, this should not be construed restrictively. Instead of using a detector specifically designed to detect the transporting speed of the magnetic tape, it is also possible to provide a rotation detector for detecting the rotation of the capstan shaft for transporting the magnetic tape. In that case, information on the transporting speed of the magnetic tape can be obtained on the basis of a signal output from this rotation detector. Further, it is also possible to use, instead of a speed detector of the above-described type, which uses a roller held in direct contact with the magnetic tape, a non-contact-type speed detector, such as a laser doppler device.

Claims: A recording and/or reproducing apparatus for a tape-shaped recording medium (1), said apparatus comprising: a recording and/or reproducing head (2) for recording and/or reproducing analog signals on and/or from the tape-shaped recording medium; characterized by detecting means (10) for detecting any fluctuation in the transporting speed of the tape-shaped recording medium with respect to a rated transporting speed; and compensating means (11, 21, 30) which modifies, on the basis of detection results from said detecting means, the analog signals, read out from or to be recorded on the tape-shaped recording medium by said head (2), as to compensate for the effect of any fluctuation in the transporting speed of the tape-shaped recording medium (1) with respect to the rated transporting speed before outputting these analog signals or supplying them to said head. A recording and/or reproducing apparatus according to claim 1, wherein said detecting means (10) comprises computation means (18, 28, 35) for computing the ratio of a detected transporting speed of the tape-shaped recording medium (1) to said rated transporting speed. A recording and/or reproducing apparatus according to claim 1 or 2, wherein said detecting means (10) further comprises speed detecting means (10b) for detecting the transporting speed of the tape-shaped recording medium (1). A recording and/or reproducing apparatus according to claim 3, wherein said speed detecting means comprises a rotary operating section (10a) to be rotated by the tape-shaped recording medium (1) and pulse generating means (10b) for generating pulses having a cycle which varies in accordance with said rotating operation of said rotary operating section. A recording and/or reproducing apparatus according to claim 1, wherein said compensating means (11) comprises clock pulse generating means (15, 16), A/D conversion means (12) for converting analog signal read from or to be recorded on the tape-shaped recording medium (1) by said head (2) into digital signals by means of clock pulses from said clock pulse generating means (15, 16), and signal generating means (13) for generating, out of the digital signals from said A/D conversion means (12), analog signals in which effect of any fluctuation in the transporting speed of the tape-shaped recording medium (1) with respect to the rated transporting speed has been compensated for on the basis of the detection results from said detecting means (10). A recording and/or reproducing apparatus according to claim 5, wherein said signal generating means comprises D/A conversion means for converting the digital signals from said A/D conversion means (14) into analog signals, and wherein said clock pulse generating means (16) generates first clock pulses to be supplied to said A/D conversion means (12) and second clock pulses to be supplied to said D/A conversion means (14) in accordance with the output from said detecting means. A recording and/or reproducing apparatus according to claim 5, wherein said signal generating means comprises interpolation means (23) which converts the digital signals from said A/D conversion means into digital signals which would be obtained if the tape-shaped recording medium (1) were transporting at the rated speed, and performs interpolation processing on the digital signals thus obtained through conversion, and D/A conversion means (14) for converting the digital signals from said interpolation means into analog signals. A recording and/or reproducing apparatus according to claim 1, wherein said compensating means comprises first sample-and-hold means (31) which performs a sample-and-hold operation in a first cycle on analog signals read out from or to be recorded on the tape-shaped recording medium by said head, and second sample-and-hold means (32) which performs a sample-and-hold operation on the output from said first sample-hand-hold means (31), in a second cycle that is obtained by modifying said first cycle for compensation on the basis of detection results from said detecting means. An audio signal processing apparatus comprising: clock pulse generating means (15, 16; 25, 26); and A/D conversion means (12, 22) for converting analog signals input on the basis of clock pulses from said clock pulse generating means into digital signals; characterized by computation means (18, 28, 35) for computing a fluctuation in the transporting speed of a tape-shaped recording medium with respect to a rated transporting speed on the basis of results of detection of the transporting speed of the tape-shaped recording medium; and signal generating means (13, 23) which generates, out of the digital signals from said A/D conversion means, analog signals in which the effect of the fluctuation in the transporting speed with respect to the rated transporting speed has been compensated for on the basis of the computation results from said computation means, and outputs the analog signal thus generated. An audio signal processing apparatus according to claim 9, wherein said computation means (18, 28, 35) obtains the ratio of the actual transporting speed of the tape-shaped recording medium (1) to said rated transporting speed on the basis of the results of detection of the transporting speed. An audio signal processing apparatus according to claim 9, wherein said signal generating means comprises D/A conversion means (14, 24) for converting the digital signals from said A/D conversion means (12, 22), and wherein said clock pulse generating means (15, 16; 25, 26) generates first clock pulses to be supplied to said A/D conversion means (12, 22) and second clock pulses to be supplied to said D/A conversion means (14, 24) in accordance with the ratio as output from said computation means. An audio signal processing apparatus according to claim 11, wherein said signal generating means comprises interpolation means (23) which converts, on the basis of the detection results from said computation means, the digital signals from said A/D conversion means into digital signals which would be obtained if the ratio as supplied from said computation means were 1, and performs interpolation on the digital signals thus obtained, and D/A conversion means (24) for converting the digital signals from said interpolation means into analog signals.

Inventors: YAMADA EIICHI, YAMADA, EIICHI
Applicants: SONY CORP, SONY CORPORATION
Application year: 1995
Main classification: G11B5
IPC codes: G11B5, G11B20, G11B15