JPH0877710A - Sound signal reproducing device - Google Patents

Abstract

PURPOSE: To reduce the generation of an abnormal sound during reproducing at a variable speed and to reproduce a high quality audio signal by detecting the discontinuous cycle of a reproducing signal and suppressing a signal component made with this discontinuous cycle as a basic cycle and a high frequency component thereof. CONSTITUTION: During reproducing, the wave forms of reproducing signals PB obtained from a magnetic head 9 are equalized by a RF equalizer 13 after passing through an amplifier circuit 12 and converted into reproducing data by a channel decoder 14. ID information S4 is detected from these reproducing data by an ID detection circuit 15 and the error thereof is corrected by an error correction circuit 16. Further, reproducing data is deshuffled a deshuffling circuit 17, converted into a digital audio signal S5 , converted into a analog signal by a D/A conversion circuit 19 and outputted. During reproducing at a variable speed, discontinuity of reproducing signals is detected by a discontinuity detecting circuit 31, an discontinuous timing is detected, an audio signal S5 is cross-faded by a cross-fading circuit 20 based on this and a noise component made of the higher harmonic of the audio signal S5 is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio signal reproducing apparatus, and can be applied to, for example, a digital video tape recorder, a digital audio tape recorder or the like.

[0002]

2. Description of the Related Art Conventionally, in a magnetic recording / reproducing apparatus such as a digital video tape recorder or a digital audio tape recorder, recording tracks are sequentially formed obliquely on a magnetic tape to record / reproduce a digital audio signal. .

For example, in a digital video tape recorder, an audio signal input in the form of an analog signal is converted into a digital signal at a predetermined sampling frequency to generate a digital audio signal. Further, the digital video tape recorder shuffles the digital audio signal thus generated or the digital audio signal input through the digital audio interface in predetermined block units, and then performs error correction in the product code format. A code is added and modulation is performed by a predetermined modulation method.

On the other hand, a video signal is similarly converted into a digital signal, shuffled, added with an error correction code in a product code format, and modulated by a predetermined modulation method. When the data to be recorded is generated in this way, the digital video tape recorder drives a plurality of sets of magnetic heads mounted on the rotating drum by these data, and thereby a plurality of pairs of recording tracks are recorded.
The digital audio signal and the digital video signal are segment-recorded as a set.

On the other hand, at the time of reproduction, the digital video tape recorder amplifies a reproduction signal obtained through the magnetic head by a head amplifier and then demodulates the data reproduced in each processing system of the digital video signal and the digital audio signal. Then, the demodulated data is subjected to error correction processing. Further, the digital video tape recorder is adapted to deinterleave the demodulated data and interpolate the demodulated data as necessary, thereby reproducing the high density recorded digital audio signal together with the digital video signal.

In this series of processes, the digital video tape recorder adds an error correction code to record a digital audio signal and, at the time of reproduction, performs an error correction process using this error correction code, whereby the digital audio signal is recorded. Effectively avoids bit errors in.

Further, the magnetic recording / reproducing apparatus interleaves the digital audio signal at the time of recording, and performs segment recording using a plurality of pairs of recording tracks.
At the time of reproduction, the data recorded in the segment is deinterleaved and interpolated if necessary, thereby effectively avoiding the influence of dropout or the like.

As a result, the digital video tape recorder effectively avoids the deterioration of the sound quality not only of the digital video signal but also of the digital audio signal, and reproduces the digital audio signal of high sound quality even when repeatedly recorded and reproduced. Is made possible.

[0009]

By the way, in a digital video tape recorder, there is a case where variable speed reproduction is performed for the beginning of editing work. In this case, in the digital video tape recorder, one magnetic head crosses a plurality of recording tracks diagonally and outputs a reproduction signal.

Therefore, in this case, in the digital video tape recorder, discontinuous reproduction data is obtained at the boundary of the timing when the magnetic head crosses the recording track. Further, even when tracking control is performed using a so-called dynamic tracking head, by performing a track jump, discontinuous reproduction data can be obtained at the time of this track jump.

In this discontinuous reproduction data, the original audio data cannot be completely reproduced even by the interpolation process.
After all, in this case, in the digital video tape recorder,
An abnormal sound is generated in the reproduced audio signal, and there is a problem that this abnormal sound is difficult to hear.

In order to solve this problem, in the conventional digital video tape recorder, a so-called cross-fade method is applied to join discontinuous reproduction data, but this method also makes it difficult to hear. However, there is still a practically insufficient problem.

There is also a method of muting a reproduced audio signal during a period in which an abnormal sound is generated. However, since the reproduced audio signal is intermittently output,
Even in this case, there is a problem that the listening difficulty cannot be completely eliminated.

The present invention has been made in consideration of the above points, and an object thereof is to propose an audio signal reproducing apparatus capable of reducing abnormal noise during variable speed reproduction.

[0015]

In order to solve such a problem, in the first invention, a reproduction signal PB obtained from recording tracks T1, T2, T3, ... Formed on an audio signal recording medium 2 is demodulated, These recording tracks T
In the audio signal reproducing device 1 for reproducing the audio signal S5 recorded in 1, T2, T3, ... From the audio signal S5, the cycle detecting means 30 for detecting the discontinuous cycle Tj of the reproduced signal PB due to the track jump, A signal component having this discontinuous period Tj as a fundamental period and a filter circuit 21 for suppressing harmonic components 2Tj, 3Tj, ... Of this signal component are provided.

In particular, the audio signal S5 can be applied when it is a digital audio signal.

Further, an acceleration / deceleration detecting means 30 for detecting a change in the reproduction speed of the audio signal S5 is added to the audio signal reproducing apparatus 1, and the Q of the filter circuit 21 is reduced when the reproduction speed is accelerating or decelerating. To do so.

In particular, in the audio signal reproducing device 1, a reproducing speed detecting means 3 for detecting the reproducing speed of the audio signal S5.
0 is added, and the discontinuous cycle Tj is detected based on the reproduction speed detected by the reproduction speed detecting means 30.

Further, in this audio signal reproducing apparatus 1,
The discontinuity of the reproduction signal PB is detected by the address added to the digital audio signal S5.

Particularly, in the filter circuit 21, when the reproduction speed is accelerating or decelerating, the discontinuous cycle Tj detected by the reproduction speed detecting means 30 causes the discontinuous cycle Tj to be a basic cycle. , And the harmonic components 2Tj, 3Tj, ... Of this signal component are suppressed, and when the reproduction speed is held at a constant value, the discontinuous period Tj is basically determined by the discontinuous period Tj detected by the address. A signal component having a cycle and harmonic components 2Tj, 3Tj, ... Of this signal component are suppressed.

Further, when the audio signal recording medium is a magnetic tape, the acceleration / deceleration detecting means 30 uses the magnetic tape 2
The drive current I of the capstan motor 8 that drives the vehicle is monitored to detect a change in the reproduction speed of the audio signal S5,
The reproducing speed detecting means 30 detects the traveling speed of the magnetic tape 2 relative to the rotating drum 7 to detect the reproducing speed of the audio signal S5.

Further, the present invention can be applied to the case where the audio signal recording medium is a disc-shaped recording medium.

Further, in this audio signal reproducing apparatus 1,
At this discontinuous timing, the audio signal S5 obtained from the preceding recording track and the audio signal S5 obtained from the following recording track are cross-faded and output.

[0024]

The discontinuous period Tj of the reproduction signal PB due to the track jump is detected, and the signal component having the discontinuous period Tj as the basic period and the harmonic component 2T of this signal component are detected.
By suppressing j, 3Tj, ..., Abnormal noise can be reduced accordingly.

In particular, when the audio signal S5 is a digital audio signal, it can be applied to reduce annoying noise.

Further, if the acceleration / deceleration detecting means 30 for detecting the change of the reproduction speed of the audio signal S5 is added and the Q of the filter circuit 21 is reduced when the reproduction speed is accelerating or decelerating, the change of the reproduction speed. It is possible to suppress the signal component having the discontinuous period Tj as the fundamental period and the harmonic components 2Tj, 3Tj, ... Of this signal component only by intermittently switching the characteristics of the filter circuit 21 in response to the above. it can.

In particular, the audio signal reproducing apparatus 1 has a reproduction speed detecting means 3 for detecting the reproduction speed of the audio signal S5.
By adding 0, the discontinuous cycle can be detected based on the reproduction speed detected by the reproduction speed detecting means 30, and the discontinuous cycle Tj can be easily detected.

In the audio signal reproducing device 1,
The discontinuity of the reproduction signal PB can be detected by the address added to the digital audio signal S5, and the discontinuous cycle Tj can be detected with high accuracy.

As a result, in the filter circuit 21, when the reproduction speed is accelerating or decelerating, the reproduction speed detecting means 3
With the discontinuous period Tj detected by 0, the signal component having the discontinuous period Tj as the fundamental period and the harmonic components 2Tj, 3Tj, ... Of this signal component are suppressed, and the reproduction speed becomes a constant value. When held, the discontinuous period Tj detected by the address suppresses the signal component whose basic period is the discontinuous period Tj and the harmonic components 2Tj, 3Tj, ... Of this signal component. The characteristics of the filter circuit 21 can be switched according to the change in the reproduction speed, and at this time, the sound quality deterioration can be effectively avoided and these signal components can be suppressed.

In particular, when the audio signal recording medium is the magnetic tape 2, the acceleration / deceleration detecting means 30 monitors the drive current I of the capstan motor 8 that drives the magnetic tape 2 to determine the reproduction speed of the audio signal S5. The change is detected, and the reproducing speed detecting means 30 detects the relative traveling speed of the magnetic tape 2 with respect to the rotating drum 7 to detect the reproducing speed of the audio signal S5 to easily detect the discontinuous period Tj and the like. can do.

Further, the present invention can be applied to the case where the audio signal recording medium is a disc-shaped recording medium, and the abnormal noise can be reduced.

Further, in this audio signal reproducing apparatus 1,
You can crossfade and output an audio signal to further improve your hearing.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a digital video tape recorder as a whole, which records a digital audio signal and a digital video signal on a magnetic tape 2.

That is, in the digital video tape recorder 1, the magnetic tape 2 is run at a predetermined running speed by the capstan motor 8 while being wound around the rotary drum 7 by the tape guides 3 to 6. The rotary drum 7 has a plurality of pairs of magnetic heads 9 mounted thereon, and is rotated at a predetermined rotation speed by a drum motor, so that a scanning locus of the magnetic heads 9 is sequentially formed on the magnetic tape 2 obliquely.

As a result, the digital video tape recorder 1 is operated by the rotary transformer 10 in the recording mode.
A plurality of pairs of magnetic heads 9 are driven through the recording medium to sequentially form recording tracks obliquely on the magnetic tape 2 to segmentally record a digital audio signal and a digital video signal. That is, the digital video tape recorder 1 performs shuffling processing on a sequentially input digital audio signal and digital video signal in predetermined block units, and then adds an error correction code in a product code format, a sync, and the like. Further, the digital video tape recorder 1 modulates by a modulation method suitable for the characteristics of the magnetic recording / reproducing system, and drives the magnetic head 9 through the rotary transformer 10 by the resulting modulation signal.

On the other hand, in the normal reproduction mode,
The digital video tape recorder 1 obtains a control signal from a control track formed in the longitudinal direction of the magnetic tape 2 and controls the magnetic tape running system based on this control signal to perform tracking control. As a result, as shown in FIG. 2, the digital video tape recorder 1 has the recording tracks T1, T2, ...
Are scanned by the corresponding magnetic heads 9 and reproduction signals PB obtained from these magnetic heads 9 are input to the selection circuit 11 via the rotary transformer 10.

The selection circuit 11 switches the contacts at a timing synchronized with the rotation cycle of the rotary drum 7, whereby the reproduction signal PB obtained from each magnetic head 9 during the period in which each magnetic head 9 scans the magnetic tape 2. Is output to the amplifier circuit 12. The amplification circuit 12 amplifies the reproduction signal PB with a specified gain and outputs the amplified reproduction signal PB, and an RF equalizer (RF EQ).
Reference numeral 13 waveform-equalizes the output signal of the amplifier circuit 12 and outputs it.

The channel decoder 14 binarizes the output signal of the RF equalizer 13 and converts it into serial data, and then decodes and outputs this serial data, thereby performing a demodulation process corresponding to the modulation method at the time of recording. To execute. The ID detection circuit 15 uses the channel decoder 14
By detecting the sync added at the time of recording from the output data of, the address of the output data specified by this sync is detected, and this output data is sequentially output to the subsequent error correction circuit (ECC) 16 based on this address. To do.

The error correction circuit 16 performs error correction processing on this output data by using the error correction code of the product code format added at the time of recording, and outputs the error-corrected output data together with the error correction processing result. The deshuffling circuit 17 deshuffles the output data of the error correction circuit 16 to convert this data string into a data string for recording and output it. At this time, the deshuffling circuit 17 performs interpolation calculation processing based on the error correction processing result of the error correction circuit 16, and interpolates and outputs the data that has not been error corrected.

As a result, the digital video tape recorder 1 can reproduce the original digital audio signal via the deshuffling circuit 17, and the digital audio signal is converted into an analog signal by the digital-analog conversion circuit (D / A) 19. It is designed to be converted into a format and output. In the digital video tape recorder 1, even in the video system, the reproduction signal PB of the magnetic head 9 is processed to reproduce the video signal as in the audio system described above.

By the way, assuming that a sinusoidal signal of frequency fs is supplied to the magnetic head 9 to form the respective recording tracks T1, T2, ..., Thus, the recording tracks T1, T2 ,. .. are sequentially scanned correctly, the reproduction signal PB has a frequency f as shown in FIG.
At s, the signal level changes continuously in a sinusoidal manner. In this case, as shown in FIG. 4, the frequency spectrum of the reproduction signal PB is represented by a single spectrum of the frequency fs.

On the other hand, when the magnetic tape on which the recording track is formed by the sine wave signal having the frequency fs as described above is run at a double speed, for example, as shown in FIG. After the scanning of the tracks T1, T3, T5 ... Is started, the track jumps to the recording tracks T2, T4, T6. In this case, as shown in FIG. 6, the reproduction signal PB obtained from the magnetic head 9 includes track jump points P1 and P.
Discontinuity occurs at 2 and P3, and if the repetition cycle of this discontinuity is set to Tj, a spectrum can be expressed as shown in FIG.

That is, in this case, the sine wave signal of the frequency fs becomes discontinuous, which means that the sine wave signal of the frequency fs is distorted, and the frequencies 2fs, 3fs, and A harmonic of ... Is generated. From this, it can be seen that this harmonic contributes to noise.

Further, in this case, the discontinuity is repeated in the cycle Tj, whereby a noise component represented by the frequency fj = 1 / Tj is generated in the repetition cycle Tj.
Further, harmonics are also generated in the noise component of the frequency fj. Therefore, in this case, it can be seen that, by suppressing not only the harmonic of the frequency fs but also the noise component of the frequency fj and the harmonic of this noise component, abnormal noise can be reduced in terms of hearing.

On the other hand, in an actual digital video tape recorder, after the digital audio signal is shuffled, an error correction code or the like is added and further modulated and recorded. Therefore, in an actual digital video tape recorder, the original frequency band of the reproduction signal PB is wider than that in this description, and the digital audio signal after reproduction is deshuffled to
It is obvious that the spectrum and the signal waveform are different from the case of such a single frequency fs.

However, regarding the noise component having the discontinuous repeating period Tj as the basic period, the frequency of the reproduced digital audio signal is basically the frequency fj and the frequency of twice, triple, ... Of this frequency fj. The frequency band occurs due to the above-mentioned relationship, and the original frequency band of the reproduced signal PB is wide, so that the sidebands of the noise component are widened from the frequencies fj, fj, double, triple, ... .

Therefore, with respect to the noise component having the discontinuous repeating period Tj as the basic period, the frequencies fj, 2
By suppressing the noise with a comb filter in which fj, 3fj, ... Are set to cutoff frequencies, it is possible to reduce abnormal sounds in the sense of hearing. Further, the discontinuous repetition period Tj changes depending on the traveling speed of the magnetic tape 2, so that the traveling speed of the magnetic tape 2 is detected and the frequency characteristic of the comb filter is switched. Even when the reproduction speed is selected, it is possible to suppress these noise components having the discontinuous repeating cycle Tj as the basic cycle.

On the other hand, a noise component having a harmonic relationship to the original spectrum of the reproduced signal PB (in FIG. 7, components having frequencies 2fs, 3fs, ...)
Can be suppressed by executing the crossfade processing which is a conventional method. Based on this noise suppression principle,
The digital video tape recorder 1 reduces noise by using the crossfade circuit 20 and the adaptive filter circuit 21 in the variable speed reproduction mode.

That is, in the digital video tape recorder 1, the rotary drum 7 has an FG (Frequency Genera).
tor) and PG (Phase Generator)
G outputs a sinusoidal frequency signal DFG whose frequency changes according to the rotation speed of the rotating drum 7, and PG outputs a rotation phase signal DPG whose signal level rises in a pulse according to the rotation phase of the rotating drum 7. Output.

The amplifier circuits 23 and 24 amplify and output the frequency signal DFG and the rotation phase signal DPG, respectively, and the waveform shaping circuit 25 shapes the output signal of the amplifier circuit 23 into a waveform so that the rotary drum 7 is semi-translated. The detector 30 receives the drum FG signal S1 whose logical level is inverted in the rotation cycle.
Output to. The waveform shaping circuit 26 outputs the drum PG signal S2 whose logical level rises in synchronization with the rising of the signal level of the rotation phase signal DPG to the detector 30 by shaping the output signal of the amplifier circuit 24.

Thus, in the digital video tape recorder 1, the detector 30 can detect the scanning start timing of the magnetic head 9 and the rotational phase of the rotary drum 7 by the drum FG signal S1 and the drum PG signal S2. Has been done. In addition, in the digital video tape recorder 1, in addition to this, the drum FG is added.
The drum motor is driven based on the signal S1 and the drum PG signal S2, and the rotary drum 7 is rotationally driven at a constant rotational speed.

Similarly, the capstan motor 8 also has a built-in FG, the amplifier circuit 27 amplifies and outputs the frequency signal DFG output from this FG, and the waveform shaping circuit 28 outputs the output signal of the amplifier circuit 27. The waveform of the capstan FG signal S3 whose logic level is inverted in a cycle in which the capstan motor 8 rotates by a predetermined angle is applied to the detector 3
Output to 0. Thus, in the digital video tape recorder 1, the detector 30 can detect the running speed of the magnetic tape 2 by detecting the cycle of the capstan FG signal S3 with reference to the normal reproduction.

The ID detection circuit 15 determines the sync detected from the output data of the channel decoder 14 as sync information S
Output to detector 30 as 4 and detector 30
When the user selects the operation mode of variable speed reproduction, the discontinuity detection circuit 31 is activated and the sync information S4 is output to the discontinuity detection circuit 31. Here, the discontinuity detection circuit 31 determines whether or not consecutive addresses are assigned to the data sequentially input to the ID detection circuit 15 based on the sync information S4, and when consecutive addresses are not assigned here, a track jump is performed. Is determined to have occurred.

That is, in this type of digital video tape recorder 1, continuous addresses are assigned as syncs to record audio data and video data. In this embodiment, discontinuity of these addresses is detected. Detect a track jump.

Further, when the track jump is detected in this way, the discontinuity detection circuit 31 sequentially switches the parameters to be output to the crossfade circuit 20, thereby executing the crossfade processing.

That is, the crossfade circuit 20 weights the output data of the deshuffling circuit 17 according to the parameter output from the discontinuity detection circuit 31 and outputs the weighted output data, whereby the deshuffling circuit 17 corresponding to the discontinuous reproduction signal PB is output. Cross-fade output data and output. That is, as shown in FIG. 8, the crossfade circuit 20 receives the digital audio signal S5 in the period corresponding to the discontinuous points P1, P2, P3 ,.
Regarding reproduction data obtained from the preceding recording track side, the signal level becomes smaller as the data is delayed and output on the time axis with the discontinuous timing in between, and from the following recording track side. With respect to the obtained reproduction data, the audio data that are successively continuous are weighted so that the data that is delayed and output on the time axis becomes closer to the regular signal level with the discontinuous timing interposed therebetween. As a result, as shown in FIG. 9, in the digital audio signal output through the crossfade circuit 20, the harmonic components of the digital audio signal are suppressed and output, and the abnormal noise is reduced accordingly. can do.

Further, in the variable speed reproduction mode, the detector 30 detects the discontinuous repeating period Tj by the built-in notch frequency measuring circuit 32, and switches the characteristic of the adaptive filter circuit 21 according to the detection result, whereby The noise component having the discontinuous repeating cycle Tj as a basic cycle is suppressed. At this time, the detector 30 monitors the driving current I of the capstan motor 8 to monitor the acceleration and deceleration of the magnetic tape 2, and when the running speed of the magnetic tape 2 becomes a constant value, the operation of the notch frequency measuring circuit 32 is performed. And the characteristics of the adaptive filter circuit 21 are switched.

That is, when the user operates the jog dial to change the running speed of the magnetic tape 2, or when the magnetic tape 2 is rising to the reproduction speed specified by the user, the running speed of the magnetic tape 2 is accelerated. Alternatively, the decelerating state is maintained, and at this time, the detector 30 causes the capstan FG signal S3, the drum FG signal S1 and the drum P to be released.
In order to measure the repeating period Tj by the G signal S2,
The operation of the notch frequency measuring circuit 32 is switched.

As a result, the notch frequency measuring circuit 32 is
The timing at which the signal level of the capstan FG signal S3 switches is monitored with reference to the scanning timing of the magnetic head 9 (that is, the rotational phase of the rotary drum 7) detected by the drum FG signal S1 and the drum PG signal S2. Then, the reproduction speed is measured by this, and the discontinuous period Tj described above is measured.

Here, when the magnetic tape 2 is continuously running at a running speed that is an integral multiple of the speed during normal reproduction, as described above with reference to FIG. 5, it is always at a constant timing (in the case shown in FIG. The magnetic head 9 makes a track jump at almost the middle timing. However, when the running speed of the magnetic tape 2 deviates from an integral multiple during normal reproduction, in each magnetic head 9, the period from the start of scanning to the timing of the track jump changes for each scan.

Further, when the running speed of the magnetic tape 2 enters the double running speed while the running speed of the normal reproduction is changing from the running speed of the normal reproduction to the triple running speed, in this case, the magnetic head 9 makes the corresponding recording. By not starting the scanning of the track in the just tracking state, the track jump timing is deviated to the scanning start end side or the scanning end end side even though the traveling speed is an integral multiple of the normal reproduction speed.

Therefore, in this embodiment, not only the reproduction speed obtained by simply detecting the period of the capstan FG signal S3, but also the reproduction speed is taken into consideration by considering the rotation phase of the rotary drum 7 as well. Cycle Tj of
This ensures that the noise component can be suppressed.
Thus, when the notch frequency measuring circuit 32 detects the discontinuous period Tj in this way, as shown in FIG.
A noise component having this discontinuous period Tj as a basic period and a coefficient of the adaptive filter circuit 21 are set so as to suppress this noise component.

As a result, as shown in FIG. 11, the adaptive filter circuit 21 can suppress the noise component (the signal component indicated by the diagonal lines in FIG. 11) that could not be suppressed by the crossfade process, and as a result, Abnormal noise can be significantly reduced as compared with the related art, and the quality of hearing can be improved.

In this way, when the traveling speed of the magnetic tape 2 is being accelerated or decelerated, the detector 30
The coefficient is set so as to reduce the Q of the adaptive filter circuit 21. That is, when the running speed of the magnetic tape 2 is in the middle of acceleration or deceleration, the discontinuous repeating cycle Tj also changes following this change in running speed, and the filter circuit 21 follows this change in running speed. Therefore, it is necessary to switch the coefficient.

However, in such a case, when the user operates the jog dial to gently change the traveling speed, the coefficient can be switched in accordance with the change in the traveling speed. However, if this change in running speed is fast, it is necessary to change the coefficient frequently,
The configuration of the filter circuit 21 becomes complicated accordingly. However, if the Q of the filter circuit 21 is reduced as in this embodiment, frequent switching of the coefficients can be avoided, and the characteristics of the filter circuit 21 can be switched intermittently to suppress noise sufficiently. be able to.

On the other hand, when the running speed of the magnetic tape 2 is kept at a constant value, the detector 30 makes a notch so as to measure the repetition cycle Tj based on the ID information S4 output from the ID detection circuit 15. Frequency measuring circuit 32
And the Q of the filter circuit 21 is set high. Here, the notch frequency measuring circuit 32 detects the discontinuous period Tj from the actual reproduction data by applying the same method as that of the discontinuity detecting circuit 31 described above,
In order to suppress the noise component with j as the basic period,
The coefficient of the filter circuit 21 is switched.

As a result, in the digital video tape recorder 1, when the reproduction speed becomes a constant value and it becomes unnecessary to switch the coefficient of the filter circuit 21, the noise component is surely generated by the discontinuous cycle Tj detected by the actual reproduction data. The audio signal S5 reproduced by suppressing the
It effectively avoids the deterioration of sound quality and reduces noise. Further, at this time, by setting the Q of the filter circuit 21 high, for the audio signal components other than the noise component, the sound quality deterioration is effectively avoided and the noise is suppressed. It can be improved significantly.

In the above configuration, the digital audio signals sequentially input at the time of recording are shuffled in a predetermined block unit to obtain an error correction code in a product code format,
After a sync or the like is added, it is modulated and segment-recorded on the magnetic tape 2.

On the other hand, at the time of reproduction, after the reproduction signal PB obtained from the magnetic head 9 is amplified by the amplifier circuit 12,
The waveform is equalized by the RF equalizer 13 and converted into reproduction data by the subsequent channel decoder 14. This reproduced data is further decoded by the channel decoder 14, and then I
The D detection circuit 15 detects the ID information S4, and the error correction circuit 16 subsequently performs error correction processing. Further, the reproduced data is deshuffled by the subsequent deshuffling circuit 17, converted into a digital audio signal S5, converted into an analog signal by a digital / analog conversion circuit 19, and output.

In this series of reproduction systems, during variable speed reproduction, the discontinuity timing is detected in the reproduction signal PB by detecting the continuity of the sync by the discontinuity detection circuit 31, and this timing is used as a reference. In the cross-fade circuit 20, the digital audio signal S5 is cross-faded before and after the track jump, so that the noise component formed by the harmonics of the digital audio signal S5 is suppressed.

During the variable speed reproduction, the digital video tape recorder 1 detects the acceleration / deceleration of the magnetic tape 2 by the drive current I of the capstan motor 8. Here, when the magnetic tape 2 is accelerating and decelerating, the reproduction signal PB is
With the capstan FG signal S3, the drum FG signal S1, and the drum PG signal S2, a discontinuous cycle Tj is detected from the rotational speed of the capstan motor 8 based on the rotation phase of the rotary drum 7, and this discontinuous cycle Tj. Is suppressed by the filter circuit 21 and its harmonics. At this time, this filter circuit 2
By setting the Q of 1 to a low value, the filter circuit 21 suppresses the noise component having the discontinuous period Tj as the basic period corresponding to the change in the reproduction speed, and its harmonics.

Further, when the running speed of the magnetic tape 2 becomes a constant value, a discontinuous period Tj is detected from the ID information S4 in the reproduction signal PB, and a noise component having the discontinuous period Tj as a basic period, The harmonics are suppressed by the filter circuit 21. At this time, this filter circuit 2
When Q of 1 is set to a high value, the sound quality deterioration of the digital audio signal S5 is effectively avoided, and these noise components are suppressed by the filter circuit 21.

According to the above configuration, the discontinuous period Tj of the reproduction signal PB is detected, and the noise component having the discontinuous period Tj as the basic period and its harmonics are adapted so as to be suppressed. By switching the characteristics of the mold filter circuit 21, it is possible to effectively avoid the generation of abnormal noise during variable speed reproduction, and reproduce a high quality audio signal in terms of hearing.

In the above-mentioned embodiment, the case where each magnetic head jumps across the recording track obliquely during the variable speed reproduction is described, but the present invention is not limited to this, and a so-called dynamic tracking method is used. Even when it is applied, a noise component having a discontinuous period of the above-mentioned reproduced signal as a fundamental period and a harmonic of this noise component are generated. The sound can be reduced.

Further, in the above-described embodiment, the case where the crossfade circuit and the adaptive filter circuit are combined to reduce the abnormal noise is described, but the present invention is not limited to this, and the miuting process and the adaptive filter are performed. It can be widely applied to the case where it is combined with a circuit, and in a practically sufficient range, abnormal noise may be reduced only by the adaptive filter circuit.

Further, in the above-mentioned embodiment, the case where the discontinuity of the reproduced signal is directly detected from the sync information has been described, but the present invention is not limited to this, and the change of the envelope of the reproduced signal is detected to detect the discontinuity. Various detection means can be widely applied, such as in the case of detection.

Further, in the above-described embodiments, the case where the cutoff frequency and Q are switched in the adaptive filter circuit has been described, but the present invention is not limited to this, and when the practical use is sufficient, the switching of Q is omitted. May be.

Further, in the above-mentioned embodiment, the case of switching the method of detecting discontinuity between the acceleration and deceleration of the magnetic tape and the constant traveling speed is described, but the present invention is not limited to this and is practically sufficient. In the range, discontinuity may be detected by any of these methods, and switching of the discontinuity detection method may be omitted.

Further, in the above-mentioned embodiments, the case where the present invention is applied to the digital video tape recorder has been described, but the present invention is not limited to this, and for example, a digital audio tape recorder, and further an analog signal type video tape recorder. It can also be widely applied to PCM processors and the like utilizing the.

Further, in the above-mentioned embodiment, the case where the present invention is applied to the reproducing system of the digital audio signal has been described, but the present invention is not limited to this, and for example, the audio signal is frequency-multiplexed with the video signal and the magnetic tape. The present invention can also be applied to a video tape recorder or the like, which sequentially performs diagonal recording.

Further, in the above-mentioned embodiment, the case where the audio signal recorded on the magnetic tape is reproduced has been described, but the present invention is not limited to this, and the audio signal recorded on a disk-shaped recording medium such as a compact disk is recorded. It can be widely applied to the case of reproducing a signal. In this case, in the case where the recording tracks sequentially formed in the spiral shape on the disk-shaped recording medium are track-jumped and reproduced, the cycle of the track-jump is detected to detect the discontinuous cycle.

[0083]

As described above, according to the present invention, by detecting the discontinuous cycle of the reproduced signal and suppressing the signal component and the harmonic component thereof which have the discontinuous cycle as the basic cycle, It is possible to reduce the occurrence of abnormal noise during variable speed reproduction and reproduce a high quality audio signal in terms of hearing.

[Brief description of drawings]

FIG. 1 is a block diagram showing a digital video tape recorder according to an embodiment of the present invention.

2 is a schematic diagram showing a scanning locus of a magnetic head in normal reproduction by the digital video tape recorder of FIG.

FIG. 3 is a signal waveform diagram for explaining a reproduced signal in the state of FIG.

FIG. 4 is a characteristic curve diagram showing a spectrum of a reproduction signal in the state of FIG.

FIG. 5 is a schematic diagram showing a scanning locus of the magnetic head during variable speed reproduction corresponding to FIG.

FIG. 6 is a characteristic curve diagram corresponding to FIG. 3 and showing a spectrum of a reproduced signal at the time of variable speed reproduction.

FIG. 7 is a characteristic curve diagram corresponding to FIG. 4 and showing a spectrum of a reproduction signal during variable speed reproduction.

FIG. 8 is a signal waveform diagram for explaining a crossfade.

FIG. 9 is a characteristic curve diagram for explaining noise reduction by crossfade processing.

10 is a characteristic curve diagram showing frequency characteristics of the adaptive filter of the digital video tape recorder shown in FIG.

11 is a characteristic curve diagram for explaining noise reduction by the adaptive filter circuit of FIG.

[Explanation of symbols]

 1 Digital Video Tape Recorder 2 Magnetic Tape 9 Magnetic Head 20 Crossfade Circuit 21 Adaptive Filter 30 Detector 31 Discontinuity Detection Circuit 32 Notch Frequency Measurement Circuit

Claims (9)

[Claims] 1. An audio signal reproducing apparatus for demodulating a reproduction signal obtained from a recording track formed on an audio signal recording medium to reproduce an audio signal recorded on the recording track, wherein the reproduction signal is discontinuous due to a track jump. It is characterized by further comprising: cycle detecting means for detecting a cycle; a signal component of the audio signal, which has the discontinuous cycle as a basic cycle; and a filter circuit for suppressing a harmonic component of the signal component. Audio signal reproduction device. 2. The audio signal reproducing apparatus according to claim 1, wherein the audio signal is a digital audio signal. 3. The audio signal reproducing device has acceleration / deceleration detecting means for detecting a change in reproduction speed of the audio signal, and reduces Q of the filter circuit when the reproduction speed is accelerating or decelerating. The audio signal reproducing device according to claim 1 or 2, wherein 4. The audio signal reproducing apparatus has a reproducing speed detecting means for detecting a reproducing speed of the audio signal, and detects the discontinuous cycle based on the reproducing speed. The audio signal reproducing device according to claim 1, claim 2 or claim 3. 5. The audio signal reproducing apparatus according to claim 2, 3 or 4, wherein the address added to the digital audio signal detects discontinuity of the reproduced signal. Audio signal reproduction device. 6. The filter circuit, when the reproduction speed is accelerating or decelerating, the signal component having the discontinuous cycle as a basic cycle by the discontinuous cycle detected by the reproduction speed detecting means. A signal that suppresses the harmonic component of the signal component, and when the reproduction speed is held at a constant value, the discontinuous cycle detected by the address makes the discontinuous cycle a basic cycle. The audio signal reproducing device according to claim 5, wherein a component and a harmonic component of the signal component are suppressed. 7. The audio signal recording medium is a magnetic tape, and the acceleration / deceleration detecting means monitors a drive current of a capstan motor for running the magnetic tape to detect a change in reproduction speed of the audio signal. 6. The reproducing speed detecting means detects the traveling speed of the magnetic tape relative to the rotating drum to detect the reproducing speed of the audio signal. 6. The audio signal reproducing device according to item 6. 8. The audio according to claim 1, claim 2, claim 3, claim 4, claim 5 or claim 6, wherein the audio signal recording medium is a disk-shaped recording medium. Signal reproduction device. 9. The audio signal reproducing device crossfades and outputs the audio signal obtained from a preceding recording track and the audio signal obtained from a following recording track at the discontinuous timing. The audio signal reproducing apparatus according to claim 1, claim 2, claim 3, claim 4, claim 5, claim 6, claim 7, or claim 8.