JP2766065B2 - Digital signal recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable speed reproduction method in an apparatus for recording and reproducing digital audio.

[Conventional technology]

As a device for recording and reproducing digital audio, DAT is used for audio-only equipment, 8 mm VTR or digital VT is used for VTR.
There are D1 format and D2 format of R. All of the above-mentioned devices form tracks in the diagonal direction of the magnetic tape by the magnetic head provided on the rotating cylinder,
The magnetic head scans the formed track to record and reproduce digital audio signals. Digital audio is superior to conventional analog recorded audio in various characteristics, and analog audio is increasingly replacing digital audio. However, although digital audio is superior in performance, operation using analog audio is mainly performed depending on the purpose of use in some cases. In analog audio cueing, first perform coarse cueing while listening to the sound whose pitch has been increased by fast-forwarding the tape, then stop the tape and turn the reel around which the tape is wound by hand to reduce the sound that has decreased. Make fine positioning while listening. On the other hand, conventional digital audio devices have different characteristics from analog audio, such as noise, because the pitch of the reproduced audio does not change when the tape speed is changed, and the reproduced audio signal is discontinuous. Is shown. Among them, as a method for mitigating noise caused by discontinuity of a reproduced signal in variable speed reproduction, as described in Japanese Patent Application Laid-Open No. 2-148465, an example of cross-fading using audio data before and after discontinuity occurs. Have been reported.

As described above, digital audio has different properties from analog audio, and thus it may be unacceptable to users who are accustomed to operating analog audio.

[Problems to be solved by the invention]

In the conventional variable speed reproduction of digital audio, noise is generated because the reproduced audio signal is discontinuous, and it is hard to hear. Even if the generation of noise is reduced by a method such as cross-fade at a discontinuous point, the method of reproducing the audio signal especially at the time of low-speed reproduction is
It is significantly different from analog audio, and there is a problem that a user who has been accustomed to analog audio equipment has a sense of incongruity and is difficult to operate.

An object of the present invention is to provide a digital audio variable-speed playback apparatus that removes noise caused by discontinuity of an audio signal to be played back, and changes a voice pitch according to a tape speed so that digital audio can be played back. It is an object of the present invention to provide a digital audio device that can provide a feeling of use similar to that of an audio device, and does not cause a sense of incongruity to a user who is accustomed to using a conventional analog audio device.

[Means for solving the problem]

In order to achieve the above object, in a device for recording and reproducing digital audio on and from a magnetic tape by a rotating head, the rotating head is provided with a movable reproducing head movable in a rotation axis direction, and a clock whose frequency changes according to a tape traveling speed. And a memory for storing an audio signal.

[Action]

The movable reproducing head is controlled so as to always correctly scan the track recorded on the magnetic tape during variable speed reproduction, and operates so as to reproduce all the audio signals recorded on the track. The timing generation circuit obtains information related to the tape running speed and generates a clock whose frequency changes according to the information. The memory temporarily stores the reproduced audio signal and outputs an audio signal using a clock whose frequency changes according to the tape running speed as a read clock of the memory. Since the audio signal output by these becomes continuous, no noise is generated, the voice pitch changes according to the tape speed,
A feeling of use similar to that of analog audio equipment can be obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a block diagram showing a system configuration of a digital audio reproducing system according to one embodiment of the present invention. Hereinafter, the configuration of FIG. 1 will be described. 1 is a rotary cylinder, 2 is a magnetic tape, and 3 is a tape guide. The magnetic tape 2 is wound around the rotary cylinder 1 by a tape guide 3 by about 180 °. 4 is a magnetic head, 5 is a displacement element. The magnetic head 4 is fixed to the tip of the displacement element 5,
Two sets are provided 180 ° apart. The displacement element 5 is supplied with a voltage from the outside so that the rotating cylinder 2
In the direction of the rotation axis. 6 is a cylinder motor, 7 is a capstan, 8 is a pinch roller, and 9 is a capstan motor. The cylinder motor 6 is directly connected to the rotary cylinder 1. When a voltage is applied from the outside, the rotary cylinder 1 rotates and the magnetic head 4 scans the surface of the magnetic tape 2. The capstan 7 is directly connected to the capstan motor 9, and the magnetic tape 2 is
And the pinch roller 8, and further, a voltage is applied from the outside and the capstan motor 9 rotates, so that the magnetic tape 2 runs. 10 is a control head, 11 is a drum PG, 12 is a capstan FG, 13 is a servo circuit, 14 is a system control, and 15 is a tape running speed command. FIG. 2 is a diagram showing a tape pattern of the magnetic tape 2. T is a helical track, 40 is a control track, 41 is a control signal, 42 is a tape running direction, and 43 is a magnetic head scanning direction. The control head 10 scans the control track 40 and reproduces a control signal 41. The control signal 41 is one that is pulse-recorded once while one track T is recorded. The drum PG11 generates a pulse once during one rotation of the rotary cylinder 1. By detecting the timing at which the pulse is generated, the rotation phase of the rotary cylinder 1 can be detected. During reproduction, the servo circuit 13 controls the capstan motor 9 so that the timing of the control signal 41 reproduced by the control head 10 and the timing of the signal generated by the drum PG 11 become constant.
Operates to control the voltage applied to. Capstan
The FG 12 generates a signal having a frequency proportional to the rotation speed of the capstan 7. The frequency of the signal generated by the capstan FG 12 is detected by the servo circuit 13. Further, the servo circuit 13 controls the voltage applied to the capstan motor 9 so that the signal generated by the capstan FG12 becomes a frequency corresponding to the tape traveling speed instruction 15 given from the system control 14. Operate. 16 is a preamplifier 17 is a movable head control circuit, and 18 is a search dial. The preamplifier 16 is an amplifier for converting a signal generated when the magnetic head 4 scans the magnetic tape 2 to a signal level necessary for performing subsequent signal processing.

Hereinafter, the description of the configuration will be continued while describing a method of performing variable speed reproduction. When the search dial 18 is rotated, a pulse is generated accordingly. The pulse output is read by the system control 14, and this is output to the tape running speed command 15
And output. There are two modes for converting the pulse output from the search dial 18 into speed information. One is a mode for converting speed information according to the rotation angle of the search dial 18, that is, the number of pulse outputs, and the other is a search dial. There is a mode for converting into speed information according to the rotation speed of 18, that is, the frequency of the pulse output. Hereinafter, the former will be referred to as a variable throw mode, and the latter will be referred to as a jog mode. The tape running speed command 15 is transmitted to the servo circuit 13 as described above.
To the corresponding frequency.
Is operated so as to control the voltage applied to the capstan motor 9 so that the output of the capstan motor 9 is obtained. Also, during variable speed playback,
If the position of the magnetic head 4 is fixed, the inclination of the helical track T of the magnetic tape 2 does not match the inclination of the magnetic head in the scanning direction 43, and the magnetic head 4 cannot scan the helical track T correctly. Since the tape running speed and the deviation amount of the above-mentioned inclination have a fixed relationship, in order to correct this, the movable head control circuit 17 detects the frequency of the output signal of the capstan FG12 to obtain the tape running speed, and A voltage waveform to be applied to the displacement element 5 is generated to obtain a displacement amount of the magnetic head 4 that corrects a corresponding inclination shift amount. Further, in order to improve the followability of the magnetic head 4 to the helical track T, the output of the preamplifier 16 is input to the movable head control circuit 17 and is applied to the displacement element 5 so that the reproduction output level of the magnetic head 4 becomes maximum. Control is performed by subtly changing the control voltage.

Hereinafter, the description of the configuration will be continued while describing the signal processing of the reproduction signal. 19 is a waveform equalization, 20 is a data strobe, 21 is a demodulation, 22 is a decoder, and 23 is a digital audio signal. The reproduced signal from the magnetic head 4 is amplified by the preamplifier 16 and input to the waveform equalizer 19. The waveform equalizer 19 mainly functions as a filter for raising the level of a high frequency band in order to compensate for the high frequency characteristics of a signal degraded in the magnetic recording / reproducing process. With respect to the signal whose frequency characteristics have been corrected by the waveform equalization 19, the data strobe 20 detects a level change of the signal, generates a clock synchronized with the signal, and further binarizes the signal level using this clock as a detection point. A digital signal is generated. Typically,
In order to convert the signal into a signal having a spectrum that matches the frequency characteristics of the transmission path through which the signal is to be passed, the original digital signal is modulated at the time of recording based on a certain code conversion rule. In particular, in magnetic recording / reproducing using the rotating cylinder 1,
A modulation method that reduces the DC component is adopted to reduce the loss of the information amount due to the transmission path. The demodulation 21 performs an operation of restoring a modulated signal recorded and reproduced to a digital signal before modulation. Further, in recording a digital signal, in addition to converting an analog signal into a digital signal, shuffling operation of rearranging data, addition of an error correction code, a synchronization signal, an ID signal, and the like are performed. This is to prevent the quality of the finally output signal from being greatly affected by deterioration such as dropout of the signal at the time of reproduction. decoder
In the step 22, the reverse operation of the shuffling performed at the time of recording, the error correction processing by the error correction code, and the correction processing by the data interpolation or the like when the error correction is impossible, are performed. The digital audio signal 23 is generated by the above signal processing. SW1 is a playback mode switch,
24 is a DA converter and 25 is an audio signal output. The reproduction mode changeover switch SW1 is switched by a command of the system control 14, and a signal processing method is selected. When the reproduction mode changeover switch SW1 is turned to N (Normal), the digital signal is directly input to the DA converter 24 and output as the audio signal output 25. When the reproduction mode changeover switch SW1 is turned to V (Variable), audio signal processing at the time of variable speed reproduction, which is a feature of the present invention, is performed. This signal processing unit is mainly composed of two parts, a timing generation circuit 26 and a time axis processing 27. The timing generation circuit 26 outputs the capstan FG 12 and the tape traveling speed instruction 15 from the system control 14.
For example, the tape traveling speed information is obtained from the above, and the frequency of the timing signal input to the time axis processing 27 is changed accordingly. The time axis processing 27 temporarily stores the input audio signal in a memory, reads the audio signal from the memory using the timing signal generated by the timing generation circuit 26, and outputs the audio signal. These audio signal processing units will be described in more detail with reference to examples.

FIG. 3 is a block diagram showing an embodiment of the timing generation circuit 26, and FIG. 4 is a timing chart for explaining the operation of FIG. In FIG. 3, 50 is a counter, 51 is a reference clock, 52 is a microcomputer, 53 is a divider, CFG is a capstan FG output, CLK is a reference clock signal, COUNT is a count value, DIV is divider data, and NFs is an audio reference timing signal. , ^N / _M Fs is an audio conversion timing signal. The capstan FG output CFG is the capstan FG1 shown in Fig. 1.
2 is the output signal. Where the capstan FG output CFG is
It is assumed that the frequency becomes 2000 Hz when the tape running speed is 1 × speed. The reference clock 51 generates a reference clock signal CLK. The reference clock signal is Capstan FG at 1x speed
The frequency is sufficiently higher than the output CFG, and is 1 MHz here. The counter 50 is reset at the rise of the capstan FG output CFG, and counts the number of rises of the reference clock signal CLK until the next reset. The count value COUNT of the counter 50 is interrupted by the microcomputer 52 at the rise of the capstan FG output, and is taken in as data of the tape running speed. Count value at this time
The microcomputer 52 outputs divider data DIV to be given to the divider 53 according to COUNT. The divider 53 divides the audio reference timing signal NFs by M according to the divider data DIV, and outputs the audio conversion timing signal NFs. Is generated. Audio reference timing signal
NFs is a signal having a frequency that is N times (N is an integer) the sampling frequency of the digital audio signal, and is a timing signal serving as a reference for normal audio signal processing.
Audio conversion timing signal Is a reference timing signal used in the time axis processing 27. FIG. 4 shows the timing relationship of each signal when the tape running speed is operating at about 1/2 speed. Count value COUNT taken in microcomputer 52
949 for the first time and 999 for the second time. Tape running speed is 1
At double speed, the count value COUNT is 1 × 10 ⁶ (Hz) / 2 × 10 ³
(Hz) -1 = 499, so the division ratio M is Becomes

FIG. 5 is a block diagram showing one embodiment of the time axis processing 27, and FIG. 6 is a timing chart for explaining the operation of FIG. 54 is a write address counter, 55 is a read address counter, 56 is a memory, ID is an ID signal, is a write enable, WAD is a write address, RAD is a read address, AIN is an audio input, and AOUT is an audio output. The ID signal is data indicating the affiliation of itself recorded on a helical track scanned by the magnetic head 4, and corresponds to field information in the case of a digital VTR, for example. Here, as the ID signal ID, T1, T every four tracks
It is assumed that 2, T3 and T4 are repeatedly given to indicate the affiliation of the audio input AIN. The writing of the audio input AIN to the memory 56 is performed at the timing of the audio reference timing signal NFs synchronized therewith, and at the same time, the count value of the write address counter 54 that counts using the audio reference timing signal NFs as a clock is set as a write address WAD. Is determined according to the storage location. Further, reading of the audio output AOUT from the memory 56 is performed by the audio conversion timing signal generated by the timing generation circuit 26 described above. At the same time, the audio conversion timing signal at the same time Is used as a clock, the count value of the read addressing counter 55 is used as the read address RAD, and the read position is determined and performed according to the read address RAD. The write address counter 54 and the read address counter 55 count up, count down, and stop counting according to an instruction from the microcomputer 52.

The timing chart in Fig. 6 shows that the tape running speed is about 1 /
The case of double speed is assumed. When the magnetic tape 2 is running at 1/2 speed, the magnetic head 4 operates so as to continuously scan the same helical track twice. At this time, the same signal is continuously reproduced as the audio input signal AIN. Since this information can be determined by detecting the ID signal ID by the microcomputer 52, if the same ID signal ID is continuously detected in order to prevent the same information from being redundantly stored in the memory 56, the audio input corresponding to the second and subsequent times For AIN, a process is performed in which the write enable is set to “H” to prohibit writing into the memory 56. At the same time, the count of the write address counter 54 is stopped by an instruction from the microcomputer. The relationship between the write address WAD and the read address RAD is such that a timing shift is given at the start of operation so that the value of the read address RAD does not always exceed the value of the write address WAD, and the capacity of the memory 56 is accordingly adjusted. Need to estimate.
According to the above-described embodiment, at the time of variable-speed reproduction of a digital audio signal, noise due to discontinuity of the signal does not occur, and the output voice pitch is changed according to the tape running speed in the same manner as the usability of a conventional analog audio device. You can do so.

Next, an example of signal processing when the tape running is stopped will be described. In the digital audio reproducing apparatus using the rotary cylinder 1, unlike the analog audio reproducing apparatus, even when the tape is stopped, the magnetic head 4 scans the helical track and the audio signal is continuously reproduced. If the timing conversion circuit 26 generates an audio conversion timing signal proportional to the tape running speed, Is generated, the frequency becomes 0 when the tape running speed becomes 0. Then, a part of the audio input AIN written to the memory 56 becomes the audio output AOUT
May not be read. Further, since the information amount of the audio signal that is not read is undefined, it is difficult to perform accurate cueing based on the reproduced sound. Therefore, even if the tape running stops,
Audio conversion timing signal which is 56 read clocks Must be generated and all written information of the audio input AIN must be read. FIG. 7 shows a timing relationship between the audio input AIN and the audio output AOUT when the tape is stopped, which is one embodiment of the present invention.
Here, it is assumed that the tape running is stopped immediately after the magnetic head 4 moves on the helical track to be scanned. Therefore, the ID signal ID of the audio input AIN changes from T1 to T
After moving to 2, the tape running speed has become zero. Although the operation of the timing generation circuit 26 at this time is not described in FIG. 7, when the microcomputer 52 determines that the tape running speed is below a certain reference, the audio conversion timing signal is output. To generate a signal corresponding to the lowest frequency. Based on this, reading is performed as an audio output AOUT. Then, the stopped write address WAD
When the read address RAD matches the read address RAD, the microcomputer 52 stops counting by the read address counter 55. With the above operation, audio output is always performed under the same conditions when the tape running is stopped, so that accurate cueing can be performed.

Next, an embodiment of the signal processing when the tape running is performed in the direction opposite to the normal reproduction will be described. FIG. 8 shows -1
This explains signal processing in the time axis processing 27 when the tape is run at double speed. Audio input AIN ID
The signal ID is generated by repetition of T4, T3, T2 and T1, contrary to the normal reproduction. However, the signal reproduced by the magnetic head 4 scanning one helical track is not different from the normal reproduction. That is, in the reverse reproduction, audio cannot be correctly reproduced in the reverse direction unless signal processing is performed so that reproduction is performed in the reverse direction in units of signals obtained by one helical track. An embodiment for performing this signal processing will be described with reference to FIG. Of the audio input AIN, the ID signal I
Note that D is T1. Here, it is assumed that 100 samples are recorded on one track. Audio input AI to memory 56
When writing to N, the write address WAD is incremented by one. The signal whose ID signal ID is T1 is stored in addresses from 100 to 199. When all the signals with the ID signal ID of T1 are written, it is possible to read and output the audio AOUT.
When reading, the read address RAD is decremented one by one from 199. This can prevent generation of noise due to discontinuity of the reproduction signal even in reverse reproduction.

As a method of detecting the tape running speed in the timing generation circuit 26, a method of detecting a change in the ID signal to detect the frequency of the output of the capstan FG12 can be considered. This is effective when the tape runs at a constant speed as in the variable slow mode of variable speed playback, or when the tape runs without using the capstan 7.

〔The invention's effect〕

According to the present invention, in a digital audio recording / playback apparatus, noise is prevented from being generated in a playback signal at a variable speed playback from -1 to +1 times speed, and an audio pitch to be played back is changed according to a tape running speed. Since the audio signal can be reproduced in a manner similar to the manner in which the audio signal is reproduced at the time of variable-speed reproduction in the recording audio device, there is no sense of incongruity for the user who has been accustomed to using the analog recording audio device. This has the effect of making it easier to find the head.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of the entire system according to one embodiment of the present invention, FIG. 2 is a tape pattern diagram, FIG. 3 is a block diagram of a timing generation circuit, FIG. FIG. 5 is a block diagram of time axis processing, FIG. 6 is a timing chart of time axis processing, FIG. 7 is a timing chart of signal processing when tape running is stopped, and FIG. It is. DESCRIPTION OF SYMBOLS 1 ... Rotating cylinder, 2 ... Magnetic tape 4 ... Magnetic head 5, ... Displacement element 6 ... Cylinder motor, 7 ... Capstan 8 ... Pinch roller, 9 ... Capstan motor 10 ... Control head 12 ... Capstan FG

Claims (3)

(57) [Claims] 1. A rotating cylinder (1), means for rotating the rotating cylinder (1), a magnetic head (4) provided on the rotating cylinder (1), and a magnetic tape (2). Means for winding around the cylinder (1), means for running the magnetic tape (2), means for running the magnetic tape (2), and digital data from the magnetic tape (2) via the magnetic head (4). An apparatus for reproducing an audio signal (23) and a means for changing a running speed of the magnetic tape (2); a means for detecting the running speed of the magnetic hoop (2); and the detected magnetic tape Means for generating a signal having a different frequency according to the running speed of (2); means for temporarily storing the digital audio signal (23); and means for storing the detected running speed of the magnetic tape (2). frequency Using different signals, the digital signal recording and reproducing apparatus characterized by comprising a means for reading the information of the digital audio signal (23) from the means for temporarily storing said digital audio signal (23). 2. A digital signal recording / reproducing apparatus according to claim 1, further comprising means for displacing said magnetic head (4) in an axial direction of said rotary cylinder (1). 3. The means for generating a signal having a different frequency in accordance with the detected running speed of the magnetic tape (2) comprises:
Other than the digital audio signal (2
3. The digital signal recording / reproducing apparatus according to claim 1, further comprising means for reading information of the digital audio signal (23) from means for temporarily storing 3).