JP2814771B2 - Digital signal reproduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal reproducing apparatus using a rotary head recording system.

[0002]

2. Description of the Related Art In recent years, digital processing of audio and video has rapidly progressed with the development of LSI technology, and audio and video equipment capable of recording and reproducing digital signals has been actively developed. Above all, digital VTRs of the rotary head recording type have been developed for various uses, such as for business use used in broadcast stations and the like, and further for home use. For commercial VTRs, not only is the performance improved, but at least the conventional analog-recorded VT
The functions that were possible in R are required to be fully realized.

Among them, realization of a special reproduction function is one point. A high-speed and low-speed queuing function for searching for an edit point which can be easily performed by the conventional analog fixed head recording is provided by a rotary head digital recording. in the case of,
Complicated processing is required with technical difficulties. That is, in the jog / shuttle mode, variable speed special playback at a playback speed corresponding to the rotation speed of the operation dial is realized with the highest quality playback sound, and is used for detailed setting of edit points and the like. . Usually, the speed of the low-speed reproduction is 1/32 from a tape speed of ± 1 to a low speed such as ± 1/32 (or 1/30, 1/25).
(Or 1/30, 1/25) steps, while the high-speed playback is ± 2 times, ± 4 times,.
A speed of a multiple of 2, such as ± 32 times,..., Is generally used (of course, numerical values in between can be taken).

Further, in order to perform special reproduction while maintaining a good reproduction screen, an automatic tracking (hereinafter, referred to as AT) in which a height position of a head mounted on a carrier of a voltage distortion element such as a piezo element is movable. ) Mechanism is installed,
For example, within the range of about +3 to -1 times speed, it is possible to accurately trace and reproduce the recording track.

On the other hand, in the case of low-speed reproduction, since the same recording track is repeatedly traced by the AT head according to the reproduction speed, the obtained reproduction signal is, for example, in the case of 1/4 speed, each field is repeated four times. When the reproduced signal is in the form of a shape and the same processing as the reproduction processing at the normal speed is performed, the reproduced sound gives a strange feeling.

Therefore, in the case of the special reproduction of audio, some processing is required in the low-speed reproduction, and in the 1 / N-times low-speed reproduction, the reproduction signal is reproduced only once from the reproduction signal of one field period repeatedly reproduced N times. A processing operation is performed to extract the sound, extend the time axis by N times, and obtain a reproduced sound with a reduced frequency pitch similar to the conventional analog fixed head recording.

FIG. 3 is a waveform chart for explaining the operation principle of special reproduction (low-speed reproduction). In the figure, the interval between broken lines is, for example, one field period, and audio signal formatting and AT
Is performed in this unit.

In FIG. 1, (A) shows an analog input recording audio signal, (B) shows an analog output reproduction audio signal when no special reproduction processing is performed, and (A) shows an analog output reproduction audio signal when special reproduction processing is performed. The output reproduced audio signal is shown in (C).

[0009] As shown in FIG.
/ 3, 1/4,..., Gradually, the obtained reproduced signal is obtained by repeating the same field twice, three times, four times,. Can be
As shown in (C), the first field data of the repetition is extracted, and the time axis is extended using the field memory in the order of 2 times, 3 times, 4 times,. A reproduced sound with a different frequency pitch is obtained.

Conventionally, as a method of realizing the above operation,
There is a digital signal reproducing apparatus having a configuration shown in FIG. In the figure, 1 is a search dial for operating a jog / shuttle, 2 is a dial speed detection unit for detecting the angular speed of the search dial 1, 3 is a tape speed command unit for determining a tape speed according to the movement of the search dial 1, Reference numeral 4 denotes a capstan motor driving unit for driving and driving the tape, 5 denotes a capstan motor, 6 denotes a magnetic tape as a recording medium, 7 denotes an FG detection circuit that detects the number of rotations of the capstan motor 5, and 8 denotes a period of the FG pulse. A speed detection circuit for detecting the running speed of the tape from the AT; an AT control unit 9 for performing tracking control for changing the height of the reproducing head in order to accurately trace a recording track during reproduction; and 10 an output from a voltage distortion element such as a piezo element. A read head 11 mounted on a carrier made of a carrier; a read signal detecting circuit 11 for detecting a read signal from the magnetic tape 6;
Is a demodulation / synchronization detection circuit for restoring reproduced data subjected to digital modulation to the original information and for detecting and protecting a synchronization signal added to each block as a unit of signal processing. Decoding function of format and TBC (Time Base Collector)
A reproduction memory having a function of three pages, a reproduction memory controller 14 for controlling writing / reading of the reproduction memory 13, an error detection / correction circuit 15 for detecting and correcting an error due to a dropout or the like in a reproduction signal, Reference numeral 16 denotes a field update detection circuit for detecting whether or not the field data being reproduced is updated at the time of low-speed reproduction in which signals of the same field are repeatedly reproduced. Reference numeral 17 denotes a field of pages 3 to 4 for performing signal processing at the time of low-speed reproduction. A special reproduction memory consisting of a memory, 18 is a special reproduction memory 17
A special reproduction memory controller for supplying the address and timing of the digital signal; 19, a DSP (digital signal processor) for filtering interpolation of audio samples; 20, a DA conversion circuit for converting a digitized audio signal into an analog audio signal; 21 is an analog audio signal output terminal.

FIG. 4 is a waveform diagram showing the timing relationship between writing and reading of the reproduction memory 13 shown in FIG.
Write gates and read gates of the memories A, B, and C of the page are shown in order.

FIG. 5 is a waveform diagram showing the timing relationship between writing and reading of the special reproduction memory 17 shown in FIG. 2. FIG. 5 shows an update flag detected for each field and the four pages of memories A, B, C and D. The respective write gates and read gates are shown in order.

Next, the operation of the conventional digital signal reproducing apparatus having the configuration shown in FIG. 2 will be described. When a jog mode operation is performed by operating the search dial 1, a rotary encoder (not shown) coupled to the search dial 1 generates a pulse corresponding to the rotation angular velocity. The dial speed detection unit 2 counts the number of pulses input during a certain period of time, and inputs this value to the tape speed command unit 3 as dial speed information. The tape speed command unit 3 converts the dial speed information into tape speed information according to the current mode state, and outputs it to the capstan motor drive unit 4 as a speed command. The driving of the capstan motor 5 generates driving power according to the tape speed command in the capstan motor driving unit 4, and the FG corresponding to the rotation speed of the capstan motor 5.
The pulse is fed back from the FG detection circuit 7 to the capstan motor drive unit 4 to control the speed so that the capstan motor 5 rotates at a constant rotation speed. Further, although not shown, at the time of reproduction, a control signal pulse recorded on the magnetic tape 6 is detected, and a feedback for comparing a phase with a reference signal is applied to perform a more accurate phase control corresponding to the slip and expansion / contraction of the tape. Multiply.

At the time of reproduction, in order to accurately trace the inclined track formed on the magnetic tape 6 and obtain a good reproduction signal, the reproduction head 10 is mounted on a piezo element carrier (not shown), and the height thereof is adjusted. Control to deal with track deviation and track bending. The AT control unit 9 generates a driving voltage applied to the piezo element according to the tape running speed, and performs feedback control while detecting the envelope of the reproduction signal or the pilot signal so that the amplitude of the reproduction signal is maximized. . A reproduction signal detected by the reproduction head 10 is amplified, waveform-equalized, and pulse-shaped by a reproduction detection circuit 11, and a demodulation / synchronization detection circuit 12 further performs clock reproduction, demodulation, and detection and protection of a block synchronization signal.

The reproduction memory 13 is composed of three pages of field memories A, B, and C, and writes the reproduced digital audio signals to the memories A, B, and C in order for each field. The write timing at this time is based on the block synchronization signal detected by the demodulation / synchronization detection circuit 12. The function of the playback memory 13 is to decode a format in which a playback signal whose time axis is compressed based on the recording signal format and the data arrangement is rearranged is expanded back to the original audio time series, The TBC function for removing the time axis fluctuation by rereading the reproduced signal including the component from the crystal oscillator with the divided clock from the crystal oscillator and the temporary storage function for error correction are performed. Reproduction memory 13
Are supplied from the reproduction memory controller 14. For errors caused by dropout due to scratches or dust on the tape included in the reproduced signal, the data once written to the reproduction memory 13 is read and input to the error detection / correction circuit 15 for error detection and correction. Is executed by a predetermined calculation process.

Although the timing of error correction is omitted in FIG. 4, the timing of writing the reproduction signal to the memories A, B and C and the timing of decompressing and reading the audio signal are sequentially switched on a field-by-field basis. And read signals are continuously performed without time overlap with each other and without interruption.

On the other hand, at the time of low-speed reproduction, the same field is repeatedly reproduced by the operation of the AT control. Therefore, the repetition is identified by detecting a field address signal woven into the reproduction signal. Generally, a field address is stored and recorded in each block in the form of an ID signal. The field update detection circuit 16 compares the field addresses of the preceding and succeeding fields, and if not identical, recognizes that the field has changed, and outputs an update flag.

On the other hand, an FG pulse that follows the rotation speed of the capstan motor 5 is detected by an FG detection circuit 7, the pulse width is measured by a speed detection circuit 8, and the measurement result is stored in a table stored therein. The data is converted into a tape speed and transmitted to the trick play memory controller 18 as tape speed information.

The special reproduction memory 17 has three pages or four pages.
Although it is composed of a page-structured field memory, the description will be made for a case of three-page-structured memories A, B and C. Writing to the special reproduction memory 17 is controlled by the special reproduction memory controller 18 so that data is written in field units only when the update flag output from the field update detection circuit 16 is output. Therefore, the reproduction signal after the repeated reproduction is not redundantly written in the special reproduction memory 17. Reading from the special reproduction memory 17 is performed based on speed information output from the speed detection circuit 8. That is, when the tape speed is 1/2, the frequency of the read clock is equivalently reduced to 1/2, and when the tape speed is N / M, the read clock frequency is similarly adjusted to be N / M. A selection is made. In the example shown in FIG. 5, the tape speed is 1, 1/2, 1 /
3, 1/4,... Show a changing state.

In the case of audio data whose time axis is expanded, for example, by N times, the sampling period has been expanded by N times, so that N-1 sample points during that time lack data. If this is used as it is as a reproduction output signal, the signal quality becomes insufficient. An interpolation digital filter configured using the DSP 19 compensates for this by interpolation using a digital filter, and a weighting coefficient corresponding to the reproduction speed is stored in a ROM or the like in advance, and realized by software processing.

Finally, the special reproduction sound converted into an analog signal by the DA conversion circuit 20 is output from an output terminal 21.

[0022]

However, in the above-mentioned conventional digital signal reproducing apparatus, since an editing point is determined finely by, for example, a jog mode operation, it is necessary to obtain an agile response corresponding to a sudden change in the movement of the search dial. , The rotation control of the capstan motor performs only coarse speed control,
High-precision phase control cannot be applied. In addition, in the tape running at a very low speed such as 1/30 speed, the frequency to be controlled by the capstan control becomes too low, and it is difficult to realize high control accuracy in terms of the hardware configuration.

On the other hand, if the phase control is not applied, slip and expansion and contraction of the tape running cannot be avoided in a long time unit. As a result, a deviation occurs between the tape speed detected by the FG pulse and the time axis of the actually obtained reproduction signal, and an error occurs in the time relationship between the speed information obtained in the special reproduction memory 17 and the input reproduction signal. Therefore, an error occurs in the expansion ratio corresponding to the tape speed of the read pulse interval, in other words, the length of the read time, and when these errors are accumulated, the write and read gates shown in FIG. The data issued is erroneous and this error condition is not instantaneous but persistent. As a result, the reproduction sound of special reproduction can be roughly obtained, but good special reproduction sound cannot be obtained in all cases such as when using the special reproduction mode for a long time.

The present invention has been made in view of the above problems, and provides a digital signal reproducing apparatus capable of reproducing a good digital audio signal at a frequency pitch corresponding to a tape reproducing speed during a variable speed special reproducing operation.

[0025]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a digital signal reproducing apparatus according to the present invention forms an inclined track on a tape by a rotary head recording method, so that a video signal is generated at a predetermined unit time. What is claimed is: 1. A digital signal reproducing apparatus for reproducing a digital audio signal recorded in a divided block, comprising: system control means for outputting a tape traveling speed command according to an operation mode; and driving a tape based on the tape traveling speed command. Tape driving means, a tape speed detecting means for detecting the tape running speed as tape speed information from a tape driving motor, and such that the rotating head accurately tracks a predetermined track on the tape during variable speed special reproduction. Auto-tracking means for variably controlling the mounting height of the rotating head; Reproduction signal processing means for demodulating a reproduction signal from the head and returning it to the original digital audio signal; separating and extracting an address added for each field; and a field address update determining means for determining continuity of the address; Memory means for storing a plurality of fields of digital audio signals output from the reproduction signal processing means in field units; and writing of the digital audio signals to the memory means based on the determination result of the field address update determination means, and Memory control means for controlling reading of a digital audio signal from the memory means in accordance with speed information; control means for controlling the tape running speed command based on a difference between a writing timing of the digital audio signal and a reading timing of the digital audio signal; Correct tape speed information And velocity information correcting unit that, the digital audio signal read out from said memory means, and a interpolating filter means for interpolating in response to said tape speed information.

[0026]

With the above arrangement, during variable speed special reproduction, when the timing of writing and reading of the special reproduction memory approaches, this is detected, the tape speed command is corrected, and the tape driving means for driving the tape is controlled. Thereby, the timing of writing to the special reproduction memory can be controlled, and the collision between the writing and reading timing for the special reproduction memory can be avoided.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A digital signal reproducing apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a digital signal reproducing apparatus according to an embodiment of the present invention.

In FIG. 1, 1, 2, 4 to 17 and 1
9 to 21 are the same components as those in the conventional example shown in FIG. Reference numeral 3 denotes a tape speed command unit that determines a tape speed according to the movement of the search dial 1 and controls the tape speed based on a tape speed correction command from the special reproduction memory controller 18. Reference numeral 18 denotes a special reproduction memory controller, which has a function of controlling reading and writing of the special reproduction memory 17 and outputting a correction command as described in the conventional example. A speed information correction circuit 22 corrects and outputs the tape speed information from the speed detection circuit 8 based on a speed correction command from the trick play memory controller 18.

The operation of the digital signal reproducing apparatus of the present invention configured as described above will be described below with reference to FIGS.

The basic operations from the operation of the search dial 1 to the writing, error correction, and reading to the reproduction memory 13 are not different from those of the conventional example shown in FIG.

The digital audio signal read out from the reproduction memory 13 is written into the special reproduction memory 17 by the special reproduction memory controller 18 on a field basis only when an update flag is output based on the detection result of the field update detection circuit 16. It is. Reading with time axis expansion from the special reproduction memory 17 is performed by changing the read clock frequency in accordance with the reproduction tape speed information from the speed information correction circuit 22. At this time, the trick play memory controller 18 compares the write address and the read address to the trick play memory 17 and outputs a correction command to the speed information correction circuit 22 and the tape speed command unit 3 based on the difference between the two. That is, in the timing chart of writing and reading of the special reproduction memory shown in FIG. 5, when the reading timing approaches the writing timing to the memory and the interval between the two becomes less than a certain value, the tape speed command unit 3 informs the tape speed command unit 3 of the tape speed. The tape speed correction command is output so that the reading speed of the trick play memory 17 is kept constant, and the tape information is supplied to the speed information correction circuit 22 to keep the reading speed of the trick play memory 17 constant. A speed correction command is issued to lower the speed information to the lower speed side in the same manner as the command to the speed command unit 3. Conversely, when the write timing approaches the read timing and the interval between the two becomes less than or equal to a certain value, the tape speed instructing unit 3 reduces the tape speed by one unit in the minimum controllable unit of the capstan motor driving unit 4. In order to output the tape speed correction command and to keep the reading speed of the special reproduction memory 17 constant, the speed information correction circuit 22 sends the speed information to the high speed side in the same manner as the command to the tape speed command unit 3. Issue speed correction command to increase. In response to the tape speed correction command, the tape speed command unit 3 controls the tape speed determined based on the dial speed information to increase or decrease by one controllable minimum unit, and outputs the result to the capstan motor drive unit 4. As a result, the tape speed changes,
It is possible to control the timing of writing to the special reproduction memory 17. Therefore, in the timing chart of writing and reading of the special reproduction memory shown in FIG. 5, the reading timing approaches the writing timing to the memory, and when the interval between the two becomes less than a certain value, the tape speed increases by one unit and the writing timing increases. Hasten. Conversely, when the write timing approaches the read timing and the interval between the two becomes less than a certain value, the tape speed decreases by one unit and the write timing is delayed. However, at this time, the tape speed information from the speed detection circuit 8 also changes in accordance with the change in the speed for the tape speed correction performed by the tape speed command unit 3, and the speed information correction circuit 22 cancels this change. The speed information is corrected based on the speed correction command from the trick play memory controller 18 and output to the trick play memory controller 18. As a result, the read timing of the special reproduction memory 17 becomes the same regardless of the presence or absence of the tape speed correction performed by the tape speed command unit 3, and the write timing and the read timing of the special reproduction memory come closer to each other. Overlapping read errors can be prevented by controlling the write timing.

In the description of the embodiment of the present invention, the case where the digital audio signal is constituted by the field unit of the video signal has been described. However, even in the case of the longer frame unit, the field is further subdivided. Even when the unit is a constituent unit, only the size of the field memory and the like are changed, and the present invention is not limited.

[0034]

As described above, according to the present invention, even when the phase control of the capstan motor is not performed at the time of the variable speed special reproduction and the sufficient tape running control is not performed, the time axis fluctuation of the reproduction signal can be achieved. The error of the speed information supplied to the trick play field memory can be corrected, the read timing can be controlled, and the frequency can be converted to a frequency proportional to the tape playback speed and output.
A digital audio signal can be reproduced with the same operational feeling as that of a conventional analog device. In particular, the heading operation at the time of editing can be performed quickly, and the effect is great.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a digital signal reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional digital signal reproducing apparatus.

FIG. 3 is a waveform chart showing a general digital audio processing method during low-speed reproduction.

FIG. 4 is a waveform chart showing an operation of the reproduction memory 13 in FIGS. 1 and 2;

FIG. 5 is a waveform chart showing an operation of the special reproduction memory 17 in FIGS. 1 and 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Search dial 2 Dial speed detection part 3 Tape speed detection part 4 Capstan motor drive part 5 Capstan motor 7 FG detection part 8 Speed detection circuit 9 AT control part 16 Field update detection circuit 17 Special reproduction memory 18 Special reproduction memory controller 22 Tape speed correction circuit

Claims (1)

(57) [Claims] 1. A digital signal reproducing apparatus for forming an inclined track on a tape by a rotary head recording method, dividing a video signal into fixed blocks at a predetermined unit time, and reproducing a recorded digital audio signal. A tape speed command means for outputting a tape running speed command according to the operation mode; a tape driving means for driving the tape based on the tape running speed command; and a tape driving motor which outputs the tape running speed as tape speed information. Tape speed detecting means for detecting, automatic tracking means for variably controlling the mounting height of the rotary head so that the rotary head accurately tracks a predetermined track on the tape during variable speed special reproduction, and Playback signal processing means for demodulating the playback signal from the head and returning it to the original digital audio signal; Field address update determining means for separating and extracting the address added for each field and determining the continuity of the address; and memory means for storing a plurality of fields of the digital audio signal read from the reproduction signal processing means in field units. Memory control means for controlling writing of a digital audio signal to the memory means in accordance with the result of determination by the field address update determining means, and controlling reading of the digital audio signal from the memory means in accordance with the tape speed information; Control means for controlling the tape running speed command based on the difference between the signal writing timing and the digital audio signal reading timing; speed information correcting means for correcting the tape running speed information; and digital audio read from the memory means. The signal Digital signal reproducing apparatus and a interpolation filter means for interpolating in accordance with the flop velocity information.