JPH04176003A - Digital signal reproducer - Google Patents

Abstract

PURPOSE:To enable outputting with a converted frequency proportional to a tape reproduction speed by detecting an error in variations of time axis of a reproduction signal to correct errors of speed information to be supplied to a special reproduction field memory thereby controlling the read out timing. CONSTITUTION:A function is added to a special reproduction memory controller 18 to control reading out and writing into a special reproduction memory while outputting speed correction information. Then, a speed information correcting circuit 22 corrects and outputs speed information from a speed detection circuit 8 based on the speed correction information from the special reproduction memory controller 18. As a result, in variable speed special reproduction, approaching is detected between timings of writing into and reading out of the special reproduction memory 17 whenever it occurs to correct tape speed information. Reading clock of the special reproduction memory 17 is made to fit the time axis of a reproduction signal thereby enabling the avoiding of collision between writing and reading timings in the special reproduction memory 17. This enables better reproduction of a digital voice signal at a frequency pitch corresponding to a tape reproduction speed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a digital signal reproducing apparatus using a rotary head recording method.

2. Description of the Related Art In recent years, as LSI technology has progressed, digital processing of audio and video has progressed rapidly, and audio and video equipment that can record and reproduce digital signals has been actively developed. Among them, rotary head recording type digital VTR
is being developed for a variety of uses, from commercial use at broadcast stations to home use. VTR for business use
In addition to improvements in performance, it is required that at least the functions that were possible with conventional analog recording VTRs be fully realized.

One of the key points was to realize the special playback function.
High-speed and low-speed queuing functions to search for edit points, which can be easily done with conventional analog fixed head recording, are available.
Rotating head digital recording requires technical difficulties and complex processing. In other words, the aim is to achieve variable speed special playback with the highest possible quality of playback sound at a playback speed that corresponds to the rotation speed of the operating dial in the zilog/shuttle mode, and to utilize it for detailed settings of editing points, etc. . Usually, the tape speed for low-speed playback is, for example, from ±11 times to ±1/32 (or ±1/30).
±1/25) Reduce the speed in steps of 1/32 (or 1/30.1/25) to a low speed such as double speed,
On the other hand, high-speed playback is ±2 times, ±4 times, ...
Speeds in multiples of 2 are generally used, such as ±32 times, etc., but of course values in between are also possible.

In addition, automatic tracking (hereinafter referred to as AT) allows the height position of a head mounted on a carrier of a voltage distortion element such as a piezo element to be movable so that special playback can be performed while maintaining a good playback screen. A mechanism is installed, and recording tracks can be accurately traced and reproduced within a range of, for example, +3 times speed - 1 times speed.

The audio signal played using this AT head in the J-e-goo shuttle mode is
Interlaced scanning is performed in field units, and if the format period of the audio signal is one field, for example, in the case of triple speed, a signal of one field period is obtained only once every three fields, and the signal of one field period is obtained only once every three fields. The signal for one field is lost and not detected. If this is processed in the same way as signal processing at normal speed, the resulting reproduced sound will be a sampled sound obtained by extracting one field's worth of sound from a three-field period. This is different from the playback sound with a raised frequency pitch during high-speed playback using conventional analog fixed head recording, but since the recorded content is missing but the pitch of the audio has not changed, it is not useful for checking the recorded content. On the contrary, it is easy to understand and there is no problem in practical use.

On the other hand, in the case of low-speed playback, the AT head repeatedly traces the same recording track according to the playback speed, so the resulting playback signal is, for example, in the case of 1/4 speed, a playback in which each field is repeated four times. It becomes a signal,
If processing similar to normal speed playback processing is performed, the playback sound will give a sense of discomfort.

Therefore, in the case of special playback of audio, some processing is required for low-speed playback, and for 1/N times low-speed playback, this is taken only once from the playback signal of one field period that is repeatedly played back N times. Then, the time axis is extended N times, and a processing operation is performed to obtain reproduced sound with a lowered frequency pitch, similar to conventional analog fixed head recording.

FIG. 3 shows a waveform diagram illustrating the operating principle of special playback (low speed playback). In the figure, it is assumed that the interval between broken lines is, for example, one field period, and audio signal formatting and AT control are performed in this unit.

In the same figure, the recorded audio signal of the analog input is shown in (A), the reproduced audio signal of the analog output when no special reproduction processing is performed is shown in CB), and the reproduced audio signal of the analog output when special reproduction processing is performed. The signal is shown in (C).

As shown in the figure, the playback speed is reduced to 1/2. 1/3゜1/
4. ..., the reproduced signal obtained is as shown in (B), where the same field is repeated twice,
It can be obtained repeatedly 3 times, 4 times, etc.

As shown in (C), if the first field data of the repetition is extracted and the time axis is stretched by 2 times, 3 times, 4 times, etc. using field memory, the time axis will be expanded according to the playback tape speed. You can obtain reproduced sound with a different frequency pitch.

Conventionally, as a method for realizing the above operation, there is a digital signal reproducing apparatus having the configuration shown in FIG.

In the figure, ■ is a search dial that performs jog/shuttle operations, 2 is a dial speed detection unit that detects the angular velocity of the search dial 1, 3 is a tape speed command unit that determines the tape speed according to the movement of the search dial 1; 4 is a capstan motor drive unit that drives the tape to run; 5 is a capstan motor; 6 is a magnetic tape that is a recording medium; 7 is an FG detection circuit that detects the rotational speed of the capstan motor 5;
8 is a speed detection circuit that detects the running speed of the tape from the period of the FG pulse; 9 is an AT control unit that performs tracking control to change the height of the playback head in order to accurately trace the recording track during playback; and 10 is a piezo 11 is a reproduction signal detection circuit for detecting a reproduction signal from the magnetic tape 6; 12 is a reproduction signal detecting circuit for restoring digitally modulated reproduction data to the original information; and a demodulation 9 synchronization detection circuit that detects and protects synchronization signals added to each block, which is a unit of signal processing;
13 is a playback memory consisting of three pages that stores the playback signal in units of one field and has a format decoding function and a TBC (time base collector) function;
14 is a playback memory controller for the playback memory 13; 15;
16 is an error detection/correction circuit that detects and corrects errors caused by dropouts in the reproduced signal, and 16 is an error detection/correction circuit that detects whether or not the field data being reproduced has been updated during low-speed reproduction in which the signal of the same field is reproduced repeatedly. A field update detection circuit 17 detects a field update, and 3 performs signal processing during low-speed playback.
18 is a special playback memory controller that supplies addresses and timing to the special playback memory 17; 19 is a DSP (digital signal processor) that filters interpolation of audio samples; 20 21 is a DA conversion circuit that converts a digital audio signal into an analog audio signal, and 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.
The gate signals are shown in order.

FIG. 5 is a waveform diagram showing the timing relationship between writing and reading of the special playback memory 17 shown in FIG.
The write gate signals and read gate signals of , B, C, and D are shown in order.

Next, the operation of the conventional device having the configuration shown in FIG. 2 will be explained.

When the nog mode is operated by operating the search dial 1 shown in FIG. 1, a rotary encoder (not shown) connected to the search dial 1 generates pulses corresponding to its rotational angular velocity. The dial speed detection section 2 counts the number of pulses input in a certain period of time, and inputs this value to the tape speed command section 3 as dial speed information. The tape speed command section 3 converts the dial speed information into tape speed information according to the current mode state, and outputs the tape speed information to the capstan motor drive section 4 as a speed command. To drive the capstan motor 5, the capstan motor drive section 4 generates drive power according to the tape speed command, and FG pulses corresponding to the rotation speed of the capstan motor 5 are sent from the FG detection circuit 7 to the capstan motor drive section 4. is fed back to apply speed control so that the capstan motor 5 rotates at a constant rotation speed. Furthermore, although not shown, during playback, the control signal pulse recorded on the magnetic tape 6 is detected, and feedback is applied to compare the phase with a reference signal, thereby providing more accurate phase control in response to tape slipping and expansion/contraction. put on.

During 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 its height is controlled. Corresponds to track misalignment and track bending. The AT control unit 8 generates a drive voltage to be applied to the piezo element according to the tape running speed, and performs feedback control while detecting the envelope of the reproduced signal or the pilot signal so as to maximize the amplitude of the reproduced signal. . The reproduced signal detected by the reproduction head 10 is amplified, waveform equalized, and pulse-shaped by the reproduced signal detection circuit 11, and is further subjected to clock reproduction, demodulation, and block synchronization signal detection and protection in the demodulation/synchronization detection circuit 12. .

The playback memory 13 is a 3-page field memory A,
It consists of B and C, and the reproduced digital audio signal is sequentially written into the memories A, B, and C one field at a time. At this time, the writing/input timing is based on the block synchronization signal detected by the demodulation/synchronization detection circuit 12. The functions of the playback memory 13 are to decode the playback signal, which has been time-axis compressed based on the recording signal format and whose data arrangement has been rearranged, and expand the playback signal back to the original audio time series, and to decode the format by tape running. It performs a TBC function by rereading the reproduced signal containing jitter components using a clock frequency-divided from a crystal oscillator to remove time axis fluctuations, and also functions as a temporary storage function for error correction. The address and timing of the playback memory 13 are provided by the playback memory controller 14. In addition, for errors caused by dropouts caused by scratches or dust on the tape included in the playback signal, the data written in the playback memory 13 is read out and input to the error detection and correction circuit 815, and the data is detected and corrected. Correction is performed by predetermined arithmetic processing.

Although the timing of error correction is omitted in FIG. 4 because it is not directly related to the present invention, the timing of writing the playback signal to each memory A, B, and C and the timing of decompressing and reading the audio signal are shown for each field. The figure shows a situation in which the write signal and the read signal are sequentially switched, and the write signal and the read signal are performed continuously without overlapping each other in time and without any interruption.

On the other hand, during low-speed reproduction, the same field is repeatedly reproduced due to the action of AT control, and this repetition is identified by detecting a field address signal woven into the reproduced signal. - In boat fishing, 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 previous and next fields, and if they are not the same, it recognizes that the field has changed and outputs an update flag.

On the other hand, the FG pulse that follows the rotational speed of the capstan motor 5 is detected by the FG detection circuit 7, the pulse width is measured by the speed detection circuit 8, and the measurement result is converted to the tape speed using an internally stored table. The data is converted and transmitted to the special playback memory controller 18 as tape speed information.

The special playback memory 17 consists of a field memory with a 3-page or 4-page configuration, and the explanation will be given for the case where it consists of memories A, B, and C with a 3-page configuration. Writing into the special playback memory 17 is controlled by a special playback memory controller 18 so that data is written in field units only when an update flag, which is the output of the field update detection circuit 16, is output. Therefore, the reproduced signals after being repeatedly reproduced are not written redundantly to 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, if the tape speed is 172, the frequency of the read clock is isometrically 172.
/M, the special reproduction memory controller 18 selects the read clock so that the same <N/M holds. In the example shown in FIG. 5, the tape speed is 1. 1/2. 1/
3. This figure shows how it changes to 1/4.

For example, in the case of audio data whose time axis has been expanded by N times, the sampling period has been expanded by N times, so the N-1 sampling points in between are missing data, and this can be ignored. If the reproduced output signal is used as it is, the signal quality will be insufficient.

An interpolation digital filter configured using the DSP 19 compensates for this by interpolation using a digital filter, and is realized by software processing with weighting coefficients corresponding to the playback speed stored in advance in a ROM or the like.

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

Problems to be Solved by the Invention However, in the conventional digital signal reproducing apparatus described above, in order to quickly determine the editing point by operating in the geolog mode, for example, it is necessary to obtain a quick response in response to sudden changes in the movement of the search dial. The rotation of the capstan motor is controlled only by coarse speed control, and highly accurate phase control is not possible. Further, when the tape runs at an extremely low speed such as 1/30 times speed, the frequency to be controlled by the capstan control becomes too low, making it difficult to achieve high control accuracy in terms of hardware configuration.

On the other hand, if phase control is not applied, slippage and expansion/contraction of the tape running over a long period of time are unavoidable. As a result, a shift occurs between the tape speed detected by the FG pulse and the time axis of the actually obtained playback signal, and an error occurs in the time relationship between the speed information obtained in the special playback memory 17 and the input playback signal. As a result, an error occurs in the expansion ratio according to the tape speed of the read pulse interval, in other words, in the length of the read time, and when this is accumulated, the write and read gates shown in Figure 5 overlap, and in this case The read data will be erroneous, and this error state is not instantaneous but persistent. As a result, although the device with the configuration shown in Figure 2 can generally produce special playback sound, it is not possible to obtain good special playback sound in all cases, such as when using the special playback mode for a long time. .

SUMMARY OF THE INVENTION The present invention addresses the above-mentioned problems and provides a digital signal reproducing apparatus capable of reproducing a digital audio signal with good quality at a frequency pitch corresponding to the tape reproducing speed during variable speed special reproducing operation.

Means for Solving the Problems In order to solve the above problems, an inclined track was formed on the tape using a rotating head recording method, and a video signal field, etc., was divided into blocks for each fixed unit time and recorded. In a digital signal reproducing apparatus for reproducing digital audio signals, a system control means outputs a tape running speed command in accordance with an operator code, a tape driving means drives the tape based on the tape running speed command, and the tape tape speed detection means for detecting running speed as tape speed information from a tape drive motor;
auto-tracking means for variably controlling the height of the rotary head so that the rotary head accurately tracks a predetermined track on the tape during variable speed special playback of the tape; and demodulating the playback signal from the rotary head; a reproduction signal processing means for returning the digital audio signal to the original digital audio signal; a field address update determination means for separating and extracting the address added to each field and determining the continuity of the address; A memory means for storing a plurality of digital audio signals field by field, a memory means for controlling the writing of the digital audio signal into the memory means according to the determination result of the field address update determination means, and a memory means for storing a plurality of digital audio signals in field units; memory control means for controlling readout of the audio signal; means for controlling the tape running speed information based on the difference between the writing timing of the digital audio signal and the reading timing of the digital audio signal;
and interpolation filter means for interpolating the digital audio signal read from the memory means in accordance with the corrected tape running speed information.

Operation With the above configuration, during variable speed special playback, it is detected when the write and read timings of the special playback memory approach each other, the tape speed information is corrected, and the readout clock of the special playback memory is adapted to the time axis of the playback signal. By doing so, it is possible to avoid conflicts between write and read timings in the special playback memory.

Embodiment Hereinafter, a digital signal reproducing apparatus of the present invention will be explained with reference to the drawings.

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

In Figure 1, engineering ~ 17 and engineering 19 ~ 2 are the 2nd
Since the configuration is the same as the conventional example shown in the figure, the explanation will be omitted. Reference numeral 18 denotes a special playback memory controller, which, as described in the conventional example, controls the reading and writing of the special playback memory and also has the function of outputting speed correction information. 22 is a speed information correction circuit;
Based on the speed correction information from the special reproduction memory controller 8, the speed information from the speed detection circuit 8 is corrected and output.

The operation of the digital signal reproducing apparatus configured as described above will be explained below using the configuration diagram of FIG. 1 and the waveform diagram of FIG. 5.

Starting from the operation of search dial 1, playback memory 13
The basic operations from writing to, error correction, and reading are no different from the conventional example shown in FIG. 2, so their explanation will be omitted.

The digital audio signal read from the playback memory 13 is written into the special playback memory 17 in units of one field by the special playback memory controller 18 only when an update flag is output based on the detection result of the field update detection circuit 16. . Reading with time axis expansion from the special playback memory 17 is performed by changing the readout clock frequency according to the playback tape speed information from the speed information correction circuit 22. At this time, the special playback memory controller 8 compares the write address and the read address to the special playback memory, and outputs speed correction information based on the difference between the two. That is, in the write and read timing diagram of the special playback memory shown in FIG. outputs speed correction information to lower the speed information by one rank to the lower speed side, and conversely, when the write timing approaches the read timing and the gap between the two becomes less than a certain value, the speed information is output to the speed information correction circuit 22. To the high speed side 1
Provide speed correction information to increase rank. The speed information correction circuit 22 corrects speed information based on the speed correction information from the special playback memory controller 18 and outputs the corrected speed information to the special playback memory controller 18. As a result, it is possible to prevent a read error from occurring due to overlap between the write timing and read timing of the special playback memory as they approach each other.

In the detailed explanation of the present invention, a case has been described in which a digital audio signal is configured in units of fields of a video signal, but even if this is a longer frame unit, conversely, a unit in which the field is further subdivided can be used as a configuration unit. Even in this case, the only difference is the size of the field memory, etc., and this does not limit the present invention.

Effects of the Invention As described above, the present invention has the above-described configuration, so that even when phase control of the capstan motor is not applied during variable speed special playback and sufficient tape running control is not performed,
It detects errors in the time axis fluctuations of the playback signal, corrects errors in the speed information supplied to the special playback field memory, controls the readout timing, and converts to a frequency proportional to the tape playback speed for output. It is possible to reproduce digital audio signals with the same operating feeling as conventional analog equipment, and in particular, cueing operations can be performed quickly during editing work, which is highly effective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a digital signal reproducing device according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of a conventional digital signal reproducing device, and FIG. 3 is a block diagram showing the configuration of a conventional digital signal reproducing device. 4 is a waveform diagram showing the digital audio processing method, FIG. 4 is a waveform diagram showing the operation of the playback memory 13, and FIG.
The figure is a waveform diagram showing the operation of the special playback memory 17. 1... Search dial, 2... Dial speed detection section, 3... Tape speed detection section, 4... Capstan motor drive section, 5... Capstan motor, 7... FG @ output Circuit, 8... Speed detection circuit, 9... AT control section, 10... Playback head,
11... Reproduction signal detection circuit, 12... Demodulation/synchronization detection circuit, 13... Reproduction memory circuit, 16
... field update detection circuit, 17... special playback memory, 18... special playback memory controller,
19...DSPl 22...Tape speed correction circuit. Name of agent: Patent attorney Akira Okaji and 2 others! @Figure 4 Figure 5

Claims (1)

[Claims] A digital signal reproducing device that uses a rotary head recording method to form an inclined track on a tape and reproduces a digital audio signal that is divided into blocks for each fixed unit time such as a video signal field and recorded. system control means for outputting a tape running speed command according to an operation mode; tape driving means for driving the tape based on the tape running speed command; and tape speed information for determining the tape running speed from a tape drive motor. and auto-tracking means for variably controlling the height of the rotary head so that the rotary head accurately tracks a predetermined track on the tape during variable speed special playback of the tape; a reproduction signal processing means for demodulating the reproduction signal from the rotary head and returning it to the original digital audio signal; and a field address update determination means for separating and extracting the address added for each field and determining the continuity of the address. , memory means for storing a plurality of fields of the digital audio signal read out from the reproduction signal processing means; controlling writing of the digital audio signal into the memory means according to the determination result of the field address update determination means; memory control means for controlling readout of the digital audio signal from the memory means according to tape running speed information; and control means for controlling the tape running speed information based on the difference between the writing timing of the digital audio signal and the reading timing of the digital audio signal. and interpolation filter means for interpolating the digital audio signal read from the memory means according to the corrected tape running speed information.