JPH0693309B2 - Magnetic tape recording / reproducing device - Google Patents

Description

The present invention relates to a magnetic tape recording / reproducing apparatus for recording / reproducing video and digital audio, and more particularly to a method of generating an audio sampling signal during reproduction.

[Conventional technology]

Figure 6 shows, for example, the 1986 ICASSP draft "Research on digitization of audio signals in video tape recorders".
(A STUDY ON THE DIGITIZATION OF AUDIO SIGNALS FOR
FIG. 2 is a block diagram showing a video and digital audio recording / reproducing apparatus shown in “VIDEO TAPE RECORDER” (Hitachi),
In the figure, 1 is a video signal recording processing circuit, 2 is a video recording amplifier, 3 is a rotary drum incorporating a video head and an audio head, 4 is a magnetic tape, 5 is a video head amplifier, and 6 is a video signal reproduction processing circuit. Is. Further, 7 is an analog-digital converter (hereinafter simply referred to as ADC), 8 is a digital signal recording processing circuit, 9 is a 4-phase phase signal modulation circuit (hereinafter simply referred to as 4-phase phase modulation circuit),
Reference numeral 10 is an audio recording amplifier, 11 is an audio head amplifier, 12 is a 4-phase phase modulation signal demodulation circuit (hereinafter simply referred to as a 4-phase phase demodulation circuit), 13 is a digital signal reproduction processing circuit, and 14 is a digital-analog converter. (Hereinafter simply referred to as DAC).

Next, the operation will be described. The input video signal (video signal) is input to the video signal recording processing circuit 1, the luminance signal is FM-modulated, the chrominance signal is frequency-converted to a reduced frequency, and the video is stored in the recording amplifier 2 and the rotary drum 3. Data is recorded on the magnetic tape 4 via a head (not shown).
The signal reproduced by the video head is amplified by the head amplifier 5 and restored to a video signal by the video signal reproduction processing circuit 6. The above operation is similar to the operation of a home VTR such as VHS method and β method.

On the other hand, the input audio signal is converted into a digital signal by the ADC 7, converted into a PCM signal which is pulse code modulated by adding an error correction code and the like by the digital signal recording processing circuit 8 and further by the 4-phase phase modulation circuit 9. It is converted into a four-phase modulation signal and recorded on the magnetic tape 4 via the recording amplifier 10 and an audio head (not shown) built in the rotary drum 3. The audio signal is recorded on the lower side (so-called deep layer) of the video signal, similar to the VHS type Hi-Fi audio signal. The signal reproduced by the audio head is amplified by the head amplifier 11, the PCM signal is restored by the four-phase phase demodulation circuit 12, the error correction is performed by the digital signal reproduction processing circuit 13, and the DAC 14 is executed by the DAC 14. Restored to audio signal.

Here, the recording and reproducing operations of the audio signal will be described in more detail with reference to FIGS. 3 and 4.

First, the recording operation will be described with reference to FIG. The audio signal is input as an analog-audio signal (hereinafter referred to as AA signal) or a digital-audio signal (hereinafter referred to as DA signal). FS generation circuit that generates sampling signal FS for audio signal when AA signal is input
16 generates an FS signal having a constant frequency or a frequency synchronized with the video signal. On the other hand, sampling frequency 48KHz or 32K
When the Hz DA signal is input, the FS signal is restored from the data transmission rate (128FS) of the input signal. The AA signal and the DA signal are generated by the FS signal generated or restored by the FS generation circuit 16,
The signal is converted into, for example, a 16-bit 2-channel digital signal by the ADC 7 or the DA interface circuit 15, and is converted by the digital signal recording processing circuit 8 into, for example, 1 as shown in FIG.
It is divided into several blocks of data in units of fields, and is converted into a PCM signal to which an error correction code and the like are added. Fifth
In the case of the figure, since one field has 428644 bits, the transmission rate is about 2.57 Mbps. Therefore, the clock generator
17 may generate a clock signal FCL of about 2.57 MHz. FC
The PCM signal transmitted by the L signal from the digital signal recording processing circuit 8 at a constant speed is differentially encoded in the PCM data processing circuit 18 of the four-phase phase modulation circuit 9 to facilitate serial / parallel conversion and data demodulation. And so on, and converted into signals of two systems of P and Q. The carrier signal is approximately 2MHz due to the relationship with the video signal, assuming that it is deeply recorded like the VHS Hi-Fi audio signal.
The degree is appropriate. The carrier signal FC generated by the carrier generation circuit 20 is supplied to the phase modulation circuit 19 at the P, Q
For example, (P, Q) = (0,0), (0,1), (1,
For 1) and (1,0), the phase is controlled like 0, π / 2, π, and 3/2 · π. The four-phase phase-modulated signal (hereinafter simply referred to as PSK signal) obtained as described above passes through the head amplifier 10, the rotary transformer 21 built in the rotary drum 3, and the audio head 22 to the magnetic tape 4
Recorded in.

Next, the reproducing operation will be described with reference to FIG. The PSK signal recorded on the magnetic tape 4 is amplified by the head amplifier 11 via the head 22 and the rotary transformer 21, and is composed of a synchronous detection circuit 23, a carrier reproduction circuit 24, a clock reproduction circuit 25 and a data reproduction circuit 26. It is demodulated as a PCM signal by the 4-phase phase demodulation circuit 12. 4 phase demodulation circuit 1
2 includes, for example, “PCM satellite demodulator for direct satellite broadcasting” (Nati
onal Technical Report Vol.30 No.1 Fed.1984) P15 F
The P, Q data reproduction by the synchronous detection method shown in ig.6 and the carrier signal reproduction by the inverse modulation method and the digital phase comparison type clock signal reproduction shown in Fig.15 of P19 are performed. In the data reproduction circuit 26, signal processing such as differential decoding and parallel-serial conversion is performed, and the original
Restored to PCM signal.

The PCM signal restored in this way is restored to the original audio data in the digital signal reproduction processing circuit 13, but the transmission rate of the PCM signal, that is, the clock signal is not the net number of audio data. Since there is no direct relationship, the sampling signal that determines the transmission rate of the net audio data cannot be directly restored from the reproduction signal like the carrier signal and the clock signal. If this sampling signal cannot be restored correctly, DAC14 or D
Not only does the audio data become discontinuous in the A interface circuit 28, but a problem may occur in the operation of the digital signal reproduction processing circuit 13. Therefore, in order to avoid this, it is necessary to supply the sampling signal of an appropriate frequency from the FS generation circuit 27.

[Problems to be solved by the invention]

As described above, what is particularly important in the audio digital recording / reproducing apparatus using the rotary head as described above is the restoration of the sampling signal of the audio signal. Since the sampling signal is temporarily lost during the recording process of the digital signal for recording by the rotary head, it is necessary to newly generate it by some method during reproduction.

As shown in FIG. 6, when the audio signal is sampled and restored in one recording / reproducing apparatus, the number of samples to be recorded is accurately controlled every one rotation or half rotation (one field) of the rotary head. However, if the video signal is input from a TV tuner and the audio signal is input from a digital audio tape recorder (hereinafter simply referred to as DAT) in the form of a digital signal, the video signal and the audio signal can be input. The relationship with the signal is not constant. Therefore, the sampling signal cannot be restored from the cycle or transmission rate of the reproduced digital signal, and some special means is required.

That is, in a device that records and reproduces a video signal and a digital audio signal that are basically not in synchronization with each other (hereinafter, referred to as a video-audio asynchronous system), it is an important technical problem to restore the sampling signal, and it is necessary to accurately restore the sampling signal. If it is not possible, the reproduced audio signal will be discontinuous.

The present invention has been made in order to prevent the occurrence of the above problems, and an object thereof is to obtain a magnetic tape recording / reproducing apparatus capable of accurately restoring a sampling signal of an audio signal even in a video-audio asynchronous system. .

[Means for solving problems]

The magnetic tape recording / reproducing apparatus according to the present invention is capable of reproducing the sampling signal from the reproduction carrier signal by keeping the sampling frequency of the digital audio signal and the four-phase phase modulation carrier frequency in a synchronous relationship.

[Action]

In the present invention, a signal (for example, M · SF / N) obtained by dividing a signal (for example, M · FS) having a frequency that is an integral multiple of the frequency of the sampling signal FS of the digital audio signal into an integer (for example, M · SF / N).
Is a four-phase phase-modulated carrier signal, a perfect synchronization relationship is established between the reproduced carrier signal and the sampling signal during reproduction. Therefore, the audio sampling signal can be accurately restored from the reproduced carrier signal, the discontinuity of the reproduced audio signal as in the conventional case does not occur, and the uneven rotation of the rotary head can be followed.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an audio signal recording system of a video / digital audio recording / reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram of the reproducing system. In these figures, 4 is a magnetic tape, 7 is an ADC, 8 is a digital signal recording processing circuit, 9 is a 4-phase phase modulation circuit composed of a PCM data processing circuit 18 and a phase modulation circuit 19, 10 is an audio system recording amplifier,
Reference numeral 15 is a DA interface circuit, 16 is an FS generation circuit, 17 is a clock generation circuit, 21 is a rotary transformer, and 22 is an audio head. Also, 11 is an audio head amplifier,
12 is a four-phase phase demodulation circuit including a synchronous detection circuit 23, a carrier recovery circuit 24, a clock recovery circuit 25, and a data recovery circuit 26, 13 is a digital signal reproduction processing circuit, 14 is a DAC, 28 is D
A interface circuit.

Further, 29 is a frequency dividing circuit for dividing a signal having a frequency of an integer multiple of FS to generate a carrier of a 4-phase phase modulation signal, and 30 is an FS reproducing circuit for reproducing FS from the reproduced carrier signal. In the FS reproducing circuit 30, 31 is a phase comparison circuit, 32 is a voltage control type oscillation circuit, and 33, 34 and 35 are frequency dividing circuits.

Next, the operation will be described. The operation of each of the circuits 4 to 28 shown in FIGS. 1 and 2 is the same as that shown in FIGS. 3 and 4, and the description thereof will be omitted.

In recording system, when FS is 48KHz, 2 × 128FS = 12.288
Since the frequency is in MHz, the frequency dividing circuit 29 performs 1/6 frequency division (N = 6) to obtain a carrier signal FC = 2.048 MHz. On the other hand, when FS is 32 KHz, 2 × 128FS = 8.192MHz, so the frequency divider circuit 29 is 1/4.
The carrier signal FC = 2.048 MHz is obtained by frequency division (N = 4).
In any case, the carrier signal is 2.048MHz and is synchronized with the FS of the input DA signal. For simplicity, it is assumed that FS is 48 KHz.

In the reproducing system, the carrier signal FC is reproduced from the reproduced PSK signal by the carrier reproducing circuit 24 of the 4-phase phase demodulating circuit 12. This reproduced FC signal is input to one input terminal of a phase comparison circuit 31 incorporated in the FS reproduction circuit 30. Further, the output of the voltage control type oscillation circuit 32 for generating a signal of a frequency of approximately 2 × 128 FS is divided by 1 / N by the frequency dividing circuit 33 and input to the other input terminal of the phase comparing circuit 31 for phase comparison. Is done. The phase difference signal of the phase comparison circuit 31 becomes a control input of the voltage control type oscillation circuit 32 via a loop filter (not shown). In this way, the FS reproducing circuit 30
A signal with a frequency of × 128FS is reproduced. Further, if this signal is frequency-divided by the frequency dividing circuit 34, a signal with a DA signal transmission rate of 128 FS is obtained, and if it is further divided by 1/128, a sample signal FS is obtained. This reproduced FS maintains the relationship at the time of recording with the number of samples of the reproduced audio signal, even if rotation irregularity or deviation occurs in the audio head.

As described above, in this embodiment, since the audio sampling signal and the carrier signal of the four-phase phase modulation signal recorded on the magnetic tape have a synchronous relationship, the audio sampling signal at the time of reproduction is reproduced by the reproduced carrier. It can be easily created from signals.

In the above embodiment, the modulation method for recording on the magnetic tape is described as four-phase modulation, but this may be two-phase modulation.

In the above embodiment, the carrier signal frequency is 2.048MHz.
However, the frequency of the carrier signal may be another frequency as long as it has a synchronous relationship with the audio sampling signal.

Further, the magnetic tape recording / reproducing apparatus has been described as recording / reproducing video and audio, but it may be one which records / reproducing only audio.

〔The invention's effect〕

As described above, according to the present invention, since the phase-modulated carrier signal is synchronized with the audio sampling signal, there is an effect that an accurate audio sampling signal can be easily restored from the reproduced carrier signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing a recording system of a magnetic tape recording / reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram showing a reproducing system of the recording / reproducing apparatus, and FIG. 3 is a conventional video signal / digital system. FIG. 4 is a block diagram showing the recording system of the audio signal recording / reproducing apparatus, and FIG. 4 is a block diagram showing the reproducing system of the conventional apparatus.
FIG. 6 is a diagram showing an example of a recording signal format, and FIG. 6 is a block diagram of a conventional video signal / digital audio signal recording / reproducing apparatus. 4 ... Magnetic tape, 7 ... ADC, 8 ... Digital signal recording processing circuit, 9 ... 4-phase phase modulation circuit, 10 ... Recording amplifier, 11 ... Head amplifier, 12 ... 4-phase phase demodulation circuit,
13 ... Digital signal reproduction processing circuit, 14 ... DAC, 15 ...
DA interface circuit, 16 FS circuit, 17 clock generation circuit, 18 PCM data processing circuit, 19 phase modulation circuit, 21 rotary transformer, 22 audio head, 23 synchronization Detection circuit, 24 …… Carrier regeneration circuit, 25 …… Clock regeneration circuit, 26 …… Data regeneration circuit,
28 …… DA interface circuit, 29 …… divider circuit, 30 ……
FS regeneration circuit, 31 …… Phase comparison circuit, 32 …… Voltage control type oscillation circuit, 33,34,35 …… Dividing circuit. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A rotary head helical scan type magnetic tape recording / reproducing apparatus for converting a digital audio signal into data corresponding to a video field, phase-modulating the digital audio data and recording / reproducing the data on a magnetic tape. And sampling signal generating means for generating a signal having a frequency that is an integral multiple of the audio sampling signal, and generating a carrier signal for phase modulation by dividing the signal having a frequency that is an integral multiple of the audio sampling signal by an integer A recording circuit having a carrier signal generating means for reproducing the carrier signal, a carrier signal reproducing means for reproducing the carrier signal, and a sampling for recovering the audio sampling signal and a signal having a frequency of an integral multiple of the audio sampling signal from the reproduced carrier signal. And a reproducing circuit having a signal restoring means. A magnetic tape recording / reproducing device for collection.