JPH0353792A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the performance of time base correction and to reproduce the picture for which jitter is reduced, with high quality by switching the level of a video signal to which a burst signal is superimposed, corresponding to a recording mode. CONSTITUTION:In a magnetic recording and reproducing device, a first burst signal generating circuit 4 is provided to generate the burst signal superimposed to the level of the video signal so as to generate an inverting phenomenon, and a second burst signal generating circuit 17 is provided to generate the burst signal superimposed to the level of the video signal not so as to generate the inverting phenomenon. The outputs of the first and second burst signal generating circuits 4 and 17 are simultaneously applied to a switch circuit 5 and according to a recording mode signal IREC to be applied from a microcomputer, the switch circuit 5 selects any one of the two burst signals and applies the selected signal to a burst signal inserting circuit 6 in the next step. Accordingly, at the time of reproducing, the phenomenon to invert the burst signal can be always suppressed and stable operation can be always obtained for the time base correction of the video signal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic recording and reproducing device that performs FM modulation on a video signal to record and reproduce the video signal, and particularly has a function of correcting time axis fluctuations of the video signal. The present invention relates to a magnetic recording/reproducing device.

[Prior Art] Conventionally, magnetic recording and reproducing devices, such as video tape recorders, which have the function of recording and reproducing provided video signals, have been equipped with video signal digital processing technology to improve the image quality during playback. There is. In particular, among this digital processing technology, the T
BC (abbreviation for time base corrector) is a device that uses a digital method to correct time axis fluctuations in video signals to improve image quality during playback. This is because the video signal is transferred to the storage element inside the TBC once at a timing generated based on the phase of the burst signal inserted into the blanking period, and is retrieved at stable time intervals. This means that fluctuations in the time axis are corrected.

Hereinafter, burst signal insertion into a video signal and correction of TBC time axis fluctuations in a conventional video table recorder will be described in detail with reference to the drawings.

FIG. 3 is a schematic block diagram showing the functional configuration of a conventional video table recorder for recording and reproducing video signals.

In the figure, the functional structure of recording and playback is as follows: input terminal 2
A recording system inputs a composite video signal containing a mixture of a video signal and a synchronization signal from 6, and performs processing up to recording the video signal on a tape 11, which is a recording medium for the video signal, and a recording system that processes the video signal recorded on the tape 11. It includes two systems: a reproduction system that performs processing from reading to outputting the reproduced video signal from the output terminal 27.

In the figure, the recording system includes an A/D converter 1 that converts a video signal supplied from an input terminal 26 into a digital signal, a synchronization separation circuit 3 that separates a synchronization signal from the video signal,
A video signal and a synchronization signal are inputted from an A/D converter 1 and a synchronization separation circuit 3, and a recording system signal processing circuit 2 that performs signal processing for recording the video signal, and a video signal is inputted from the recording system signal processing circuit 2. , a burst signal generating circuit 4a . A burst signal insertion circuit receives the video signal and the burst signal from the recording system signal processing circuit 2 and the burst signal generation circuit 4a, and inserts the burst signal during the blanking period of the video signal according to the synchronization signal from the synchronization separation circuit 3. Contains 6. Furthermore, the recording system includes a D/A converter 7 that converts the video signal into which the burst signal has been inserted into an analog signal, and a D/A converter 7 that manually converts the video signal into an analog signal to perform frequency modulation of the signal. FM modulation circuit 8, a recording amplifier 9 which amplifies the FM signal from the FM modulation circuit 8 so as to record it with a constant current, and a head 10 which records the amplified FM signal on tape 11.

Note that the head 10 has both the functions of recording and reproducing video signals.

On the other hand, the reproduction system includes a reproduction amplifier 12 for amplifying the reproduction FM signal read from the tape 11 by the head 10;
A reproduction equalizer 13 that manually inputs the reproduced FM signal amplified from 2 and compensates the frequency characteristics of this signal; an FM demodulation circuit 14 that demodulates the reproduced FM signal whose frequency characteristics have been compensated;
TBC15, which manually inputs the reproduced video signal demodulated from the FM demodulation circuit 14 and corrects the time axis fluctuation of the signal.
It includes a reproduction system signal processing circuit 16 which inputs the reproduced video signal whose time axis fluctuation has been corrected and performs various signal processing, and an output terminal 27 which outputs the signal-processed reproduced video signal.

Next, the video signal recording and reproducing operations of the conventional video tape recorder shown in FIG. 3 will be explained with reference to FIGS. 3 to 5.

FIG. 4 is a signal waveform diagram for explaining the circuit operation of generating and inserting the burst signal shown in FIG. 3.

FIG. 5 is a schematic block diagram showing the functional configuration of the TBC 15 shown in FIG. 3.

In FIG. 3, a composite video signal inputted manually to the apparatus via the input terminal 26 is converted into a digital signal by the A/D converter 1 and is then applied to the recording system signal processing circuit 2. Further, from this composite video signal, only the synchronization signal is separated by the synchronization separation circuit 3 as shown in FIG. 4(b). The separated synchronization signal is given to the recording system signal processing circuit 2 and the burst signal insertion circuit 6.

The video signal converted into a digital signal by the A/D converter 1 is given to the recording system signal processing circuit 2, where signal processing suitable for recording the video signal on the tape 11 is performed, as shown in FIG.
It is processed into a signal like a). This signal is applied to burst signal generation circuit 4a and burst signal insertion circuit 6. The burst signal generation circuit 4a performs RO during the blanking period of the video signal supplied from the recording system signal processing circuit 2.
M (abbreviation for Read Only Memory) or the like generates a color burst signal superimposed on a certain video signal level as shown in FIG. 4(c).

This burst signal is applied to the burst signal intrusion circuit 6 to demodulate the color signal. Burst signal divine circuit 6
In the blanking period of the video signal in FIG. 4(a), the fourth
The burst signal shown in FIG. 4(C) is inserted based on the synchronization signal shown in FIG. 4(b), and a video signal as shown in FIG. 4(d) is output. To explain further, the burst signal insertion circuit 6 receives the video signal of FIG. 4(a) and the video signal of FIG. 4(b).
The blanking period of the video signal is detected from the synchronization signal. Thereafter, the burst signal shown in FIG. 4(C) is inserted into the video signal of FIG. 4(a) in accordance with the detected blanking period, and the burst signal shown in FIG. 4(d) is generated. A video signal into which is inserted is obtained and fed to the D/A converter 7. Thereafter, the video signal applied to the D/A converter 7 is converted into an analog signal and FM modulated by the FM modulation circuit 8 at the next stage. This FM signal is amplified by a recording amplifier 9 and recorded on a tape 11 via a head 10.

Next, the reproduction operation of the reproduction system will be explained.

During playback, the head 10 plays the FM recorded on the tape 11.
The signal is read out, and this reproduced FM signal is given to the regenerative amplifier 12. In response, the regenerative amplifier 12 amplifies the signal, and the amplified regenerative FM signal is given to the regenerative equalizer 13 at the next stage. The reproduction equalizer 13 compensates for losses during reproduction of the reproduced FM signal, processes the signal into a signal having optimal characteristics, demodulates the signal in the next stage FM demodulation circuit 14, and supplies it to the TBC 15 as a reproduced video signal. In the TBCI 5, time axis fluctuations in the video signal due to expansion of the tape 11 and the like are corrected. Thereafter, the video signal is subjected to signal processing necessary for reproduction in the next-stage reproduction system signal processing circuit 16, and is outputted to the outside of the apparatus via the output terminal 27.

Next, the functional configuration of the TBC 15 described above will be explained with reference to FIG.

In FIG. 5, the TBC 15 inputs the FM demodulated reproduced video signal from the FM demodulation circuit A 14 via the input terminal 26a, corrects the time axis fluctuation of the reproduced video signal within the circuit, and outputs the output terminal 27a. The functional configuration is such that the signal is outputted to the next stage reproduction system signal processing circuit 16 via the reproducing signal processing circuit 16.

Specifically, the TBC 15 includes a synchronization separation circuit 3 that separates a synchronization signal from a reproduced video signal, a burst separation circuit 18 that separates and outputs a burst signal from a reproduced video signal, and a digital digital signal that synchronizes the reproduced video signal with a write clock pulse W. It includes a TBC A/D converter 21 for converting into a signal. Also TB
C15 has one AFC (automatic frequency control) circuit that outputs a clock pulse A synchronized with a synchronization signal that includes time axis fluctuations, and a clock pulse A and a burst signal that are manually generated.
An APC (automatic position control) circuit 20 that phase-locks the clock pulse A to the burst signal and outputs the write clock pulse W, a memory 22 that stores digital data of the video signal, and a memory 22 that writes/writes data to the memory 22. It includes a memory control circuit 25 that controls reading. Furthermore, the TBC 15 includes a reference clock generation circuit 24 that stably outputs a read clock pulse R for reading data from the memory 22, and a TBC D/C circuit that converts the data read from the memory 22 into an analog signal in synchronization with the read clock pulse R. A'
& converter 23 is included.

Note that the memory 22 is a digital memory (RAM: Ran
dom Access Memory).

Next, correction of time axis fluctuations in the reproduced video signal of the TBC 15 will be explained.

In FIG. 5, since the reproduced video signal manually input from the input terminal 26g includes time axis fluctuations due to elongation of the tape 11, etc., the synchronization signal detected by the synchronization separation circuit 3 also includes time axis fluctuations. included. Therefore, the AFC circuit 19 generates a clock pulse A in synchronization with the synchronization signal, and the APC circuit 20 generates a write clock pulse W by locking the phase of this pulse to the burst signal. Therefore, the reproduced video signal including time axis fluctuations is
Data is written into the memory 22 using a write clock pulse W that includes a similar time axis variation. On the other hand, since the readout from the memory 22 is performed sequentially using the readout clock pulse R that is always locked to a stable reference signal, a good reproduced video signal with a well-balanced horizontal synchronization signal frequency and no time axis fluctuation can be obtained. will be obtained.

As described above, the reproduced video signal with the input time axis error is A/D converted at high speed by the write clock pulse W based on the reproduced burst signal with the same time axis error, and is written to the memory. Therefore, it is necessary to always maintain a constant phase relationship between the write clock pulse W and the video signal regardless of the time axis error.

[Problems to be Solved by the Invention] However, the playback equalizer included in the playback system of the conventional video tape recorder as described above
In order to improve the S/N ratio of the M signal, it generally has a characteristic of uniformly suppressing both sideband waves around the carrier wave of the reproduced FM signal, as shown in FIG. However, if left as is, the lower sideband of the reproduced FM signal will be emphasized due to the nonlinearity of the tape head system, and the upper sideband will be suppressed.
The unbalanced characteristics of the M signal will remain. Furthermore, during the recording operation of a conventional video table recorder, a burst signal of the same amplitude is always inserted into the video signal. To explain in detail, even if the recording conditions are different, such as the standard mode and long-time mode of a video table recorder, such as the tape speed of the tape head system during recording, the recording density of the head, etc., the Takagi frequency component is emphasized. , and a burst signal with a large amplitude is uniformly inserted into the blanking period. However, in the long-time mode, the output of the Takagi frequency component of the video signal is attenuated compared to the standard mode. Therefore, if a burst signal with high amplitude and emphasized Takagi frequency components is used in the long-time mode as in the standard mode, even if no inversion phenomenon occurs in the video signal after FM demodulation, For example, an inversion phenomenon as shown in Fig. 7 occurs in the burst signal part,
Phase fluctuations will occur in the burst portion. Therefore, since the burst signal that has caused the inversion phenomenon is given as is to the TBC at the next stage, this phase variation is included in the write clock pulse to the memory, and the write/read of the reproduced video signal to/from the memory is There is a problem in that a time lag occurs between the two operations, making the operation of the TBC unstable and, as a result, causing jitter on the playback screen.

Therefore, an object of the present invention is to always obtain stable operation of the time axis correction of the video signal even when the tape head system conditions differ in the recording mode of the video signal, and to achieve high speed correction with little jitter. It is an object of the present invention to provide a magnetic recording and reproducing device for video signals capable of reproducing high quality video.

[Means for Solving the Problems] A magnetic recording and reproducing device according to the present invention is a magnetic recording and reproducing device that records and reproduces a video signal by FM modulating the video signal, and the inversion phenomenon occurs within the blanking period of the video signal during recording. The first one generates a burst signal superimposed on the video signal level that produces
a second burst signal generating means for generating a burst signal superimposed on a video signal level that does not cause an inversion phenomenon within a blanking period of the video signal; burst signal selection means for selecting one of the burst signal selection means, and burst signal insertion means for inserting the burst signal selected by the burst signal selection means into the video signal.

[Function] The magnetic recording/reproducing device according to the present invention has a first magnetic recording/reproducing device that generates a burst signal superimposed on a video level at which an inversion phenomenon occurs.
and a second burst signal generating means for generating a burst signal superimposed on a video level such that an inversion phenomenon does not occur. Therefore, depending on the recording mode, one of the burst signals is selected and inserted into the video signal for recording.
During reproduction, the inversion phenomenon of the burst signal can be suppressed at all times, and stable operation of time axis correction of the video signal can always be obtained.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic block diagram showing the recording and playback functional configuration of a video tape recorder according to an embodiment of the present invention.

In FIG. 1, the improvement compared to the conventional functional configuration shown in FIG. , the second burst signal generating circuit 17 and the switch circuit 5 which generate the second burst signal are used instead. To explain in detail, the first and second burst signal generation circuits 4 and 17 respectively output first and second burst signals having different characteristics, and apply these to the switch circuit 5 simultaneously. Accordingly, the switch circuit 5 performs a switching operation in accordance with a recording mode signal IREC given from a microcomputer (not shown), and selects one of the two simultaneously given burst signals. The selected burst signal is applied to the burst signal insertion circuit 6 at the next stage. The rest of the functional configuration is the same as the conventional one, so the explanation will be omitted.

Next, the recording and reproducing operations of the video table recorder shown in FIG. 1 will be explained in detail with reference to FIGS. 1 and 2.

FIG. 2 is a schematic diagram showing waveforms of first and second burst signals according to an embodiment of the present invention.

In FIG. 1, a composite video signal containing a domei signal is applied to the recording system of a video table recorder via a human input terminal 26.

First, in the recording system, a video signal applied via the input terminal 26 is processed by the A/D converter 1, the recording system signal processing circuit 2, and the synchronization separation circuit 3, as in the conventional case. In the processed video signal, a burst signal insertion circuit 6 inserts either the first or second burst signal applied from the switch circuit 5 into the blanking period.

The video signal into which the burst signal has been inserted is D
The signal is processed by the /A converter 7, the FM modulation circuit 8, and the recording amplifier 9, and is recorded as an FM signal on the tape 11 via the head 10.

Next, two burst signals and switch switching operations in the recording system will be explained in detail.

A first burst signal generation circuit 4 shown in FIG. 1 supplies a burst signal superimposed on the gray level of a video signal as shown in FIG. 2(a) to a switch circuit 5, for example.

On the other hand, the second burst signal generation circuit 17 is designed to prevent an inversion phenomenon from occurring in the burst signal portion even when the conditions of the tape head system during recording are severe. A burst signal superimposed on the black level of the video signal as shown is applied to the switch circuit 5.

Note that, as shown in FIG. 2, the amplitudes of the first and second burst signals are equal.

Next, the switch circuit 5 selects one of the two provided burst signals by a switch switching operation based on the recording mode signal IREC provided by the microcomputer.
It is applied to the burst signal insertion circuit 6 at the next stage. For example, if the signal content of the recording mode signal IREC is the standard mode, the switch circuit 5 operates to select the first burst signal and provide it to the burst signal insertion circuit 6. on the other hand,
If the signal peak of the recording mode signal IREC is the long-time mode, the switch circuit 5 operates to select the second burst signal and apply it to the burst signal insertion circuit 6.

Therefore, in the standard mode, a burst signal superimposed on the gray level of the video signal is recorded, and in the long time mode, the burst signal superimposed on the black level of the video signal is recorded.

Next, in the playback system, the tape 1 is
As in the conventional case, the FM signal recorded on the TBC 15 is read by the head 10, processed by the reproducing amplifier 12, the reproducing equalizer 13, and the FM demodulating circuit 14, and then provided to the TBC 15 as a reproduced video signal.

The TBC 15 operates to perform time axis correction based on the phase information of the burst signal added to the reproduced video signal provided as in the conventional case. That is, in the standard mode, since the frequency of the carrier wave signal of the video signal is high, it is possible to perform time axis correction using the first burst signal with less moiré, thereby further reducing residual jitter on the reproduced screen.

On the other hand, in the long-time mode, time axis correction is performed using a second burst signal superimposed on a video signal level that does not cause an inversion phenomenon. Therefore, even if the video signal is recorded in long-time mode, the burst signal period does not include the phase fluctuation due to the inversion phenomenon, so TBC15
The time axis correction operation can be stabilized by

As described above, the reproduced video signal subjected to time axis correction by the TBC 15 is subjected to signal processing in the next stage reproduction system signal processing circuit 16, and is outputted to the outside via the output terminal 27, as in the conventional case.

In this embodiment, the long-duration mode is cited as a case where the conditions of the tape head system are severe, but the present invention is not limited to this, and may be, for example, a case where recording and playback are performed using tapes with different characteristics. .

Further, in this embodiment, the first and second burst signals have the same amplitude, but the amplitudes may be different.

[Effects of the Invention] As described above, according to the present invention, since the video signal level on which the burst signal is superimposed is switched according to the recording mode, the performance of time axis correction is improved and the jitter is reduced. This has the effect of being able to reproduce high-quality screens with fewer images.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing the recording and playback functional configuration of a video tape recorder according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing waveforms of first and second burst signals according to an embodiment of the present invention. FIG. 3 is a schematic block diagram showing the recording and playback functional structure of a conventional video table recorder. FIG. 4 is a signal waveform diagram for explaining the circuit operation of generating and inserting the burst signal shown in FIG. 3. FIG. 5 is a schematic block diagram showing the functional configuration of the TBC shown in FIG. 3. FIG. 6 is a diagram illustrating an example of the characteristics of the resoil equalizer. FIG. 7 is a schematic diagram of a waveform when a burst signal causes an inversion phenomenon. In the figure, 4 is a first burst signal generation circuit, 17 is a second burst signal generation circuit, 5 is a switch circuit, and IREC is a recording mode signal. In each figure, the same reference numerals indicate the same or equivalent parts. Agent Masuo Oiwa

Claims (1)

[Claims] A magnetic recording and reproducing device that records a video signal by FM modulating it, which generates a burst signal superimposed on the video signal level that causes an inversion phenomenon within the blanking period of the video signal during recording. a first burst signal generating means; a second burst signal generating means for generating a burst signal superimposed on a video signal level that does not cause an inversion phenomenon within a blanking period of the video signal; A magnetic recording and reproducing device comprising: burst signal selection means for selecting one of the burst signals; and burst signal insertion means for inserting the burst signal selected by the burst signal selection means into a video signal.