JPH0444475B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a video tape recorder (hereinafter simply referred to as
It's called a VTR. ) and other video signal reproducing devices, in particular, by running the magnetic tape at a speed different from that during recording during playback and controlling the deviation of the rotational height position of a pair of rotating heads, The present invention relates to a video signal reproducing apparatus which reproduces a video signal by tracing a recorded track using the pair of rotating heads.

[Background technology and its problems]

Conventionally, in VTRs that record and reproduce video signals using magnetic tape as an information recording medium, as shown in FIG. A so-called helical scanning method is widely used in which a magnetic tape 4 is wound diagonally around the head drum 3 of the rotating magnetic head device 10 and is run. The head motor 1 uses a fixed head (so-called PG head) 7 to detect the passage of a magnetic body 6 for detecting rotational phase, which is disposed on a disk 5 provided on the rotating shaft 1a.
Rotational phase servo is applied based on the detected output. The pair of rotating heads 2A and 2B rotated at a constant speed by the head motor 1 are installed on electromechanical transducer plates, for example, bimorph plates 8A and 8B, respectively, in order to perform tracking control during variable speed playback, which will be described later. , each rotational height position is shift controllable.

In a helical scan type VTR using the rotating magnetic head device 10, as shown in FIG. 2, the tape format of the magnetic tape 4 is a recording track TR _A in a direction y inclined with respect to the tape running direction x. , TR _B to the pair of rotating heads 2A,
2B, trace each recording track sequentially.
One field's worth of composite video signals are recorded on TR _A and TR _B , respectively, with some overlap.
Here, in FIG. 2, the shaded section indicates the overlap part of the signal, and Tsync indicates the section in which the vertical synchronization signal in the composite video signal is recorded.
Furthermore, Tvideo indicates a video section in which one field of video signal is recorded.

In the VTR of the tape format shown in FIG. 2, a reproduced composite video signal is conventionally obtained by a reproduction circuit having a configuration as shown in the block diagram of FIG.

In the reproduction system circuit shown in FIG. 3, each reproduction signal obtained by the pair of rotating heads 2A and 2B described above
S _A and S _B are regenerative amplifiers 11A and 11B, respectively.
After being amplified by the signal selection circuit 12,
The signal is supplied to the sideband equalizer 13.

The signal selection circuit 12 is connected to the magnetic head 7 described above.
The operation is controlled so that the rotational phase detection signal obtained by is switched in accordance with each field by a control signal from a switching pulse forming circuit 19 which is supplied via an amplifier 18. For example, as shown in FIG.
is controlled to switch at timing _ts during the overlap period when the pair of rotary heads 2A, 2B simultaneously trace the recording tracks TR _A , TR _B of the magnetic tape 4, and each of the recording tracks obtained by the rotary heads 2A, 2B is The reproduced signals S _A and S _B are alternately selected and output for each field.

Here, the above-mentioned reproduction signals S _A and _SB are generated by the FM of the luminance signal in the video signal in a recording circuit (not shown).
The sideband of the modulation component is band limited.

Therefore, after the sideband components of the reproduced signals S _A and _SB are compensated by the sideband equalizer 13 , the reproduced signals S _A and _SB are supplied to the signal demodulation circuit 15 via the limiter 14 . The signal demodulation circuit 15 demodulates the reproduced signals S _A and S _B and outputs the reproduced composite video signal Sout to the output amplifier 1.
The signal is output from the signal output terminal 17 via the signal line 6.

By the way, in general, in VTRs, it is unavoidable that the reproduced composite video signal includes time axis errors due to the effects of expansion and contraction of the magnetic tape itself and running errors in the tape running system. A time axis correction process is performed on the reproduced composite video signal Sout using a time axis error correction device 20 whose basic configuration is shown in FIG.

The time axis error correction device 20 shown in FIG. 5 uses a digital memory 23, and is a write control device that operates based on a synchronization signal in a composite video signal containing a time axis error that is supplied to a signal input terminal 21. The circuit 27 controls the writing of the digital memory 23, and the read control circuit 29 operates based on the synchronization signal provided by the reference synchronization signal generator 28.
The readout of the digital memory 23 is controlled by. Then, the composite video signal containing the time axis error supplied to the signal input terminal 21 is digitized by the digital-to-analog converter 22 and written to the digital memory 23, and is then digitized by the digital-to-analog converter 22 and written into the digital memory 23 to provide regular synchronization with no time axis error. By reading out the signal from the digital memory 23 based on the signal, time axis errors are removed. The readout output of the digital memory 23 is converted into an analog signal by a digital/analog converter 24 and returned to a video signal, and then supplied to a signal synthesizer 25. The signal synthesizer 25 is supplied with a composite synchronization signal consisting of a burst signal, a blanking signal, etc. from the reference synchronization signal generator 28, and by adding this composite synchronization signal to the video signal, generates a composite video signal. is formed and output from the signal output terminal 26. That is, in this time axis error correction device 20, the digital memory 23 performs time axis correction of the video signal, and the signal synthesizer 25 replaces the composite synchronization signal.

By the way, the tape format as mentioned above
In a VTR, when the magnetic tape 4 is run at a speed different from that during recording during playback to perform variable speed playback during so-called slow playback or double speed playback, the pair of rotating heads 2A, 2B of the rotating magnetic head device 10 and the magnetic tape 4, the recording tracks TR _A and TR _B on the magnetic tape 4 cannot be correctly traced by the pair of rotating heads 2A and 2B. Therefore, conventionally, the pair of rotary heads 2A and 2B of the rotary magnetic head device 10 are installed on the bimorph plates 8A and 8B as described above, and the rotational height position of the rotary heads 2A and 2B is adjusted according to the tracking error. Tracking control is performed by shifting the

In double-speed reproduction, in which the tape running speed is increased to perform a reproduction operation, the rotary head traces a track TR' in an inclination direction y' that is different from the normal recording track TR, as shown by the broken line in FIG. 6, for example. Even if tracking control is performed by driving the bimorph plates 8A and 8B according to the tracking error amount ΔDT with respect to the normal recording track TR, one horizontal scan will be required as the tape running speed increases. Since the period 1H becomes longer, the number of scanning lines obtained during one field period decreases.

Here, when performing time axis correction using the time axis error correction device that replaces the composite sync signal as described above, the composite sync signal must be added at a predetermined position to the time axis corrected video signal. Therefore, information on the reference position to which the composite synchronization signal is to be added is required, and a vertical synchronization signal is generally used as the information on the reference position. Therefore,
Even during variable-speed reproduction as described above, the vertical synchronization section Tsync of the recording track TR on the magnetic tape 4 must be reproduced, and the shortage of scanning lines will occur in the video section Tvideo.

Therefore, when the time axis error correction device performs time axis correction on the reproduced composite video signal obtained during double-speed playback as described above, the missing portion of the scanning line appears in the image as a no-signal period, and moreover, it appears This results in a composite video signal in which the vertical blanking period V _BLK becomes longer. In Figure 7, 3
A time chart is shown when time axis correction is performed on the reproduced composite video signal obtained during double-speed reproduction.

Vertical blanking period in composite video signal
V _BLK is standardized by various standard television systems such as the NTSC system, so if it becomes apparently long as mentioned above, it may have a serious negative effect on the signal processing at the subsequent stage, which is extremely inconvenient. It is.

[Purpose of the invention]

Therefore, in view of the above-mentioned conventional problems, the present invention provides a variable speed system that completely reproduces one field's worth of video signal and vertical synchronization signal, in order to correctly perform time axis correction processing even during variable speed playback. An object of the present invention is to provide a video signal reproducing device with a new configuration that enables a reproducing operation.

[Summary of the invention]

In order to achieve the above-mentioned object, the video signal reproducing apparatus according to the present invention runs a magnetic tape at a speed different from that during recording during playback, and controls the deviation of the rotational height position of a pair of rotary heads. In a video signal reproducing device that reproduces a video signal by tracing a recording track inclined with respect to the running direction using the pair of rotary heads, at least a vertical synchronization signal is obtained from each reproduction signal obtained by the pair of rotary heads. a first switch circuit that extracts and outputs a reproduced signal including a signal of the section; a first signal demodulator that demodulates a composite video signal from the reproduced signal extracted by the first switch circuit; a synchronization separation circuit for separating a synchronization signal from the composite video signal demodulated by the signal demodulator; and a synchronization separation circuit for extracting and outputting a reproduction signal including a signal of at least one vertical video section from each reproduction signal obtained by the pair of rotary heads. a second switch circuit; a second signal demodulator that demodulates a composite video signal from the reproduced signal extracted by the second switch circuit;
The present invention is characterized in that a signal synthesizer is provided for forming a reproduced composite video signal from the composite video signal demodulated by the second signal demodulator and the synchronization signal obtained by the separation circuit.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a video signal reproducing apparatus according to the present invention will be described in detail below with reference to the drawings.

FIG. 8 shows a helical scan type VTR using the rotating magnetic head device 10 shown in FIG. 1 above.
6 is a block diagram showing an embodiment of a reproduction system circuit when the present invention is applied to a video system which performs double-speed reproduction and performs the time axis correction process shown in FIG. 5. FIG. Further, signal waveforms of various parts of the reproducing circuit shown in the block diagram of FIG. 8 are shown in FIG. In this embodiment, the same components as those of the conventional reproduction circuit shown in FIG. 3 above are denoted by the same reference numerals in the drawings, and detailed explanation thereof will be omitted.

In this embodiment, a pair of rotary heads 2A and 2B of the rotary magnetic head device 10 are used during double-speed reproduction operation.
The reproduced signals S _A and S _B (see FIG. 9 A and B) obtained in
The signal is supplied to the first signal selection circuit 32 via the buffer amplifiers 41A and 41B, and is also supplied to the second signal selection circuit 42 via the respective buffer amplifiers 41A and 41B.

The first signal selection circuit 32 performs a switching operation to completely extract at least the vertical synchronization signal Vsync from the reproduced video signal, which lacks the number of scanning lines during double-speed reproduction, as described above. The operation is controlled by a control signal _S1 from a switching pulse forming circuit 19. The switching pulse forming circuit 19 outputs a rotational phase detection signal obtained from the fixed head 7 to the amplifier 1.
8, and based on this rotational phase detection signal, a control signal for extracting a reproduced signal to be reproduced from the signal section _T1 including the vertical synchronization section Tsync of the recording track TR as shown in FIG. S ₁ (see FIG. 9C), and the operation of the first signal selection circuit 32 is controlled by this control signal S ₁ .

The reproduced signal _SPB1 (see FIG. 9D) obtained via the first signal selection circuit 32 is supplied to the signal demodulator 34 via the limiter circuit 33 of the synchronization signal reproduction system. The signal demodulator 34 always contains all the signals of the vertical synchronization period Tsync, and the video period Tsync.
A reproduced composite video signal S _cpn1 as shown in FIG. 9E in which a portion of the Tvideo signal is missing is obtained. Regenerated composite video signal S _cpn1 obtained by this signal demodulator 34
is supplied to the synchronization separation circuit 35, where the synchronization signal Sync (see FIG. 9F) is taken out. The synchronization signal Sync is then supplied to the vertical synchronization signal detection circuit 36. This vertical synchronization signal detection circuit 36 detects the vertical synchronization signal Vsync in the synchronization signal Sync to provide a reference signal for replacing the composite synchronization signal in the above-mentioned time axis error device 20.
Form S _REF (see Figure 9G). This reference signal
S _REF is supplied from the signal output terminal 37 to the time axis error correction device 20 .

Further, the second signal selection circuit 42 selects at least one vertical video section in the reproduced video signal in which the number of scanning lines is insufficient during double-speed reproduction as described above.
It performs a switching operation to completely take out the video signal of TVideo, and its operation is controlled by the control signal S ₂ (see FIG. 9H) supplied from the switching pulse forming circuit 19 via the delay circuit 30. There is. That is, the second signal selection circuit 42 is operated by the control signal _S2 to extract the reproduction signal to be reproduced from the signal section _T2 including the video section Tvideo of the recording track TR, as shown in FIG. controlled.

The reproduction signal _SPB2 (see FIG. 9I) obtained through the second signal selection circuit 42 is supplied to the sideband equalizer 13 of the video signal reproduction system.
The video signal reproduction system in this embodiment has the same configuration as the reproduction system circuit shown in FIG. There is. Signal demodulator 1 of the above video signal reproduction system
5, the reproduced composite video signal as shown in FIG. 9J always includes the video signal of one vertical video section Tvideo and the signal of the vertical synchronization section Tsync is partially omitted.
S _cpn2 is demodulated.

The reproduced composite video signal S _cpn2 obtained by the video signal reproduction system is supplied from the signal output terminal 17 to the time axis error correction device 20, where it is subjected to time axis correction processing.

In this embodiment, as mentioned above, the synchronization signal regeneration system completely regenerates the vertical synchronization signal from the reproduction signal that lacks the number of scanning lines during double-speed reproduction and generates the reference signal.
In addition to forming S _REF , 1 in the video signal reproduction system
Since the video signal for the vertical scanning period of 1V is completely reproduced and output, the time axis error correction device 20 can reliably perform the time axis correction process and the composite synchronization signal replacement process.

Here, since the synchronization signal reproduction system in the above embodiment only needs to reproduce the synchronization signal, it operates as a limiter circuit 33 and a signal demodulator 34, compared to a video signal reproduction system that reproduces a video signal with a large amount of information. Those with lower performance can be used.

〔Effect of the invention〕

As is clear from the description of the above embodiments, according to the present invention, the video signal and the vertical synchronization signal can be completely reproduced during variable speed reproduction, and the intended purpose can be fully achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing the basic structure of a rotating magnetic head device used in a helical scan type VTR to which the present invention is applied. Second
The figure is a schematic diagram showing the tape format of the magnetic tape in the VTR. Figure 3 is above
1 is a block diagram showing the configuration of a general reproduction circuit in a VTR. FIG. FIG. 4 is a waveform diagram of a reproduction signal for explaining the operation of the signal selection circuit in the reproduction system circuit. FIG. 5 is a block diagram showing the basic structure of a general time axis error correction device that performs time axis correction processing on a reproduced composite video signal obtained by the above-mentioned VTR. FIG. 6 is a schematic diagram for explaining the tracking control state in the variable speed playback operation by the VTR. FIG. 7 is a signal waveform diagram when time axis correction processing is applied to the reproduced composite video signal obtained from the VTR during the variable speed reproduction. FIG. 8 is a block diagram of a reproduction system circuit showing one embodiment of the present invention. FIG. 9 is a diagram of signal waveforms at various parts in the above embodiment. FIG. 10 is a schematic diagram for explaining the operation of each signal selection circuit in the above embodiment. 2A, 2B... Rotating head, 4... Magnetic tape, 7
...Fixed head, 8A, 8B...Bimorph plate, 10
...Rotating magnetic head, 15, 34...Signal demodulator, 1
9... Switching pulse forming circuit, 20... Time axis error correction device, 30... Delay circuit, 32, 42... Signal selection circuit.

Claims (1)

[Claims] 1. During playback, the magnetic tape is run at a speed different from that during recording, and the rotational height position of a pair of rotary heads is controlled to shift, so that a recording track that is inclined with respect to the tape running direction is In a video signal reproducing device which reproduces a video signal by tracing it with a pair of rotating heads, a reproduced signal including at least a signal in a vertical synchronization signal section is extracted from each reproduced signal obtained by the pair of rotary heads and outputted. a first switch circuit; a first signal demodulator that demodulates a composite video signal from the reproduced signal extracted by the first switch circuit; and a synchronization from the composite video signal demodulated by the first signal demodulator. a synchronous separation circuit that separates signals; a second switch circuit that extracts and outputs a reproduced signal including a signal of at least one vertical video section from each reproduced signal obtained by the pair of rotating heads; a second signal demodulator that demodulates a composite video signal from the reproduced signal extracted by the second signal demodulator; and a composite video signal that is reproduced from the composite video signal demodulated by the second signal demodulator and the synchronization signal obtained by the separation circuit. A video signal reproducing device comprising: a signal synthesizer for forming a signal.