JPH03190490A - Intermittent recording or recording and reproducing method - Google Patents

Abstract

PURPOSE:To avoid discontinuity of phase switching order of a reproduced color signal by using a recording head so as to apply intermittent recording to a tape driven stably by a cylinder. CONSTITUTION:A pulse delay circuit 4 generates a comparison signal coincident with a vertical synchronization timing and an RF switching pulse for head output changeover respectively and a control signal generating circuit 7 receiving an RF switching pulse generates a head motor brake pulse at a field just before the recording timing. Then the drive speed of the cylinder is decelerated by one horizontal synchronization period at one field just before the recording timing and a tape is intermittently driven by one pitch for 4-field period just after the end of the recording timing. Thus, recording tracks by an integral number of H are formed in a prescribed recording range in the case of the intermittent recording to eliminate the discontinuity of a phase change in a color subcarrier.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an intermittent recording or recording/playback system in a video tape recorder.

(b) Conventional technology A VH8 video tape recorder that records PAL color video signals has a recording track of 1.5 in the scanning direction.
H is recorded in advance, so-called H alignment recording is performed. When performing intermittent recording according to this method,
The tape must be run at a constant speed at the recording timing. However, even if the tape is driven intermittently and recorded at that moment, the tape does not run stably, so it is not only impossible to ensure the linearity of the recording track, but also the so-called H alignment with adjacent tracks cannot be secured. , skew distortion also occurs during high-speed playback.

Therefore, it may be possible to record on static tape, but
If the recording track is simply formed by stopping the tape running, skew distortion will occur when the head output is switched during still image playback.

Therefore, in order to eliminate this skew distortion, it is conceivable to reduce the rotational speed of the head by 1.5H and perform recording to form a recording track with the same horizontal synchronization length as normal recording.

(c) Problems to be Solved by the Invention However, as described in L, in order to correctly lower the recording speed by 1.5H from the normal speed, a considerable gap is required.

If the time is delayed due to a decrease in the rotational speed, the rotational phase of the head will be significantly deviated, making it impossible to record a desired recording signal on a single recording track.

Therefore, it is necessary to realize intermittent recording that does not cause skew distortion during still image reproduction and also does not deviate the rotational phase of the head from the recorded video signal.

(d) Means for Solving the Problems Therefore, the present invention provides a first method for recording by reducing the rotational speed of the video head by one horizontal synchronization period immediately before the intermittent recording period.
The second feature is that when the recorded video signal is a PAL color video signal, the phase change of the color subcarrier is continuously corrected during reproduction.

(e) According to the present invention, recording trunks for an integer number of H are formed in a predetermined recording range during intermittent recording, and the phase change of color subcarriers is discontinuous when recording and reproducing a PAL color video signal. Gender is explained;

(f) Example The present invention will be described below with reference to an illustrative embodiment.

In this embodiment, the present invention is applied to a video tape recorder of 7HS type to which PAL video signals are processed.

First, FIG. 1 shows a block diagram of the recording control circuit of this embodiment.
Further, FIG. 2 shows an explanatory diagram of the signal waveforms.

In this embodiment, when performing intermittent recording of 1/'6, odd fields and even fields are sampled and recorded at predetermined intervals. Further, in this embodiment, the rotational speed of the cylinder is decelerated by one horizontal synchronization period in one field immediately before the recording timing, and the tape is intermittently driven by one pinch during the four-field period immediately after the recording timing ends. It is.

First, the head servo obtains FG pulses and PG pulses from the cylinder motor 2 that drives the cylinder 1, and inputs the FG pulses to the speed control circuit 3 and the PG pulses to the pulse delay circuit 4. The pulse delay circuit 4 generates a comparison signal matching the vertical synchronization timing and an RF switching pulse for switching the head output. The speed control circuit 3 detects the period of the FG pulse and constantly generates a speed control output. Further, the phase control circuit 5 to which the comparison signal is input generates a phase comparison output using the vertical synchronization signal of the recording signal as a reference input. Therefore, the cylinder drive circuit 6 adds the speed control output and the phase control output and supplies the drive output to the cylinder motor 2 to rotate the cylinder 1 in synchronization with the recording signal.

In this state, the control signal forming circuit 7 to which the RF switching pulse is input generates a head motor braking pulse in the field immediately before the recording timing. This head motor control pulse has its level set appropriately and is multiplexed onto the phase control output line. As a result, at the recording timing, the rotation speed of the cylinder motor 2 is exactly 1
The rotational speed is decelerated by the amount corresponding to the horizontal synchronization period, and the rotational speed is stabilized in the decelerated state during the l field period.

In this embodiment, the recording timing is set alternately at a period of 5 fields and 7 fields, and the control signal forming circuit 7 generates a gate control signal for one field period when the recording timing comes, and The gate circuit 11 is opened by the control signal, and a recording signal for one field is supplied to a recording head (not shown), thereby forming a recording track on the stationary tape.

When recording is completed, the capstan 13 is driven by one track pitch. This intermittent drive requires four fields, and the capstan motor 9 is started in the first field immediately after recording, and reversely braked in the fourth field. Therefore, the control signal forming circuit 7 derives start/stop signals for the first field and the first field. This start/stop signal is input to the capstan drive circuit 8 and supplied to the capstan motor 9 as a drive output. Further, in order to switch the rotation direction of the capstan motor, a rotation direction switching signal is derived from the control signal forming circuit 7 in synchronization with the signal of the 4 fields [1], and is supplied to the capstan motor 9. The capstan motor 9 has a first motor with a slightly different phase.
A rotational direction detection circuit 10 which generates a G pulse and a second FG pulse and which receives both FG pulses generates a reverse rotation detection output of the capstan motor 9. In synchronization with the generation of this reverse rotation detection output, the control signal forming circuit 7 deactivates the rotation direction switching signal.

There is a third recording track formed by this intermittent recording.
As shown in the figure, video signals for 313 horizontal synchronization periods are recorded per recording track, and the recording tracks of odd and even fields are recorded in H alignment with different recording azimuths.

When this recording track is normally reproduced or still images are reproduced as it is, the color phase switching order becomes discontinuous, causing achromatic phenomenon on the reproduced screen. This achromatic phenomenon will be explained with reference to FIGS. 3 and 4.

First, in normal reproduction, for convenience of explanation, it is assumed that the recording signal in the hatched portion is reproduced by scanning the center of the starting end of the recording track for reproduction, and then the reproduction output will have a relationship as shown in FIG. That is, at one head output switching timing, the 312H and 313H signals are switched,
At the other head output switching timing, the 624th H and I
The H-th signal is switched, and the color subcarrier phase change becomes discontinuous at one head output switching timing.

Furthermore, when playing still images, for the sake of explanation, it is assumed that the center of the starting end of the recording track is scanned for playback and the recorded signal in the hatched area is played back, and the playback output will have a relationship as shown in Figure 4. . That is, the 312H and 313I-1 signals are switched at one head output switching timing, and the 624th signal is switched at the other head output switching timing.
The H-th and IH-th signals are switched, and the color subcarrier phase change becomes discontinuous at both head output switching timings.

Therefore, it is necessary to make the color phase switching order of the PAL color video signal continuous even in the playback mode.

FIG. 5 is a block diagram of a reproduced color signal processing circuit for making this color phase switching order continuous. As is clear from the diagram, the reproduced color signal is input to the phase comparison circuit] 9 and the frequency conversion circuit 21. .

On the other hand, the horizontal synchronization separation signal is 17' 2 H killer circuit 1
After 7, 1. The signal is input to the /2 frequency divider circuit 18 and the burst gate pulse generation circuit 20. Furthermore, carrier oscillation circuit 1
4 generates a fixed oscillation output with a frequency corresponding to the color subcarrier at a predetermined phase, and this fixed oscillation output is input to the doubler circuit 21 and the phase inversion circuit 15. This phase inverted output and fixed oscillation output are supplied to a first changeover switch 6. The first changeover switch 16 alternately performs switching using the 1/2 frequency divided output, and the first changeover output is inverted at ±90 degrees with respect to the reference phase in the horizontal synchronization period.

The phase comparison circuit 19 compares the phases of the reproduced color signal and the first switching output at the burst generation timing, and outputs a positive output when the phase switching order of the reproduced burst signal and the switching output match. When the opposite occurs, a negative output is generated.

Further, the doubling circuit 21 doubles the fixed oscillation output and supplies it to the frequency conversion circuit 22, and the frequency conversion output includes a phase-inverted reproduced color signal.

The second changeover switch 23 has the reproduced color signal and the frequency conversion output as switching inputs, and is switched by the phase comparison output. Therefore, the second switching output selects and derives a phase component that matches the switching order of the first switching output, and outputs it as a reproduced color signal with continuous phase inversion via the bandpass filter 24. The derived reproduced color signal is added to the peak phase variation signal in an adder circuit 25, and is derived as a reproduced PAL color video signal.

(g) As a result of the invention, according to the present invention, intermittent recording is performed by rotating the tape stably in a stationary state, and during reproduction, the tape is stably reproduced without skinny distortion. Also,
Discontinuities in the phase switching order of reproduced color signals are also eliminated,
The effect is great.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of its signal waveform, FIG. 3 is a schematic explanatory diagram of a recording track, FIG. 4 is an explanatory diagram of a color phase inversion state, and FIG. 1A and 1B respectively show block diagrams of reproduction color signal processing circuits.

Claims (2)

[Claims] (1) Two heads that run the tape intermittently and record video signals field by field in a stationary state, and form recording tracks by shifting them in the scanning direction by 1.5H (where H is the length equivalent to horizontal synchronization). An intermittent recording method in a helical scan type video tape recorder, characterized in that immediately before intermittent recording, the rotational speed of the video head is reduced by one horizontal synchronization period. (2) The tape is run intermittently and in a stationary state, PAL color video signals are intermittently recorded field by field, and recording tracks are formed by shifting them in the scanning direction by 1.5H (where H is the length equivalent to horizontal synchronization). A two-head helical scan type video tape recorder is characterized in that immediately before intermittent recording, the rotational speed of the video head is decelerated by one horizontal synchronization period, and the color subcarrier phase change is made continuous during playback. Intermittent recording and playback method.