JP2523338B2 - Magnetic recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a magnetic recording / reproducing apparatus (hereinafter referred to as VTR).
And particularly to a VTR that employs a multi-channel recording system.

[Prior Art] A video signal band of a conventional television signal (hereinafter referred to as a TV signal), for example, an NTSC TV signal is about 4.2 MHz. On the other hand, the TV signal used in the high-definition TV system, which has been developed and put into practical use as a next-generation system, has a wide video signal band of about 20 MHz. In the case of recording such a wide band signal, it is not possible to record if the drum diameter is the same in the method of recording the video signal of one field on one track by the rotary head like the conventional VTR. Therefore, as a recording method used in a VTR for recording a wideband signal such as a high-definition TV signal, an input video signal is converted into an N-channel (N is an integer of 2 or more) video signal and a 1-field video signal is converted. There is a multi-channel recording method in which recording is performed by dividing into N tracks.

Hereinafter, the 2-channel recording method will be described. The two-channel recording method means that the input video signal (one channel component time division signal) is used for one horizontal scanning period (hereinafter, 1H
2 units with CH.A and CH.
The time axis is doubled. As a result, the signal bandwidth of each channel is halved.

FIG. 8 is a view showing the arrangement of rotary heads used in the above-mentioned two-channel recording type VTR. Rotating drum
100 includes rotary heads 101a and 101b for recording CH.A signals.
And rotary heads 102a and 102b for recording CH.B signals. Rotary heads 101a, 102a and rotary heads 101b,
102b are arranged adjacent to each other, the gap distance is La, and the head step is Lp (corresponding to the track pitch). Magnetic tape is about 1 on the rotating drum 100
It is tightly wound by 80 °, and part of the video signal is recorded at different positions on the magnetic tape by the two heads.

FIG. 9 is a block diagram showing the configuration of a conventional VTR recording system of a two-channel recording system. In the figure, the 2-channel conversion circuit 21 shows a 1H input signal (luminance signal Y, broadband color signal
C _W and narrow band color signal C _N ) are time-extended to 2H, and 2 channel video signals (video signals with odd scan line numbers are
It is a circuit that converts the video signals of even scan line numbers to CH.A and CH.B and vice versa). The CH.A signal output from the 2-channel conversion circuit 21 is applied to the rotary heads 101a and 101b via the FM modulation circuit 4a and the recording amplifier 5a. CH.B output from the 2-channel conversion circuit 21
Is applied to the rotary heads 102a and 102b via the FM modulation circuit 4b and the recording amplifier 5b.

FIG. 10 is a block diagram showing the structure of a reproducing system of a conventional 2-channel recording VTR. In the figure, the rotary head
C reproduced from magnetic tape 1 by 101a and 101b
The HA signal is given to the channel synthesis circuit 22 via the head amplifier 6a and the FM demodulation circuit 7a. On the other hand, the CH.B signal reproduced by the rotary heads 102a and 102b is given to the channel synthesis circuit 22 via the head amplifier 6b and the FM demodulation circuit 7b. The channel synthesizing circuit 22 is a circuit for restoring a video signal of two channels into a video signal of one channel.

Next, the operation of the conventional two-channel recording system VTR shown in FIGS. 8 to 10 will be described.

FIG. 11 is a diagram for explaining the operation of the 2-channel conversion circuit 21. Figure 11 (a) shows the input video signals (Y, C _W , C _N ).
In the unit of one horizontal scanning period, and the numbers in the figure represent scanning line numbers. The 2-channel conversion circuit 21 expands the input luminance signal Y by about two times on the time axis, and
After band-limiting C _W and C _N and performing line-sequential processing, time axis compression is performed to about half. Then, the luminance signal Y of the odd scan line number
And the wide band color signal C _W is distributed to CH.A, and the luminance signal Y and the narrow band signal C _N of even scan line numbers are distributed to CH.B. A synchronization signal and a burst signal are added to these, and as shown in FIGS. 11 (b) and 11 (c), they are time-division-multiplexed to 2
The channel video signals, that is, the CH.A and CH.B video signals are output. Note that SB shown in the drawing indicates the insertion position of the synchronization signal and the burst signal. Where C
In HA and CH.B, the 1H period of the input signal is extended to the 2H period.

The outputs of the 2-channel conversion circuit 21, that is, the CH.A and CH.B signals are input to the FM modulation circuits 4a and 4b, respectively, and are FM-modulated. The FM signals output from the FM modulation circuits 4a and 4b are respectively passed through recording amplifiers 5a and 5b, and CH and A rotary heads 101a and 101a.
101b and CH.B rotary heads 102a and 102b, and recorded on the magnetic tape 1.

Next, the operation at the time of reproduction of the conventional example will be described.
The reproduced signals output from the CH.A heads 101a and 101b and the CH.B heads 102a and 102b are respectively head amplifiers 6a and 6a.
After being amplified by b, it is FM demodulated by the FM demodulation circuits 7a and 7b, and reproduced video signals of two channels CH.A and CH.B are obtained. In the channel synthesizing circuit 22, the operation reverse to that at the time of recording,
That is, the synchronization signal and the burst signal are removed, the luminance signal Y is compressed on the time axis, the color signals C _W and C _N are expanded on the time axis, and the interpolation processing is performed to alternate between the CH.A video signal and the CH.B video signal. The original video signal is obtained by selecting and combining.

[Problems to be Solved by the Invention] The conventional magnetic recording / reproducing apparatus is configured as described above, and the luminance signal Y and the broadband color signal C _W of odd scan line numbers are always in CH.A and the even scan lines are The numbered luminance signal Y and the narrow band color signal C _N are distributed to CH.B.

In that case, for example, when the DC level of the video signal of CH.A before channel combination is higher than the DC level of the video signal of CH.B, that is, when there is a characteristic difference between channels, as shown in Fig. 12. If channel combination is performed in that state, the DC level will rise and fall for each scanning line as shown in FIG. At this time, on the screen, as shown in FIG. 14, the odd-numbered scanning lines in the first field and the second scanning lines
The odd-numbered scanning lines in the field are always bright, and when the first field and the second field are overwritten, it becomes as shown in Fig. 15. The lightness and darkness on the screen is twice as thick as the scanning lines. The image appears as if the scanning lines were halved. Further, this causes a problem that a good image cannot be obtained because it is conspicuous on the screen even if there is a difference in characteristics between other channels, such as a difference in video signal amplitude, S / N and frequency characteristics. The present invention has been made to solve the above-mentioned problems, and provides a magnetic recording / reproducing apparatus capable of obtaining a reproduced image that is visually inconspicuous even if a characteristic difference between channels occurs. The purpose is to

[Means for Solving Problems] A magnetic recording / reproducing apparatus according to the present invention is a magnetic recording / reproducing apparatus for converting an input video signal into video signals of a plurality of channels and recording the video signals on a recording medium. A conversion means for converting the effective video signal portion of the signal into video signals of a plurality of channels in units of one horizontal scanning period, a determination means for determining whether the field of the input video signal is an odd field or an even field, and a conversion means for the plurality of channels. Switching means for switching the recording channel of the video signal, a plurality of recording heads provided by the number corresponding to the video signals of the plurality of channels, and a plurality of output from the switching means using the corresponding heads of the plurality of recording heads. Recording means for recording the video signal of the channel on the recording medium, wherein the switching means has at least two consecutive lines on the field screen. Input video signals are recorded on the same channel, and the recording channels of the video signals of a plurality of channels are switched field by field using the field discrimination result output from the discriminating means. The signal is output to the recording means.

[Operation] According to the present invention, the input video signals of at least two consecutive lines are recorded on the same channel on the field screen, and the recording channels of the video signals of a plurality of channels are used for each field by using the field determination result. By recording video signals of multiple channels so that they are switched to, even if there is a characteristic difference between the channels, the characteristic difference is dispersed over the entire screen, and the image quality is visually deteriorated due to the characteristic difference between the channels. Can be reduced.

[Embodiment] FIG. 1 is a schematic block diagram showing the configuration of a recording system according to an embodiment of the present invention. FIG. 2 is a schematic block diagram showing the structure of a reproducing system according to an embodiment of the present invention. In the figure, the same reference numerals are given to parts having the same configurations as those in FIGS. 9 and 10.

First, the configuration of a recording system according to an embodiment of the present invention will be described with reference to FIG. The sync separation circuit 2 is a circuit that detects a sync signal from an input video signal (Y, C _W , C _N ) and generates a horizontal sync signal and a vertical sync signal in synchronization with the sync signal. The field discrimination circuit 3 is the synchronization separation circuit 2
It is a circuit that determines whether the input video signal is an even field or an odd field based on the output of. Two
The channelization circuit 11 divides the input video signal into two-channel video signals and doubles the time axis (1H to 2H)
It is a circuit for extending to. Switches 9a and 9b are
This switch is switched in response to the output of the field discrimination circuit 3, and switches the connection relationship between the output of the 2-channel conversion circuit 11 and the FM modulation circuits 4a and 4b depending on whether the input video signal is an odd field or an even field. There is. In this embodiment, when the field discrimination circuit 3 discriminates the odd field (first field) of the input video signal, the switch 9a selects the CH.A signal and the switch 9b selects the CH.B signal. select. On the other hand, when the field discrimination circuit 3 discriminates the even field (second field) of the input video signal, the switch 9a selects the CH.B signal and the switch 9b switches.
Select the CH.A signal. The signals selected by the switches 9a and 9b are given to the FM modulation circuits 4a and 4b, respectively.

Next, with reference to FIG. 2, the structure of the reproducing system according to the embodiment of the present invention will be described. Similar to the case of FIG. 10, the reproduction signals output from the rotary heads 101a and 101b are given to the FM demodulation circuit 7a via the head amplifier 6a. On the other hand, the reproduction signals output from the rotary heads 102a and 102b are given to the FM demodulation circuit 7b via the head amplifier 6b. The channel synthesizing circuit 8 synthesizes the reproduced signals output from the FM demodulating circuits 7a and 7b to obtain the original video signals (Y, C _W , C
It is a circuit that restores to _N ). Further, the channel synthesizing circuit 8 includes a circuit which separates the sync signal from the reproduced video signal and generates a field discrimination signal based on the sync signal. This field discrimination signal is given to the switches 10a and 10b as a switching control signal. In this embodiment, the field discrimination signal is an odd field (first field).
Switch 10a gives the output signal of the FM demodulation circuit 7a to the channel synthesis circuit 8 as a CH.A signal, and the switch 10b outputs the output of the FM demodulation circuit 7b to CH.B.
The signal is switched to be applied to the channel synthesis circuit 8. On the other hand, when it is determined that the field determination signal is the even field (second field),
The switch 10a gives the output of the FM demodulation circuit 7a to the channel synthesis circuit 8 as a CH.B signal, and the switch 10b supplies the output of the FM demodulation circuit 7a.
It is switched so that the output of b is given to the channel synthesizing circuit 8 as a signal of CH.A. Therefore, the switches 10a and 10b constitute means for switching the two reproduced signals from the FM demodulation circuits 7a and 7b so as to correspond to the original channel.

Next, the operation of the above embodiment will be described. FIG. 3 is a diagram for explaining the operation of the 2-channel conversion circuit 11 and the switches 9a and 9b. FIGS. 3A and 3D show input video signals (Y, C _W , C _N ) in 1H units. The numbers in the figure correspond to the scanning line numbers in each field.
The luminance signal Y input to the 2-channel conversion circuit 11 is expanded about twice in time. On the other hand, the color signals C _W and C _N are subjected to band limitation and then subjected to line-sequential processing and time-axis compressed to about half. Then, in a format as shown in FIGS. 3 (b) and 3 (c), during the 2H period, the burst signal and the synchronization signal (denoted by SB in the figure), the time axis compressed color signal, and the time axis expanded. Luminance signals are time-division multiplexed. That is,
In this embodiment, the input video signal is CH.A and
Converted to video signals of two channels of CH.B. Based on the field discriminating signal from the field discriminating circuit 3, the switches 9a, 9b switch the video signals of the two channels to the second channel as shown in FIGS. 3 (b), (c), (e) and (f). 1
Switching between field and second field. That is, the switches 9a and 9b respectively select the video signals of CH.A and CH.B output from the 2-channel conversion circuit 11 in the first field and apply them to the FM modulation circuits 4a and 4b. On the other hand, in the second field, the switch 9a selects the video signal of CH.A output from the 2-channel conversion circuit 11 and supplies it to the FM modulation circuit 4b.
The switch 9b selects the video signal of CH.B output from the 2-channel conversion circuit 11 and applies it to the FM modulation circuit 4a. Therefore, in the second field, the CH.A video signal is processed by the CH.B signal processing system, and the CH.B video signal is processed by the CH.A signal processing system. The signals of these two channels are FM-modulated by the FM modulation circuits 4a and 4b, amplified by the recording amplifiers 5a and 5b, and then recorded on the magnetic tape 1.

Next, the operation of the reproducing system shown in FIG. 2 will be described. In this reproducing system, the signal recorded on the magnetic tape 1 is transferred to the rotary head.
After playing with 101a, 101b and 102a, 102b, head amplifier
Amplified by 6a and 6b, and FM demodulated by FM demodulation circuits 7a and 7b.
Demodulate. The outputs of the FM demodulation circuits 7a and 7b are input to the channel synthesizing circuit 8 via the switches 10a and 10b. In the channel synthesizing circuit 8, the sync signal is separated from the input reproduction signal and the separated signals are separated. The field of the reproduced signal is discriminated based on the synchronizing signal. As a result of this field discrimination, the field discrimination signal output from the channel synthesizing circuit 8 is given to the switches 10a and 10b to control the switching of each. As described above, in the first field, the output of the FM demodulation circuit 7a is given to the channel synthesis circuit 8 as the CH.A signal, and the output of the FM demodulation circuit 7b is output.
CH.B and a signal are given to the channel synthesis circuit 8. On the other hand, in the second field, the output of the FM demodulation circuit 7a is C
The signal of HB is given to the channel synthesizing circuit 8, and the output of the FM demodulation circuit 7b is the signal of CH.A.
Given to. Therefore, each reproduced signal is returned to the original channel. The channel synthesizing circuit 8 synthesizes the two given reproduction signals to obtain the original 1-channel video signal (Y,
Create and output C _W , C _N ).

Unlike the conventional example (see Fig. 11), the color signals C _W and C _N
Is distributed to each channel in order to obtain a correlative track pattern and reduce the influence of crosstalk from adjacent tracks during reproduction.

Here, as in the conventional example, C before channel combination is performed.
Let us consider a case where there is a characteristic difference between channels such that the DC level of the HA signal is higher than the DC level of the CH.B signal (see Fig. 12). The output waveform of the channel synthesis circuit 8 is shown in FIG. In each field, the inter-channel characteristic appears every two scanning lines, and the DC level rises and falls. That is, in the first field, the first, second, fifth, and
6, ... The brightness of the scanning line is always bright, and the brightness of the third, fourth, seventh, eighth, ... scanning line is always dark, and in the second field, the third, fourth, seventh, eighth , ... The brightness of the scanning line is always bright,
The luminance of the second, fifth, sixth, ... Scanning lines is always dark (see FIG. 5 (a)). Here, when the video signal of the first field and the video signal of the second field interlaced with the first field are overlaid and written, it becomes as shown in FIG. 5 (b). This is because the bright and dark parts are dispersed over the entire screen as compared with the case shown in the conventional example (FIG. 12), so that the deterioration of the image quality due to the characteristic difference between the channels is visually reduced. In addition, even if there is a difference in other inter-channel characteristics such as video signal amplitude, S / N, and frequency characteristics, deterioration of the image quality is visually reduced on the screen, and a relatively good reproduced image can be obtained.

In the above-described embodiment, when the input video signal is distributed to the two channels, the distribution is performed in units of two horizontal scanning periods of the input video signal. The same effect can be obtained even if the allocation is performed with the period as a unit.

Further, in the above-described embodiment, the case where the recording is distributed to the two channels is shown, but the same effect can be obtained even in the case where the recording is distributed to the three or more channels. For example, an example of a 3-channel recording system will be described with reference to FIGS. 6 and 7.

First, the input video signal is divided into three channel signals of CH.A, CH.B, and CH.C. Thereafter, the signals of these three channels are switched to change the respective channels, for example, as shown in FIG. 6 (a) in the first field and as shown in FIG. 6 (b) in the second field. At this time, if there is a characteristic difference between the channels, if the signal processing system of each channel is replaced in each field as described above, it is displayed on the screen as 7th.
As shown in the figure. In Fig. 7, the symbol ○ indicates the characteristics of the signal processing system of CH.A, the symbol × indicates the characteristics of the signal processing system of CH.B, and the symbol △ indicates the characteristics of the signal processing system of CH.C. Is represented. Here, when there is a characteristic difference between the channels, the reproduction screens of the first field and the second field are as shown on the left side and the right side of FIG. 7 (a), respectively. Similar to the above-described embodiment, when the first field and the second field interlaced with the first field are overwritten, this is as shown in FIG. 7 (b). This is similar to the above-described embodiment in that the characteristic differences between channels are dispersed over the entire screen. Therefore, the deterioration of the image quality is visually reduced. Even in this case, the characteristic difference between the channels is, for example,
Even if there is a difference in image amplitude, S / N, frequency characteristics, etc., deterioration of image quality is visually reduced on the screen.

As described above, even in the case of a VTR that employs a multi-channel recording method that has a signal processing system of 3 channels or more, when allocating channels, select the channel allocation method for each field, and further select each channel between fields. If the signal processing system is switched, the characteristic difference between the channels is dispersed over the entire screen, and the deterioration of the image quality is visually reduced on the screen, and the same effect as that of the above-described embodiment is obtained.

It should be noted that in the above-described embodiment, one track has one track.
Although the case where a video signal for one field of a channel is recorded has been shown, the same effect can be obtained even in a recording system having a plurality of tracks (multi-segment recording), that is, a VTR adopting a multi-channel multi-segment recording system. .

[Effects of the Invention] As described above, according to the present invention, even if the characteristic difference between channels occurs, the characteristic difference between channels is dispersed over the entire screen, so that the image quality due to the characteristic difference between channels is visually recognized. Deterioration can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing the configuration of a recording system of a magnetic recording / reproducing apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing the structure of the reproducing system of the magnetic recording / reproducing apparatus according to an embodiment of the present invention. FIG. 3 is a diagram for explaining the channel distribution operation in the embodiment of FIGS. 1 and 2. FIG. 4 is a diagram showing a signal waveform when a characteristic difference occurs between channels in the embodiments of FIGS. 1 and 2. FIG. 5 is a diagram showing an example of a reproduction screen for explaining the advantages of the embodiments of FIGS. 1 and 2. FIG. 6 is a time chart for explaining the operation of another embodiment of the present invention. FIG. 7 is a diagram showing a reproduction screen for explaining the advantages of another embodiment of the present invention. FIG. 8 is a diagram showing the arrangement of heads in a conventional two-channel recording VTR. FIG. 9 is a block diagram showing the structure of a conventional VTR recording system of a two-channel recording system. FIG. 10 is a block diagram showing the structure of a reproducing system of a conventional two-channel recording VTR. FIG. 11 is a timing chart for explaining the operation of the conventional example shown in FIGS. FIG. 12 is a signal waveform diagram showing a characteristic difference occurring between channels. FIG. 13 is a diagram showing a signal waveform when a signal having a characteristic difference between channels as shown in FIG. 12 is synthesized by a conventional VTR. FIG. 14 and FIG. 15 are views showing playback screens for explaining the drawbacks of the conventional VTR. In the figure, 1 is a magnetic tape, 2 is a sync separation circuit, 3 is a field discrimination circuit, 4a and 4b are FM modulation circuits, 5a and 5b are recording amplifiers, 6a and 6b are head amplifiers, and 7a and 7b are FM demodulation. Circuit, 8 is a channel synthesis circuit, 9a and 9b
Is a switch in the recording system, 10a and 10b are switches in the reproducing system, 11 is a two-channel circuit, 100 is a rotary drum, and 101a, 101b, 102a and 102b are rotary heads.

Claims (2)

(57) [Claims] 1. A magnetic recording / reproducing apparatus for converting an input video signal into video signals of a plurality of channels and recording it on a recording medium, wherein an effective video signal portion of the input video signal is set in units of one horizontal scanning period. Conversion means for converting the video signals of the plurality of channels, determination means for determining whether the field of the input video signal is an odd field or an even field, and switching means for switching the recording channels of the video signals of the plurality of channels, Using a plurality of recording heads provided in a number corresponding to the video signals of the plurality of channels, and using a corresponding head among the plurality of recording heads,
Recording means for recording the video signals of the plurality of channels output from the switching means on the recording medium, wherein the switching means has at least two continuous lines of the input video signals in the same channel on the field screen. As recorded,
Also, magnetic recording / reproducing for outputting the video signals of the plurality of channels to the recording means so that the recording channels of the video signals of the plurality of channels are switched field by field using the field discrimination result output from the discrimination means. apparatus. 2. An input video signal is converted into a video signal of a plurality of channels, and at least two consecutive input video signals on a field screen are recorded on the same channel, and field information of the input video signal is used. A magnetic recording / reproducing apparatus for reproducing the recording medium on which the input video signal is recorded by switching the recording channels of the video signals of the plurality of channels for each field, the number of which corresponds to the video signals of the plurality of channels. Using a plurality of reproducing heads provided, a discriminating means for discriminating whether the field of the reproduced video signal reproduced by the plurality of reproducing heads is an odd field or an even field, and a field discrimination result outputted from the discriminating means. Switching the processing channel of the playback video signal, converting the playback video signal to the input video signal Magnetic recording and reproducing apparatus comprising a switching means that.