JP2947432B2 - Video signal recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal recording apparatus, and more particularly to a video signal recording apparatus for preemphasizing a frequency of a video signal in a time axis direction and recording the preemphasized frequency on a recording medium.

[0002]

2. Description of the Related Art When a video signal is recorded on a recording medium such as a magnetic tape, a high-frequency component of the video signal is enhanced (pre-emphasis) in comparison with a low-frequency component in order to reduce the influence of noise in recording and reproduction. By recording and reproducing, and attenuating high frequency components (de-emphasis) at the time of reproduction, the SN ratio is improved. Conventionally, as an apparatus for performing emphasis and de-emphasis in the time axis direction of a video signal, there is an apparatus described in Japanese Patent Publication No. 3-9679.

FIG. 7 is a diagram showing a schematic block system of a conventional video signal recording apparatus. For convenience of explanation, FIG. 1 also includes a video signal reproducing device. In FIG. 1, a video signal to be recorded which has entered an input terminal 1 is supplied to a pre-emphasis circuit 2, where a high frequency component of a frequency in a time axis direction is relatively enhanced in level as compared with a low frequency component. After that, the signal is supplied to a recording system signal processing circuit 3, where signal processing suitable for recording a video signal, for example, frequency modulation is performed. The video signal extracted from the recording signal processing circuit 3 is supplied to a magnetic head (not shown) via a recording amplifier (not shown) and the like, and is recorded on the magnetic tape 4.

On the other hand, at the time of reproduction, a magnetic head (not shown)
A video signal recorded on the magnetic tape 4 is reproduced by a reproduction signal processing circuit 5 through a reproduction amplifier (not shown) and the like, and a signal processing reverse to the signal processing at the time of recording is performed. Supplied to The de-emphasis circuit 6 is provided to attenuate the high frequency component of the frequency in the time axis direction enhanced by the pre-emphasis circuit 2 and restore it to its original state. The output reproduced video signal is taken out from the output terminal 7.

FIG. 8 is a diagram showing a configuration of the pre-emphasis circuit 2. In FIG. 1, a video signal input to an input terminal 10 is supplied to an addition circuit 11 and a subtraction circuit 12, respectively. The video signal extracted from the adding circuit 11 is supplied to the delay circuit 13. The delay circuit 13 has a delay time of 2m field or {(2m + 1) field−0.5H} of the video signal (where m is 0, 1, 2,...).
And H indicates one horizontal period. same as below). Delay circuit 13
The extracted delayed video signal is attenuated by a coefficient circuit 14 multiplied by a coefficient K1 and then supplied to an addition circuit 11, where it is added to the video signal from an input terminal 10 and then supplied to a delay circuit 13 again. It is patroled. The output video signal of the delay circuit 13 is supplied to the subtraction circuit 12 through a coefficient circuit 15 for multiplying by a coefficient K2. Subtraction circuit 12
Performs an operation of subtracting a video signal before a period that is a natural number multiple of one field from the coefficient circuit 15 from the input video signal from the input terminal 10 so that the high frequency component of the frequency of the input video signal in the time axis direction is a low frequency component. And outputs a video signal to the output terminal 16 to which the pre-emphasis characteristic whose level is relatively enhanced is provided.

FIG. 9 is a diagram showing a configuration of the de-emphasis circuit 6. In FIG. 1, a reproduced video signal converted into an original signal form comes into an input terminal 20. However,
This reproduced video signal has the pre-emphasis characteristic. The reproduced video signal is supplied to the delay circuit 23 through the addition circuit 21 and is also supplied to the addition circuit 22. The delay circuit 23 is set to have the same delay time as the delay circuit 13 of FIG.
Is supplied to the addition circuit 21 through a coefficient circuit 24 for multiplying by the coefficient N2, while the addition circuit 22 is supplied through a coefficient circuit 25 to be multiplied by a coefficient N2.
Supplied to The output signal of the addition circuit 22 is output to an output terminal 26.
Output to

The output signal from the output terminal 26 has a characteristic that the high frequency component of the frequency in the time axis direction of the input video signal is relatively attenuated as compared with the low frequency component, and the output signal shown in FIG.
This is a reproduced video signal to which characteristics complementary to the characteristics of the pre-emphasis circuit 2 shown are added, and is a reproduced video signal restored to the same waveform as the input video signal of the input terminal 10 of the pre-emphasis circuit 2.

As examples of the pre-emphasis circuit 2 and the de-emphasis circuit shown in FIG. 7, there are a pre-emphasis circuit shown in FIG. 10 and a de-emphasis circuit shown in FIG. Although the respective circuit configurations are slightly different from those shown in FIGS. 8 and 9, their characteristics are as shown in FIG.
And FIG.

[0009]

According to the above-mentioned prior art, the pre-emphasis circuit 2 and the de-emphasis circuit 6 have complementary characteristics, so that the original signal waveform can be restored. Since the operation is the same as that of a so-called cyclic noise reduction circuit, the SN ratio of the reproduced video signal can be improved.

However, if the re-pause (pause of recording) is instructed during the recording of the video signal using the above-described emphasis in the time axis direction, the recording of the VTR is temporarily stopped and the feeding of the magnetic tape 4 is stopped. Is stopped, and the recording is started again when the recoupling is released. Since the pre-emphasis circuit 2 continues the pre-emphasis operation during the re-pause, the pre-emphasis circuit 2 is not actually recorded by the feedback loop including the delay circuit 13, the coefficient circuit 14 and the addition circuit 11 when the re-pause is released. Pre-emphasis is performed based on the video signal during the repose. When the magnetic tape 4 recorded in this manner is reproduced, when the reproduced video signal of the portion where the splicing was performed by the recompose is deemphasized, the deemphasis circuit 6 circulates the reproduced video signal before the recompose. The de-emphasis is performed based on this. Therefore, the signals that are circulated between the pre-emphasis and the de-emphasis at the splicing shooting part are different.Therefore, when the images are continuously played back, the afterimage or blurring occurs in the reproduced image immediately after the splicing shooting. there were.

[0011]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a characteristic that a high frequency component of a frequency in a time axis direction is enhanced relative to a low frequency component in a video signal. In a video signal recording apparatus for providing a pre-emphasis circuit for applying the characteristic and recording the video signal provided with the characteristic on a recording medium, the pre-emphasis circuit is configured to stop the immediately preceding pre-emphasis when a recording pause is instructed. And a pre-emphasis operation is performed on the basis of the held state when the temporary stop is released.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic block system of the embodiment. FIG. 1 also shows a portion of the video signal reproducing apparatus which is not directly related to the present invention for convenience of explanation. 2 is a diagram showing the configuration of the pre-emphasis circuit shown in FIG. 1, FIG. 3 is a diagram showing the configuration of the delay circuit 70 of FIG. 2, and FIG. 4 is an explanatory diagram for explaining the operation of the embodiment. The same components as those described above are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 1, a video signal to be recorded is input to a terminal 31. The input video signal is pre-emphasized in the time axis direction by a pre-emphasis circuit 69, and further subjected to signal processing suitable for recording by the recording system signal processing circuit 3. Then, a recording signal from the recording signal processing circuit 3 is recorded on a magnetic tape 4 as a recording medium. A freeze signal is input to the terminal 34. The freeze signal is, for example, at a high level during a stop period when a recompose (pause of recording) is instructed during recording on a VTR (video tape recorder). The change point of this signal is preferably synchronized with the frame of the video signal to be recorded. The freeze signal supplied to the terminal 34 is supplied to a pre-emphasis circuit 69.

FIG. 2 shows the configuration of the pre-emphasis circuit 69. The video signal to be recorded that has entered the input terminal 10 is supplied to a subtraction circuit 17, a subtraction circuit 18, and an addition circuit 19. The output of the subtraction circuit 17 is supplied to the subtraction circuit 18 via the delay circuit 70, and is subtracted from the input video signal. The above-mentioned freeze signal is supplied to the terminal 71. When the freeze signal is, for example, at a high level, the delay circuit 70 is configured to store one frame of the immediately preceding input signal. The output of the subtraction circuit 18 is supplied to the coefficient circuit 14 and the coefficient circuit 15. Then, the output of the coefficient circuit 14 is supplied to the subtraction circuit 17 to be subtracted from the input video signal, and is again supplied to the delay circuit 70 for circulation. On the other hand, the output of the coefficient circuit 15 is subtracted from the input video signal by the addition
Then, an output signal to which a pre-emphasis characteristic in which the high frequency component of the frequency in the time axis direction is enhanced compared with the low frequency component is added is extracted.

In the apparatus of the present invention, during recording of a video signal,
When the pause of the recording, that is, the re-pause is instructed, a freeze signal which becomes a high level while the recording of the video signal is stopped is supplied to the terminal 34 in FIG. 1, that is, the terminal 71 in FIG. The delay circuit 70 in the pre-emphasis circuit 69 is configured as shown in FIG. Here, the output signal of the subtraction circuit 17 is input to the terminal 72, and this is supplied to the A terminal of the signal selection circuit 73. When the freeze signal supplied to the terminal 71 is at a low level, A
The signal supplied to the terminal is selected and taken out from the signal selection circuit 73. The signal extracted from the signal selection circuit 73 is stored in a FIFO (first-in first-out) type frame memory 74 and
The output is delayed by the frame period. The output of the frame memory 74 is the terminal B and the terminal 75 of the signal selection circuit 73.
Is supplied to Then, the video signal extracted from the terminal 75 is supplied to the subtraction circuit 18 in FIG. here,
When the freeze signal goes high, the signal selection circuit 73
Selects the signal supplied to the B terminal and supplies it to the frame memory 74. Therefore, the frame memory 74
During the period in which the freeze signal supplied to the terminal 71 is at the high level, one frame of the input signal immediately before the freeze signal goes to the high level is circulated, and this is held.

Next, the operation of the apparatus of the present embodiment having the above-described configuration will be described with reference to FIG. Now
Consider the case where the video signal 76 shown in FIG. 4A is recorded. It is assumed that a repose is instructed from the time point (a) when the video signal 76 is recorded up to the frame An-1 to the time point (b) at which the recording of the frame Bm is started. At this time, the freeze signal 77 supplied to the terminal 71 is at a high level between the times (a) and (b) as shown in FIG. Therefore, the pre-emphasis circuit 69 in FIG. 2 performs a pre-emphasis operation for enhancing the high frequency component of the frequency in the normal time axis direction until the time point (a).
Between the time point (a) and the time point (b), the delay circuit 70
Since the contents at the time point are retained, the pre-emphasis operation after the frame Bm is performed based on the video signal 76 before the frame An-1 from the time (b). In this way, the video signal 78 is continuously recorded on the magnetic tape 4 as shown in FIG.

When the magnetic tape 4 recorded as described above is reproduced and de-emphasis is performed by the conventional de-emphasis circuit 6 shown in FIG. Since the de-emphasis after Bm is performed based on the frames An-1, An-2, ..., the pre-emphasis during recording and the de-emphasis during playback at the portion shot by recoupling are always complementary, and the recoupling is performed. As a result, afterimages and blurring do not occur on the playback screen of the playback video signal at the portion where the spliced image was taken.

In the delay circuit 70, when a RAM (random access memory) is used as a frame memory, writing of a video signal to the RAM is prohibited only during a high-level period of a freeze signal supplied to a terminal 71. With such a configuration, the signal selection circuit 73 does not need to be provided.

FIG. 5 shows the pre-emphasis circuit 69 of FIG.
FIG. 9 is a diagram illustrating another configuration example. The same components as those described above are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 5, a freeze signal is input to a terminal 71 and supplied to a delay circuit 70. Therefore, when the freeze signal input to the terminal 71 is at a low level, for example, when the VTR is recorded normally, the pre-emphasis operation in the time axis direction is indicated. On the other hand, when the freeze signal input to the terminal 71 is, for example, at a high level, that is, during recoupling, the delay circuit 70 holds the contents immediately before recoupling. Then, when the recovery is released, the pre-emphasis circuit 69 restarts the pre-emphasis operation based on the contents held in the delay circuit 70.

FIG. 6 shows the pre-emphasis circuit 69 of FIG.
FIG. 9 is a diagram illustrating another configuration example. The same components as those described above are denoted by the same reference numerals, and description thereof will be omitted. 6, a freeze signal is input to a terminal 71 and a delay circuit 70
Supplied to 6 is different from the configuration shown in FIG. 2 in that the output of the subtraction circuit 18 is supplied to the nonlinear circuit 64 via the coefficient circuit 63, and the output of the nonlinear circuit 64 is subtracted via the coefficient circuit 65. The point is that while being fed back to the circuit 17, it is directly supplied to the adding circuit 19. The non-linear circuit 64 is an amplitude limiter for limiting the amplitude of the signal input from the coefficient circuit 63 to a constant value. It is configured to be. As a result, the pre-emphasis circuit changes the pre-emphasis amount in accordance with the amplitude of the video signal input to the input terminal 10, and the non-linear pre-emphasis circuit increases the pre-emphasis amount as the amplitude of the input video signal decreases. It will have emphasis characteristics. Therefore, even when the screen is switched in a state where the amplitude of the video signal is large in the transition shooting portion by the recoupling, the overshoot amount of the video signal after the pre-emphasis can be reduced.

As a method for holding the state of the pre-emphasis circuit 69, when the repose is instructed, the information in the delay circuit 70 is recorded on the magnetic tape 4, for example, in a recording track for a video signal as holding information. Alternatively, when the recovery is released, the recorded information may be reproduced and taken into the delay circuit 70.
At this time, the video signal is overwritten and recorded on this track after the release of the repose, and the held information is erased. Further, as a method of recording the information held by the pre-emphasis circuit, other information signal recording tracks, for example, tracks for digital audio signals can be used.

[0022]

As described above, there is provided a pre-emphasis circuit for imparting a characteristic of enhancing the high frequency component of the frequency in the time axis direction to the low frequency component to the video signal, and this pre-emphasis circuit In a device that records a video signal that has been recorded on a magnetic medium, during recording of a video signal, when a so-called re-pause that temporarily stops recording and then resumes recording is performed, during the re-pause, the pre-emphasis circuit immediately before the re-pause is performed. When the pre-emphasis circuit resumes the pre-emphasis operation based on the retained state when the recording is resumed after the release, the pre-emphasis circuit resumes the pre-emphasis operation. When performing de-emphasis to attenuate compared to the low-frequency component and playing back the joint shooting part by The pre-emphasis during recording and the de-emphasis during playback are always complementary, and video signal recording is performed so that afterimages and blurring do not occur on the playback screen of the playback video signal at the portion where the splicing was performed by recoupling. It can be carried out.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic block system of an embodiment of a video signal recording device of the present invention.

FIG. 2 is a diagram showing a configuration of a pre-emphasis circuit in an embodiment of the video signal recording device of the present invention.

FIG. 3 is a diagram illustrating a configuration of a delay circuit illustrated in FIG. 2;

FIG. 4 is an explanatory diagram for explaining the operation of the embodiment of the video signal recording device of the present invention.

FIG. 5 is a diagram showing another configuration example of the pre-emphasis circuit in the embodiment of the video signal recording device of the present invention.

FIG. 6 is a diagram showing another configuration example of the pre-emphasis circuit in the embodiment of the video signal recording device of the present invention.

FIG. 7 is a diagram showing a schematic block system of a conventional video signal recording device.

FIG. 8 is a diagram illustrating a configuration of a pre-emphasis circuit of FIG. 7;

FIG. 9 is a diagram illustrating a configuration of a de-emphasis circuit of FIG. 7;

FIG. 10 is a diagram illustrating another configuration of the pre-emphasis circuit of FIG. 7;

FIG. 11 is a diagram illustrating another configuration of the de-emphasis circuit of FIG. 7;

[Explanation of symbols]

 Reference Signs List 3 Recording system signal processing circuit 4 Magnetic tape 10 Input terminal 11, 19 Addition circuit 12, 17, 18 Subtraction circuit 14, 15, 16, 65 Coefficient circuit 16 Output terminal 64 Non-linear circuit 69 Pre-emphasis circuit 70 Delay circuit 73 Signal selection circuit 74 frame memory

Claims (1)

(57) [Claims] 1. A pre-emphasis circuit for providing, to a video signal, a characteristic in which a high-frequency component of a frequency in a time axis direction is relatively enhanced in level as compared with a low-frequency component, and the pre-emphasis circuit is provided. In a video signal recording apparatus that records a video signal on a recording medium, the pre-emphasis circuit holds a pre-emphasis state immediately before the pause when recording pause is instructed, and the pause is released. A pre-emphasis operation based on the held state when the video signal is recorded.