JPH06339102A - Aspect ratio discrimination device - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the erroneous discrimination between the "L" and "S" pulses of the reproduction control signal and to accurately determine the aspect ratio of the recorded video signal. [Structure] The control signal reproduced by the control head 1 is waveform-shaped by the waveform shaper 2 and then input to the reproduction control signal detector 31. The discriminating unit 32 obtains the duty ratio of the pulse of the control signal detected by the reproduction control signal detecting unit 31 from the rising edge and the falling edge of the pulse, and compares the obtained duty ratio with one of the two threshold values to determine the input pulse The type “L” or “S” is determined. At this time, when the type of the pulse determined this time is different from the type of the pulse determined the previous time, the determination unit 32 determines the type of the pulse input next by using the other threshold value. This makes it possible to select a threshold value that does not always cause erroneous determination, as the threshold value for determining "S" and "L" of the pulse of the control signal indicating the normal aspect ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video tape recorder, and more particularly to an aspect ratio discriminating circuit for discriminating an aspect ratio of a recorded video signal from a duty ratio of a pulse of a reproduction control signal.

[0002]

2. Description of the Related Art In a conventional video tape recorder, by using a rising edge of a reproduction control pulse obtained by reproducing a control pulse recorded on a tape as a frame reference, by applying a phase servo to a capstan motor, The video signal recorded on the tape is reproduced. By defining two kinds of “0” pulse (60%) and “1” pulse (27.5%) by changing the duty ratio of the control pulse, the control pulse can be expressed in binary. By using this binary number, various information can be recorded / reproduced on / from the tape. Therefore, conventionally, the VISS (VHS index search system) and VASS (VHS address search system) have been put to practical use by using the above-mentioned "0" pulse and "1" pulse. Here, the "0" pulse and the "1" pulse are distinguished by determining whether the duty ratio of the reproduced control pulse is larger or smaller than 50% by a threshold value provided near the duty ratio of 50%. Was done easily and accurately.

By the way, in recent years (June 1990), S-
When recording a video signal having a wide aspect ratio of 16: 9 on a video cassette tape recorder based on the VHS recording method, the identification information (ID) relating to the aspect ratio is changed by changing the duty ratio of the control signal.
Regulations were made regarding the recording method for recording. FIG. 5 is a diagram showing the duty ratio of the control signal according to this standard (S-VHS-31 standard), and FIG. 6 is a standard (VHS-standard when defining the “0” pulse and the “1” pulse by the control signal). 21 standard).

As shown in FIG. 5, in this standard, the duty ratio of the “0” pulse is 62.5% ± 0.5% as a long pulse (“L” pulse), and 57.5% ± 0.5%. Is defined as a short pulse (“S” pulse). or,
The duty ratio of 30% ± 0.5% of the “1” pulse is defined as “L” pulse, and 25% ± 0.5% is defined as “S” pulse. FIG. 6A shows a “0” pulse, and FIG.
(B) shows a "1" pulse. By using the “L” pulse and the “S” pulse defined in this way, for example, FIG.
When the control signal is tape-recorded as shown in,
It is shown that the video signal recorded on this tape adopts a wide aspect ratio of 16: 9.

Those having a large difference in duty ratio, such as the above-mentioned "0" pulse or "1" pulse, can be easily and definitely distinguished. However, when the "L" pulse and the "S" pulse are discriminated, the change in the duty ratio of the "L" pulse and the "S" pulse is small as shown in FIG. It is very difficult to discriminate it due to the influence of (capstan type wow and flutter etc.) and the influence of operation fluctuation of the control signal amplifying system and the waveform shaping system. In order to discriminate between “L” and “S” pulses that require such strict discrimination, a threshold having a duty ratio in the vicinity of the middle of the duty ratios of the “L” and “S” pulses is provided. The "L" pulse and the "S" pulse are discriminated depending on whether the duty ratio is larger or smaller than that. In the actual discrimination, the discrimination result based on the above-mentioned threshold value is stored in the memory for each frame, and when the patterns as shown in (1) to (4) of FIG. It is determined that the ratio is adopted.

However, a conventional tape (a video signal having a normal aspect ratio) in which a control signal pulse having the same duty ratio is continuously recorded in the vicinity of a threshold value for discriminating between the "L" pulse and the "S" pulse described above. When the tape on which is recorded) is reproduced, the pulse of the continuously recorded control signal becomes "L" pulse or "S" pulse with the threshold value as a threshold due to the fluctuation of the tape running and the effect of the waveform shaping circuit. May be discriminated, and the patterns may happen to be as shown in (1) to (4) of FIG. In this case, the tape recorded with the normal aspect ratio of 4: 3 may be erroneously determined to be the tape with the video signal recorded with the wide aspect ratio. When such a misjudgment occurs, the video tape recorder initially informs the wide monitor television that the recorded video signal having the aspect ratio of 4: 3 is reproduced. A control signal for informing that it is a reproduction is output to the monitor, and the screen of the monitor becomes 16: 9 or 4: 3, which makes the screen very difficult to see and unstable. It had the drawback of becoming

[0007]

A video signal recorded on a reproduction tape with a wide aspect ratio by discriminating whether the reproduction control signal is an "L" pulse or an "S" pulse. In the aspect ratio discriminating device for discriminating whether or not the control signal is continuously recorded with a pulse having a duty ratio near a threshold value provided for discriminating between the “L” pulse and the “S” pulse. When it is necessary to determine the type of the video signal, it is necessary to determine that the video signal was recorded with the conventional aspect ratio of 4: 3, but the control signal is changed to the “L” pulse due to the tape running fluctuation and the influence of the waveform shaping circuit. In some cases, the tape may be judged to be the “S” pulse, and it may be erroneously judged that the tape is recorded with a wide aspect ratio. That if the aspect ratio of the wide monitor television is 4: 3 to 16: 9, or fluctuates to the reverse in a short cycle, there is a disadvantage that becomes very difficult to see the screen.

Therefore, the present invention eliminates the above-mentioned drawbacks, and whether the pulse of the reproduction control signal is the "L" pulse,
An object is to provide an aspect ratio discriminating apparatus capable of accurately discriminating the aspect ratio of a video signal recorded on a reproduction tape by preventing erroneous discrimination when discriminating whether or not it is an “S” pulse. There is.

[0009]

According to the present invention, it is determined whether the type of the pulse is a long pulse or a short pulse from the duty ratio of the pulse of the control signal obtained by reproducing the tape with the magnetic reproducing device. Whether the video signal recorded on the tape is recorded with an aspect ratio of 16: 9 or 4: 3 depending on the type pattern of the pulses of a plurality of consecutive frames obtained by this determination.
In the aspect ratio discriminating apparatus for discriminating whether or not the data is recorded at the normal aspect ratio, the first judging means for judging whether the pulse of the reproduction control signal is the "1" pulse or the "0" pulse. When the input pulse is a “0” pulse, the first determining means determines whether the input pulse is a long pulse or a short pulse by setting the duty ratio of the input pulse to the first pulse. Second judging means for judging by comparing with either of the threshold value or the second threshold value and storing the judgment result, and the first judging means for judging that the inputted pulse is a "1" pulse. If the input pulse is determined to be a long pulse or a short pulse, the duty ratio of the input pulse is set to one of the third threshold value and the fourth threshold value. And a determination unit that stores the determination result and a determination unit that determines the type of the input pulse determined this time by the second or third determination unit for the pulse that was input last time. If it is different from the determination result by the above, it has a configuration including threshold switching means for controlling the threshold used for pulse type determination by the second determination means or the third determination means to another threshold.

[0010]

In the aspect ratio discriminating apparatus of the present invention, the first aspect
The determination means determines whether the pulse of the reproduction control signal is a "1" pulse or a "0" pulse. Second
When the first determining means determines that the input pulse is a “0” pulse, the determining means determines whether the input pulse is a long pulse or a short pulse by determining the duty ratio of the input pulse. First threshold or second
Judgment by comparing with either of the thresholds of
The judgment result is stored. The third judging means determines whether the input pulse is a long pulse or a short pulse when the inputted pulse is judged to be a "1" pulse by the duty of the input pulse. A determination is made by comparing the ratio with either the third threshold value or the fourth threshold value, and the determination result is stored. If the type of the input pulse judged this time by the second or the third judging means is different from the judgment result of the pulse inputted last time by the judging means, the threshold value switching means sets the second pulse.
The control for switching the threshold used for the pulse type determination to another threshold by the determination means or the third determination means. Accordingly, it is possible to determine whether the input pulse is the long pulse or the short pulse by using the threshold value that does not misjudge the duty ratio of the input pulse in both the second determining means and the third determining means. Therefore, the aspect ratio of the recorded video signal can be accurately determined.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a reproducing system of a video tape recorder equipped with an aspect ratio discriminating apparatus of the present invention. 1 is a control head for reproducing a control signal from a tape control track, 2
Is a waveform shaping section for shaping the waveform of the control signal reproduced by the control head 1, and is composed of an amplifier 21 and a Schmitt circuit 23. Reference numeral 3 denotes a microcomputer, which includes a reproduction control signal detection unit 31, a determination unit 32 that determines the duty of the reproduction control signal and a frame, and a video control unit 33 that generates a control signal for the determined aspect ratio. An aspect ratio discriminating apparatus is constituted by these three functions. Four
Is a video circuit for performing processing such as superimposing a DC voltage on a color signal of a 16: 9 wide aspect ratio video signal reproduced simultaneously from the tape, and 5 is a wide monitor capable of projecting a wide aspect ratio video signal. It's television.

Next, the operation of this embodiment will be described. During reproduction of a tape (not shown), the control head 1 reproduces a control signal from the control track of the tape. The reproduced control signal is amplified by the amplifier 21 of the waveform shaping section 2 and then waveform-shaped by the Schmitt circuit 22 to be restored into a square wave control pulse. Entered in. The reproduction control signal detector 31 detects the rising edge and the falling edge of the input control signal,
This is notified to the determination unit 32. The discriminating unit 32 obtains the duty ratio of the pulse of the control signal by measuring the time from the rising edge to the falling edge of the input control signal. Next, the determination unit 32 determines that the duty ratio is 50% from the obtained duty ratio.
After determining whether the pulse is a “0” pulse or a “1” pulse with a threshold value of, the duty ratio of this pulse is further compared with one of two preset threshold values,
It is determined whether the input pulse of the control signal is the "S" pulse or the "L" pulse, and the "S" pulse is further determined.
Alternatively, the aspect ratio of the video signal recorded on the tape is determined from the frame continuity of the “L” pulse, and the determination result is output to the video control unit 33.

Whether the discriminating unit 32 discriminates that the aspect ratio is a wide aspect ratio of 16: 9 in the video control unit 33 is 4
The video circuit 4 is informed of whether or not the normal aspect ratio of 3 is determined. As a result, when the video circuit 4 is informed that the video signal has a wide aspect ratio, the DC voltage is superimposed on the color signal of the video signal which is reproduced at the same time by a video head (not shown) and output to the wide monitor television 5.
The wide monitor television 5 projects a video signal with an aspect ratio of 16: 9 when a DC voltage is superimposed on an input color signal, and otherwise outputs a video signal with a normal aspect ratio of 4: 3. After processing into a video signal with a wide aspect ratio of 16: 9, switching control for projecting this is automatically performed. The automatic switching control signal of the aspect ratio output from the video circuit 4 is based on the EIJ standard.

Next, the operation of the discriminating section 32 of the microcomputer 3 will be described in more detail. The discriminating section 32 measures the time from the rising edge to the falling edge of the reproduction control pulse notified from the reproduction control signal detecting section 31 and measures the duty ratio thereof. If the reproduction control signal is a "0" pulse from the measurement result of the duty ratio, the discrimination unit 32 causes the first threshold value α0 (duty ratio 59% shown in FIG. 2).
Value) or the second threshold value β0 (value of duty ratio 61%) is used to determine whether the input pulse of the reproduction control signal is the "S" pulse or the "L" pulse. Initially, the discriminating unit 32 determines the position of the “S” pulse in FIG. 2 with respect to the first threshold value α0 as the duty ratio of the pulse of the control signal input using the first threshold value α0, for example. It is determined whether there is a pulse or an "L" pulse. That is, when the duty ratio of the input control signal pulse is on the left side compared to the first threshold value α shown in FIG. 2, it is determined to be the “S” pulse, and when it is on the right side, it is “L”. "Judge as a pulse. In this way, it is determined whether the control signal of 5 frames is the "S" pulse or the "L" pulse, and each determination result is stored in the memory (not shown).

At this time, when the determination unit 32 determines that the input pulse of the control signal is the "S" pulse by using the first threshold value α0, if the previous determination result is the "S" pulse, the determination unit 32 continues as it is. The input pulse of the control signal is also determined using the first threshold value α0. However, if the previous determination result is the "L" pulse, the second threshold value β0 is used for the next control signal to determine the "L" or "S" of the pulse. That is, if the pulses of the input control signal are of the same type (either “L” pulse or “S” pulse) in succession, the determination unit 32 uses the threshold value currently used as it is. The pulse of the control signal to be input next is determined. If the type of the pulse determined this time and the type of the pulse determined last time are different, the threshold value is switched to another threshold value and the control signal of the next input control signal is changed. Determine the type of pulse.

The discriminating unit 32 discriminates whether the pulse of the reproduction control signal input by the above method is the "L" pulse or the "S" pulse, and the discriminating result is stored in the discriminating unit 32. Store 5 frames in memory.
After that, the discriminating unit 32 determines that the video signal is recorded on the tape with a wide aspect ratio of 16: 9 when the storage patterns for the five frames are of the types (1) to (4) in FIG. To do. However, when the pattern stored in the memory is of the types (5) to (8), it is determined that the conventional video signal having the aspect ratio of 4: 3 is recorded on the tape. In addition, (7) of FIG.
The pattern (8) is a small drum system used in a video tape recorder integrated with a camera, and in this case as well, the aspect ratio of the recorded video signal is 4: 3.

FIG. 3 shows the relationship between the two types of threshold values used by the discriminating unit 32 and the "S" pulse and "L" pulse when the reproduction control signal input to the discriminating unit 32 is determined to be the "1" pulse. It is the figure shown. In this case, the determination unit 32 sets α1 as the first threshold value (value of duty ratio 26.5%).
Is used as the second threshold value (value of duty ratio 28.5%), and the determination method is the same as that for the “0” pulse shown in FIG.

Here, the reason why the discrimination accuracy of the control signal by the discrimination unit 32 of this example is improved as compared with the conventional one will be described. Now, when reproducing a conventional tape in which a video signal is recorded with an aspect ratio of 4: 3, one kind of threshold value is used to discriminate between "S" pulse and "L" pulse as in the conventional case.
For example, suppose that the position is γ as shown in FIG. At this time, the pulse of the reproduction control signal has a duty ratio of 6
When it is continuously around 0%, the duty ratio of the pulse of the control signal may fluctuate to the left or right of FIG. 2 with the threshold value γ interposed due to the tape fluctuation and the influence of the waveform shaping circuit. . In such a case, for example, originally "L"
The pulse of the control signal which is a pulse is, for example, LL
-S-S may be erroneously determined, and eventually, the video signal recorded on the tape may be erroneously determined to be recorded with a wide aspect ratio.

However, in this embodiment, for example, the pulse of the control signal for reproducing the conventional tape is the duty ratio 59.
%, When the duty ratio of the pulse of the control signal is erroneously determined due to the influence of the tape fluctuation and the waveform shaping section 2 as described above, that is, the present determination If the type of the generated pulse is different from the previously determined pulse type, the determination of the type of the next control pulse will be performed using the second threshold value β0. Therefore, it is considered that there is an influence of the tape fluctuation and the waveform shaping unit 2. However, since the duty ratio of the control pulse does not cross the second threshold value β0 to the left side or the right side in FIG. 2, it is possible to reproduce the conventional tape as described above by using the second threshold value β0. In this case, misjudgment does not occur.

Moreover, in the present embodiment, the "S" and "L" discrimination patterns of the pulses of the continuous reproduction control signal for 5 frames are obtained, and the aspect ratio is discriminated by this pattern. The determination result of the ratio can be obtained. For example, if a control signal that originally has a continuous “S” pulse is erroneously determined to be an “L” pulse or an “L” pulse, and then the control signal is determined to be an “S” pulse, the threshold value changes here. Judge continuously with the pulse. In such a case, if a pattern of only 4 frames is viewed, it becomes LLS-S-S, which is erroneously determined to be a wide aspect ratio.
Since it is L-S-S-S, it can be correctly determined that the image signal has a normal aspect ratio of 4: 3.

According to this embodiment, the pulse of the reproduction control signal is, for example, a "0" pulse, and it is necessary to determine whether this "0" pulse is a long pulse or a short pulse.
When the type of the pulse determined this time is different from the type of the pulse determined the previous time when the determination is made by either one of the two thresholds α0 or β0 at the beginning, the next pulse is By using a threshold value to determine whether it is a long pulse or a short pulse, it is possible to prevent erroneous determination of the pulse type of the control signal obtained by playing a video signal recording tape with a normal aspect ratio. It is possible to determine whether the video signal recorded on the tape has a wide aspect ratio of 16: 9 or a normal aspect ratio of 4: 3 by obtaining the pulse type patterns for 5 frames in succession. It is possible to accurately determine whether or not the data is recorded as a ratio without being affected by the running variation of the tape or the waveform shaping section. Therefore, it is possible to prevent a difficult-to-see screen that frequently changes the projection aspect ratio of the video signal on the wide monitor television 5 by erroneously determining the aspect ratio of the reproduced video signal. The same applies when the reproduction control signal is a "1" pulse, and the same effect is obtained.

[0022]

As described above, according to the aspect ratio discriminating apparatus of the present invention, erroneous discrimination when discriminating whether the pulse of the reproduction control signal is the "L" pulse or the "S" pulse is prevented. Then, the aspect ratio of the video signal recorded on the reproduction tape can be accurately determined.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a reproduction system of a video tape recorder equipped with an aspect ratio discrimination device of the present invention.

FIG. 2 is a diagram showing a positional relationship between “S” pulse and “L” pulse positions in a “0” pulse of a reproduction control signal and two threshold values.

FIG. 3 is a diagram showing a positional relationship between “S” pulse and “L” pulse positions in a “1” pulse of a reproduction control signal and two threshold values.

FIG. 4 is a diagram showing an example of a type pattern of continuous pulses for 5 frames of a reproduction control signal.

FIG. 5 is a diagram showing an example of S-VHS-31 standard relating to a control signal.

FIG. 6 is a diagram showing an example of VHS-21 standard relating to a control signal.

FIG. 7 is a diagram showing a pattern example of a control signal recorded on a control track.

FIG. 8 is a diagram showing an example of the positional relationship between the “S” pulse and the “L” pulse in each of the “1” pulse and the “0” pulse of the control signal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Control head 2 ... Waveform shaping part 3 ... Microcomputer 4 ... Video circuit 5 ... Wide monitor television 21 ... Amplifier 22 ... Schmitt circuit 31 ... Reproduction control signal detection part 32 ... Discrimination part 33 ... Video control part

Claims (2)

[Claims] 1. A continuous signal obtained by discriminating whether the type of the pulse is a long pulse or a short pulse from the duty ratio of the pulse of a control signal obtained by reproducing a tape with a magnetic reproducing device. An aspect for discriminating whether the video signal recorded on the tape is recorded at an aspect ratio of 16: 9 or a normal aspect ratio of 4: 3 according to the pulse type patterns of a plurality of frames. In the ratio discriminating apparatus, the first discriminating means for discriminating whether the pulse of the reproduction control signal is the "1" pulse or the "0" pulse, and the inputted pulse is the "0" pulse. When judged by the first judging means, whether the input pulse is a long pulse or a short pulse is determined by the duty cycle of the input pulse. A second judgment means for judging by comparing the duty ratio with either the first threshold value or the second threshold value and storing the judgment result; and the inputted pulse is a "1" pulse. When judged by the first judging means, whether the input pulse is a long pulse or a short pulse is compared with the duty ratio of the input pulse with either the third threshold value or the fourth threshold value. And the determination result of the pulse input last time, which is the type of the input pulse determined this time by the second or third determination means. And a threshold value switching unit for performing control to switch the threshold value used for the pulse type determination by the second determination unit or the third determination unit to another threshold value. That the aspect ratio discrimination apparatus. 2. The aspect ratio of the video signal recorded on the tape is determined by a pulse type pattern of 5 frames of the input pulse determined by the second or third determination means. The aspect ratio discriminating apparatus according to claim 1.