JP3007768B2 - Recording mode discriminator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording mode discriminating apparatus for discriminating a recording mode of a recorded video signal when a video signal recorded on a recording medium is slowly reproduced.

[0002]

2. Description of the Related Art As a recording mode of a home VTR, there are β (registered trademark) I, β II, and β III modes in a beta system, and a standard mode and a triple mode in a VHS (registered trademark) system. The reproducing device determines the recording mode of the video signal recorded on the recording medium at the time of reproduction, and performs capstan control, head selection, and the like in accordance with the mode.

FIG. 6 is a block diagram showing an example of a conventional recording mode discriminating apparatus. In the figure, a counter circuit 21 counts an FG signal PFG from a capstan FG attached to a rotating head shaft of a capstan (not shown), and supplies the count value to a latch circuit 22.

The latch circuit 22 has a control signal CTL.
The count value is latched by a latch pulse LP from a differentiating circuit 23 for detecting a rising edge of the control signal CTL, and the counter circuit 21 resets the count value by a reset pulse RP from a differentiating circuit 24 for detecting a falling edge of the control signal CTL. Therefore, the latch value is latched in the latch circuit 22 by the count value immediately before the reset of the counter circuit 21, that is, the number of pulses of the capstan FG signal PFG generated during one cycle of the control signal CTL.

[0005] The comparison circuit 25 is a circuit for comparing the count value latched by the latch circuit 22 with a threshold value stored in the memory circuit 26 in advance to determine the recording mode. For example, when distinguishing between the VHS standard mode and the triple mode, if the number of the capstan FG signals PFG generated in one cycle of the control signal CTL is n in the triple mode, it is 3n in the standard mode. . Therefore, the threshold is set to 2n
If the count value is set to 2, the recording mode can be determined such that the standard mode is set when the count value is larger than the threshold value 2n, and the triple mode is set when the count value is small.

That is, paying attention to the fact that the control signal CTL is recorded on the magnetic tape for each field (or one frame), the number of the capstan FG signals PFG generated during one cycle of the control signal CTL, That is, the running speed of the magnetic tape is detected by detecting the rotation speed of the capstan, and it is determined whether the recording mode is the low-speed recording mode or the high-speed recording mode.

[0007]

SUMMARY OF THE INVENTION A home VT
R slow playback is one field (or one frame)
Is performed by repeating the still reproduction in which the reproduction is performed several times and the normal traveling reproduction. This is because if the slow reproduction is simply performed by slow running of the tape, a noise band appears on the screen and moves in the vertical direction, which hinders the visual sense.

However, in the above-described conventional technique of counting the capstan FG signal, the capstan FG signal generates an electromotive force in the stator winding wound around the rotating shaft by the rotation of the magnet attached to the rotating shaft of the capstan. When the capstan is rotated intermittently for slow reproduction, the rotation speed decreases at the time of start-up and immediately before stop due to repetition of starting, running, and stopping of the capstan, and the output level of the FG signal becomes extremely low. This makes it impossible to reliably detect the FG signal.

Therefore, in the conventional reproducing apparatus, the mode discriminating function is stopped during the slow reproduction, and the slow reproduction is performed with the mode fixed. Therefore, if video signals are recorded on the same tape in different recording modes, even if the recording mode changes during slow playback, the playback device cannot be switched to a state suitable for that mode. In order to switch the mode, it is necessary to return to the normal playback mode once, determine the mode, and then switch to the slow playback again.

It is therefore an object of the present invention to provide a recording mode discriminating apparatus capable of discriminating a recording mode even during slow reproduction.

[0011]

According to the present invention, there is provided a recording medium.
The same field or the same frame of the recorded video signal
And still reproduction repeatedly to play the over-time, fee to be continuous
A first counter means for measuring a time required for the normal traveling reproduction, in a video signal reproducing apparatus for performing the slow reproduction of the video signal by alternately repeating the normal traveling reproduction for sequentially reproducing the fields, and the first counter. comprising comparing means for comparing the time preset as the time measured data by means the data, and a second counter means for counting the number of control signals arriving during normal traveling regeneration per due to the comparison means Setting measurement time data
The output of the magnitude varies with time data, based on the output of the single multiple changes in the control signal by the second counter means, configured to detect a change in the recording mode if there is change output to at least one.

[0012]

In the recording mode discriminating apparatus according to the present invention, the time from the start to the end of the intermittent operation of the capstan is measured by the first counter means, and the measurement result is set in advance as a threshold value. The change of the recording mode is detected by comparing the time data with the comparing means.

That is, the amount of tape movement by one intermittent operation of the capstan is defined by the number of control signals, and if the recording mode is different, the tape is recorded every field (or one frame). Since the pitch intervals of the control signals are different, the change of the recording mode is detected by measuring the operation time per capstan operation by the first counter means, that is, by measuring the amount of movement of the tape.

Immediately after the recording mode is changed from the low-speed mode to the high-speed mode, a control signal of a prescribed number or more is received by one operation of the capstan, so that the number of control signals arriving during the operation of the capstan is reduced. Is measured by the second counter means to detect a change in the recording mode.

[0015]

FIG. 1 is a block diagram showing an embodiment of a recording mode discriminating apparatus according to the present invention. In the following description, a case will be described in which the present invention is applied to the recording mode of the VHS system, that is, the discrimination between the standard mode and the triple mode.

In FIG. 1, a counter circuit 1 counts a clock pulse CP supplied from a clock pulse generating circuit 2 via a switch circuit 3 while a capstan drive signal SCD described later arrives. The operation is enabled by a signal obtained by delaying the capstan drive signal SCD by the delay circuit 4.

The count value of the counter circuit 1 is supplied to a latch circuit 5, and a latch pulse LP from a differentiating circuit 6 for detecting a falling edge of the capstan drive signal SCD.
Latched by

The comparison circuit 7 compares the count value latched by the latch circuit 5 with a threshold value stored in the memory circuit 8 in advance. The comparison result is supplied to one input terminal of the AND circuit 9. . The memory circuit 8 has two thresholds, a threshold for detecting that the recording mode has been switched from the standard mode to the triple mode and a threshold for detecting that the recording mode has been switched to the standard mode. Is stored, and one of the thresholds is selected by the mode switching signal MSW.

The second counter circuit 10 counts the number of control signals CTL read from the magnetic tape while the capstan is rotating, and can be operated only while the capstan drive signal SCD arrives. ,
The output is supplied to the other input terminal of the AND circuit 9. The output of the counter circuit 10 becomes logic "L" when the control signal CTL is counted two or more times in the operable state, and becomes logic "H" otherwise.

Next, the operation of this embodiment will be described.
First, the operation in the case where the mode is switched to the triple mode during the slow reproduction in the standard mode will be described with reference to the waveform diagram shown in FIG.

As described above, the slow reproduction is performed by repeating the still reproduction and the normal reproduction. For this reason,
The capstan repeats an intermittent operation of stopping during still playback and rotating during normal playback. Specifically, after performing the still reproduction for a certain period, the capstan is rotated in synchronization with the rotation of the magnetic head to feed the tape. When the control head detects one control signal, the capstan is stopped again to perform still reproduction.

FIG. 2A shows a change in the rotation speed of the capstan which operates intermittently, FIG. 2B shows the capstan drive signal SCD at that time, and FIG. 2C shows the control signal CTL. Represents The rotation speed of the capstan is gradually increased by the activation of the capstan motor (acceleration period), maintains a predetermined constant speed state (constant speed period), gradually decreases (brake period), and returns to the stopped state again. . The amount of movement of the magnetic tape moved by this one run is equivalent to one pitch of the control signal CTL.

While the capstan is rotating, the capstan drive signal SCD is at logic "H", so that the switch circuit 3 is closed, the count circuit 1 becomes operable, and the clock pulse CP is counted. When the capstan stops, the capstan drive signal SCD falls to logic “L”, and the differentiating circuit 6 sends the latch pulse LP to the latch circuit 5.
Is output. Thus, the latch circuit 5 latches the count value of the counter circuit 1. At the same time, the switch circuit 3 is opened, and the count circuit 1 is reset with a slight delay.

The comparison circuit 7 counts the data latched by the latch circuit 5, that is, data A representing the running time of the tape.
And the time data B stored as a threshold value in the memory circuit 8 are compared. If the comparison result is A> B, a logical "H" comparison signal is output to the AND circuit 9, and otherwise, a logical "L" comparison signal is output. Although the contents of the threshold value will be described later, during slow playback in the standard mode, the output is output from the comparison circuit 7 at logic "H" because A> B is set.

The output of the counter circuit 10 keeps the state of the logic "H" during the slow reproduction in the standard mode. Therefore, during slow reproduction in the standard mode, the outputs of the comparison circuit 7 and the counter circuit 10 are both at logic "H", and the output of the AND circuit 9 is also at logic "H".

In this state, when the recording mode of the magnetic tape changes to the triple mode, as shown in FIG.
The pitch of the control signal CTL recorded above is 3
It's a fraction. For this reason, at the beginning of the change, a plurality of control signals CTL arrive during the arrival of the capstan drive signal SCD, as shown in FIG. 2D. Therefore, the output of the counter circuit 10 changes from logic “H” to “L”,
As a result, the output of the AND circuit 9 also changes from logic "H" to "L".

Further, as described above, the capstan drive signal SCD changes to logic "H" when the capstan starts rotating.
, And becomes logical "L" upon detection of the control signal CTL. Therefore, when the recording mode changes to the triple mode, the period of the logical "H" becomes 1/3 as shown in FIG. 2 (e).
become. Therefore, the count value of the counter circuit 1 latched by the latch circuit 5 decreases, and the comparison result of the comparison circuit 7 satisfies A <B. Therefore, the output of the comparison circuit 7 changes from logic “H” to “L”, and the output of the AND circuit 9 also changes from logic “H” to “L”.

As described above, when the recording mode changes from the standard mode to the triple mode, one or both of the output of the counter circuit 10 and the output of the comparison circuit 7 changes from logic "H" to "L". The output of the AND circuit 9 also changes from logic "H" to "L". The playback device detects this change by a control circuit (not shown), and switches the acceleration time of the capstan, the speed at the time of constant speed running, the brake amount, etc. to values suitable for the triple mode, and performs slow playback in the triple mode. Do.

Next, referring to the waveform diagram shown in FIG.
The operation when the mode is switched to the standard mode during the slow reproduction in the double mode will be described. FIG. 4A shows the change in the rotation speed from the start to the stop of the intermittently driven capstan, FIG. 4B shows the capstan drive signal SCD, and FIG. 4C shows the control signal CTL. ing.

The operation during the slow reproduction in the triple mode is the same as that in the standard mode described above, and therefore detailed description is omitted. However, the threshold value of the memory circuit 8 is set by the mode switching signal MSW in the triple mode. The time data at the time of is selected. Although the content of the threshold value will be described later, A <B during slow playback in the triple mode,
The output of the comparison circuit 7 is at logic "L". Therefore, during slow reproduction in the triple mode, the output of the AND circuit 9 is at logic "L".

When the recording mode of the magnetic tape changes to the standard mode in this state, as shown in FIG.
The pitch of the control signal CTL recorded above is 3
Spread twice. For this reason, the pulse width of the capstan drive signal SCD which falls to logic "L" upon detection of the control signal CTL is tripled as shown in FIG. 4 (d). Therefore, the count value of the counter circuit 1 latched by the latch circuit 5 increases, and the comparison result of the comparison circuit 7 becomes A> B. Therefore, the output of the comparison circuit 7 changes from logic “L” to “H”, and the output of the AND circuit 9 also changes from logic “L” to “H”.

As described above, when the recording mode changes from the triple mode to the standard mode, the output of the comparison circuit 7 changes from logic "L" to "H".
Also changes from logic "L" to "H". The reproducing apparatus detects this change by a control circuit (not shown), switches the acceleration time of the capstan, the speed at the time of constant speed running, the brake amount, and the like to optimal values for the standard mode, and performs slow reproduction in the standard mode.

Here, the threshold value stored in the memory circuit 8 will be described. First, when detecting the change from the standard mode to the triple mode, the pulse width of the capstan drive signal SCD in the standard mode is reduced because the pulse width of the capstan drive signal SCD is reduced to 1/3 as described above. If the width is Tsp, the pulse width of the capstan drive signal SCD in the triple mode is 1/3 Tsp. Therefore,
The threshold value may be set at about 1/2 Tsp in the middle.

Next, when the change from the triple mode to the standard mode is detected, the pulse width of the capstan drive signal SCD is expanded by three times. When the pulse width of the signal SCD is Tep, the pulse width of the capstan drive signal SCD in the standard mode is 3 Tep. Therefore, the threshold value may be set to about 2Tep in the middle.

In the above-described embodiment, the discrimination of the recording mode of the VHS system has been described. However, the present invention is not limited to this, and it has a plurality of recording modes and can perform intermittent slow reproduction. Of course, the present invention can be applied to a recording method, for example, a β method.

[0036]

According to the present invention, it is possible to reliably determine the recording mode at the time of slow reproduction, and even if the recording mode changes during the slow reproduction, the optimum capping is performed according to the changed recording mode. It is possible to perform stun control, head selection, and the like, and it is possible to minimize screen disturbance due to a mode change during slow playback.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a recording mode discriminating apparatus according to the present invention.

FIG. 2 is a diagram illustrating an operation when the mode is changed from a standard mode to a triple mode.

FIG. 3 is a diagram showing a change in a recording state of a control signal on a magnetic tape.

FIG. 4 is a diagram illustrating an operation when the mode is changed from the triple mode to the standard mode.

FIG. 5 is a diagram showing a change in a recording state of a control signal on a magnetic tape.

FIG. 6 is a block diagram illustrating an example of a conventional recording mode discriminating apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 counter circuit 2 clock pulse generation circuit 3 switch circuit 4 delay circuit 5 latch circuit 6 differentiating circuit 7 comparison circuit 8 memory circuit 9 AND circuit 10 counter circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 15/087 G11B 15/087 101

Claims (1)

(57) [Claims] 1. A slow reproduction of the video signal by alternately repeating a still reproduction for repeatedly reproducing the same field or the same frame of a video signal recorded on a recording medium and a normal running reproduction for sequentially reproducing continuous fields. In a video signal reproducing apparatus for performing reproduction, first counter means for measuring the time required for the normal traveling reproduction, and comparing means for comparing time data measured by the first counter means with preset time data; A second counter means for counting the number of control signals arriving during the normal traveling reproduction per time , wherein the setting time data of the measurement time data by the comparing means is provided.
The output of the magnitude change against, the second counter means
Based on the output of the single multiple change of that control signal,
Change in the recording mode and if there is a change the output to at least one
Recording mode discriminating apparatus characterized by detecting by.