GB2151818A - Color frame servo circuit for a recording and reproducing apparatus designed for editing - Google Patents
Color frame servo circuit for a recording and reproducing apparatus designed for editing Download PDFInfo
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- GB2151818A GB2151818A GB08431531A GB8431531A GB2151818A GB 2151818 A GB2151818 A GB 2151818A GB 08431531 A GB08431531 A GB 08431531A GB 8431531 A GB8431531 A GB 8431531A GB 2151818 A GB2151818 A GB 2151818A
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
- G11B27/10—Indexing; Addressing; Timing or synchronising; Measuring tape travel
- G11B27/19—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B15/00—Driving, starting or stopping record carriers of filamentary or web form; Driving both such record carriers and heads; Guiding such record carriers or containers therefor; Control thereof; Control of operating function
- G11B15/18—Driving; Starting; Stopping; Arrangements for control or regulation thereof
- G11B15/1808—Driving of both record carrier and head
- G11B15/1875—Driving of both record carrier and head adaptations for special effects or editing
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
- G11B27/02—Editing, e.g. varying the order of information signals recorded on, or reproduced from, record carriers
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
- G11B27/02—Editing, e.g. varying the order of information signals recorded on, or reproduced from, record carriers
- G11B27/022—Electronic editing of analogue information signals, e.g. audio or video signals
- G11B27/029—Insert-editing
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- Signal Processing (AREA)
- Multimedia (AREA)
- Television Signal Processing For Recording (AREA)
- Management Or Editing Of Information On Record Carriers (AREA)
Abstract
A color frame servo circuit 21 for a recording and reproducing apparatus which is designed for editing, comprises a first circuit 15 for detecting a first flag pulse indicating a predetermined field among first through fourth fields of an external PAL system color video signal which is to be recorded, a second circuit 18 for detecting a second flag pulse indicating the predetermined field among first through fourth fields of a PAL system color video signal which is reproduced from a pre-recorded recording medium which is to be edited, a third circuit 19 at least supplied with the first and second flag pulses, for producing a detection signal by detecting whether the phases of the first and second flag pulses coincide, and for generating a control signal for gradually increasing or decreasing the rotational speed of a capstan motor 24 which rotates a capstan for moving the pre-recorded recording medium, and a switching circuit 20 controlled responsive to the detection signal. The switching circuit selectively supplies the control signal to the capstan motor when the phases of the first and second flag pulses do not coincide, and selectively supplies a phase error signal to the capstan motor when the phases of the first and second flag pulses coincide. <IMAGE>
Description
SPECIFICATION
Color frame servo circuit for a recording and reproducing apparatus designed for editing
The present invention generally relates to color frame servo circuits for recording and reproducing apparatuses which are designed for editing (hereinafter simply referred to as editing apparatuses), and more particularly to a color frame servo circuit for an editing apparatus which is supplied with a PAL system color video signal which is reproduced in an external reproducing apparatus such as a video tape recorder (hereinafter simply referred to as a VTR) and carries out an electronic editing by performing an assemble editing or by performing an insert recording.The reproduced color video signal which is obtained from the external VTR, is recorded on a recording medium with a regular field sequence according to a field sequence of a color video signal which is prerecorded on the recording medium.
In the present specification, an 'assemble editing" refers to a type of editing wherein a recording which is performed to record a new video information is started from a part of a recording medium where a previous recording was ended. On the other hand, an "insert recording" refers to a type of editing wherein a new video information is recorded within a predetermined part of a recording medium which is pre-recorded with a video information.
A known editing apparatus is supplied with a color video signal which is reproduced in an external reproducing apparatus such as a VTR, and carries out an electronic editing by performing an assemble editing or by peforming an insert recording. As is well known, a frame servo circuit is provided in the editing apparatus, so that when carrying out an electronic editing, the phase of a vertical synchronizing signal in the reproduced color video signal which is to be recorded on a magnetic tape matches with the phase of a vertical synchronizing signal in a pre-recorded color video signal on the magnetic tape at an edit point, and so that the two color video signals connect in terms of frames.In an editing apparatus designed for the NTSC system color video signal, an upper part of a reproduced picture becomes instantaneously distorted at the edit point because the phases of the vertical synchronizing signals differ by H12 between odd and even fields due to the interlaced scanning, where Hrepresents one horizontal scanning period. However, such a phenomenon may be prevented by the provision of the frame servo circuit.
On the other hand, the frame servo circuit is also provided in an editing apparatus designed for the
PAL system color video signal. As a result, a color flash phenomenon is generated at the edit point with a probability of 1/2. In the present specification, a "color flash phenomenon" refers to a phenomenon in which the color of a reproduced picture becomes unpredictable. That is, as is well known, the luminance signal and the carrier chrominance signal are band share multiplexed in the PAL system color video signal, and the carrier chrominance signal is obtained by subjecting a chrominance subcarrier having a frequency fSc to a carrier suppression system quadrature modulation by color difference signals (R-Y) and (B- Y). Further, the phase of the chrominance subcarrier of the color difference signal (R-Y) is inverted for every scanning line.As is well known, the chrominance subcarrier frequency fsc can be described by 1284 - (1/4)lah + 25 (Hz), where fH represents the horizontal scanning frequency. The phase of the chrominance subcarrier is inverted for every approximately 1 Hl4, and due to the second term of 25 (Hz) which is intended to reduce the dot interference, the phase of the chrominance subcarrier is also inverted for every frame.
On the other hand, the phase of the vertical synchronizing signal in one field of the PAL system color video signal differs from the phase of the vertical synchronizing signal in a subsequent field by 1 Hl2, due to the interlaced scanning. Accordingly, in the case of the PAL system color video signal, the phase of the chrominance subcarrier changes with a period offourfields.
However, the conventional frame servo circuit is designed to discriminate whether the field is an odd field or an even field, and the recording is performed so that the odd and even fields connect with each other. Thus, in the case of the PAL system color video signal, the signal related to one of a third field and a first field which are odd fields, is recorded as a signal related to a field which should be recorded subsequent to the signal related to a second field. In this case, no problems will occur when the signal related to the third field is recorded subsequent to the signal related to the second field. But in a case where the signal related to the first field is recorded subsequent to the signal related to the second field, a burst phase discriminator within a monitoring receiver detects that the field sequence at the edit point is not the regular field sequence.A line switch is selectively switched so as to produce a signal having the chrominance subcarrier frequency fsc and having the phase which is inverted for every line, and this signal from the line switch is supplied to a synchronization detecting circuit for detecting a modulated wave which is obtained by modulating a carrier by the color difference signal (R-y). From a time when the burst phase discriminator makes the detection described above, it takes a predetermined time until the line switch is switched again. As a result, the colorflash phenomenon occurs during this predetermined time. Moreover, there is a problem in that this predetermined time is a relatively long period of time.
Accordingly, it is a general object of the present invention to provide a novel and useful color servo circuit for an editing apparatus, in which the problems described heretofore are eliminated.
The present invention provides a color frame servo circuit for a recording and reproducing apparatus which is designed for editing, said color frame servo circuit comprising, a first detecting circuit for detecting a first flag pulse indicating a predetermined field among first through fourth fields of an external PAL system color video signal which is to be recorded, a second detecting circuit for detecting a second flag pulse indicating the predetermined field among first through fourth fields of a PAL system color video signal which is reproduced from a pre-recorded recording medium which is to be edited, a comparing and controlling circuit at least supplied with the first and second flag pulses from said first and second detecting circuits, for producing a detection signal by detecting whether the phases of the first and second flag pulses coincide, and for generating a control signal for gradually increasing or decreasing the rotational speed of a capstan motor which rotates a capstan for moving said pre-recorded recording medium, and a switching circuit controlled responsive to the output detection signal of said comparing and controlling circuit, said switching circuit selectively supplying the output control signal of said comparing and controlling circuit to said capstan motor when the phases of the first and second flag pulses do not coincide and selectively supplying a phase error signal to said capstan motor when the phases of the first and second flag pulses coincide, said phase error signal being independently produced for rotating said capstan motor at a constant rotational speed.
Another and more specific object of the present invention is to provide a color frame servo circuit which detects whether the phase of a first flag pulse indicating a predetermined one field among first through fourth fields of an external PAL system color video signal which is to be recorded, coincides with the phase of a second flag pulse indicating the same predetermined one field among first through fourth fields of a PAL system color video signal which is reproduced from a pre-recorded recording medium which is to be subjected to an editing. The color frame servo circuit is designed to increase or decrease the rotational speed of a capstan motor for driving a capstan which moves the pre-recorded recording medium, until the two compared phases coincide with each other.
According to the color frame servo circuit of the present invention, it is possible to prevent the color flash phenomenon from occurring in a vicinity of an edit point. Moreover, since a voltage applied to the capstan motor increases or decreases in an accelerative manner in a state where the field of the external color video signal and the field of the reproduced color video signal differ, the capstan motor is controlled so that the two color video signals quickly become synchronized with each other and stabilize in the synchronized state. Hence, it is possible to shorten the time which is required to perform the color framing, and as a result, it is possible to improve the editing efficiency.
Still another object of the present invention is to provide a color frame servo circuit comprising sample and hold means for sampling a sloping part of a trapezoidal wave which is formed from the first flag pulse, by a sampling pulse which is formed based on the second flag pulse and a reproduced control signal extracted in correspondence with a predetermined one field from the reproduced control signal which is obtained by reproducing a control signal which is pre-recorded on the recording medium with a specific period.
In a case where the sampling pulse is formed based on a reproduced vertical synchronizing signal, there is a problem in that the sampling becomes inaccurate when the moving speed of the prerecorded recording medium is gradually increased or decreased so that the phases of the first and second flag pulses coincide, due to noise which mixes into a reproduced color video signal because of a tracking error of a rotary head with respect to a video track. However, according to the color frame servo circuit of the present invention, a tracking error of a control head will not occur with respect to a control track, and such a problem will not occur.
Therefore, it is possible to perform an accurate sampling according to the present invention.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.
Figure 1 is a systematic block diagram showing an example of an editing apparatus provided with a color frame servo circuit according to the present invention;
Figures 2(A) through 2KE) respectively show the waveform of a PAL system color video signal in a vicinity of a vertical synchronizing pulse in each field and the phase of a color burst signal;
Figure 3 is a systematic block diagram showing an embodiment of an essential part of the color frame servo circuit according to the present invention;
Figures 4A and 4B are systematic circuit diagrams respectively showing an embodiment of the block system shown in Figure 3;
Figures 5(A) through 5(L) are timing charts for explaining the operation of the block system shown in Figure 3; and
Figures 6A, 6B, and 6C respectively show a tape pattern on a magnetic tape from which a color video signal to be recorded by an editing is reproduced, a tape pattern on a pre-recorded magnetic tape which is to be subjected to the editing, and a tape pattern on the pre-recorded magnetic tape after the editing is performed.
In Figure 1, a PAL system color video signal which is reproduced from an external VTR and is to be recorded by an editing operation, for example, is applied to an input terminal 11. As described before, the phase of the chrominance subcarrier of the PAL system color video signal varies with a period of four fields. This will be described in conjunction with
Figures 2(A) through 2(E).
In Figure 2(A) through 2(E), an arrow indicates a position where a color burst signal is transmitted. An arrow pointing upwardly indicates that the phase of the color burst signal is +135' with respect to the
R-Y axis, and an arrow pointing downwardly indicates that the phase of the color burst signal is -135 with respect to the R-Y axis. Figures 2(A), 2(B), 2(C) and 2(D) respectively show the signal waveform in the vicinity of a starting position of the first, second, third, and fourth fields. As may be seen from Figures 2(A) and 2(C), the phases of the vertical synchronizing signals coincide in the first and third fields, however, the phases of the color burst signals differ in the first and third fields.Similarly, as may be seen from Figures 2(B) and 2(D), the phases of the vertical synchronizing signals coincide in the second and fourth fields, however, the phases of the color burst signals differ in the second and fourth fields. In addition, as shown in Figures 2(A) through 2(D), the phases of the vertical synchronizing signals and the color burst signals in the first and third fields, differ i'rr.rn the phases of the vertical synchronizing signals and 4'ne color burst signals in the second and fourth fi ~sds.
:-lov.'evSr, a field subsequent to the fourth field is as shown in Figure 2(E), and the phases of the vertical synchronizing signal and the color burst signal in this subsequent field coincide with the phases of the vertical synchronizing signal and the color burst signal in the first field shown in Figure 2(A). Accordingly, in the PAL system color video signal, the phase of the chrominance subcarrier varies with a period of four fields.
Returning now to the description of Figure 1, the external PAL system color video signal which is to be recorded, is applied to the input terminal 11 and is supplied to a video recording circuit 12, a phase comparator 13, a control signal generating circuit 14, and a color frame pulse detecting circuit 15. When recording the external PAL system color video signal by an electronic editing, switches SW1, SW2, and
SWs are connected to respective terminals R. On the other hand, a pre-recorded magnetic tape (not shown, and hereinafter simply referred to as a pre-recorded tape) is played prior to the recording of the external PAL system color video signal, in order to find the edit point.The switches SW1, SW2, and SW3 a,-e connected to respective terminals Pwhen e pre-recorded tape is played in this manner.
Accordincjly, a pre-recorded signal on the pre recorded tape which is reproduced by a rotary head id fom .he pre-recorded tape, is passed through the switch 2 1 and is supplied to the video reproducing circuit 17. The signal supplied to the video reproducing circuit 17 is subjected to a known signal processing, and is converted into a reproduced color video signal which is in conformance with the PAL system.
The output reproduced color video signal of the video reproducing circuit 17 is supplied to a color frame pulse detecting circuit 18. As will be described later on in the specification, the color frame pulse detecting circuits 15 and 18 detect one predetermined field among the first through fourth fields of the PAL system color video signal, and generate a flag pulse (hereinafter referred to as a color frame pulse). The output color frame pulses of the color frame pulse detecting circuits 15 and 18 are supplied to a comparing and controlling circuit 19.
The comparing and controlling circuit 19 generates a signal for gradually increasing or decreasing the rotational speed of a capstan motor 24, until the phases of the two color frame pulses supplied to the comparing and controlling circuit 19 coincide. The output signal of the comparing and controlling circuit 19 is supplied to a terminal 20a of a switching circuit 20. The switching of the switching circuit 20 is controlled responsive to a signal which is obtained from a part of the comparing and controlling circuit 19, and the switching circuit 20 is connected to the terminal 20a when the phases of the two color frame pulses do not coincide, and is switched and connected to a terminal 20b when the phases of the two color frame pulses coincide. The switching circuit 20 is always connected to the terminal 20b when finding the edit point.The color frame pulse detecting circuits 15 and 18, the comparing and controlling circuit 19, and the switching circuit 20 constitute a color frame servo circuit 21 according to the present invention.
When recording the external PAL system color video signal by an assemble editing or by an insert recording by finding and storing into a memory (not shown) an edit starting point and an edit ending point on the pre-recorded tape, the pre-recorded tape is once rewound to a position on the upstream side of the pre-recorded tape and the pre-recorded tape is played by moving the pre-recorded tape in a forward direction from the position which is on the upstream side of the edit starting point. When the phases of the output color frame pulses of the color frame pulse detecting circuits 15 and 18 do not coincide while the pre-recorded tape is being played, the output signal of the comparing and controlling circuit 19 is obtained from the switching circuit 20 and is supplied to a mixing circuit 22.An output signal of the mixing circuit 22 is passed through a driving circuit 23, and is supplied to a capstan motor 24. Hence, the capstan motor 24 is controlled so that the rotational speed thereof gradually increases or decreases. As a result, the moving speed of the pre-recorded tape gradually increases or decreases accordingly.
The rotational speed of the capstan motor 24 is detected by a known frequency generator (FG) 25.
An output rotational speed detection signal of the FG 25 having a frequency responsive to the detected rotational speed of the capstan motor 24, is supplied to a frequency-to-voltage (fix) converting circuit 26 wherein the signal is subjected to a frequency-tovoltage conversion. An output speed error voltage of the FiV converting circuit 26 is supplied to the mixing circuit 22. When the phases of the two color frame pulses coincide, the switching circuit 20 is switched and connected to the terminal 20b. A point where the phases of the two color frame pulses coincide is located on the upstream side of the pre-recorded tape with respect to the edit starting point.
On the other hand, in the play mode described above, a control signal is reproduced from a control track on the pre-recorded tape by a control head 27.
The reproduced control signal is passed through the switch SW2, an amplifier circuit 28, and the switch
SW3, and is supplied to the phase comparator 13.
The phase comparator 13 compares the phase of the reproduced control signal from the switch SW3, with the phase of the vertical synchronizing signal within the external PAL system color video signal, for example. Accordingly, from a time when the phases of the two color frame pulses coincide, an output phase error voltage of the phase comparator 13 and the output speed error voltage of the F1V converting circuit 26 are respectively supplied to the mixing circuit 22 and are mixed. The output signal of the mixing circuit 22 is supplied to the capstan motor 24 through the driving circuit 23, so as to control the rotational speed of the capstan motor 24.
When a reproducing position on the pre-recorded tape reaches the edit starting point in the state described above, the editing apparatus automatically assumes a recording mode, and the switches SW1,
SW2, and SW3 are switched and connected to the respective terminals R. Thus, the signal which is obtained by converting the signal format of the external PAL system color video signal into a predetermined signal format in the video recording circuit 12, is supplied to the rotary head 16 through the switch SWr, and the assemble editing or insert recording is started. At the same time, a control signal which is obtained in the control signal generating circuit 14 byfrequency-dividino the vertical synchronizing signal within the reproduced color video signal from the input terminal 11, is supplied to the control head 27 through the switch SW2.Thus, the control signal is recorded on the control track when the first and third fields are recorded, for example, that is, with a period of one frame. The rotational speed detection signal obtained from the
FG 25, is frequency-divided in a frequency dividing circuit 29. An output signal of the frequency dividing circuit 29 having a period of one frame, is supplied to the phase comparator 13 through the switch SW3.
The recording mode is continued up to the edit ending point, and the electronic editing is performed in this manner.
Next, a more detailed description will be given with respect to the color frame servo circuit according to the present invention, by referring to Figures 3, 4A, and 4B. In Figures 3, 4A, and 4B, those parts which are the same as those corresponding parts in
Figure 1 are designated by the same reference numerals.
In Figure 3, the external PAL system color video signal is applied to the input terminal 11 at the start of an automatic editing. Further, the PAL system color video signal which is reproduced from the pre-recorded tape in the editing apparatus from the position on the pre-recorded tape which is on the upstream side of the pre-recorded tape with respect to the edit starting point, is applied to an input terminal 30. It will be assumed that the external PAL system color video signal a shown in Figure 5(A) wherein the field sequence is schematically illustrated is applied to the input terminal 11, and that the
reproduced PAL system color video signal g shown
in Figure 5(G) wherein the field sequence is schematically illustrated is applied to the input terminal 30.
The PAL system color video signals a and g
applied to the respective input terminals 11 and 30,
are supplied to the respective color frame pulse
detecting circuits 15 and 18. As may be understood from Figures 2(A) through 2(E), there are the follow
ing two methods of generating the color frame
pulse. According to a first method, the color frame
pulse is generated by discriminating a phase error
between color burst signals on an arbitrary line in the odd or even fields when observed from a vertical
synchronizing pulse. On the other hand, according tc
a second method, the color frame pulse is generated
by discriminating the field, by noting that the timing with which the color burst signal appears immediately after a vertical synchronizing pulse is quickest in an order from the third, second, first, and fourth fields.In other words, when the color burst signal appears in the sixth horizontal scanning period, for example, the third field is detected. Either one of the above two methods may be used in the present invention. However, in the present embodiment, the second method is used since the construction of the color frame pulse detecting circuits 15 and 18 will be relatively simple. For convenience' sake, it will be assumed that the color frame pulse is generated when the third field among the first through fourth fields is detected.
Accordingly, the color frame pulse detecting circuit 15 generates a first color frame pulse b shown in
Figure 5(B), and the color frame pulse detecting circuit 18 generates a second color frame pulse h shown in Figure 5(H). The first color frame pulse b is supplied to a timing pulse generating circuit 31 and a reference color frame pulse generating circuit 32 within the comparing and controlling circuit 19. As shown in Figure 4B, the timing pulse generating circuit 31 comprises monostable multivibrators 52 through 55, and delays the first color frame pulse b by a delay time of one field and a delay time of three fields. As a result, pulsescand deach having a constant width as shown in Figures 5(C) and 5(D), are generated from the timing pulse generating circuit 31 and are supplied to a trapezoidal wave generating circuit 33.
The first color frame pulse b triggers the monostable multivibrator 52 shown in Figure 4B by a rise thereof, and is converted into a negative polarity pulse having a low-level period of 20.0 msec (one field). The output negative polarity pulse of the monostable multivibrator 52 is supplied to the monostable multivibrators 53 and 54, and triggers the monostable multivibrators 53 and 54 by a rise thereof. Hence, the output negative polarity pulse of the monostable multivibrator 52 is further delayed by 8.7 msec in the monostable multivibrator 53. A pulse having a period of 80 msec and having a pulse width of 8.7 msec, is produced from the monostable multivibrator 53 and is supplied to a switching circuit 56.On the other hand, the monostable multivibrator 54 produces a negative polarity pulse having a pulse width of 38.0 msec, and this negative polarity pulse triggers a monostable multivibrator 55 by a rise thereof. The monostable multivibrator 55 produces a positive polarity pulse having a pulse width of 4.0 msec.
The trapezoidal wave generating circuit 33 has the construction shown in Figure 4B, and generates a trapezoidal wave e shown in Figure 5(E). The trapezoidal wave e rises with a predetermined slope during a time period corresponding to the pulse width of the pulse c, and falls with a predetermined slope during a time period corresponding to the pulse width of the pulsed. During a time period from the fall in the pulse c to a rise in the pulse and during a time period from the fall in the pulse dto a
rise in the pulse c, the level of the trapezoidal wave e gradually decreases with time. The trapezoidal wave e is supplied to a sample and hold circuit 34 wherein the sloping part of the trapezoidal wave e is sampled and held.
The trapezoidal wave e has a rising slope part and a falling slope part. The rising slope part of the trapezoidal wave e, which is in correspondence with the pulse width of the pulse c, is used to produce an error voltage which is applied to the capstan motor 24 for controlling the rotational speed of the capstan motor 24 so that the phase error between the field of the color video signal a and the field of the color video signal g decreases within a range in which the two fields are synchronized. In other words, the rising slope part of the trapezoidal wave e is used to produce the error voltage for controlling the rotational speed of the capstan motor 24 so that the rotational speed of the capstan motor 24 stabilizes and the phase error between the two color frame pulses decreases.On the other hand, in a case where the above phase error exceeds a predetermined range, the falling slope part of the trapezoidal wave e, which is in correspondence with the pulse width of the pulse d, is used to produce an error voltage for increasing (or decreasing) the rotational speed of the capstan motor 24 in an accelerative manner so that the capstan servo can be performed stably.
As shown in Figure 4B, the trapezoidal wave generating circuit 33 is basically an integrating circuit which comprises an operational amplifier 58 and a capacitor 59. A power source terminal of 12 volts is coupled to an inverting input terminal of the operational amplifier 58, through a switching circuit 57 and a resistor 60 which are coupled in series. A
Q-output terminal of the monostable multivibrator 53 is coupled to the inverting input terminal of the operational amplifier 58 through a resistor 61.
Further, the0-output terminal of the monostable multivibrator 53 is also coupled to the inverting input terminal of the operational amplifier 58, through a switching circuit 56 and a resistor 62 which are coupled in series. A bias setting voltage which is obtained by voltage-dividing the power source voltage of 12 volts by resistors 63 and 64, is applied to a non-inverting input terminal of the operational amplifier 58. A feedback resistor 65 is coupled between the inverting input terminal of the operational amplifier 58 and the output terminal of the operational amplifier 58. When the resistances of the resistors 60, 61, 62, and 65 are respectively designated by R1,
R2, R3, and R4, the following relation stands.
R4 > > R3 > R1
The switching circuit 56 is turned ON only during a high-level period (8.7 msec) of the pulse c which is obtained through a Q-output terminal of the monostable multivibrator 53. The switching circuit 57 is only turned ON during a high-level period (4.0 msec) of the pulse dwhich is obtained through a Output terminal of the monostable multivibrator 55. When the switching circuit 56 is turned ON, a low-level signal which is obtained through the Q-output terminal of the monostable multivibrator 53 is supplied to the inverting input terminal of the operational amplifier 58 through the switching circuit 56 and the resistor 62.As a result, a current flows toward the resistor 62 from the inverting input terminal of the operational amplifier 58, and the level of the output voltage of the operational amplifier 58 increases during the high-level period of the pulse c with a sharp slope which is determined by the resistance R3 of the resistor 62 or the like. During a period in which the switching circuits 56 and 57 are both OFF, a current passes through the resistor 61 and is applied to the inverting input terminal of the operational amplifier 58, and the level of the output voltage of the operational amplifier 58 decreases with a relatively gradual slope.During a high-level period of the pulse dwhen the switching circuit 57 is
ON and the switching circuit 56 is OFF, a current passes through the resistor 60 and a current passes through the resistor 61, and these currents are applied to the inverting input terminal of the operational amplifier 58. Thus, the level of the output voltage of the operational amplifier 58 decreases with a sharp slope. Therefore, the trapezoidal wave e having the waveform shown in Figure 5(E) is obtained at the output side of the operational amplifier 58.
On the other hand, the reference color frame pulse generating circuit 32 delays the color frame pulse b by a time which is slightly smaller than four fields, and generates a pulse fshown in Figure 5(F) having a predetermined pulse width which is wider than the pulse width of the color frame pulse (b). The output pulse fof the reference color frame pulse generating circuit 32 is supplied to a coincidence detecting circuit 35 as a reference color frame pulse. The coincidence detecting circuit 35 comprises an AND circuit, for example, and detects whether the phase of the color frame pulse h coincides with the phase of the reference color frame pulse f. In a time period
T1 shown above Figure 5(A), the fields of the color video signals a and g do not coincide, and thus, a low-level signal is obtained from the coincidence detecting circuit 35.This low-level signal from the coincidence detecting circuit 35 is supplied to the switching circuit 20 shown in Figure 1 through an output terminal 36, as a switching signal, so as to switch and connect the switching circuit 20 to the terminal 20a.
The color frame pulse h is supplied to a gate circuit 37 wherein the color frame pulse h is delayed by a time which is slightly smaller than four fields and is converted into a gate pulse shown in Figure 5(J) having a predetermined pulse width. The gate circuit 37 passes a reproduced control signal ishown in
Figure 5(1) which is applied to an input terminal 38, during a high-level period of the gate pulse. On the other hand, the gate circuit 37 blocks the reproduced control signal during a low-level period of the gate pulse. The reproduced control signal iis reproduced from the control track on the pre-recorded tape which is played in the editing apparatus. Since the control signal is recorded in correspondence with the starting positions of the first and third fields of the PAL system color video signal which is reproduced from the pre-recorded tape and is obtained from the input terminal 30, the reproduced control signal i is obtained with a period of two fields (one frame) at the starting positions of the first and third fields as may be seen from Figures 5(G) and 5(1).
In the present embodiment, the trapezoidal wave e is sampled by the reproduced control signal ias will be described later on in the specification. Because the reproduced control signal iis obtained twice in fourfields,the reproduced control signal obtained at the starting position of the third field which is in correspondence with the color frame pulses band h, must be used as the sampling pulse. This is the reason why the gate circuit 37 is provided. The gate circuit 37 is provided so that the high-level period of the gate pulse shown in Figure 5(J) is a pradetermined time period which begins from a point before and ends at a point after the starting position of the third field of the color video signal g.Hence, only a control signal kshown in Figure 5(K) which is reproduced in a vicinity of the starting position of the third field of the color video signal g, is obtained from the gate circuit 37 and is supplied to a sampling pulse generating circuit 39.
The sampling pulse generating circuit 39 delays the reproduced control signal k by a predetermined time and generates a sampling pulse,' shown in
Figure 5(L). The sampling pulse f is supplied to the sample and hold circuit 34, and samples the sloping part of the trapezoidal wave e. During the time period T1 in which the phases of the color frame pulses b and h do not coincide, the phase of the sampling pulse z is selected such that the sampling pulse b occurs at a falling slope part of the trapezoidal wave e.
The reference color frame pulse generating circuit 32, the coincidence detecting circuit 35, the gate circuit 37, and the sampling pulse generating circuit 39 have the circuit construction shown in Figure 4A.
The reference color pulse generating circuit 32 comprises a monostable multivibrator 45 for generating a negative polarity pulse having a pulse width of 40.0 msec, and a monostable multivibrator 46 for generating a positive polarity pulse fhaving a pulse width of 10.0 msec, which monostable multivibrators 45 and 46 are coupled in series. The coincidence detecting circuit 35 comprises a D-type flip-flop 47 which receives the output pulse f of the monostable multivibrator 46 by a data terminal thereof and produces a voltage which is obtained by sampling the pulse fry the rise in the color frame pulse h. The output voltage of the flip-flop 47 is obtained through the output terminal 36. The gate circuit 37 comprises monostable multivibrators 48 and 49 and an AND circuit 50.
The monostable multivibrator 48 is triggered by the rise in the color frame pulse h, and supplies to the monostable multivibrator 49 a negative polarity pulse having a pulse width of 30.0 msec. The monostable multivibrator 49 is triggered by the rise in the output negative polarity pulse of the monostable multivibrator 48, and produces a positive polarity pulse shown in Figure 5(J) having a pulse width of 10.0 msec. The output positive polarity pulse of the monostable multivibrator 49 is supplied to the AND circuit 50. The reproduced control signal which is supplied to the AND circuit 50 through the input terminal 38, is passed through the AND circuit 50 only during the time period of 10.0 msec in which the output positive pclarity pulse of the monostable multivibrator 49 is supplied to the AND circuit 50.
The output signal of the AND circuit 50 is supplied to a monostable multivibrator 51 which constitutes the sampling pulse generating circuit 39. The monostable multivibrator 51 is triggered by the output signal of the AND circuit 50, and produces a positive polarity pulse (having a pulse width of 100 Fsec, for example. The output positive polarity pulse of the monostable multivibrator 51 is obtained through a terminal 66, and is supplied to the sample and hold circuit 34 shown in Figure 4B as the sampling pulse.
In Figure 4B, the trapezoidal wave e is supplied to a switching circuit 68 after being inverted and amplified in an operational amplifier 67. The switching circuit 68 is turned ON only during the high-level period of the sampling pulse (which is obtained from the terminal 66, and applies to a holding capacitor 69 the voltage at a sloping part of an output trapezoidal wave of the operational amplifier 67. An operational amplifier 70 has a high input impedance, and maintains the charged voltage in the holding capacitor 69 essentially without a discharge. Accordingly, the voltage at the sloping part of the trapezoidal wave which is sampled during the
ON period of the switching circuit 69 and held during the OFF period of the switching circuit 68, is obtained across the terminals of the holding capacitor 69.This voltage across the terminals of the holding capacitor 69 is passed through the operational amplifier 70, and is obtained through an output terminal 40.
The sample and hold circuit 34 repeats the operation of holding the voltage which is obtained by sampling the falling slope part of the trapezoidal wave e by the sampling pulse a, until a sampling is performed by a subsequent sampling pulse (which is received approximately four fields thereafter.
Hence, an error voltage m indicated by a one-dot chain line in Figure 5(E) is obtained through the output terminal 40.
The error voltage m is passed through the switching circuit 20, the mixing circuit 22, and the driving circuit 23, and is supplied to the capstan motor 24 so as to control the rotational speed of the capstan motor 24. The capstan motor 24 is controlled so that the rotational speed increases as the error voltage m increases. As may be seen from Figures 5(E) and 5(L), the phase of the sampling pulse 6 is selected so that the sampling pulse 6 samples the falling slope part (the sloping part which slopes in the opposite direction compared to the sloping part of the trapezoidal wave which is sampled in a phase control system of a normal capstan servo circuit) of the trapezoidal wave e. Hence, the comparing and control circuit 19 which comprises the circuits 31 through 35,37, and 39, operates so as to gradually increase the speed error of the capstan motor 24.
Consequently, the error voltage m gradually increases, and the rotational speed of the capstan motor 24 also increases gradually.
Accordingly, the moving speed of the prerecorded tape is gradually increased forcibly, and the fields of the color video signals a and g will coincide within a time which is short compared to the time required in the conventional circuit. In
Figures 5(A) through 5(L), the reproduced fields of the color video signals a and g coincide in the second field at a time t1, for example. However, the color frame pulses b and g are not produced at the time1. The color frame pulses b and h are produced at a time t in the vicinity of the starting position where the subsequent third field is reproduced, and the color frame pulses hand h are detected simultaneously.Therefore, a high-level coincidence signal is produced from the coincidence detecting circuit 35, and is supplied to the switching circuit 20 shown in Figure 1 so as to switch and connect the switching circuit 20 to the terminal 20b. During a time period T2 after the time t2, the rotational speed of the capstan motor 24 is controlled to become constant by the normal capstan servo circuit described before in conjunction with Figure 1.
When it is assumed that the external PAL system color video signal supplied to the input terminal 11 of the editing apparatus is reproduced from a magnetic tape 41 having the tape pattern shown in
Figure 6A, and that the color video signal reproduced from the pre-recorded video tracks on the tape 41 subsequent to a recorded position GA of a 329-th control signal isto be recorded bythe assemble editing over the pre-recorded video tracks subsequentto a position (ss) of a 127-th control signal on a pre-recorded magnetic tape 42a which is played in the editing apparatus, a magnetic tape 42b having the tape pattern shown in Figure 6C is obtained.
In Figures 6A through 6C, the third field of the PAL system color video signal is recorded on the video tracks represented by blanks, the fourth field is recorded on the video tracks represented by hatchings which slope downwardly to the right, the first field is recorded on the video tracks represented by black, and the second field is recorded on the video tracks represented by hatchings which slope downwardly to the left. Accordingly, the PAL system color video signal is recorded in the regular field sequence before and afterthe edit point(@, and the colorflash phenomenon will not occur.
In a case where the field at the edit starting point (E) on the tape 41 is different from the field at the edit starting point (ss) on the pre-recorded tape 42a, the recording is started from a track position which is closest to the edit starting point # a and where the recorded field is the same as the field at the edit starting point@. For example, when it is assumed that the edit starting point (8) in Figure 6A is a position where a 330-th control signal and the third field are recorded, the PAL system color video signal which is reproduced from this position is recorded by the assemble editing from a position shown in
Figure 6B where a 126-th or 128-th control signal and the third field are recorded, even if the edit starting point on the pre-recorded tape 42a shown in Figure 6B is located at the position~.
In the embodiment described heretofore, the capstan motor 24 is controlled so that the rotational speed thereof gradually increases in an accelerative manner when the phase error between the field of the external color video signal and the field of the reproduced color video signal exceeds the predetermined range. However, the capstan motor may be controlled so that the rotational speed thereof gradually decreases in an accelerative manner.
Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention.
Claims (4)
1. A color frame servo circuit for a recording and reproducing apparatus which is designed for editing, said color frame servo circuit comprising:
a first detecting circuit for detecting a first flag pulse indicating a predetermined field among first through fourth fields of an external PAL system color video signal which is to be recorded;
a second detecting circuit for detecting a second flag pulse indicating the predetermined field among first through fourth fields of a PAL system color video signal which is reproduced from a prerecorded recording medium which is to be edited;;
a comparing and controlling circuit at least supplied with the first and second flag pulses from said first and second detecting circuits, for producing a detection signal by detecting whether the phases of the first and second flag pulses coincide, and for generating a control signal for gradually increasing or decreasing the rotational speed of a capstan motor which rotates a capstan for moving said pre-recorded recording medium; and
a switching circuit controlled responsive to the output detection signal of said comparing and controlling circuit, said switching circuit selectively supplying the output control signal of said comparing and controlling circuit to said capstan motor when the phases of the first and second flag pulses do not coincide and selectively supplying a phase error signal to said capstan motor when the phases of the first and second flag pulses coincide, said phase error signal being independently produced for rotating said capstan motor at a constant rotational speed.
2. A color frame servo circuit as claimed in claim 1 in which said comparing and controlling circuit comprises coincidence detecting means for detecting that the phases of the first and second flag pulses coincide and for producing said detection signal, trapezoidal wave generating means for generating from the first flag pulse a trapezoidal wave having a period of four fields and having first and second voltage sloping parts which slope in mutually opposite directions, sampling pulse generating means for producing a sampling pulse at least from the second flag pulse, and a sample and hold circuit for producing as said control signal a signal which is obtained by sampling and holding the first sloping part of the output trapezoidal wave of said trapezoidal wave generating means by the output sampling pulse of said sampling pulse generating means when the phases of the first and second flag pulses do not coincide, and for sampling and holding the second sloping part of the trapezoidal wave by the sampling pulse when the phases of the first and second flag pulses coincide.
3. A color frame servo circuit as claimed in claim 2 in which said sampling pulse generating means comprises a gate circuit supplied with the second flag pulse and a reproduced control signal which is obtained by reproducing a control signal which is pre-recorded on said pre-recorded recording medium with a predetermined period, for gating only the reproduced control signal corresponding to said predetermined field, and a sampling pulse generating circuit for generating the sampling pulse based on the output reproduced control signal of said gate circuit.
4. A color frame servo circuit as claimed in claim 2 in which said trapezoidal wave generating means comprises a timing pulse generating circuit supplied with the first flag pulse, for generating first and second pulses, said first pulse being delayed by one field with respect to the first flag pulse and having a predetermined pulse width, said second pulse being delayed by three fields with respect to the first flag pulse and having a predetermined pulse width, and a trapezoidal wave generating circuit supplied with the output first and second pulses of said timing pulse generating circuit, for generating the trapezoidal wave having the first sloping part during a time period corresponding to the pulse width of said first pulse and having the second sloping part during a time period corresponding to the pulse width of said second pulse.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP58234694A JPS60126988A (en) | 1983-12-13 | 1983-12-13 | Color frame servo circuit in recording and reproducing device for edition |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8431531D0 GB8431531D0 (en) | 1985-01-23 |
| GB2151818A true GB2151818A (en) | 1985-07-24 |
| GB2151818B GB2151818B (en) | 1987-03-18 |
Family
ID=16974949
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08431531A Expired GB2151818B (en) | 1983-12-13 | 1984-12-13 | Color frame servo circuit for a recording and reproducing apparatus designed for editing |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS60126988A (en) |
| DE (1) | DE3445467A1 (en) |
| GB (1) | GB2151818B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0206728A2 (en) * | 1985-06-19 | 1986-12-30 | Sony Corporation | Apparatus for reproducing signals from a magnetic tape |
| EP0242130A2 (en) * | 1986-04-12 | 1987-10-21 | Sony Corporation | Electronic editing apparatus |
| EP0729154A2 (en) * | 1995-02-27 | 1996-08-28 | Matsushita Electric Industrial Co., Ltd. | Recording method and apparatus for control track |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2820477B2 (en) * | 1990-01-09 | 1998-11-05 | 松下電器産業株式会社 | Recording device and playback device |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1157940A (en) * | 1966-07-14 | 1969-07-09 | Fernseh Gmbh | Improvements in or relating to Colour Television |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3890638A (en) * | 1973-08-22 | 1975-06-17 | Cmx Systems | Color phase matching system for magnetic video tape recordings |
| GB1549855A (en) * | 1975-05-20 | 1979-08-08 | Rca Corp | Pal four-frame subcarrier phase detector |
| DE2921962C2 (en) * | 1979-05-30 | 1981-10-01 | Institut für Rundfunktechnik GmbH, 8000 München | Method and circuit arrangement for determining a specific sequence of eight successive fields of a PAL-coded color television signal |
-
1983
- 1983-12-13 JP JP58234694A patent/JPS60126988A/en active Granted
-
1984
- 1984-12-13 GB GB08431531A patent/GB2151818B/en not_active Expired
- 1984-12-13 DE DE19843445467 patent/DE3445467A1/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1157940A (en) * | 1966-07-14 | 1969-07-09 | Fernseh Gmbh | Improvements in or relating to Colour Television |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0206728A2 (en) * | 1985-06-19 | 1986-12-30 | Sony Corporation | Apparatus for reproducing signals from a magnetic tape |
| EP0206728A3 (en) * | 1985-06-19 | 1988-03-23 | Sony Corporation | Apparatus for reproducing signals from a magnetic tape |
| EP0242130A2 (en) * | 1986-04-12 | 1987-10-21 | Sony Corporation | Electronic editing apparatus |
| EP0242130A3 (en) * | 1986-04-12 | 1989-01-25 | Sony Corporation | Electronic editing apparatus |
| EP0729154A2 (en) * | 1995-02-27 | 1996-08-28 | Matsushita Electric Industrial Co., Ltd. | Recording method and apparatus for control track |
| EP0729154A3 (en) * | 1995-02-27 | 1997-05-28 | Matsushita Electric Ind Co Ltd | Recording method and apparatus for control track |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3445467C2 (en) | 1988-05-26 |
| JPS60126988A (en) | 1985-07-06 |
| GB2151818B (en) | 1987-03-18 |
| DE3445467A1 (en) | 1985-10-03 |
| JPH0223119B2 (en) | 1990-05-22 |
| GB8431531D0 (en) | 1985-01-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19931213 |