JP3017645U - Rotary head switching timing adjustment circuit - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] To simplify the circuit configuration and facilitate rotary head switching timing adjustment according to the NTSC system or the PAL system. [Structure] A delay time adjusting means 7 for adjusting a rotary head switching timing corresponding to one of the NTSC system and the PAL system by a microcomputer 1, a PG pulse period ratio of the NTSC system to the PAL system, and a delay of the NTSC system. An arithmetic means for converting the product of the time and the delay time of the PAL system and an arithmetic means for converting the product of the PG pulse period ratio of the PAL system with respect to the NTSC system and the delay time of the PAL system to the delay time of the NTSC system are provided. And a switching signal generating means for generating an RF-SW pulse based on the calculation result by those calculating means and outputting it from 6.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a rotary head switching timing adjusting circuit in a video reproducing apparatus capable of reproducing video compatible with the NTSC system and the PAL system, respectively.

[0002]

[Prior art]

 FIG. 4 is a circuit diagram showing the configuration of a conventional rotary head switching timing adjusting circuit using a microcomputer. In the figure, 1 is a micro computer (calculation) that generates a head switching pulse (hereinafter referred to as an RF-SW pulse) for defining a switching timing between two rotary heads according to the NTSC system or the PAL system. Means, switching signal generating means), 1a is an A / D converter, and 2 is a delay time given to a PG pulse signal (hereinafter referred to as a reference PG pulse) corresponding to a vertical synchronizing signal indicating the signal switching timing of two rotating heads. Input port for PG delay voltage input that defines Reference numeral 3 is a semi-fixed resistor, and 4 is a fixed resistor connected in series with the semi-fixed resistor 3. Reference numeral 5 denotes a transistor connected in parallel to the fixed resistor 4. A base terminal 5a is provided with a delay time setting signal which is a pulse signal for setting a delay time according to the NTSC system or the PAL system to be switched. Supplied. Reference numeral 6 denotes an RF-SW pulse output port in the microcomputer 1. Reference numeral 9 is a terminal for inputting a PG pulse from the PG head for detecting the cylinder rotation phase of the rotary head.

In this case, the resistance value of the fixed resistor 4 is set to a value corresponding to the difference between the delay time in the NTSC system or PAL system before switching and the delay time in the PAL system or NTSC system after switching. ing.

Next, the operation will be described. FIG. 5 is a flowchart showing the operation of the conventional rotary head switching timing adjusting circuit. In this rotary head switching timing adjusting circuit, a delay time setting signal of "H" level is supplied to the base terminal of the transistor 5 during NTSC reproduction. As a result, the transistor 5 is turned on, the fixed resistor 4 is short-circuited, and the level of the PG delay voltage input supplied to the input port 2 becomes a low value (a value corresponding to the delay time of the NTSC system). . On the other hand, at the time of PAL reproduction, the base terminal of the transistor 5 becomes'L 'level. As a result, the transistor 5 is turned off, and the level of the PG delay voltage input supplied to the input port 2 is higher than that at the time of NTSC reproduction. (A value corresponding to the delay time of the PAL system). The PG delay voltage input supplied to the input port 2 is converted into digital data by the A / D converter 1a inside the microcomputer 1.

Based on this digital data, the microcomputer 1 determines whether the reproduction is based on the NTSC system or the PAL system (step S100). When it is judged that the reproduction is based on the NTSC system, the delay time according to the NTSC system is added to the reference PG pulse indicating the signal switching timing of the two rotary heads generated by the PG head (not shown). A switching switch pulse of an RF signal from one rotary head, that is, an RF-SW pulse is generated and output from the output port 6 (step S101).

On the other hand, when it is determined in step S100 that the reproduction is based on the PAL system, a delay time corresponding to the PAL system is similarly added to the reference PG pulse to generate an RF-SW pulse, and the output port 6 To output (step S102).

[0007]

[Problems to be solved by the device]

 Since the conventional rotary head switching timing adjusting circuit is configured as described above, a circuit including the transistor 5, the semi-fixed resistor 3 and the fixed resistor 4 for setting the rotary head switching timing according to the NTSC system and the PAL system is configured. Since it must be externally attached to the micro computer 1 and both the resistance values of the semi-fixed resistor 3 and the fixed resistor 4 must be set to values according to NTSC playback and PAL playback, adjustment is not easy. was there.

The present invention has been made to solve the above-mentioned problems, and simplifies the circuit configuration and facilitates the adjustment of the rotary head switching timing according to the NTSC system or the PAL system. It is an object to provide a head switching timing adjustment circuit.

[0009]

[Means for Solving the Problems]

 The rotary head switching timing adjusting circuit according to the present invention corresponds to the NTSC system or the PAL system based on the delay time corresponding to the NTSC system or the PAL system and the reference PG pulse corresponding to the vertical synchronizing signal, respectively, Either the NTSC system or the PAL system is used in the rotary head switching timing adjustment circuit that generates and outputs the RF-SW pulse that switches the video signals read by the two rotary heads that read the video information recorded on the tape. Delay time adjusting means for adjusting the rotary head switching timing corresponding to the PAL method, and arithmetic means for converting the product of the PG pulse period ratio of the NTSC method against the PAL method and the delay time of the NTSC method into the delay time of the PAL method. And the PAL PG pulse period ratio for the NTSC system An arithmetic means for converting the product of the delay times of the AL method into the delay time of the NTSC method, and a switching signal generating means for generating and outputting the RF-SW pulse based on the operation results of these arithmetic means are provided. Is characterized by.

[0010]

[Action]

 In the rotary head switching timing adjusting circuit according to the present invention, when the delay time adjusting means adjusts the timing corresponding to the NTSC system, the ratio of the PG pulse period of the NTSC system to the PG pulse period of the PAL system is obtained. If the delay time of the PAL system is calculated by the product of the NTSC system delay time and the timing adjustment corresponding to the PAL system is performed by the delay time adjusting means, the PG pulse period of the NTSC system is calculated. The delay time of the NTSC system is calculated by the product of the ratio of the PG pulse period of the PAL system to the PAL system delay time. An RF-SW pulse for switching the rotary head is generated at a timing corresponding to the delay time thus obtained.

[0011]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of a rotary head switching timing adjusting circuit of this embodiment. In FIG. 1, parts that are the same as or equivalent to those in FIG. 4 are assigned the same reference numerals and explanations thereof are omitted. In the figure, 1b is a ROM in which the program shown by the flowchart of FIG. 3 is stored. The ROM 1b also has a conversion formula of a delay time to be added to the reference PG pulse in order to match the switching timing of the rotary head with the timing corresponding to each NTSC system or PAL system when reproducing from the NTSC system to the PAL system. It is stored. Reference numeral 7 is a semi-fixed resistor for adjusting the rotary head switching timing corresponding to one of the NTSC system and the PAL system. Set the delay time to be given to the pulse.

Next, the operation will be described based on the flowchart shown in FIG. Now, assuming that the PG delay voltage input according to the NTSC system is generated by the semi-fixed resistor 7 and is supplied to the input port 2 and the reproduction according to the NTSC system is performed, the process proceeds from step S1 to step S2. Further, in step S10, an RF-SW pulse for NTSC is generated, a loop process is returned to step S1, and NTSC reproduction is performed. When the NTSC system is switched to the PAL system in this state, how the RF-SW pulse according to the PAL system is generated will be described below.

At the time of switching to the PAL system, it is determined in step S2 that the NTSC reproduction is not performed, so that the process exits from the loop process in step S2 and proceeds to step S3. In step S3, the PG delay time according to the PAL method is calculated and obtained from the conversion formula stored in the ROM 1b in advance.

This conversion formula is different between the case where the number of revolutions of the cylinder is in the reproduction by the NTSC system and the case where the reproduction is in the PAL system, and therefore the period of the reference P G pulse in the case of the reproduction by the NTSC system is 33.37 msec The period of the reference PG pulse in the PAL system reproduction is 40.00 msec, and the period of the reference PG pulse is shorter in the NTSC system reproduction than in the PAL system reproduction. Therefore, the delay time given to the reference PG pulse for adjusting the switching timing of the rotary head is smaller in the case of the reproduction by the NTSC system than in the case of the reproduction by the PAL system.

FIG. 2A shows a reference PG pulse output according to the signal switching timing of the rotary head, and FIG. 2B shows a reference PG pulse corresponding to NTSC reproduction by the semi-fixed resistor 7. The given delay time T1 is shown. The figure (c) is the RF-SW pulse for NTSC regeneration that rises after the delay time set for NTSC regeneration from the reference PG pulse, and it rotates according to the rotation speed of the cylinder during NTSC regeneration. The head switching timing is synchronized. Further, FIG. 9D shows the delay time T2 given to the reference PG pulse by the semi-fixed resistor 7 corresponding to the PAL reproduction.

The respective different delay times are calculated by calculating the delay time according to the NTSC system or the PAL system before switching. The arithmetic expression used at this time is the above-mentioned conversion expression, and the RF-SW pulse used for reproduction by the PAL system or the NTSC system to be switched is generated based on the delay time obtained by this conversion formula.

In this case, the conversion formula used when switching from the state in which the reproduction by the NTSC system is performed to the reproduction by the PAL system is (1.198) × (delay time for NTSC reproduction), The conversion formula used when switching from the state in which the system reproduction is performed to the reproduction in the NTSC system is (0.834) × (PAL reproduction delay time). The constants (1.198) and (0.834) are the values obtained from the number of rotations of the cylinder in the case of NTSC reproduction and PAL reproduction, and (NTSC reproduction delay time) and (PAL reproduction time). The delay time) is the delay time corresponding to either the NTSC system or the PAL system set by the semi-fixed resistor 7.

Returning to FIG. 3, in the subsequent step S4, the PG delay time obtained in step S3 is stored in the memory, and in the next step S5, the RF-SW pulse is based on the PG delay time data stored in the memory. To generate.

On the other hand, when the PG delay voltage input according to the PAL system is generated by the semi-fixed resistor 7 and is supplied to the input port 2, the process proceeds from step S1 to step S6, and according to the PAL system at step S6. It is judged whether or not the reproduction is performed, and when the reproduction by the PAL system is performed, the RF-SW pulse for the PAL is generated in step S11, and the loop processing is returned to step S1 to perform the PAL reproduction. There is. In the case where the PAL system is switched to the NTSC system in this state, how the RF-SW pulse according to the NTSC system is generated will be described below.

That is, in step S6, it is determined that the PAL reproduction is not performed, and in step S6, the process exits the loop process and proceeds to step S7. In step S7, the PG delay time according to the NTSC method is calculated and obtained from the conversion formula stored in the ROM 1b in advance. The conversion formula in this case is (0.834) × (PAL reproduction delay time).

In the subsequent step S8, the PG delay time obtained in step S7 is stored in memory, and in the next step S9, an RF-SW pulse is generated based on the PG delay time data stored in the memory.

As described above, according to this embodiment, the rotary head switching timing is adjusted by the semi-fixed resistor 7 in accordance with either NTSC or PAL, and the delay time is set. The delay time for either NTSC or PAL method and the delay time required for the PAL or NTSC method to be switched are calculated in advance, and either PAL or NTSC after switching is calculated. In this method, the delay time to be added to the reference PG pulse when switching the rotary head is calculated by the conversion formula, and the timing for switching the rotary head in either PAL or NTSC method after switching is determined. Since it is configured to generate the specified RF-SW pulse, PA L It is not necessary to adjust the rotary head switching timings corresponding to both the NTSC and NTSC systems, and the delay time according to one system can be adjusted by setting with a semi-fixed resistor 7, which facilitates the adjustment. The configuration is also simplified.

[0023]

[Effect of device]

 As described above, according to the present invention, the NTSC playback or the PAL playback when switching from NTSC to PAL or PAL to NTSC is performed only by adjusting the switching timing corresponding to either NTSC or PAL. The synchronization of the rotary head switching timing is automatically adjusted, which has the effect of facilitating the adjustment and simplifying the circuit configuration.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a rotary head switching timing adjusting circuit according to an embodiment of the present invention.

[Fig. 2] Reference P during NTSC playback or PAL playback
It is a wave form diagram which shows the delay time given to G pulse.

FIG. 3 is a flowchart showing the operation of a rotary head switching timing adjusting circuit according to an embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a conventional rotary head switching timing adjusting circuit.

FIG. 5 is a flowchart showing the operation of a conventional rotary head switching timing adjustment circuit.

[Explanation of symbols]

1 Microcomputer (arithmetic means, switching signal generating means) 7 Semi-fixed resistance (delay time setting means)

Claims (1)

[Scope of utility model registration request] 1. The video information recorded on a magnetic tape is read in accordance with the NTSC system or the PAL system based on the delay time corresponding to the NTSC system or the PAL system and the reference PG pulse corresponding to the vertical synchronizing signal, respectively. In a rotary head switching timing adjusting circuit for generating and outputting an RF-SW pulse for switching a video signal read by two rotary heads, an NTSC system or P
Delay time adjusting means for adjusting the rotary head switching timing corresponding to either one of the AL methods, and P
NTSC PG pulse period ratio to NAL and N
An arithmetic means for converting the product of the TSC system delay time into the PAL system delay time, and a calculation for converting the product of the PAL system PG pulse period ratio for the NTSC system and the PAL system delay time into the NTSC system delay time. A rotary head switching timing adjusting circuit comprising: means and switching signal generating means for generating and outputting the RF-SW pulse based on a calculation result by the calculating means.