KR100498410B1 - Automatic correction device and method for delay characteristics during recording / playback of video signal - Google Patents

Abstract

Disclosed are an apparatus and a method for automatically correcting delay characteristics during recording / reproducing of an image signal. An apparatus for automatically adjusting delay characteristics during recording / reproducing of a video signal according to the present invention includes: video signal delay means for inputting a color signal or a luminance signal of a video signal, delaying the predetermined time by a predetermined delay time, and outputting the delayed video signal; A delay time control means for determining a delay time in accordance with a predetermined oscillation frequency and maintaining a delay time by supplying an error current corresponding to a change in oscillation frequency, and reducing the delay time in correspondence with a delay time difference between a color signal and a luminance signal. Delay time adjustment means for adjusting the delay time by increasing or increasing.

Description

Automatic correction device and method for delay characteristics during recording / playback of video signal

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing system, and in particular, to automatically correct a delay time of a luminance signal and a color signal during recording / reproduction in a video signal processing for a VHS (Video Home System) video tape recorder (VTR). An apparatus and method for automatically correcting delay characteristics during recording / reproducing of a video signal are described.

In general, in video signal processing for a VHS (Video Home System) Video Tape Recorder (VTR), one video signal is separated into a color signal and a luminance signal during recording, and processed for each separated signal. Then record. In addition, during reproduction, one image signal is obtained by synthesizing the two signals after processing the separated color signal and the luminance signal, respectively.

Here, in the case of recording / reproducing, since the basic processing methods of the luminance signal and the color signal are different, the respective delay times appear differently. Therefore, a delay characteristic correction circuit (Record / PlayBack Delay Equalizer: REC / PB DL EQ) for correcting such a delay time is provided outside of an integrated circuit (IC) for image processing and adjusted externally. It is supposed to.

That is, the delay time correction method currently used in the video cassette recorder (VCR) includes a circuit for adjusting the delay characteristic during recording and a circuit for adjusting the delay characteristic during playback, that is, two low pass filters (LOW). PASS FILTER (LFP) is provided outside the IC to calibrate. In addition, although the IC is built-in, there are cases in which the delay time of the initial design is used inherently. Therefore, as the delay time is adjusted from the outside, an incorrect value may not only be obtained, but there is a problem that automatic adjustment is impossible when the initial delay time is used as it is.

An object of the present invention is to implement a delay time adjustment circuit inside an image processing IC, so that a video signal capable of automatically correcting that a delay time of a color signal and a luminance signal is different when a video signal is recorded or played back is realized. It is to provide a device for automatically correcting the delay characteristics during recording / playback.

Another object of the present invention is to provide a correction method performed by an apparatus for automatically correcting delay characteristics during recording / reproducing of an image signal.

In order to achieve the above object, the apparatus for automatically correcting delay characteristics during recording / reproducing of a video signal according to the present invention inputs a color signal or a luminance signal of a video signal, delays the predetermined time by a predetermined delay time, and outputs the delayed video signal. A video signal delay means for determining a delay time in accordance with a predetermined oscillation frequency, maintaining a delay time by supplying an error current corresponding to a change in oscillation frequency, and a delay time difference between a color signal and a luminance signal. Preferably, the delay time adjusting means adjusts the delay time by decreasing or increasing the delay time.

In order to achieve the above another object, a method of automatically correcting a delay characteristic during recording / reproducing of an image signal according to the present invention is a delay characteristic correction method for correcting a delay time of a color signal or luminance time during recording / reproducing of an image signal processing system. (A) determining the delay time of the color signal or the luminance signal, (b) if the delay time is determined, delaying the color signal or the luminance signal by the determined time, and (c) Determining whether the delay time is different, (d) maintaining the delay time if the color signal and the luminance signal are the same, and (e) maintaining the delay time of the color signal if the delay time of the color signal and the luminance signal is different. Adjusting the delay time by decreasing or increasing, and (f) outputting a color signal or a luminance signal delayed by a sustained delay time or adjusted time. The.

Hereinafter, an apparatus and method for automatically correcting delay characteristics during recording / reproducing of a video signal according to the present invention will be described with reference to the accompanying drawings.

1 is a schematic block diagram of a preferred embodiment for explaining an apparatus for automatically correcting delay characteristics in recording / reproducing of a video signal according to the present invention. The delay time controller 11, the image signal delay unit 130, and the delay time adjuster 150, wherein the delay time controller 110 includes a voltage controlled oscillator 112, a divider 114, a phase comparator ( 116 and the voltage / current converter 118, the image signal delay unit 130 includes first to eighth delay units 131 to 138, and the delay time adjustment unit 150 includes an octal counter 152. ), A decoder 154 and a switch driver 156.

2 (a) and 2 (b) are waveform diagrams for explaining the burst gate pulse BGP and the burst signal BURST in normal and abnormal cases, respectively, and 2 (a) is a high level burst in normal cases. 8 to 9 burst signals BURST occur during the gate pulse BGP, and 2 (b) is less than 8 to 9 during the high level burst gate pulse BGP during the abnormal case. Indicates that the number of burst signals BURST occurs.

The video signal delay unit 130 shown in FIG. 1 is a portion that delays a predetermined time by a predetermined delay time for a color signal or a luminance signal during recording or playback. The video signal delay unit 130 includes one or more delay units. The delay units 131 to 138 are configured. The first delay unit 131 inputs a video signal during recording / reproduction, that is, a color signal or a luminance signal, through the input terminal IN, and outputs a color signal or luminance signal which is delayed by a predetermined time through the output terminal OUT. That is, the color signal or luminance signal delayed by the first delay unit 131 for a predetermined time is output to the second delay unit 132, and the second delay unit 132 delays the input signal by a predetermined time and then the third delay unit. Output to (133). The color signal or the luminance signal input in this manner is delayed by the number of delay parts for a predetermined time and then output through the output terminal OUT. In addition, each of the delay units 131 to 138 is designed as a low pass filter using an Operational Transconduntance Amplifier (OTA). The delay time of each of the delay units 131 to 138 is preferably 1/16 of the width of the burst gate pulse (BGP). However, the delay time may be variously set according to the designer's design method. Here, the delay time of the image signal delay unit 130 may be obtained by changing the mutual conductance value of the delay time controller 110 shown in FIG. 1, and the delay time controller 110 may have a mutual conductance. The delay time of the image signal delay unit 130 is controlled by generating a control voltage or an error voltage to have a constant delay time corresponding to the value.

That is, the delay time controller 110 shown in FIG. 1 is a block for determining and controlling the inherent delay time of the image signal delay unit 130, and a voltage controlled oscillator (VCO) 112 and a divider. 114, phase comparator 116, voltage / current converter 118. That is, the VCO 112, the divider 114, the phase comparator 116, and the low pass filter 117 form a phase locked loop (PLL). The VCO 112 generates an oscillation frequency signal of about 5 MHz, which is the VCO frequency of a general image processing IC, that is, a frequency signal having 320 fH. The divider 114 divides the generated 320fH signal into 320 to generate a signal having a frequency of 1fH (horizontal sync signal). In addition, the phase comparator 116 compares the phase of the oscillation frequency signal divided by the frequency divider with the reference signal REF and generates an output corresponding to the compared phase difference. This low-pass component is filtered by the low pass filter 117, and this output signal is output as a filtered direct current signal, i.e., an error voltage. This error voltage is input to the VCO 112, and the VCO 112 generates an oscillation frequency signal corresponding to the input error voltage.

Here, the VCO 112 is implemented as a band pass filter using an OTA having the same characteristics as the OTA used for each delay unit of the image signal delay unit 130. In addition, the voltage / current converter 118 converts the applied error voltage into a corresponding error current EI and outputs the same. The error current EI is applied to the delay units 131 to 138 of the image signal delay unit 130 to adjust the delay time of the image signal, that is, the color signal or the luminance signal. That is, when the PLL is locked because the oscillation frequency and the reference frequency of the VCO 112 are locked, the image signal delay unit 130 outputs a constant voltage so that the image signal delay unit 130 maintains a constant delay time. In addition, when the oscillation frequency of the VCO 112 is changed to generate a phase difference from the reference frequency signal, the phase comparator 116 generates an error voltage corresponding to the phase difference. Thus, the voltage / current converter 118 Is converted into an error current (EI). The image signal delay unit 130 changes the mutual conductance value gm of the OTAs constituting the delay units 131 to 138 according to the error current, and adjusts the amount of current of the low pass filter implemented by the OTA. It can be varied to maintain the inherent delay time or to have a new delay time.

In addition, the delay time adjusting unit 150 shown in FIG. 1 selects a desired number of delay units from the image signal delay unit 130 by inputting a burst signal BURST and a burst gate pulse BGP, which are color synchronization signals of the image signal. By adjusting the delay time, it consists of an octal counter 152, decoder 154 and switch driver 156. That is, the octal counter 152 inputs the burst signal BURST, counts the burst signal BURST corresponding to the burst gate pulse BGP applied from the outside, and outputs the counted result as 3-bit data. do. The counted value is decoded by the decoder 154 and output as 8-bit switch drive data, which is input to the switch driver 156. The switch driver 156 includes eight switches connected to the eight delay units 131 to 138 of the image signal delay unit 130 to drive the number of switches corresponding to the decoded 8-bit outputs. Accordingly, the delay unit of the image signal delay unit 130 connected to the driven switch is driven, and as a result, the color signal has a delay time corresponding to the number of the delay units driven.

3 is a flowchart illustrating a method for automatically correcting a delay characteristic during recording / reproducing of an image signal according to the present invention, which determines a delay time of a color signal or a luminance signal and delays the color signal or a luminance signal by the determined delay time. In step 302 to 304, it is determined whether the delay time between the color signal and the luminance time is different. If the delay time of the two signals is the same, the current delay time is maintained. If the delay times are different, the delay time of the color signal is different. (Steps 306 to 309) and outputting the delayed color signal or the luminance signal (step 310).

Hereinafter, an operation and a correction method of an apparatus for automatically correcting delay characteristics when recording / reproducing an image signal according to the present invention will be described in detail with reference to the accompanying drawings.

First, the delay time of the initial color signal or the luminance signal is determined corresponding to the gm value of the image signal delay unit 130 and the OTA implementing the VCO 112 of the delay time controller 110 (step 302). That is, since the VCO 112 is implemented with an OTA having the same characteristics as the OTA used for the image signal delay unit 130, the VCO 112 generates a constant oscillation frequency signal according to the gm value. Therefore, the PLL outputs a constant voltage when the oscillation frequency maintains a constant frequency equal to the reference frequency to obtain a desired delay time. If the oscillation frequency is changed for some reason, the delay times of the voltage controlled oscillator 112 and the image signal delay unit 130 are relatively the same.

As described above, the VCO 112 of the delay time control unit 110 generates an oscillation frequency signal of 5 MHz, that is, an oscillation frequency signal having 320 fH, and is minutely compared to a reference signal of 15.75 KHz (based on NTSC). 320 is divided in period 114 to produce a frequency signal of 1H. Here, the phase comparator 116 generates an output corresponding to the phase difference between the reference frequency signal REF of 15.75 KHz, which is 1fH applied, and the frequency signal output from the frequency divider 114, When the oscillation frequency changes to change the frequency signal of the frequency divider 114, a signal corresponding to the phase difference is output. The low pass filter 117 low pass filters the output of the phase comparator 116 and outputs a filtered direct current signal, i.e., an error voltage. The voltage / current converter 118 converts the error voltage into an error current EI and applies it to the respective delay units 131 to 138 of the image signal delay unit 130. That is, the inherent delay time of the delay unit itself is constantly controlled by the VCO 112 of the delay time controller 110. The video signal delay unit 130 that outputs the delayed video signal inputs the error current EI output from the delay time controller 110 to each of the eight delay units 131 to 138. The video signal delay unit 130 changes the Igm value inside corresponding to the input error current EI, and adjusts the current amount of the low pass filter using the OTA constituting the delay units 131 to 138. Is controlled to maintain the delay time. That is, since the circuit using the OTA is composed of a combination of unit circuit elements having high independence, it has a high degree of freedom and varies the current corresponding to the mutual conductance value, that is, the Igm value, so that the delay time of the image signal delay unit 130 Since the oscillation frequency signal of the voltage controlled oscillator 112 can be simultaneously adjusted, it is suitable for automatic adjustment. In addition, when the pair characteristics of elements such as the resistance ratio inside the image processing IC are good, it is possible to collectively adjust the plurality of OTAs. Therefore, it is controlled to maintain the inherent delay time, and the video signal input through the input terminal IN, that is, the color signal or the luminance signal, is delayed by a predetermined time by a predetermined time (step 304).

However, unlike the theoretical elements at the time of designing, the characteristics inside the image processing IC can actually find many problems different from those in the case of layout. For example, metal (METAL) devices that connect between devices in a layout state actually act as a resistor, and are generated in a voltage controlled oscillator when the core of the OTA cannot be symmetrically disposed due to a problem of chip area. The error current and the current are input to the image signal delay unit 130, so that the repeated current difference may actually be larger. In addition, an error delay time occurring in the processing path of the luminance signal and the color signal processing path may be unpredictable.

Therefore, when it is determined that the delay time of the color signal and the luminance signal is different due to the various factors as described above, the delay signal adjusting unit 150 generates a control signal therein to adjust the delay time of the image signal delay unit 110. do.

First, the delay signal adjusting unit 150 determines whether delay times of two signals, that is, a color signal and a luminance signal are different from each other (step 306). If the delay times of the color signal and the luminance signal are the same, the delay time determined initially is maintained (step 309). If the delay time of the color signal and the luminance signal is different from each other when the video signal is processed, the delay time of the color signal is adjusted (step 308). That is, when the color signal is delayed more than the luminance signal, the time adjusting unit 150 is controlled to reduce the delay time of the color signal.

When described in more detail with reference to the accompanying drawings, as follows. First, the octal counter 152 of the delay time adjusting unit 150 clocks the color synchronization signal, that is, the burst signal BURST, and generates the burst signal BURST only while the high level burst gate pulse BGP is generated. Counting, it generates eight different 3-bit output signals. Here, the octal counter 152 is reset every 1H, and performs a counting operation again every 1H. That is, as shown in FIG. 2A, when the delay time between the color signal and the luminance signal is the same, when the burst gate pulse BGP of high level occurs once, the burst signal BURST is 8 to 9 times. Occurs. Thus, the output of octal counter 152 is 111, and decoder 154 generates decoded 8 bits of data. That is, the octal counter 152 determines that the delay times of the color signal and the luminance signal are the same (step 306). Accordingly, the switch driver 156 includes eight switches connected to the delay units 131 to 138, respectively, to drive only the switches corresponding to the decoded data. In the normal operation, the switch driver 156 drives all switches according to the decoded output data, and the image signal delay unit 130 maintains an initially determined delay time (step 309).

On the other hand, when the delay time of the luminance signal and the color signal is different from each other, as shown in FIG. 2 (b), the burst signal BURST is less than 8 to 9 in the period where the burst gate pulse BGP is at a high level. ) Is generated. In general, the phase of the burst signal BURST is designed to be later than the burst gate pulse BGP. Therefore, the delay time adjusting unit 150 may determine that the color signals are delayed more than the luminance signal so that the delay times of the two signals are different from each other (step 306), and may adjust the delay time by reducing the delay time of the color signals ( Step 308). That is, the octal counter 152 counts a smaller number of burst signals BURST than normal when referring to the diagram shown in FIG. 2A, and outputs 3 bits of data corresponding to the counted value. do. The decoder 154 decodes the input 3-bit data and generates corresponding 8-bit switch driving data. The switch driver 156 drives only a switch corresponding to the decoded output value, and thus operates only a delay unit connected to the driven switch. If the number of burst signals BURST is 6 during the period when the burst gate pulse BGP is at the high level, the output of the octal counter 152 is 101 because the color signals are delayed by two burst signals. Then, only six of the switches of the switch operation unit 156 are operated in accordance with the value output from the decoder 154. Accordingly, the image signal delay unit 150 may restore only the delay time difference between the two signals by driving only the delay units connected to the six switches to reduce the delay time of the color signal delayed by two burst signals BURST. That is, the counted value is changed according to how much the color signal is delayed, and the delay time of the color signal can be controlled to be equal to the delay time of the luminance signal by selecting the number of delay units that operate according to the counting value. In this case, the larger the number of delay units, the wider the adjustment range. Therefore, more accurate adjustment can be performed by increasing the number to implement the video signal delay unit. In this process, the color signal or luminance signal having the same delay time corrected is output through the output terminal OUT (step 310). Since the correction of the delay time is performed every 1H (horizontal synchronization signal), the delay time of the luminance signal and the color signal can be kept constant at all times. As a result, the inherent delay time of the video signal delay unit 110 is controlled by a phase locked loop PLL including a VCO, and other error delay times are the burst gate pulse BGP and the burst signal BURST. Correctly corrected using

According to the present invention, not only can automatic adjustment be performed using a voltage controlled oscillator used for conventional color signal processing, but also more accurate correction because the delay time is corrected for every horizontal synchronization signal. In addition, by implementing a delay time adjustment circuit using a simple logic circuit, the desired delay characteristics can be obtained simply, and the chip size is not affected even when embedded in an image processing IC. In addition, the delay characteristic correction circuit can be applied not only to the VHS VTR system but also to other analog circuits.

FIG. 1 is a block diagram of a preferred embodiment for explaining an apparatus for automatically correcting delay characteristics during recording / reproducing of a video signal according to the present invention.

2 (a) and 2 (b) are waveform diagrams for explaining burst gate pulses and burst signals in normal and abnormal cases, respectively.

FIG. 3 is a flowchart for describing a correction method performed by the apparatus for automatically correcting delay characteristics during recording / reproducing of the video signal shown in FIG. 1.

Claims (10)

Video signal delay means for inputting a color signal or a luminance signal of a video signal and delaying the predetermined time by a predetermined delay time and outputting the delayed video signal; Delay time control means for determining the delay time corresponding to a predetermined oscillation frequency and maintaining the delay time by supplying an error current corresponding to the oscillation frequency change; And And delay time adjusting means for adjusting the delay time by decreasing or increasing the delay time corresponding to the delay time difference between the color signal and the luminance signal. Correction device. The video signal delay means of claim 1, It has one or more delay parts having the same delay time, And the delay time is 1/16 of a burst gate pulse width. The apparatus of claim 2, wherein the delay unit is implemented as a low pass filter using an operational mutual conductance amplifier. The method of claim 3, wherein the delay time control means, Voltage controlled oscillation means for generating an oscillation frequency signal corresponding to the error voltage; Dividing means for dividing the oscillation frequency signal at a predetermined rate; Phase comparison means for comparing a phase of a reference frequency signal and the divided oscillation frequency signal and generating an output corresponding to the compared result; A low pass filter for filtering the output of the phase comparing means and outputting the filtered output as the error voltage; And And a voltage / current conversion means for converting the error voltage into an error current and outputting the converted error current. 5. The delay in recording / reproducing an image signal according to claim 4, wherein the voltage controlled oscillation means is implemented as a band pass filter using an operational cross-conductance amplifier having the same characteristics as the operational cross-conductance amplifier of the delay unit. Characteristic automatic correction device. The method of claim 5, wherein the delay time adjustment means, Counting means for counting a burst signal corresponding to a burst gate pulse and outputting the counted result as N bits of data; A decoder for decoding the N bits of data and outputting the decoded result as M (= 2 ^N ) bits of switch driving data; And And switch driving means for driving the switch in response to the switch driving data of the M bits. 7. The apparatus of claim 6, wherein the delay time adjustment is performed for every horizontal synchronizing signal. A delay characteristic correction method for correcting a delay time of a color signal or a luminance time during recording / reproducing of an image signal processing system, determining a delay time of the color signal or the luminance signal; (b) if the delay time is determined, delaying the color signal or the luminance signal by the determined time; (c) determining whether a delay time between the color signal and the luminance signal is different; (d) maintaining the delay time if the color signal and the luminance signal have the same delay time; (e) if the delay time between the color signal and the luminance signal is different, adjusting the delay time by reducing or increasing the delay time of the color signal; And and (f) outputting a color signal or a luminance signal delayed by the maintained delay time or adjusted time. The method of claim 8, wherein step (a) comprises: Generating an oscillation frequency signal and a delay time corresponding to the mutual conductance value; Determining whether the oscillation frequency signal has changed and maintaining the delay time if the oscillation frequency signal has not changed; If the oscillation frequency signal has changed, generating an error current corresponding to the changed frequency; And Maintaining the delay time by applying the error current; The method of claim 9, wherein the steps (c) to (e), Counting a burst signal during a section in which a burst gate pulse occurs; Determining that the delay time between the color signal and the luminance signal is equal if the counted burst signal is K (the number of burst signals in a normal case); Determining that the color signal is delayed than the luminance signal when the burst signal is smaller than K, and reducing the delay time of the color signal by the delayed time. Calibration method.

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