KR0139158B1 - Gcr signal detection method and apparatus thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for detecting a ghost removal reference (GCR) signal, and more particularly to a technique for accurately detecting a transmitted GCR signal even when a horizontal synchronization signal of an input signal of a television receiver or a VTR is distorted due to ghost phenomenon. . The window pulse generator for generating the window pulse for detecting the transmitted GCR signal detects the section containing the GCR signal in the video signal by using the vertical synchronization signal and the system clock which are relatively stable compared to the horizontal synchronization signal. A write reset signal and a write enable signal corresponding to the detected GCR signal section are generated. Therefore, even if the horizontal synchronization signal is distorted, the GCR signal can be stably detected and ghost can be removed.

Description

Ghost removal criteria (GCR) signal detection method and device

1 is a block diagram showing a general ghost removal system,

Conceptual block diagram showing a ghost removal unit and its peripheral device in the second and first device,

3 is a flow chart for explaining the ghost removal operation of the device of FIG.

4 is a waveform diagram showing one line of a television signal distorted by the influence of ghost,

5 is a block diagram showing a ghost removal system to which the present invention is applied;

6 is a detailed view showing a window pulse generator in the apparatus of FIG.

Explanation of symbols on the main parts of the drawings

52: vertical synchronous separator 53: window pulse generator

56: FIFO memory 57: microprocessor

61,62: Register 63: Multiplexer

64: counting and pulse generator

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ghost cancellation system for removing ghosts present in an input signal of a television receiver or a VTR. In particular, the present invention relates to a ghost cancellation reference (GCR) signal transmitted for ghost cancellation even when a horizontal synchronization signal is distorted. The present invention relates to a method and apparatus for detecting a ghost cancellation reference (GCR) signal that can be accurately detected at a receiving side.

Ghost or multipath distortion is the result of multipath channels caused by radio wave reflections by mountains, buildings, or airplanes in terrestrial broadcasting. Ghost appears in the form of another superimposed image with delay and attenuation for the original signal of the television receiver, distorting the frequency characteristics of the television signal. Since such ghosting drastically degrades the image quality of the image displayed on the television set, various attempts have been made to reduce the ghost. In general, a ghost elimination technique inserts and transmits a ghost elimination reference signal into a transmitted television signal, and removes ghosts contained in a television signal by comparing a ghost elimination reference signal stored with a received ghost elimination reference signal.

FIG. 1 is a block diagram showing a general ghost elimination system. Since the system is generally used, the description of the system will be briefly described.

In FIG. 1, the A / D converter 11 and the sync and field identifier separator 12 receive a ghosted video signal. The A / D converter 11 performs analog digital conversion on the input video signal. The digital video signal is applied to the multiplexer 14 and the ghost remover 15. The video signal from which the ghost is removed by the ghost removal unit 15 is supplied to the multiplexer 14 and the D / A converter 20. The multiplexer 14 selectively outputs one of the input signals to the FIFO memory 16 according to the selection signal SEL input from the microprocessor 17.

On the other hand, the synchronization and field identifier separator 12 detects the horizontal synchronization signal HD, the vertical synchronization signal VD, and the field identifier signal FID from the input image signal and supplies them to the window pulse generator 13. The window pulse generator 13 detects a predetermined GCR signal insertion line by counting the horizontal synchronization signal HD based on the input vertical synchronization signal VD. The window pulse generator 13 generates a write reset signal WRST and a write enable signal WE corresponding to the detected GCR signal insertion line based on the pulse information applied from the microprocessor 17. The window pulse generator 13 adjusts the pulse information for the odd and even fields generated by the microprocessor 17 with the input field identifier signal FID.

The FIFO memory 16 stores only the GCR signal transmitted from the video signal applied from the multiplexer 14 in accordance with the write reset signal WRST and the write enable signal WE from the window pulse generator 13. The write enable signal WE generated by the window pulse generator 13 is also input to the microprocessor 17. The microprocessor 17 receives the write enable signal WE and detects a rising edge of the write enable signal WE. The microprocessor 17 generates a read reset signal RRST and a read clock signal RCLK based on the detected rising edges. The FIFO memory 16 receives the read reset signal RRST and the read clock signal RCLK from the microprocessor 17 and outputs the stored signal to the microprocessor 17. The microprocessor 17 compares the transmission GCR signal read out from the FIFO memory 16 with the reference GCR signal stored in the GCR ROM 18 to determine channel characteristics. The reverse characteristic of the identified channel characteristic is applied to the ghost removal section 15 as a control signal. The ghost removal unit 15 includes infinite impulse response (IIR) filters for removing post-ghosts caused by delay of a normal video signal, and front ghosts generated by the opposite conditions. It consists of Finite-Impulse Response (FIR) filters to eliminate pre-ghosts. A detailed operation of the ghost removing unit 15 will be described with reference to FIGS. 2 and 3.

FIG. 2 is a conceptual block diagram illustrating the ghost removal unit 15 and its peripheral device in FIG. 1, and FIG. 3 is a flowchart for explaining ghost removal by the device of FIG.

2 and 3 show ghost cancellation of ACTV systems using complementary sequences (S. Roy, J. Yang, CB Patel, Ghost Cancellation for advanced compatible TV System using Complementary sequences, IEEE Trans.on Consumer Electronics, Vol. 38, No. 4, November 1992, pp. 767-777). The GCR signal presence determination step 307 of FIG. 3 is not in the above document but is a general description and is added for the purpose of describing the present invention.

When the apparatus of FIG. 2 starts operation, the channel characteristic detector 25 initializes all ghost elimination filters (step 301). When the television signal containing the ghost is input, the clock generator 21 generates a reference clock signal for the operation of the second degree apparatus using the input signal. When the television signal passing through the ghost eliminators 22 and 23 and the waveform equalizer 24 is input to the channel characteristic detector 25, the channel characteristic detector 25 uses the reference clock signal of the clock generator 21. The received GCR signal is detected (step 303). Channel characteristics are detected according to the detected GCR signal (step 305). The channel characteristic detector 25 then determines whether a received GCR signal is present (step 307), and returns to the data detection process (step 303) if there is no GCR signal. If the GCR signal is present in the determination step (307), the channel characteristic detector 25 updates the filter coefficients based on the detected channel characteristic (steps 309 and 311). The updated filter coefficients are input to the rear ghost eliminator 22 and the front ghost eliminator 23. The rear ghost remover 22 and the front ghost remover 23 remove the ghost signal contained in the television signal according to the filter coefficients input from the channel characteristic detector 25, respectively. The ghost-free television signal is output via the waveform equalizer 24 and the D / A converter 20. When the television signals de-ghosted by the ghost eliminators 22 and 23 are re-input to the channel characteristic detector 25, the channel characteristic detector 25 presets the magnitude of the residual ghost signal remaining in the de-ghosted television signal. It is compared with a threshold value which is a ghost removal reference level (step 313). If the magnitude of the residual ghost signal is larger than the threshold value, the channel characteristic detector 25 detects the received GCR signal contained in the GCR signal insertion line of the next field and performs the signal processing from steps 303 to 311 for the residual ghost signal level. Repeat until this becomes smaller than the above-described threshold. When the level of the residual ghost signal is less than the threshold value, the channel characteristic detector 25 outputs filter coefficients for waveform equalization to the waveform equalizer. The waveform equalizer 24 waveform-equalizes the input television signal according to filter coefficients supplied from the channel characteristic detector 25 and outputs the waveform.

The conventional ghost elimination system is a technique for detecting a transmission GCR signal inserted in a predetermined line of the vertical retrace period. When the ghost is severe, the horizontal synchronous signal contained in the transmitted television signal is shown in FIG. As with the waveform diagram, the degree of distortion is also increased. The waveform of FIG. 4 (a) is an original signal unaffected by ghost, and the waveform of FIG. 4 (b) is a signal affected by ghost. Therefore, the channel characteristic detector 25 detects the transmitted GCR signal using the reference clock signal obtained from the distorted synchronization signal. As a result, the GCR signal detection step 303 turns from the GCR signal presence determination step 307 to an infinite loop, which makes it difficult to detect the transmitted GCR signal and remove the ghost.

Another type of ghost removal technology is mentioned in Korean Patent Application No. 91-22255. The above application refers to a technique for generating a ghost correction signal by transversal filtering input of an image signal, and synthesizing the ghost correction signal with the original image signal to automatically remove the ghost. In particular, the above application performs a correlation operation between the input video signal and the GCR signal to improve the ghost removal speed, and determines the initial filter coefficient of the transversal filter from the result.

On the other hand, as a technique for detecting the GCR signal has been mentioned in Korean Patent Application No. 92-15935 and Korean Patent Application No. 92-21978. The above applications refer to a technique for finding a line into which a transmitted GCR signal is inserted when a line into which a GCR signal is inserted is not constant according to different broadcasting standards. In particular, the above applications, when the line into which the GCR signal is inserted is determined, only the signal contained in the line is detected and the correlation with the stored GCR signal is calculated. However, the above-described patent applications are a technique of finding a line into which a GCR signal is inserted when the line into which the GCR signal is inserted is different as described above, so that the synchronization signal is distorted when the line into which the GCR signal is inserted is determined. The problem of not correctly detecting the transmitted GCR signal still remains.

Prior art for solving the above problems is mentioned in Korean Patent Application No. 93-12086. In the above application, the GCR signal is detected for a plurality of lines located in front and rear with respect to the line into which the transmitted GCR signal is inserted, so that even if distortion occurs in sync signals included in the transmitted television signal, Ghost elimination technology that can detect GCR signals.

The above prior art also generates a window pulse (write enable signal) for transmission GCR detection using the distorted horizontal synchronization signal. However, when the horizontal synchronizing signal is distorted, the position of the write enable signal used for storing the transmission GCR signal is changed. Accordingly, there is a problem in that the correct write enable signal cannot be generated according to the distortion degree of the horizontal synchronization signal, and the control due to the line search is complicated.

Accordingly, an object of the present invention is to provide a method for detecting a stable transmission GCR signal by generating a write enable signal using a vertical synchronization signal and a clock signal instead of a horizontal synchronization signal distorted by ghost so as to solve the above problems. Is in.

Another object of the present invention for solving the above problems is to provide a ghost removal reference signal detection device implementing the above method.

The object of the present invention is a vertical synchronization separation step of detecting a vertical synchronization signal of an input video signal in a method for detecting a ghost removal reference (GCR) signal inserted in a predetermined line of a received video signal. And a window pulse generation step of generating window pulses according to predetermined line information based on the vertical synchronization signal detected in the vertical synchronization separation step and a clock signal of a predetermined frequency, and receiving the window pulses as a write enable signal. A storage step of storing only a signal corresponding to a write enable signal section among the received image signals, and determining whether the stored signal is a transmission GCR signal by investigating the relationship between the stored signal and a reference GCR signal previously stored on the receiving side; And a predetermined line according to the vertical synchronous signal detected in the vertical synchronous separation step and the determination result of the determination step. Comprising the step of generating the information is achieved by removing the ghost reference signal detection method.

Another object of the present invention is to provide a device for detecting a ghost cancellation reference (GCR) signal inserted into a predetermined line of a received video signal, the vertical sync separator for detecting a vertical synchronous signal from an input video signal. And a section in which the GCR signal is included in the video signal by using the vertical synchronization signal applied from the vertical synchronization separator and a clock signal having a constant frequency, and detected based on the predetermined line information applied from the microprocessor. A window pulse generator for generating a window pulse corresponding to the signal section, a memory configured to receive the window pulse of the window pulse generator as a write enable signal and to store only a signal corresponding to the write enable signal section among the received image signals; And examines the relationship between the signal applied from the memory and a preset reference GCR signal. And a microprocessor for determining whether the call is a transmission GCR signal, and outputting the corresponding line information to the window pulse generator according to the vertical synchronization signal applied from the vertical synchronization separator and the determination result. Achieved by a detection device.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

5 is a block diagram showing a ghost removal system to which the present invention is applied. The apparatus of FIG. 5 includes an A / D converter 51 and a vertical synchronous separator 52 that receive ghosted video signals. The window wee pulse generator 53 is connected to the output terminal of the vertical synchronous separator 52. The window pulse generator 53 receives the vertical synchronization signal VD and the system clock signal CLK from the vertical synchronization separator 52. An output terminal of the window pulse generator 53 is connected with a FIFO memory 56 for storing a transmission GCR signal, which is a GCR signal included in an image signal. The ghost removal apparatus of the present invention also includes a ghost removal unit 55, a GCR ROM 58 for storing a reference GCR signal which is a reference signal for ghost removal, and a RAM 59. An output terminal of the A / D converter 51 and the ghost removing unit 55 is connected to a multiplexer 54 having two terminals for receiving two output signals. The microprocessor 57 is connected between the GCR ROM 58 and the RAM 59. The microprocessor 57 is connected to receive the vertical synchronous signal VD of the vertical synchronous separator 52 and to supply line information to the window pulse generator 53. The microprocessor 57 receives the write enable signal WE from the window pulse generator 53, and is connected to supply the filter coefficients for removing the ghost and various control signals to the ghost removal unit 55. The multiplexer 54 selectively connects the signal input terminals to the signal input terminal of the FIFO memory 56 according to the selection signal SEL input from the microprocessor 57. The FIFO memory 56 stores a signal input according to the write reset signal WRST and the write enable signal WE from the window pulse generator 53. The microprocessor 57 also applies the read reset signal RRST and the read clock signal RCLK to the FIFO memory 56 so that the signal stored in the FIFO memory 56 can be supplied. The output terminal of the ghost removal unit 55 is also configured to be connected to the D / A converter (60).

On the other hand, by removing the multiplexer 54 in the above configuration and by directly connecting the ghost removal unit 55 and the FIFO memory 56, a separate circuit and FIFO memory 56 for offset correction of the ghost removal unit 55 The circuit configuration related to the control of) may be simplified.

In Fig. 5, the ghosted video signal is input to the A / D converter 51 and the vertical synchronous separator 52. The digital video signal generated by the A / D converter 51 is supplied to the multiplexer 54 and the ghost removal unit 55. The image signal ghost removed by the ghost removal unit 55 is output to the D / A converter 60 and the multiplexer 54. The microprocessor 57 controls the multiplexer 54 such that any one of the image signals supplied from the A / D converter 51 and the ghost removing unit 55 to the multiplexer 54 is supplied to the FIFO memory 56. do.

Meanwhile, the vertical synchronous separator 52 detects the vertical synchronous signal VD from the input image signal and supplies the same to the window pulse generator 53 and the microprocessor 57. The vertical synchronous separator 52 supplies a clock signal CLK generated from a clock generator (not shown) to the window pulse generator 53. Here, the clock signal CLK uses 4fsc (fsc is 3.58 MHz in the NTSC method as the color part carrier frequency). The window pulse generator 53 receives pulse information from the microprocessor 57. A detailed operation of the window pulse generator 53 will be described with reference to FIG. 6.

6 is a detailed view of the window pulse generator 53 in the apparatus of FIG. As shown, the window pulse generator 53 has two registers 61 and 62 for storing line information for the odd and even fields of the video signal, respectively. The multiplexer 63 is connected to the two registers 61 and 62. The output terminal of the multiplexer 63 detects a section in which the GCR signal is contained in the video signal by using the input vertical synchronization signal VD and the system clock CLK, and writes a write reset signal corresponding to the detected GCR signal section. WRST and the coefficient and pulse generator 64 for generating the write enable signal WE are connected.

In the window pulse generator 53 configured as described above, the two registers 61 and 62 write the line information applied from the microprocessor 57, that is, the position data of the transmission GCR signal of each of the odd and even fields, and the write clock signal (WCLK). Save it according to). The position of the transmission GCR of each field corresponds to the clock of a predetermined period from the vertical synchronization signal VD. The multiplexer 63 transmits the position data of the transmission GCR signal carried on the line set in the odd field and even field applied from the two registers 61 and 62 to the selection signal SEL applied from the microprocessor 57. According to select one output. The multiplexer 63 counts the position data of the radix field input from the first register 61 when the initial value of the selection signal SEL set by the microprocessor 57 is a low level. ). The multiplexer 63 counts the position data of the even field input from the second register 62 when the initial value of the selection signal SEL set by the microprocessor 57 is high. To supply. The count and pulse generator 64 are cleared by the vertical synchronizing signal VD input from the vertical synchronizing separator 52, and counts the rising edge of the system clock CLK input from the clock generator (not shown). . The count and pulse generator 64 generates a write enable signal WE corresponding to a section from the count portion equal to the position data input from the multiplexer 63 to the position plus the preset GCR length data (normally 1K). do. The count and pulse generator 64 also generates a write reset signal WRST at the front end of the write enable signal WE. If the detection of the GCR signal by the write reset signal WRST and the write enable signal WE is a correct signal, the microprocessor 57 multiplexes the multiplexer according to the vertical synchronization signal VD applied from the vertical synchronization separator 52. The selection signal SEL supplied to (63) is adjusted to toggle in field units. However, if it is not the correct GCR signal, the odd and even fields are changed, and the microprocessor 57 adjusts to toggle from the next field after maintaining the initial value of the selection signal SEL supplied to the multiplexer 63 as it is. do.

If the transmitted GCR signal is fixed to a predetermined line, the microprocessor 57 does not need to supply the line information and the write clock signal WCLK to the first register 61 and the second register 62. In addition, the two registers 61 and 62 also independently store the predetermined line information of the odd / excellent field carrying the transmission GCR signal to the microprocessor 57 to generate the write enable signal WE.

Referring again to FIG. 5, the FIFO memory 56 stores only the GCR signal transmitted from the video signal applied through the multiplexer 54 by the write reset signal WRST and the write enable signal WE. The microprocessor 57 receives the write enable signal WE and detects a rising edge of the write enable signal WE. The microprocessor 57 generates a read reset signal RRST and a read clock signal RCLK based on the detected rising edges and reads out the transmission GCR signal stored in the FIFO memory 56. The microprocessor 57 checks the channel state for transmitting the video signal using the transmission GCR signal applied from the FIFO memory 56 and the reference GCR signal stored in the GCR ROM 58. According to the test result, the microprocessor 57 supplies the filter coefficient and the control signal to the ghost removal unit 55. The ghost removal unit 55 removes and outputs ghosts from the video signal applied from the A / D converter 51 as described above. The ghost-removed video signal is digitally analog converted by the D / A converter 60.

The above-described method and apparatus for detecting a ghost signal (GCR) signal of the present invention is relatively stable to a horizontal synchronous signal compared to a conventional synchronous signal in which a transmission GCR signal inserted into an image signal cannot be accurately detected by distortion of a horizontal synchronous signal. The write enable signal is generated using the synchronization signal and the clock signal, thereby producing the effect of accurately detecting the transmitted GCR signal.

Claims (11)

An apparatus for detecting a ghost removal reference (GCR) signal inserted in a predetermined line of a received video signal, A vertical synchronous separator for detecting a vertical synchronous signal from an input video signal; By using the vertical synchronization signal applied from the vertical synchronization separator and a clock signal of a constant frequency, a section in which the GCR signal is included in the video signal is detected, and the detected GCR signal section is based on predetermined line information applied from the microprocessor. A window pulse generator for generating a window pulse corresponding to the window pulse generator; A memory configured to receive the window pulse of the window pulse generator as a write enable signal and to store only a signal corresponding to a write enable signal section among the received image signals; And The relationship between the signal applied from the memory and the preset reference GCR signal is examined to determine whether the applied signal is a transmission GCR signal, and the window pulse according to the vertical synchronous signal applied from the vertical synchronous separator and the determination result. GCR signal detection device comprising a microprocessor for outputting the line information to the generator. The GCR signal detection apparatus of claim 1, further comprising a multiplexer connected to an input terminal of the memory, the multiplexer configured to supply one of the received video signal and the ghost removed video signal to the memory. 3. The apparatus of claim 1 or 2, wherein the window pulse generator comprises: two registers for storing line information applied from the microprocessor for the odd field and the even field, respectively; A multiplexer for selecting and outputting any one of the line information applied from the two registers; And The vertical synchronous signal of the vertical synchronous separator is applied as a clear signal, and the clock signal of a predetermined frequency is counted according to the line information applied from the multiplexer to detect the position of the transmission GCR of the corresponding field, and the preset GCR length from that position. And a pulse generator for generating a window pulse signal corresponding to a section up to the position where data is added. 4. The GCR signal detection apparatus of claim 3, wherein the register prestores the fixed line information when the transmission GCR signal is fixedly transmitted to a predetermined line. 4. The GCR signal detection of claim 3, wherein the microprocessor determines whether a signal applied from the memory is a transmission GCR signal and adjusts the multiplexer to alternately select a field unit if the transmission GCR signal is a transmission GCR signal. Device. 4. The method of claim 3, wherein the micropressor determines whether the signal applied from the memory is a transmission GCR signal, and maintains the initial selection operation of the multiplexer in one field if it is not a transmission GCR signal, and then alternates from the next field unit. GCR signal detection apparatus, characterized in that for adjusting the selection operation. In the method for detecting a ghost removal reference (GCR) signal inserted in a predetermined line of the received video signal, A vertical synchronous separation step of detecting a vertical synchronous signal of an input video signal; A window pulse generation step of generating window pulses according to predetermined line information based on the vertical synchronization signal detected in the vertical synchronization separation step and a clock signal having a predetermined frequency; A storage step of receiving the window pulse as a write enable signal and storing only a signal corresponding to a write enable signal section among the received image signals; Determining whether the stored signal is a transmission GCR signal by examining a relationship between the stored signal and a reference GCR signal previously stored in a receiving side; And And generating predetermined line information according to the vertical synchronization signal detected in the vertical synchronization separation step and the determination result of the determination step. The method of claim 7, wherein the storing further comprises selecting one of the received video signal and a video signal from which ghost is removed. 9. The method of claim 7 or 8, wherein the generating window pulses comprises: a storing step of storing the line information for odd and even fields, respectively; Selecting and outputting any one of line information of the stored odd field and the even field; Detecting a position of a transmission GCR of a corresponding field by receiving a vertical synchronization signal of the vertical synchronization separation step as a clear signal and counting a clock signal having a predetermined frequency according to the selected line information; And And generating a window pulse signal corresponding to a section from the detected position to a position obtained by adding a predetermined GCR length data. 10. The method of claim 9, wherein the determining step adjusts the line information to be alternately selected on a field basis in the line information selection step if the stored signal is a transmission GCR signal. 10. The method of claim 9, wherein in the determining step, if the stored signal is not a transmission GCR signal, the initial selection operation of the line information is maintained in one field and the line information is alternately selected from the next field unit. GCR signal detection method.