KR100284423B1 - Jitter correction method of degoster input signal - Google Patents

Abstract

The present invention relates to a technique for correcting jitter of a degoster input signal. In the conventional ghost removing means, the input field signal is stored in a first-in, first-out, and then output to the filter coefficient calculation processor as it is to be equalized. There is a defect that the equalization process is wrong when the field is shifted in time. To solve this problem, the present invention compensates for a field shift that occurs when data is directly output from the first-in-first-out machine to the filter coefficient calculation processor and stored. It is possible to match the starting point of the input signal for performing equalization, thereby preventing the equalization from being wrong due to the deviation of each field.

Description

Jitter correction method of degoster input signal

1 is a block diagram of a typical ghost removal device.

2 is a diagram illustrating jitter generation of image fields sequentially input.

3 is a signal flow diagram for the jitter correction method of the present invention.

* Explanation of symbols for main parts of the drawings

1: Input buffer 2: A / D converter

3: clock signal generator 4: timing signal generator

5: first-in, first-out 6: interface

7: filter coefficient calculation processor 8: filter

9: D / A Converter 10: Output Buffer

The present invention relates to a technique for correcting jitter of a deghoster input signal. In particular, the field misalignment generated when a data sample is directly output from a first-in-first-out machine to a filter coefficient calculating processor and stored. The present invention relates to a jitter correction method of a degoster input signal which is adapted to make the start point of an input signal for performing an equalizer coincide.

FIG. 1 is a block diagram of a ghost eliminator according to the prior art. As shown therein, an A / D for sampling an analog video signal input through an input buffer 1 at a predetermined frequency (14 MHz) and converting it into a digital signal is shown. A transducer 2; A clock signal generator (3) which separates the synchronization signal from the input video signal and outputs it as a clock signal and generates 4f _SC in phase locked with the color burst signal; A timing signal generator 4 for outputting various timing signals required by each block; A filter coefficient calculation processor 7 for receiving a field signal from the first-in-first-out unit 5 and calculating a filter coefficient for removing ghosts; A filter (8) for converging the input digital signal and the filter coefficient obtained by the filter coefficient calculating processor (7) to control ghosting; The D / A converter 9 converts the digital signal output from the filter 8 into an analog signal and outputs the analog signal to the output buffer 10. The operation thereof will be described with reference to FIG.

In general, a reference signal is required to obtain ghost information, which is referred to as a Ghost Canceler Reference (GCR) signal, which is inserted into a vertical blanking interval of an image signal.

The analog video signal as described above is supplied to the A / D converter 2 through the input buffer 1, where it is sampled at a predetermined frequency (14 MHz) and converted into a digital signal. The first-in, first-out 5 is used to store the GCR signal in real time.

On the other hand, the clock signal generator 3 separates the synchronous signal from the input video signal to generate an in-phase 4f _SC locked with the color burst signal, and the timing signal generator 4 outputs the clock output from the clock signal generator 3. The signals are used to generate various timing signals required for each block.

The filter coefficient calculation processor 7 receives a field-based image signal through the first-in, first-out (5), analyzes how the GCR signal is distorted through the multi-channel, and obtains a filter coefficient to remove ghosts. In other words, the filter coefficient calculating processor 7 is a processor capable of performing a high speed operation for executing ghost elimination software.

The filter coefficients obtained by the filter coefficient calculating processor 7 are transferred to the hardware so that the ghost-containing signal becomes the original signal. That is, the filter 8 convolves the digital signal inputted through the A / D converter 2 and the filter coefficient obtained by the filter coefficient calculating processor 7 to output a ghost-free digital video signal. .

The ghost-free digital video signal is converted back to an analog video signal through the D / A converter 9 and then output to the outside through the output buffer 10.

By the way, the input video signal is stored in the first-in, first-out (5) field unit and then passed to the filter coefficient calculating processor 7 as it is to be equalized. That is, odd field G and even field Are subtracted from each other to obtain 2G to equalize.

In such a case, when the field of the video signal is input as shown in FIG. 2, that is, the nth field and the (n + 3) th field are shifted by ε ₁ in time, and the (n + 1) th field and (n + 2). ) Th field is shifted by ε ₂ Does not become 2G, which causes the equalization to be erratic at all.

As described above, in the ghost elimination means according to the prior art, the input field signal is stored in the first-in, first-out, and then output to the filter coefficient calculation processor as it is to perform the equalization process. There was this.

The present invention has been made a method for correcting the deviation of the input field in order to solve such a conventional defect, which will be described in detail with reference to the accompanying drawings.

In the jitter correction method of the degoster input signal according to the present invention, a predetermined sample is computed for an odd field of a video signal input from a first-in-first-out machine to remove unnecessary bits on the most significant bit side and correlate with a ternary signal. Obtaining and storing the first process; A second step of multiplying the input video signal by a ternary signal to add correlations; When the result of subtracting the maximum value from the correlation value of the input video signal is greater than or equal to 0, the temporary maximum value of a predetermined section is changed to a new value, and the process of storing the X value at that time is repeated. A third process of finding a; The operation of the even field of the input image signal is performed in the same manner as the odd field. The operation of the present invention will be described in detail with reference to FIGS. 1 and 3 as follows.

To check whether the field of the video signal input from the first-in-first-out (5) is even or odd, and if it is odd, input 140 samples of the odd field to remove unnecessary 8 bits of the most significant bit (MSB). Each sample is computed (Logical AND OOFF _H ) to obtain a correlation with a ternary signal, and then stored in the calculated value (S1-S4).

The correlation refers to a process of multiplying an input signal by a ternary signal and adding the multiplication signal. However, before and after a predetermined sample (limited to 20 samples for convenience), it is calculated by multiplying from the 32nd of the input signal (because the GCR signal should start from the 52nd sample). 140 is enough.

That is, the correlation is obtained by multiplying the number of 140 samples while sliding from the 32nd to 71st of the input video signal. The 32nd means that there can be up to 20 samples of forward deviation.

Therefore, if the result is subtracted from the maximum value and the result is greater than or equal to 0, the temporary maximum value is changed to the new value, and the X value, that is, the position value of the data sample of the new maximum value is stored in the ROM. Perform 40 times from the 1st to 71st to find the maximum value and its position (S5-S8).

The above process will be described in more detail. When the correlation value is obtained by sliding from the 32nd to 71st in order to correct the input video signal so that the GCR starts at 52nd, if the peak value appears at 52nd, the correction is not performed. It should be made so that the correction value is “0”.

To do this, initialize the virtual information value X corresponding to the first 32nd to 39 (because 32 ~ 71 = 40), and find the correlation peak value and its position by decreasing X by one each time it is increased by 32.

However, since the jitter correction value should be "0" at the 52nd time, (X-19) becomes the number of samples which actually shifted. In other words, if (X-19) is “+”, it means that the correction value is “+” and pushed forward because it is pushed forward. If (X-19) is “-”, the correction value is “-” and the correction value is This means that it has been pushed back, so you have to pull it forward.

For example, the maximum value at the 52nd time would be decreased by one at X = 39, so the maximum value was retrieved at X = 19, and the value 19 is stored at X. Therefore, the corrected value (X-19) = 0 is the number of samples substantially shifted (S9).

With this value, jitter correction can be performed by moving to the new data area of the original odd field parts: 8000 _{H to} 83B5 _H to B500 _H + (X-19) _H + 3B5 _H. (S10)

If even Therefore, when sorting by correlation, the minimum value is obtained instead of the maximum value. The rest of the rest is the same. Similarly, jitter correction can be performed by moving to the new data area of the even field part: 83B6 _{H to} 876B _H ⇒ B000 _H + (X-19) _{H to} B000 _H + (X-19) _H + 3B5 _H in memory conversion. .

As described in detail above, the present invention corrects field shifts generated when data is directly output from the first-in-first-out machine to the filter coefficient calculating processor, thereby matching the starting point of the input signal for performing equalization. This makes it possible to prevent wrong equalization due to the deviation of each field.

Claims (1)

A first process of arithmetic processing a predetermined sample on an odd field of an input video signal to remove unnecessary bits on the most significant bit side, correlating and storing the input video signal and a ternary signal; A second step of multiplying and multiplying, and subtracting the maximum value from the correlation value of the input video signal when the result is greater than or equal to 0, changing the temporary maximum value of the predetermined period to a new value, and then X value Repeating the process of storing the second process to obtain the maximum value and its position, and to process the even field of the input image signal in the same manner as the odd field, jitter correction of the degoster input signal Way.