KR20040068672A - Apparatus for compensating frequency in an optical-disc playback equipment - Google Patents

Abstract

PURPOSE: A device of compensating for a frequency for an optical disk player is provided to generate a frequency compensated value by using minimal and maximum continuous lengths within an assigned window size, thereby generating a more exact compensated value to accomplish a quick synchronization of a frequency PLL. CONSTITUTION: A histogram generator(21) calculates the frequency of each continuous length based on continuous lengths of inputted bit data. A minimal/maximum continuous length detector(24) compares the frequency of each continuous length inputted from the histogram generator(21) with a frequency threshold value, detects minimal/maximum continuous lengths, and outputs the detected minimal/maximum continuous lengths. A compensated value generator(27) generates a compensated value by using the detected minimal/maximum continuous lengths.

Description

Frequency correction device for optical disc player {APPARATUS FOR COMPENSATING FREQUENCY IN AN OPTICAL-DISC PLAYBACK EQUIPMENT}

The present invention relates to a digital bit reproducing apparatus for an optical disc player, and more particularly to a frequency compensating apparatus capable of calculating an accurate frequency correction value.

Optical discs such as conventional Compact Discs, Digital Audio Discs and Digital Video Discs are " 0 " or " 0 " by Pits that change the reflectance or refractive index of the light beam. Stores digital bit data having a value of "1".

In this case, the digital bit data may have a logical value of "1" or "0" in order to prevent the light beam from moving off the track due to excessive DC component generation during reproduction. To 11 and 3 to 14 for DVD). As a result, the radio frequency (hereinafter referred to as RF) signal picked up from the optical disc by the optical pickup must always maintain a width in a prescribed range (for example, 3T to 11T or 3T to 14T). To this end, a conventional reproducing apparatus is provided with a phase locked loop (PLL) for synchronizing with a reproducing signal for accurate data reproducing.

On the other hand, spots of the light beams irradiated onto the optical disc may not always maintain a constant size and shape due to mechanical tolerances of the optical pickup. For this reason, the width of the RF signal picked up from the orphan disk by the optical pickup exceeds or falls short of the prescribed range, and an error may occur in the digital bit data. In addition, when the pits are densely formed to increase the recording capacity, noise components are included in the RF signal due to interference between adjacent pits, thereby increasing the error occurrence rate in the digital bit data.

A digital bit player for solving this problem is disclosed in Korean Patent Laid-Open Publication No. 1998-20547. A domestic patent publication No. 1998-20547 will be described in detail with reference to FIG. 1.

1 shows a block diagram of a conventional digital bit reproducing apparatus for an optical disc player. Referring to FIG. 1, the A-D converter 1 generates RF data by sampling an RF signal each time a clock pulse from the crystal oscillator 2 is applied and encoding the sampled signal in the form of a binary code.

The interpolator 3 interpolates the RF data input from the A-D converter 1 for each period of the bit clock signal.

The subtractor 4 generates RF correction data by subtracting the RF interpolation data from the interpolator 3 from the RF data by subtracting the asymmetric error value from the error detector 8 from the RF data.

The first bit detector 5 generates a bit stream by absolute substitution of the RF correction data and supplies this bit stream to the continuous length detector 6 and the phase detector 9.

The continuous length detector 6 detects the continuous length of the bit data by counting the number of " 1 " or " 0 " s that are repeatedly repeated in the bit stream.

The frequency detector 7 detects the transmission speed of the RF data by the continuous length, thereby generating frequency correction data for the frequency error amount. To illustrate this in detail, the frequency detector may transmit RF data faster than the specified transmission rate if the continuous length is "1" or "2" smaller than the specified minimum length (e.g., 3 in CD and DVD). In response to the determination, frequency correction data is generated to increase the frequency of the bit clock signal. Alternatively, if the continuous length is longer than the specified maximum continuous length (eg 11 for CD and 14 for DVD), the frequency detector 7 is transmitting the RF data slower than the specified transmission rate. In response to the determination, frequency correction data for reducing the frequency of the bit clock signal is generated.

The error detector 8 detects the asymmetric error amount due to the asymmetry of the optical disk by the continuous length and the RF correction data and supplies the detected asymmetric error amount to the subtractor 4.

The phase detector 9 compares the phase of the bit stream to detect the phase difference between the RF correction data and the bit clock signal.

The first adder 10 adds a frequency error correction value from the frequency detector 7 to the phase error value from the phase detector 9 to obtain a synchronous correction value for correcting the frequency and phase difference between the RF data and the bit clock signal. Occurs.

The loop filter 11 low-pass filters the synchronization correction value from the first adder to mitigate the sudden change in the synchronization correction value.

The digital controlled oscillator (DCO) 12 accumulates the filtered synchronization correction value from the loop filter 11 to generate a bit clock signal synchronized with the RF signal. The bit clock signal is supplied to the interpolator 3 to designate an interpolation time point of the interpolator 3 and to provide data for interpolation.

In addition, the bit compensator 13 compensates the RF correction data using a compensation value according to the logic value of the bit data of the bit stream when the continuous length is less than 3, and digitally replaces the compensated RF compensation data by absolute value replacement. They occur sequentially.

As a result, the first bit detector 5, the continuous length detector 6, the frequency detector 7, the phase detector 9, the first adder 10, the loop filter 11 and the DCO 12 are interpolators. Implement a digital phase locked loop to provide a bit clock signal synchronized with the RF signal to (3).

However, in the conventional digital bit reproducing apparatus for optical disc players, the frequency detector has a problem in that it is difficult to determine the frequency correction value because the minimum continuous length is not defined. That is, since the maximum continuous length is periodically generated in front of every frame (588T for CD and 1488T for DVD), there is no difficulty in determining the frequency correction value. On the contrary, since the minimum continuous length is data existing in a frame, there is no regulation on how many times occur in one frame. As a result, the frequency at which the minimum continuous length occurs may vary from disk to disk, and even within another disk. Therefore, since the occurrence frequency of the minimum continuous length is unknown, it is impossible to determine the frequency correction value corresponding thereto.

SUMMARY OF THE INVENTION An object of the present invention is to provide a frequency correction device for an optical disc player that solves the problem of difficulty in determining the frequency correction value in the prior art as described above.

It is another object of the present invention to provide a frequency correction device for an optical disc player that eliminates the influence of frequency synchronization due to an incorrect continuous length which may be caused by data distortion.

1 is a block diagram of a digital bit reproducing apparatus for a conventional optical disc player.

2 is a diagram showing the configuration of a frequency correction device for an optical disc player according to a preferred embodiment of the present invention.

3 is a flowchart illustrating a method of calculating a frequency in a histogram generator according to a preferred embodiment of the present invention.

4 is a flow chart illustrating a method for detecting minimum and maximum continuous length in a minimum / maximum continuous length detector in accordance with a preferred embodiment of the present invention.

5 is a flow chart illustrating a method of generating a correction value in a correction value generator according to a preferred embodiment of the present invention.

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21: Histogram Generator 24: Min / Max Continuous Length Detector

27: correction value generator

According to a preferred embodiment of the present invention for achieving the above object, the frequency correction device for an optical disc player uses a frequency for each of the consecutive lengths of the bit data input within a given window size section to obtain a minimum and maximum continuous length. And detecting and calculating a correction value according to the difference between the minimum and maximum continuous length and the prescribed minimum and maximum continuous length.

According to another preferred embodiment of the present invention, a frequency correction apparatus for an optical disc player comprises: a histogram generator for calculating a frequency for each of the consecutive lengths of bit data continuously input within a given window size section; A minimum / maximum continuous length detector for detecting a minimum and maximum continuous length by comparing the respective calculated frequencies with a frequency threshold; And a correction value generator for comparing the detected minimum and maximum continuous lengths with a prescribed minimum and maximum continuous lengths and generating a frequency correction value according to the difference.

The given window size is set to contain 2 to 4 frame data.

The histogram generator counts the frequency of the continuous length each time a continuous length is input, and accumulates the consecutive lengths counted, while the sum of the continuous lengths matches the given window size, within the given window size interval. Output counted consecutive lengths.

The minimum / maximum continuous length detector is compared with the first threshold in ascending order from the smallest continuous length where frequency is present, or with the second threshold in order from the largest continuous length where frequency is present. Here, the first continuous length having a frequency greater than the first threshold is determined as the minimum continuous length, and the first continuous length having a frequency greater than the second threshold is determined as the maximum continuous length.

The correction value generator calculates the difference between the minimum continuous length and the prescribed minimum continuous length and the difference between the maximum continuous length and the prescribed maximum continuous length, respectively, so that the sign of both calculated values is different from the minimum / maximum. One of the minimum and maximum continuous lengths detected by the continuous length detector is determined to have been detected incorrectly and outputs a previous correction value.

At this time, if the signs of the calculated values are the same, a correction value for raising the frequency is output if the sign is positive, and a correction value for decreasing the frequency is output if the sign is negative.

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

2 shows the configuration of a frequency correction apparatus for an optical disc player according to a preferred embodiment of the present invention. Here, the frequency correction device corresponds to the frequency detector 7 of FIG.

Referring to FIG. 2, the frequency correction device includes a histogram generator 21, a minimum / maximum continuous length detector 24, and a correction value generator 27. The frequency correction device outputs a frequency correction value using the input continuous lengths.

The histogram generator 21 calculates a frequency for each continuous length based on the continuous lengths of the input bit data. That is, the histogram generator 21 receives successive lengths sequentially within a given window size section, and counts the frequencies in the corresponding continuous lengths until the sum of the continuous lengths of these successive lengths matches the given window size. In this way, the counted frequency is output when the continuous length sum matches the given window size, and the frequency of each successive length counted during that time.

The minimum / maximum continuous length detector 24 detects and outputs the minimum and maximum continuous lengths by comparing the frequency of each continuous length input from the histogram generator 21 with a frequency threshold.

In other words, the frequency is compared with the first threshold from the smallest continuous length in which the frequency of each successive length exists. For example, if the smallest continuous length where the frequency is present is 1T, the frequency is compared with the first threshold from the frequency of the continuous length that is 1T. If the frequency of consecutive lengths of 1T is less than the first threshold, then the frequency of 2T, which is the next largest continuous length, is compared with the first threshold. If there is an initial continuous length having a frequency greater than the first threshold through this process, the initial continuous length is determined as the minimum continuous length.

Similarly, the frequency of each of the combustion lengths is compared with the second threshold from the largest continuous length at which the frequency exists. The frequency of the smaller continuous length is then compared with the second threshold. This process determines the maximum continuous length.

In this case, the first and second thresholds mean frequency thresholds, and these thresholds may be arbitrarily set by the user. It is desirable to set the threshold through as many experiments as possible.

The correction value generator 27 generates a correction value using the minimum and maximum continuous lengths detected from the minimum / maximum continuous length detector 24. That is, the difference between each of the minimum and maximum continuous lengths and the prescribed minimum and maximum continuous lengths is obtained.

At this time, it is determined whether the minimum and maximum continuous lengths are erroneously detected depending on whether the signs of the difference values are the same. That is, when the sign of each of the difference values is different, one of the minimum and maximum continuous lengths detected by the minimum / maximum continuous length detector 24 is determined to have been detected incorrectly, and the previous correction value is output. For example, the maximum continuous length detected is greater than the prescribed maximum continuous length (14T for DVD, 11T for CD), while the minimum continuous length detected is less than the prescribed minimum continuous length (3T for both DVD and CD). If so, the continuous length of either the maximum detected continuous length or the minimum detected continuous length is incorrectly detected. This is because, when considering the maximum continuous length detected, the clock frequency should be lowered, but when considering the detected minimum continuous length, a logical error occurs that requires increasing the clock frequency.

When the sign of each difference value is the same, the correction value generator 27 generates a correction value for whether the frequency is added or decreased according to whether the sign is a positive number. That is, if the sign is positive, a correction value for raising the frequency is generated. If the sign is negative, a correction value for lowering the frequency is generated.

At this time, how much the correction value is generated is determined according to the size of each difference value. In other words, when the difference is large, the size of the correction value increases, and conversely, when the difference is small, the size of the correction value is small. As a result, it can be seen that the magnitude of the correction value and the magnitude of the difference value are proportional to each other.

Hereinafter, the operation of each configuration of the frequency correction device for an optical disc player according to the present invention will be described in more detail.

3 is a flowchart illustrating a method of calculating a frequency in a histogram generator according to a preferred embodiment of the present invention.

As shown in Fig. 3, first, successive lengths of bit data are sequentially input (S31). At this time, a window size section is given. The window size is preferably set to include approximately 2 to 4 frame data. One frame data is 588T for CD and 1488T for DVD.

A continuous length sum is calculated by accumulating each successive length within a given window size section (S 32). At this time, the accumulated continuous length sum is compared with the window size (S 33). As a result of the comparison, if the sum of the continuous lengths is smaller than the window size, the frequency for the corresponding continuous length is increased (S 34). The frequency increase increases the frequency of the inputted continuous length by '1' when the continuous length input using the counter is accumulated and the sum of the continuous lengths is smaller than the window size. At this time, the range of the continuous length may be set to about 1T ~ 42T for the case. This value is three times the maximum continuous length 13T specified in the case of DVD. Of course, it is natural that the range of the continuous length can be varied depending on the situation.

When the frequency for the corresponding continuous length is increased in S 34, the frequency is calculated using the continuous length input again.

If the sum of the continuous lengths is greater than or equal to the window size in S 33, the successive lengths of which the frequency is counted within the range of the continuous lengths are output (S 35). At this time, the frequency of each successive length and the sum of the successive lengths are reset to '0' and used to calculate the frequency again within the next given window size section (S 36).

4 is a flow chart illustrating a method for detecting minimum and maximum continuous length in a minimum / maximum continuous length detector according to a preferred embodiment of the present invention.

As shown in Fig. 4, the histogram generator 21 inputs the frequency of each continuous length (S41).

At this time, some of the frequencies of the continuous lengths are sequentially compared with the first threshold value (S 43). Here, the first threshold means the minimum threshold for detecting the minimum continuous length. The continuous length for comparison with this first threshold is preferably the frequency of the smallest continuous lengths possible. For example, if the range of continuous lengths is 1T to 42T, the frequency of the continuous lengths corresponding to approximately 5T to 7T or less can be compared with the first threshold.

At this time, the comparison order is preferably compared with the first threshold value from the frequency of the smallest continuous length as possible. For example, if the smallest continuous length for which a frequency exists is 1T, the frequency of 1T is compared with the first threshold, and then the frequency of 2T is compared.

If the frequency of any particular continuous length is greater than the first threshold during this comparison operation, the first continuous length greater than the first threshold is determined as the minimum continuous length and the value is output (S45).

When the minimum continuous length is output in S 45, some other frequencies among the frequencies of the continuous lengths are sequentially compared with the second threshold (S 47). Here, the second threshold means the maximum threshold for detecting the maximum continuous length. The continuous length for comparison with this second threshold is preferably the frequency of the largest continuous lengths possible. For example, the frequency of consecutive lengths corresponding to approximately 5T-7T or more may be compared with the second threshold.

At this time, the comparison order is preferably compared with the second threshold value starting from the largest frequency of continuous length. That is, the frequency of 42T is compared, and then compared with the second threshold in order of the frequency of 41T, the frequency of 40T, and so on.

When the frequency of any particular continuous length is greater than the second threshold by the comparison process, the first continuous length larger than the second threshold is determined as the maximum continuous length and the maximum continuous length is output (S 49).

5 is a flowchart illustrating a method of generating a correction value in a correction value generator according to a preferred embodiment of the present invention.

As shown in FIG. 5, first, the minimum and maximum continuous lengths detected by the minimum / maximum continuous length detector 24 are respectively input (S 51).

The type of optical disc determines the minimum and maximum continuous lengths specified. For CDs, 3T and 11T are the minimum and maximum continuous lengths specified, and for DVDs, the minimum and maximum continuous lengths specified are 3T and 14T. do.

The correction value generator 27 receives from the outside a minimum and maximum continuous length defined according to the type of optical disc currently used.

At this time, the difference between the specified minimum continuous length and the detected minimum continuous length is obtained, and the difference between the specified maximum continuous length and the detected maximum continuous length is obtained (S 52 and S 53).

When the difference between the minimum and maximum continuous lengths is obtained as described above, it is determined whether the signs of the obtained difference values are the same (S 54).

If the sign of each of the obtained difference values is the same, a correction value previously calculated by judging that the continuous length of any one of the minimum continuous length and the maximum continuous length detected by the minimum / maximum continuous length detector 24 is incorrectly detected. Output (S 55).

If the signs of the obtained difference values are the same, it is determined whether the signs are positive (S56).

If the sign is positive, the frequency of the current frequency phase locked loop is low, and accordingly a correction value for raising the frequency is output (S 57).

On the contrary, if the sign is negative, the frequency of the modern frequency phase locked loop is high, and accordingly, a correction value for lowering the frequency is output (S 58).

At this time, the magnitude of the correction value is determined in proportion to the magnitude of the difference value calculated at S 52 and S 53, respectively. In other words, when the magnitude of the difference value becomes large, the magnitude of the correction value accordingly becomes large, and conversely, when the magnitude of the difference value becomes small, the magnitude of the correction value is also set small.

As described above, a more accurate correction value can be generated by calculating the correction value through the difference between the minimum and maximum continuous lengths calculated using the frequency of each successive length from the prescribed minimum and maximum continuous lengths.

As described above, according to the frequency correction device for an optical disc player according to the present invention, by generating a frequency correction value using the minimum and maximum continuous length within a given window size, it is more accurate than the conventional to generate a frequency Fast synchronization of the phase locked loop can be achieved.

In addition, according to the present invention, by comparing the sign according to the difference between the specified minimum and maximum continuous length and the detected minimum and maximum continuous length, the influence of the frequency synchronization due to the wrong continuous length which may be caused by data distortion is previously determined. Can be removed.

Claims (10)

An apparatus for correcting frequency by using successive lengths of bit data continuously input from an optical disc player, wherein the minimum and maximum continuous lengths are determined using a frequency for each of the successive lengths of the input bit data within a given window size section. Detecting and calculating a correction value according to a difference between the minimum and maximum continuous length and a prescribed minimum and maximum continuous length. An apparatus for correcting frequency using successive lengths of bit data continuously input from an optical disc player, comprising: a histogram generator for calculating a frequency for each successive length of the continuously input bit data within a given window size section; A minimum / maximum continuous length detector for detecting a minimum and maximum continuous length by comparing the respective calculated frequencies with a frequency threshold; And a correction value generator for comparing the detected minimum and maximum continuous lengths with a prescribed minimum and maximum continuous lengths and generating a frequency correction value according to the difference. 3. The apparatus of claim 2, wherein the given window size is set to include 2-4 frame data. 3. The method of claim 2, wherein the histogram generator counts the frequency of the continuous length each time a continuous length is input, and accumulates the continuous length counted frequency while the sum of the continuous lengths coincides with the given window size. A frequency compensating device for an optical disc player, characterized by outputting continuous lengths counted within a given window size section. 5. The apparatus of claim 4, wherein when the counted consecutive lengths are output, the frequency of the continuous lengths and the sum of the continuous lengths are reset to zero. 3. The minimum / maximum continuous length detector of claim 2, wherein the minimum / maximum continuous length detector is compared with the first threshold in ascending order from the smallest continuous length in which the frequency is present, or the second threshold in order from the largest continuous length in which the frequency is present. A frequency correction device for an optical disc player, characterized in that. 7. The apparatus of claim 6, wherein the first continuous length having a frequency greater than the first threshold is determined as the minimum continuous length. 8. The apparatus of claim 7, wherein the first continuous length having a frequency greater than the second threshold is determined as the maximum continuous length. 3. The correction value generator according to claim 2, wherein the correction value generator calculates a difference between the minimum continuous length and a prescribed minimum continuous length and a difference between the maximum continuous length and a prescribed maximum continuous length, respectively, so that the signs of the calculated values are different. In this case, it is determined that one of the minimum and maximum continuous length detected by the minimum / maximum continuous length detector is incorrectly detected and outputs a previous correction value, characterized in that for outputting the optical disk player. 10. The frequency of an optical disc player according to claim 9, wherein if the sign of the calculated values is the same, a correction value for raising the frequency is output if the sign is positive, and a correction value for lowering the frequency is output if the sign is negative. Correction device.