CN102387397A - Method and device for detecting color sub-carrier frequency in video signal - Google Patents
Method and device for detecting color sub-carrier frequency in video signal Download PDFInfo
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Abstract
The embodiment of the invention discloses a method for detecting color sub-carrier frequency in a video signal, which comprises the following steps: respectively multiplying the input video signal with a reference color sub-carrier sine signal and a reference color sub-carrier cosine signal; filtering high-frequency signals through respectively performing low-pass filtering on an obtained sine orthogonal signal and an obtained cosine orthogonal signal; then, respectively performing accumulation in set window areas; determining a color sub-carrier frequency value according to a sine orthogonal accumulated value and a cosine orthogonal accumulated value; and simultaneously, generating the reference color sub-carrier sine signal and the reference color sub-carrier cosine signal. The invention also discloses a device for detecting the color sub-carrier frequency in the video signal, which comprises a sine orthogonal module, a cosine orthogonal module, a low-pass filter I, a low-pass filter II, an accumulation module I, an accumulation module II, a color sub-carrier frequency judgment module and a color sub-carrier generating module. The method and the device disclosed by the invention are simple to realize, and have higher detection accuracy.
Description
Technical Field
The invention relates to the field of video signal processing, in particular to a method and a device for detecting the frequency of a video signal.
Background
The traditional analog Television signals include NTSC (National Television Systems Committee), PAL (Phase-alternating Line), SECAM (Sequential colleur Avec Memoire), where the NTSC system is mainly used in countries such as usa, japan, korea, and mexico, and the PAL system is mainly used in countries such as china, uk, ireland, and a part of african countries, and the SECAM system is mainly used in countries such as france, greece, russia, and iran. The three systems are the CVBS (color full television signal) and the Y/C signal (brightness and color separation signal) output by the DVD player. The CVSB signal is a composite full television signal, which is formed by superimposing luminance Y and chrominance C.
The early television mostly adopts analog circuit identification and decoding, and has the defects of huge circuit, low integration level and insufficient flexibility of the circuit. With the rapid development of digital integrated circuits, the advantages of integrated chips are gradually shown.
As shown in FIG. 1, the NTSC system is divided into NTSC-M system, NTSC-J system, and NTSC-4.43 system; the PAL system is divided into PAL-I system, PAL-B, B1, G, H system, PAL-D system, PAL-M system, PAL-N system, in the judgement of PAL system and NTSC system, the judgement of color subcarrier is an important link for distinguishing various systems, at the same time, the judgement of color subcarrier is an important step in the video signal decoding, so that it has important meaning for accurately judging the frequency of color subcarrier.
In the prior art, the judgment of the color subcarrier frequency usually has an analog method and a digital method, wherein the analog method usually needs complicated adjustment, and the digital method is difficult to balance between complexity and judgment precision.
Disclosure of Invention
In order to solve the above technical problem, an embodiment of the present invention provides a method for detecting a frequency of a color subcarrier in a video signal, where the method includes the following steps:
multiplying the input video signal and the input reference color subcarrier sine signal to obtain a sine orthogonal signal;
multiplying an input video signal by an input reference color subcarrier cosine signal to obtain a cosine orthogonal signal;
the sine quadrature signals are subjected to low-pass filtering to filter high-frequency signals;
the cosine quadrature signal is subjected to low-pass filtering to filter out a high-frequency signal;
setting a first window area in a color synchronization area, and accumulating the sine orthogonal signals subjected to low-pass filtering in the first window area to obtain a sine orthogonal accumulated value;
setting a second window area in the color synchronization area, accumulating the cosine orthogonal signals subjected to low-pass filtering in the second window area to obtain a cosine orthogonal accumulated value, wherein the first window area and the second window area are equal in size;
determining the frequency value of the color subcarrier to be detected according to the sine orthogonal accumulated value and the cosine orthogonal accumulated value, and outputting the frequency value;
and enabling the frequency value of the reference color subcarrier to be equal to the determined frequency value of the color subcarrier to be detected, and generating a sine signal and a cosine signal of the reference color subcarrier.
Intercepting the color synchronizing signal by a frequency intercepting module before the input video signal is multiplied by the input reference color subcarrier sinusoidal signal;
before the input video signal is multiplied by the input reference color subcarrier cosine signal, a frequency intercepting module filters out a video image signal and a clutter signal, and a color synchronous signal is reserved.
And the sine orthogonal signal and the cosine orthogonal signal are subjected to low-pass filtering with the same cut-off frequency, and the condition that at least a signal with the frequency value of the sum of the frequency of the color subcarrier to be measured and the frequency of the reference color subcarrier is filtered is met.
The method for determining the frequency value of the color subcarrier to be detected according to the sine orthogonal accumulated value and the cosine orthogonal accumulated value specifically comprises the following steps:
taking absolute values of a sine orthogonal accumulated value and a cosine orthogonal accumulated value, comparing the magnitudes of the two absolute values, and selecting a larger accumulated value from the two absolute values;
comparing the larger accumulated value with a first threshold value set by a user;
and determining the frequency value of the color subcarrier to be detected according to the comparison result of the larger accumulated value and the first threshold value, the number of rows in each field and the input system information.
The method for determining the frequency value of the color subcarrier to be detected according to the sine orthogonal accumulated value and the cosine orthogonal accumulated value specifically comprises the following steps:
calculating the square sum of sine orthogonal accumulated value and cosine orthogonal accumulated value;
comparing the sum of squares with a second threshold set by a user;
and determining the frequency value of the color subcarrier to be detected according to the comparison result of the comparison unit, the line number of each field and the input system information.
Before the comparison result is obtained, the method also comprises the following steps: and accumulating the times of the same comparison result, and taking the comparison result corresponding to the times as the comparison result of the comparison unit when the accumulated times reaches a threshold value three set by a user.
An apparatus for detecting a frequency of a color subcarrier in a video signal, comprising:
the sinusoidal quadrature module is used for multiplying the input video signal with the input reference color subcarrier sinusoidal signal to obtain a sinusoidal quadrature signal;
the cosine orthogonal module is used for multiplying the input video signal and the input reference color subcarrier cosine signal to obtain a cosine orthogonal signal;
the low-pass filter I is used for performing low-pass filtering on the sine quadrature signals;
the second low-pass filter is used for performing low-pass filtering on the cosine quadrature signal;
the accumulation module I is used for setting a window area I in the color synchronization area, and in the window area, the sine orthogonal signals after low-pass filtering are accumulated;
the accumulation module II is used for setting a window area II in the color synchronization area, the cosine orthogonal signals after low-pass filtering in the area are accumulated, and the size of the window area I is equal to that of the window area II;
the color subcarrier frequency judging module is used for determining the frequency value of the color subcarrier to be detected according to the accumulated values of the accumulation module I and the accumulation module II;
and the color subcarrier generating module is used for enabling the frequency value of the reference color subcarrier to be equal to the determined frequency value of the color subcarrier to be detected and generating a sine signal and a cosine signal of the reference color subcarrier.
The detection device also comprises a frequency intercepting module, and the input video signal intercepts the color synchronizing signal through the frequency intercepting module and is input to the sine orthogonal module and the cosine orthogonal module.
The first low-pass filter and the second low-pass filter have the same structure, and the cut-off frequency at least meets the requirement of filtering a signal with the frequency being the sum of the subcarrier frequency of the color to be measured and the subcarrier frequency of the reference color.
In the method and the device for detecting the color subcarrier frequency, the size of a window area I and the size of a window area II meet the condition that the window area I and the window area II are at least larger than 1/2 periods corresponding to difference frequency and are positioned in a color synchronization area, and the difference frequency is the difference between the frequency of the color subcarrier to be detected and the frequency of a reference color subcarrier.
The size of the window area I and the window area II can also be integral multiple of the corresponding period of the difference frequency and is positioned in the color synchronization period, and the difference frequency is the difference between the frequency of the color subcarrier to be detected and the frequency of the reference color subcarrier.
The color subcarrier frequency judging module comprises a selecting unit, a comparing unit and a frequency determining unit, wherein:
the selection unit is used for taking the absolute values of the two accumulated values of the first accumulation module and the second accumulation module, comparing the two absolute values and selecting the larger accumulated value of the two absolute values;
the comparison unit is used for comparing the larger accumulated value with a first threshold value set by a user;
and the frequency determining unit is used for judging the frequency of the color subcarrier to be detected according to the comparison result of the comparing unit, the line number of each field and the input system information.
The color subcarrier frequency decision module comprises a square sum unit, a comparison unit and a frequency determination unit, wherein,
the sum of squares unit is used for calculating the sum of squares of the accumulated value of the first accumulation module and the accumulated value of the second accumulation module;
the comparison unit is used for comparing the square sum with a second threshold value set by a user;
and the frequency determining unit is used for judging the frequency of the color subcarrier to be detected according to the comparison result of the comparing unit, the line number of each field and the input system information.
The color subcarrier frequency judging module also comprises an accumulation unit which is used for accumulating the times of the same comparison result according to the comparison result of the comparison unit, and when the times accumulation reaches a threshold value three set by a user, the comparison result corresponding to the times is used as the comparison result of the comparison unit.
The embodiment of the invention provides a method and a device for detecting the frequency of a color subcarrier, which are used for detecting the frequency of a color subcarrier signal to be detected by respectively orthogonalizing the color subcarrier signal to be detected with a sine function and a cosine function and utilizing the characteristics of the sine function and the cosine function.
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In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive labor.
FIG. 1 lists the frequency and line-field characteristics of different color sub-carriers in PAL and NTSC systems of existing TV systems;
FIG. 2 is a waveform diagram of a burst signal according to the present invention;
fig. 3 is a flowchart of a method for detecting a color subcarrier frequency according to an embodiment of the present invention;
fig. 4 is a flowchart of a method for detecting a color subcarrier frequency according to a second embodiment of the present invention;
fig. 5 is a block diagram of a device for detecting a color subcarrier frequency according to an embodiment of the present invention;
fig. 6 is a block diagram of a color subcarrier frequency detection apparatus according to a second embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Some of the expertise involved in the present invention is described below.
The conventional video signals mainly include NTSC (national Television Systems committee), PAL (phase Alternation line) and SECAM (sequential Couleur a memoire), wherein the NTSC and PAL belong to the amplitude modulation mode, and the SECAM belongs to the frequency modulation mode. The CVBS is formed by adding the brightness Y and the chroma C, blue color difference U and red color difference V of NTSC and PAL are modulated to the color subcarrier frequency to generate a chroma signal C, and the NTSC can be expressed as C-Usinfsct+Vcosfsct, PAL can be expressed as C ═ Usinfsct±Vcosfsct。
The CVBS signal is composed of an image signal, a composite blanking signal, and a composite synchronization signal. The burst is located behind the line blanking pulse of the line sync signal and is a section (9 +/-1 burst period) of constant amplitude wave with the same frequency as the color subcarrier at the transmitting end and with a definite phase relation with the color subcarrier at the transmitting end, as shown in fig. 2, the purpose of which is to recover the color subcarrier with the same frequency and phase as the transmitting end at the receiving end, and A x sin (f) can be usedsct + θ) is represented byscθ is the fixed phase difference between the color burst and the color subcarrier, and A represents the amplitude of the color burst.
Example one
First, for convenience of description, the present embodiment is configured as follows:
the embodiments of the present invention mainly consider color burst region signals, and in the embodiments, f is usedsc0Representing the frequency of the sub-carrier of the colour to be measured in the input composite video signal by theta0Indicating the phase of the composite video signal for the region, the color burst composite video signal can be expressed as: sin (f)sc0t+θ0)。
Referring to fig. 1, the subcarrier frequencies involved in PAL and NTSC systems include two types of frequency values, the first type of frequencyThe frequency values comprise three frequency values of 3.579545MHz, 3.57561149MHz and 3.58205625 MHz; the second type of frequency values includes 4.43361875 MHz; in this embodiment, a reference color subcarrier sine signal and a reference color subcarrier cosine signal are set, in this embodiment, the frequencies and phases of the reference color subcarrier sine signal and the reference color subcarrier cosine signal are the same, and the reference color subcarrier frequencies of the sine signal and the reference color subcarrier cosine signal are set as fsc1Indicating that the reference color subcarrier frequency fsc1Can be set as any frequency value in the first kind of frequency values or the second kind of frequency values, and the phase of the reference color subcarrier sine signal and the reference color subcarrier cosine signal is set by theta1Then the reference color subcarrier sinusoidal signal can be represented as:
sin(fsc1t+θ1)；
the reference color subcarrier cosine signal may be represented as: cos (f)sc1t+θ1)。
When reference color subcarrier frequency fsc1After the determination, a phase θ can be arbitrarily set1To determine the reference color subcarrier sine signal sin (f)sc1t+θ1) And a reference color subcarrier cosine signal cos (f)sc1t+θ1). For example, θ can be set1If 0, the sine signal of the reference color subcarrier is sinfsc1t, the cosine signal of the reference color subcarrier is: cosfsc1t。
Fig. 3 shows a method for detecting a color subcarrier frequency of a video signal according to this embodiment, which includes the following steps:
step S00: multiplying the input composite video signal with the input reference color subcarrier sinusoidal signal to obtain a sinusoidal orthogonal signal; by simplifying the trigonometric function relationship, the following relational expression (1) can be obtained:
sin(fsc0t+θ0)*sin(fsc1t+θ1)＝1/2cos(fsc0t-fsc1t+θ0-θ1)-1/2cos(fsc0t+fsc1t+θ0+θ1)(1)
step S01: multiplying the input composite video signal by the input reference color subcarrier cosine signal to obtain a cosine orthogonal signal; by simplifying the trigonometric function relationship, the following relation (2) can be obtained: sin (f)sc0t+θ0)*cos(fsc1t+θ1)＝1/2sin(fsc0t-fsc1t+θ0-θ1)+1/2sin(fsc0t+fsc1t+θ0+θ1)(2)
Step S02: the sine quadrature signals are subjected to low-pass filtering to filter high-frequency signals;
step S03: the cosine quadrature signal is subjected to low-pass filtering to filter out a high-frequency signal;
the sine orthogonal signal and the cosine orthogonal signal are subjected to low-pass filtering with the same cut-off frequency, and the requirement of at least filtering out the frequency f of the color subcarrier to be measured is metsc0And a reference color subcarrier frequency fsc1And (4) summing.
According to FIG. 1, the frequency f of the color subcarrier to be detectedsc0And a reference color subcarrier frequency fsc1Are both of said first type of frequency and said second type of frequency, so that fsc0And fsc1The frequency values obtained by adding the frequency values have various combinations, and the range is 2 times of 3.57561149MHz to 2 times of 4.43361875 MHz; the cutoff frequencies of the first low-pass filter and the second low-pass filter are set to at least filter fsc0+fsc1After low-pass filtering, the above relation (1) is a relation (3):
sin(fsc0t+θ0)*sin(fsc1t+θ1)＝1/2cos(fsc0t-fsc1t+θ0-θ1) (3)
the relational expression (2) is subjected to low-pass filtering to obtain a relational expression (4):
sin(fsc0t+θ0)*cos(fsc1t+θ1)＝1/2sin(fsc0t-fsc1t+θ0-θ1) (4)
step S04: setting a first window area in a color synchronization area, and accumulating the sine orthogonal signals subjected to low-pass filtering in the first window area to obtain a sine orthogonal accumulated value;
if the frequency f of the color subcarrier to be measuredsc0Equal to the set reference color subcarrier frequency fsc1Then: sin (f)sc0t+θ0)*sin(fsc1t+θ1)＝1/2cos(fsc0t-fsc1t+θ0-θ1)＝1/2cos(θ0-θ1) For a time invariant value, when adding up in a window region I set in the color burst region, a plurality of 1/2cos (theta) are obtained0-θ1) The sum of (1);
setting the size of the first window area to be at least greater than 1/2 periods corresponding to the difference frequency, and the first window area is located in the color synchronization area, wherein the difference frequency is the frequency f of the color subcarrier to be detectedsc0And a reference color subcarrier frequency fsc1The difference between them. If the frequency f of the color subcarrier to be measuredsc0Reference color subcarrier frequency f not equal to settingsc1Depending on the characteristics of the sine function, the positive and negative values will cancel. Preferably, the size of the window region one satisfies an integral multiple of a period corresponding to the difference frequency, such as two periods, and satisfies that the window region one is located in the color synchronization region.
Step S05: setting a second window area in the color synchronization head area, accumulating the cosine orthogonal signals subjected to low-pass filtering in the second window area to obtain a cosine orthogonal accumulated value, wherein the first window area and the second window area are equal in size;
if the frequency f of the color subcarrier to be measuredsc0Equal to the set reference color subcarrier frequency fsc1Then: sin (f)sc0t+θ0)*cos(fsc1t+θ1)＝1/2sin(fsc0t-fsc1t+θ0-θ1)＝1/2sin(θ0-θ1) Is aA time invariant value. As in step S04, when window region two provided in the color burst region is added, several 1/2sin (θ) are obtained0-θ1) The sum of (1); if the frequency f of the color subcarrier to be measuredsc0Reference color subcarrier frequency f not equal to settingsc1According to the characteristics of the cosine function, when the window area two is greater than 1/2 periods corresponding to the difference frequency, the positive and negative values will be cancelled.
Step S06: determining the frequency value f of the color subcarrier to be detected according to the sine orthogonal accumulated value and the cosine orthogonal accumulated valueoutOutputting the frequency value fout；
The method for judging the frequency of the color subcarrier according to the sine orthogonal accumulated value and the cosine orthogonal accumulated value specifically comprises the following steps of:
s600: taking absolute values of a sine orthogonal accumulated value and a cosine orthogonal accumulated value, comparing the magnitudes of the two absolute values, and selecting a larger accumulated value from the two absolute values;
step S601: comparing the larger accumulated value with a first threshold value set by a user;
step S602: and judging the frequency of the color subcarrier to be detected according to the comparison result of the larger accumulated value and the first threshold value, the number of lines in each field and input system information.
If the larger accumulated value is smaller than the set threshold value one, the input to-be-detected color subcarrier frequency fsc0With reference colour subcarrier frequency fsc1Inconsistency; otherwise, the frequency f of the color subcarrier to be measuredsc0With reference colour subcarrier frequency fsc1And (5) the consistency is achieved.
It should be noted that the method for determining the frequency of the color subcarrier according to the sine orthogonal accumulated value and the cosine orthogonal accumulated value is not limited to the steps S600 to S602, and may also compare the sum of squares of the two accumulated values with a second threshold set by another user according to the characteristics of the trigonometric function, specifically including the following steps:
step S610: calculating the square sum of sine orthogonal accumulated value and cosine orthogonal accumulated value;
step S611: comparing the sum of squares with a second threshold set by a user;
step S612: and judging the frequency of the color subcarrier to be detected according to the comparison result of the comparison unit, the line number of each field and the input system information.
If the sum of squares is less than the set threshold value two, the input subcarrier frequency f of the color to be detectedsc0With reference colour subcarrier frequency fsc1Inconsistency; otherwise, the frequency f of the color subcarrier to be measuredsc0With reference colour subcarrier frequency fsc1And (5) the consistency is achieved.
When the frequency f of the color subcarrier to be measured is obtained by judgmentsc0With reference colour subcarrier frequency fsc1If the reference color subcarrier frequency f is consistent with the reference color subcarrier frequency f set at the momentsc1When the second frequency value is 4.43361875MHz, the input subcarrier frequency f of the color to be detected is obtainedsc04.43361875 MHz; if the reference color subcarrier frequency f is set at this timesc1If the frequency value is the first type frequency value, then as shown in fig. 1, the difference between the three first type frequency values determines the current frequency value f from the three frequency values of the first type frequency value according to the input system information P/N, i.e. PAL system or NTSC system, and the line number of each field of the input signaloutObtaining the frequency f of the color subcarrier to be measuredsc0＝fout。
When the frequency f of the input color subcarrier to be detected is obtained by judgmentsc0With reference colour subcarrier frequency fsc1When the two conditions are inconsistent, the following two conditions are distinguished:
if the reference color subcarrier frequency f is set at this timesc1When the first type of frequency value is the first type of frequency value, the frequency of the current color subcarrier to be detected is 4.43361875 MHz;
if the reference color subcarrier frequency f is set at this timesc1When the frequency value is the second kind of frequency value, it means that the current color subcarrier frequency to be measured should be the first oneClass frequency values. As shown in FIG. 1, the difference between three first-class frequency values can be obtained, and the current frequency value f can be uniquely determined from the three first-class frequency values according to the input system information P/N, i.e. PAL system or NTSC system, and the line number of each field of the input signaloutObtaining the frequency f of the color subcarrier to be measuredsc0＝fout。
Outputting the determined frequency value f of the color subcarrier to be detectedout。
Step S07: let reference color subcarrier frequency value fsc1Is equal to the determined value f of the colour subcarrier frequencyoutGenerating a reference color subcarrier sine signal and a reference color subcarrier cosine signal: sin (f)sc1t+θ1) And cos (f)sc1t+θ1) Wherein the phase θ1Any phase of 0 to 2 pi can be set.
It is noted that, in order to eliminate the influence of the accidental factors and improve the accuracy and stability, the present embodiment further adds an accumulation step before step S602 and step S612, specifically: accumulating the times of the same comparison result according to the comparison result of the comparison unit, for example, adding 1 to the accumulated times when the comparison result is inconsistent, or subtracting 1 from the accumulated times, when the accumulated times reaches a threshold value three set by a user, taking the comparison result corresponding to the times as the comparison result of the comparison unit, and taking the comparison result as the frequency f of the color subcarrier to be measuredsc0With reference colour subcarrier frequency fsc1Inconsistent ". The reverse is also possible.
Based on the same inventive concept, the present embodiment further provides a device for implementing the method for detecting a color subcarrier frequency of a video signal, as shown in fig. 5, which is a structural block diagram of the color subcarrier frequency detection device of the present embodiment, and the color subcarrier frequency detection device includes a sine orthogonal module 101, a cosine orthogonal module 102, a first low pass filter 103, a second low pass filter 104, a first accumulation module 105, a second accumulation module 106, a color subcarrier frequency determination module 107, and a color subcarrier generation module 108; wherein,
a sinusoidal quadrature module 101, configured to multiply an input composite video signal (CVBS signal) with an input reference color subcarrier sinusoidal signal to obtain a sinusoidal quadrature signal;
a cosine orthogonal module 102, configured to multiply an input composite video signal with an input reference color subcarrier cosine signal to obtain a cosine orthogonal signal;
a low-pass filter one 103 for low-pass filtering the sinusoidal quadrature signal;
a second low-pass filter 104, configured to perform low-pass filtering on the cosine quadrature signal;
the accumulation module I105 is used for setting a window area I in the color synchronization head area, and in the window area, the sine orthogonal signals after low-pass filtering are accumulated;
the second accumulation module 106 is configured to set a second window region in the color synchronization header region, wherein the cosine quadrature signals subjected to low-pass filtering in the second window region are accumulated, and the size of the first window region is equal to that of the second window region;
a color subcarrier frequency determination module 107, configured to determine a frequency value f of the color subcarrier according to the accumulated values of the accumulation module one 105 and the accumulation module two 106outOutputting the color subcarrier frequency value fout；
In the color subcarrier generation module 108, the determined color subcarrier frequency foutLet the reference color subcarrier frequency fsc1Is equal to the determined color subcarrier frequency foutAnd generating a reference color subcarrier sine signal and a reference color subcarrier cosine signal.
The first low-pass filter 103 and the second low-pass filter 104 have the same structure, and the cut-off frequency satisfies that at least the filtering frequency value is the frequency f of the color subcarrier to be measuredsc0And a reference color subcarrier frequency fsc1The sum signal.
The sizes of the first window area and the second window area in the first accumulation module 105 and the second accumulation module 106 are at least larger than 1/2 periods corresponding to the difference frequency, and the difference frequency is the difference between the frequency of the color subcarrier to be measured and the frequency of the reference color subcarrier and is located in the color synchronization area. Preferably an integer multiple of the period corresponding to the difference frequency.
The color subcarrier frequency determination module 107 includes a selection unit, a comparison unit, and a frequency determination unit, where: in the selection unit, the absolute values of two accumulated values of a first accumulation module 105 and a second accumulation module 106 are taken, the magnitude of the two absolute values is compared, and the larger accumulated value of the two accumulated values is selected; the comparison unit is used for comparing the larger accumulated value with a first threshold value set by a user; and in the frequency determining unit, the frequency of the color subcarrier to be detected is judged according to the comparison result of the comparing unit, the line number of each field and the input system information.
The color subcarrier frequency determination module 107 may also adopt another implementation structure, including a sum of squares unit, a comparison unit, and a frequency determination unit, where the sum of squares unit is configured to calculate a sum of squares of an accumulated value of the accumulation module i 105 and an accumulated value of the accumulation module ii 106; the comparison unit is used for comparing the square sum with a second threshold value set by a user; and in the frequency determining unit, the frequency of the color subcarrier to be detected is judged according to the comparison result of the comparing unit, the line number of each field and the input system information.
Corresponding to the method for detecting the frequency of the color subcarrier, in order to eliminate the influence of accidental factors and improve the accuracy and the stability, the module for determining the frequency of the color subcarrier further comprises an accumulation unit for accumulating the times of the same comparison result according to the comparison result of the comparison unit, for example, when the comparison result is inconsistent, the accumulated times is added with 1, otherwise, the accumulated times is subtracted by 1, when the accumulated times reaches a threshold value three set by a user, the comparison result corresponding to the times is used as the comparison result of the comparison unit, and the comparison result is the frequency f of the color subcarrier to be detectedsc0With reference colour subcarrier frequency fsc1Inconsistent ". The reverse is also possible.
It should be noted that, in the embodiments of the present invention, besides the input video signal being the composite video signal (CVBS signal), when the input signal is an S-terminal signal, the input video signal may also be a chrominance signal, and the method and the apparatus for detecting the color subcarrier frequency according to the embodiments of the present invention are also applicable.
Example two
The only difference between the present embodiment and the first embodiment is that, in the video signal color subcarrier frequency detection apparatus, before the sine orthogonal module 101 and the cosine orthogonal module 102, a frequency clipping module 100 is further included for filtering out video image signals and clutter signals and clipping out color synchronization signals. As shown in fig. 6, after the input CVBS signal passes through the frequency interception module, high-frequency and low-frequency signals and interference which are not in the frequency range of the color subcarrier can be filtered out, so as to improve the accuracy for the subsequent color subcarrier frequency discrimination.
Similarly, in the method for detecting the subcarrier frequency in the video signal, as shown in fig. 4, before the step S00 and the step S01, the method further includes a step S0: the video image signal and the clutter signal are filtered by a frequency interception module, and the color synchronization signal is intercepted.
In this embodiment, the frequency interception module can be implemented by a band-pass filter, and the passband frequency of the band-pass filter is required to satisfy the requirement that the frequencies of the four color subcarriers involved in the PAL system and the NTSC system shown in fig. 1 are not attenuated, and the first frequency value and the second frequency value described in the first embodiment.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
The above detailed description of the embodiments of the present invention, and the detailed description of the embodiments of the present invention used herein, is merely intended to facilitate the understanding of the methods and apparatuses of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (16)
1. A method of detecting the frequency of a color subcarrier in a video signal, the method comprising the steps of;
multiplying the input video signal and the input reference color subcarrier sine signal to obtain a sine orthogonal signal;
multiplying an input video signal by an input reference color subcarrier cosine signal to obtain a cosine orthogonal signal;
the sine quadrature signals are subjected to low-pass filtering to filter high-frequency signals;
the cosine quadrature signal is subjected to low-pass filtering to filter out a high-frequency signal;
setting a first window area in a color synchronization area, and accumulating the sine orthogonal signals subjected to low-pass filtering in the first window area to obtain a sine orthogonal accumulated value;
setting a second window area in the color synchronization area, accumulating the cosine orthogonal signals subjected to low-pass filtering in the second window area to obtain a cosine orthogonal accumulated value, wherein the first window area and the second window area are equal in size;
determining the frequency value of the color subcarrier to be detected according to the sine orthogonal accumulated value and the cosine orthogonal accumulated value, and outputting the frequency value;
and enabling the frequency value of the reference color subcarrier to be equal to the determined frequency value of the color subcarrier to be detected, and generating a sine signal and a cosine signal of the reference color subcarrier.
2. The method of claim 1, wherein the color burst signal is intercepted by a frequency intercepting module before the input video signal is multiplied by the input sinusoidal signal of the reference color subcarrier;
before the input video signal is multiplied by the input reference color subcarrier cosine signal, a frequency intercepting module filters out a video image signal and a clutter signal, and a color synchronous signal is reserved.
3. The method according to claim 1 or 2, wherein the sine quadrature signal and the cosine quadrature signal are low-pass filtered with the same cut-off frequency, and the filtering frequency value is at least the sum of the frequency of the color subcarrier to be measured and the frequency of the reference color subcarrier.
4. The method for detecting a color subcarrier frequency according to claim 3, wherein the size of the window region one and the size of the window region two are at least greater than 1/2 periods corresponding to a difference frequency, and are located in a color synchronization region, and the difference frequency is a difference between a color subcarrier frequency to be detected and a reference color subcarrier frequency.
5. The method according to claim 4, wherein the size of the window region I and the window region II is an integral multiple of a period corresponding to a difference frequency, and the window region I and the window region II are located within a color burst period, and the difference frequency is a difference between a frequency of the color subcarrier to be measured and a frequency of the reference color subcarrier.
6. The method for detecting the frequency of the color subcarrier according to claim 4, wherein the method for determining the frequency value of the color subcarrier to be detected according to the sine orthogonal accumulated value and the cosine orthogonal accumulated value specifically comprises the following steps:
taking absolute values of a sine orthogonal accumulated value and a cosine orthogonal accumulated value, comparing the magnitudes of the two absolute values, and selecting a larger accumulated value from the two absolute values;
comparing the larger accumulated value with a first threshold value set by a user;
and determining the frequency value of the color subcarrier to be detected according to the comparison result of the larger accumulated value and the first threshold value, the number of rows in each field and the input system information.
7. The method for detecting the frequency of the color subcarrier according to claim 4, wherein the method for determining the frequency value of the color subcarrier to be detected according to the sine orthogonal accumulated value and the cosine orthogonal accumulated value specifically comprises the following steps:
calculating the square sum of sine orthogonal accumulated value and cosine orthogonal accumulated value;
comparing the sum of squares with a second threshold set by a user;
and determining the frequency value of the color subcarrier to be detected according to the comparison result of the comparison unit, the line number of each field and the input system information.
8. The method according to claim 6 or 7, wherein before the comparison result is obtained, the method further comprises the following steps: and accumulating the times of the same comparison result, and taking the comparison result corresponding to the times as the comparison result of the comparison unit when the accumulated times reaches a threshold value three set by a user.
9. An apparatus for detecting a frequency of a color subcarrier in a video signal, comprising:
the sinusoidal quadrature module is used for multiplying the input video signal with the input reference color subcarrier sinusoidal signal to obtain a sinusoidal quadrature signal;
the cosine orthogonal module is used for multiplying the input video signal and the input reference color subcarrier cosine signal to obtain a cosine orthogonal signal;
the low-pass filter I is used for performing low-pass filtering on the sine quadrature signals;
the second low-pass filter is used for performing low-pass filtering on the cosine quadrature signal;
the accumulation module I is used for setting a window area I in the color synchronization area, and in the window area, the sine orthogonal signals after low-pass filtering are accumulated;
the accumulation module II is used for setting a window area II in the color synchronization area, the cosine orthogonal signals after low-pass filtering in the area are accumulated, and the size of the window area I is equal to that of the window area II;
the color subcarrier frequency judging module is used for determining the frequency value of the color subcarrier to be detected according to the accumulated values of the accumulation module I and the accumulation module II;
and the color subcarrier generating module is used for enabling the frequency value of the reference color subcarrier to be equal to the determined frequency value of the color subcarrier to be detected and generating a sine signal and a cosine signal of the reference color subcarrier.
10. The apparatus of claim 9, further comprising a frequency clipping module, wherein the input video signal is clipped by the frequency clipping module and input to the sine quadrature module and the cosine quadrature module.
11. The apparatus according to claim 9 or 10, wherein the first low-pass filter and the second low-pass filter have the same structure, and the cut-off frequency satisfies a condition of filtering at least a signal having a frequency equal to a sum of the frequency of the color subcarrier to be measured and the frequency of the reference color subcarrier.
12. The color subcarrier frequency detecting apparatus according to claim 11, wherein the first window region and the second window region have a size that is at least greater than 1/2 periods corresponding to a difference frequency that is a difference between a frequency of the color subcarrier to be detected and a frequency of the reference color subcarrier and are located in the color synchronization region.
13. The color subcarrier frequency detecting apparatus according to claim 12, wherein the size of the window region one and the size of the window region two are integral multiples of a period corresponding to the difference frequency, and are located within a color synchronization period, and the difference frequency is a difference between a frequency of the color subcarrier to be detected and a frequency of the reference color subcarrier.
14. The apparatus according to claim 12, wherein the color subcarrier frequency determination module comprises a selection unit, a comparison unit, and a frequency determination unit, wherein:
the selection unit is used for taking the absolute values of the two accumulated values of the first accumulation module and the second accumulation module, comparing the two absolute values and selecting the larger accumulated value of the two absolute values;
the comparison unit is used for comparing the larger accumulated value with a first threshold value set by a user;
and the frequency determining unit is used for judging the frequency of the color subcarrier to be detected according to the comparison result of the comparing unit, the line number of each field and the input system information.
15. The color subcarrier frequency detecting apparatus according to claim 12, wherein the color subcarrier frequency decision block includes a sum of squares unit, a comparison unit, a frequency determination unit, wherein,
the sum of squares unit is used for calculating the sum of squares of the accumulated value of the first accumulation module and the accumulated value of the second accumulation module;
the comparison unit is used for comparing the square sum with a second threshold value set by a user;
and the frequency determining unit is used for judging the frequency of the color subcarrier to be detected according to the comparison result of the comparing unit, the line number of each field and the input system information.
16. The apparatus according to claim 14 or 15, wherein the subcarrier frequency determining module further comprises an accumulating unit configured to accumulate times of the same comparison result according to the comparison result of the comparing unit, and when the times of the same comparison result reach a threshold set by a user, the comparison result corresponding to the times is used as the comparison result of the comparing unit.
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