Digital-analog hybrid automatic clamping control method and device

Abstract

The invention discloses a digital-analog hybrid automatic clamping control method and device, and relates to the technical field of image signal processing, and the method comprises the steps: initializing an analog clamping parameter and a digital clamping control parameter; coaxial video signals are sequentially input into the analog clamping unit, the analog-to-digital conversion unit and the digital clamping unit; after the analog clamping output signal is subjected to analog-to-digital conversion, a digital clamping output signal is output through a digital clamping method; and calculating a blanking difference value between the blanking level value of the coaxial video signal and the target blanking value as a clamping error, if the absolute value of the clamping error is greater than an analog clamping threshold value, performing signal adjustment by adopting an analog clamping method, and if not, performing signal adjustment by adopting a digital clamping method. A digital-analog hybrid clamping mode is adopted, analog clamping is adopted when errors are large, input signals are adjusted to be within an approximately appropriate range, and it is guaranteed that the signals are not subjected to top cutting or bottom cutting; and when the error is small, digital clamping is adopted, so that the clamping accuracy is ensured.

Description

Technical Field

[0001] The present application relates to image communication technology in electrical communication technology, and in particular to a method and device for automatically clamping a coaxial video signal. Background Art

[0002] For coaxial video signals, the commonly used clamping solutions currently use active clamping circuits for clamping, which are implemented in an analog way through a series of transformers, flyback switches, clamping switches and clamping capacitors. However, the analog active clamping control circuit can only clamp the signal within a certain approximate amplitude range, and the accuracy is insufficient; at the same time, the capacitor charging and discharging time in the analog clamp is long, and the feedback speed is slow. The digital clamping method is also a common solution in digital signal processing. Compared with the analog implementation method, digital signal processing can provide high accuracy and can accurately control the clamping value to ensure that the signal is within the required range. Digital signal processing usually involves steps such as sampling, quantization, and calculation, which will introduce a certain delay. In real-time applications, high latency may affect the response speed and performance of the system. Summary of the invention

[0003] The present invention aims at at least one defect of the above-mentioned prior art, and combines the analog and digital clamping modes to accurately clamp the signal to a certain amplitude without losing the signal content. At the same time, the clamping adjustment is performed during the line blanking period with one line of the input coaxial video signal as a cycle, without affecting the video content.

[0004] A digital-analog hybrid automatic clamping control method is provided to initialize analog clamping parameters and digital clamping control parameters;

[0005] The coaxial video signal is sequentially input into the analog clamping unit, the analog-to-digital conversion unit and the digital clamping unit; after the analog clamping output signal is converted into a digital signal, the digital clamping output signal is outputted through the digital clamping method;

[0006] The blanking difference between the blanking level value of the video signal and the target blanking value is calculated as the clamping error. If the absolute value of the clamping error is greater than the analog clamping threshold, the analog clamping method is used to adjust the signal. If not, the digital clamping method is used to adjust the signal.

[0007] The blanking level during the blanking period of the coaxial video signal line is used as the basis for clamping (hereinafter referred to as the clamping error), and the blanking level is clamped to the error tolerance range of the set target value. As a preferred solution, it is necessary to calculate the difference between the blanking level value of each line and the target blanking value as the clamping error. If the error is greater than a certain threshold (or defined as an analog clamping threshold), analog clamping is used for adjustment; otherwise, digital clamping is used for adjustment. As a more preferred solution, by calculating the difference between the blanking level value of each line and the target blanking value as the clamping error, the corresponding parameters of the clamping method to be executed in the next line are calculated according to the clamping error of the current line, and the clamping control parameters are updated in units of lines, and clamped during the line blanking period of each line so that the effective video content in the line will not be affected by clamping. The details are as follows:

[0008] The invention includes a method for adaptively adjusting analog clamping parameters and digital clamping control parameters, including:

[0009] Calculate the blanking difference between the blanking level value of each line of the video signal and the target blanking value as the clamping error. If the absolute value of the current line clamping error is greater than the analog clamping threshold, update the analog clamping control parameter according to the relationship between the current line clamping error and the error tolerance threshold, and return the updated analog control parameter to the analog clamping unit, and use the analog clamping method to adjust the signal;

[0010] If the absolute value of the current row clamp error is less than or equal to the analog clamp threshold, the digital clamp control parameter is updated according to the relationship between the current row clamp error and the error tolerance threshold, and the digital clamp method is used to perform signal adjustment.

[0011] Further, the analog clamping parameters include charging control parameters and discharging control parameters, and the method for updating the analog clamping parameters includes:

[0012] When the clamp error is greater than the analog clamp threshold, analog clamping is used for processing, otherwise the analog clamp parameters remain unchanged;

[0013] When the clamp error is negative, charging is performed without discharging;

[0014] When the clamp error is positive, discharge is performed first, and if the discharge has reached the maximum, the charge level is reduced.

[0015] Furthermore, the signal states for signal conditioning using the digital clamping method include:

[0016] When the absolute value of the clamp error is less than or equal to the analog clamp threshold analog clamp threshold, or the analog clamp parameter has been adjusted to the boundary value and the absolute value of the clamp error is still greater than the analog clamp threshold, the digital clamp method is used for processing.

[0017] The method for updating the digital clamp control parameters comprises:

[0018] The current digital clamp control parameter is the previous line clamp control parameter plus the digital clamp control parameter increment. The calculation method of the digital clamp control parameter increment includes:

[0019] If the absolute value of the clamp error is greater than the analog clamp threshold, the analog clamp parameter includes a charge control parameter and a discharge control parameter, and if the charge control parameter of the previous row is the largest and the discharge control parameter is the smallest, or the charge control parameter is the smallest and the discharge control parameter is the largest, then the digital clamp control parameter increment is the analog clamp threshold. Otherwise, the digital clamp control parameter increment is the clamp error.

[0020] As another preferred solution, a clamp lock is set. When the clamp error of several lines is less than the error tolerance threshold, it can be determined that the clamp has met the requirements, and the analog and digital clamp configurations are subsequently maintained. The several lines referred to in the present invention can be determined by a counter. The specific solution is:

[0021] Set the counter, initialize the initial parameters of the counter, and limit the counter value to a range, calculate the minimum and maximum values, and set the initial parameters to the minimum value of the range;

[0022] If the absolute value of the clamp error is greater than or equal to the error tolerance threshold, and the counter value of the previous row is not the minimum value, the counter value is reduced by 1. If the counter value of the previous row is the minimum value, the current counter value is counted as the minimum value.

[0023] If the absolute value of the clamp error is less than the error tolerance threshold, and the counter value of the previous row is the maximum value, the counter value of the current row is recorded as the maximum value;

[0024] If the absolute value of the clamp error is less than the error tolerance value, and the counter value of the previous row is not the maximum value, the counter value is increased by 1;

[0025] If the counter value is greater than or equal to 0, the clamp lock indicator is marked as clamp locked, if not, the clamp is not reached; if the clamp is not reached, the clamp parameter control logic is performed, such as the method of adaptively adjusting the analog clamp parameters and the digital clamp control parameters proposed above.

[0026] When the clamp is locked, the analog clamp parameters and digital clamp control parameters remain unchanged.

[0027] A counter is used to control the clamp lock mark. After the clamp is locked, the clamp parameters are not adjusted, which improves the stability of the clamp system and prevents the system from erroneously clamping due to a single row or several rows of erroneous signals, thereby improving the system's anti-noise capability.

[0028] As another preferred solution, the method for calculating the difference between the blanking level of each line of the coaxial video signal and the target value also includes a low-pass filtering method, in which the digital coaxial video signal output by the analog-to-digital conversion unit is subjected to the low-pass filtering method in units of samples to obtain a filtered output signal containing a low-frequency signal component of the blanking level;

[0029] The blanking difference between the blanking level value of each line of the filtered output signal and the target blanking value is calculated as the clamping error.

[0030] As another preferred scheme, the method for calculating the blanking level value includes: taking the calculated average of N consecutive sample points of the rear shoulder of the synchronization pulse of each line signal after low-pass filtering, and taking the said average as the current blanking level value; wherein, the selection of the N value can remove the interference of noise in the signal on the obtained current blanking level value, thereby ensuring its accuracy.

[0031] Furthermore, the present invention also provides a coaxial video signal automatic clamping control device, comprising: A signal receiving unit, used for receiving a coaxial video signal; An analog clamping unit, connected to the signal receiving unit, and used to implement analog clamping according to analog clamping parameters; The analog-to-digital conversion unit is connected to the analog clamping unit and is used to convert the analog signal output by the analog clamping unit into a digital signal and input the digital signal into the digital clamping unit; A digital clamping unit, connected to the analog-to-digital conversion unit, and used to implement digital clamping according to digital clamping control parameters; The main processing unit is connected to the analog-to-digital conversion unit and the digital clamping unit respectively, and is used to calculate the blanking difference between the blanking level value of the coaxial video signal and the target blanking value as the clamping error. If the absolute value of the clamping error is greater than the analog clamping threshold, the analog clamping method is used to adjust the signal. If not, the digital clamping method is used to adjust the signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] Figure 1 It is a flow chart of the automatic clamping control method of digital-analog hybrid;

[0034] Figure 2 It is a schematic diagram of the low-pass filtering method;

[0035] Figure 3 It is a schematic diagram of blanking level value;

[0036] Figure 4 It is one of the feasible analog clamp circuit diagrams;

[0037] Figure 5 This is a schematic diagram of the digital clamping method. DETAILED DESCRIPTION

[0038] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0039] Embodiment 1: A digital-analog hybrid automatic clamping control method, such as Figure 1 , including the following steps: initializing analog clamp control parameters and digital clamp control parameters, which are set to two sets of fixed values ​​in this embodiment and can be set according to the experience of technical personnel in this field. The analog clamp control parameters are generally related to the ADC to ensure that the input analog coaxial video signal is within the effective level range of the ADC; the initial value of the digital clamp control parameter is generally 0.

[0040] The coaxial video signal is sequentially input into the analog clamping unit, the analog-to-digital conversion unit and the digital clamping unit; after the analog clamping output signal is converted into a digital signal, the digital clamping output signal is outputted through the digital clamping method;

[0041] The blanking difference between the blanking level value of the coaxial video signal and the target blanking value is calculated as the clamping error. If the absolute value of the clamping error is greater than the analog clamping threshold, the analog clamping method is used for signal adjustment. If not, the digital clamping method is used for signal adjustment. The analog clamping threshold is also a parameter set based on experience. If it is set too small, it is easy to enter the analog clamping and the clamping is not easy to lock. If it is set too large, it is not easy to enter the analog clamping, which may cause the signal to be clipped at the top or bottom, affecting the signal content.

[0042] The present application discloses a hybrid digital-analog clamping method, which uses analog clamping when the error is large to adjust the input signal to a roughly appropriate range to ensure that the signal is not clipped; and uses digital clamping when the error is small to ensure clamping accuracy.

[0043] The preferred scheme also includes a low-pass filtering method before calculating the blanking difference between the blanking level value of the video signal and the target blanking value as the clamping error, wherein the digital coaxial video signal output by the analog-to-digital conversion unit is subjected to the low-pass filtering method in units of samples to obtain a filtered output signal containing a low-frequency signal component of the blanking level; and the blanking difference between the blanking level value of the filtered output signal and the target blanking value is calculated as the clamping error.

[0044] The digital coaxial video signal output by the analog-to-digital conversion unit is low-pass filtered in units of samples (data points after ADC sampling) to filter out high-frequency signals and obtain a filtered output signal, which is recorded as S flt More preferably, a two-stage filtering method is used to implement low-pass filtering, such as Figure 2 , including first-stage filtering and second-stage filtering. For example, the first-stage filtering coefficients are (7, 16, 18, 16, 7) and the second-stage filtering coefficients are (4, 1, 6, 1, 4).

[0045] The low-pass filtering in this step is to filter out the high-frequency chrominance signal and extract the low-frequency blanking level. The preferred two-stage filtering scheme is simpler and more efficient in circuit implementation.

[0046] Specifically, if the input signal is denoted as S in , the first-stage filter output signal is recorded as S0, and the filtering mathematical expression is as follows:

[0047] Formula 1

[0048] Formula 2

[0049] Among them, S0(i) and S flt (i) represents the i-th sample point of the first-stage filter output and the second-stage filter output respectively. If the coordinate corresponding to the sample point in the above expression is less than 0, the sample point value is 0; round() means rounding the content in the brackets.

[0050] Further, a method for calculating the blanking level of each line of the coaxial video signal is as follows: Figure 3 ,include:

[0051] The calculated average of N consecutive sample points on the rear shoulder of the synchronization pulse of each line of the low-pass filtered signal is taken as the current line blanking level value, recorded as blk_val. Exemplarily, in this solution, the value of N is 32.

[0052] The specific position of the value is blk_st sample points away from the falling edge of the line synchronization pulse. Due to the different line synchronization header widths of different standards (ahd / cvi / tvi) and different resolutions (1M / 2M, etc.), the value of blk_st is different. Ensure that the blanking level interval is within Figure 5 For details, please refer to the analog high-definition encoding standard.

[0053] The method for calculating the difference between the blanking level value of the video signal and the target blanking value is: calculate the difference between the current line blanking value and the target blanking value std_blk_val through the following expression, record it as blk_err, and use blk_err as the clamping error.

[0054] Formula 3

[0055] Embodiment 2: A further improved digital-analog hybrid automatic clamping control method proposes a method for updating analog clamping control parameters and digital clamping control parameters line by line. The specific steps are as follows:

[0056] According to the signal state of each line, that is, the difference between the blanking level value of the current line and the target blanking value, the analog clamping parameters or digital clamping control parameters of the next line signal adjustment are adaptively updated. At the same time, the preferred scheme of the low-pass filtering method based on this is that the blanking difference between the blanking level value of each line of video signal and the target blanking value is calculated as the clamping error, and the low-pass filtering method is also included before the digital coaxial video signal output by the analog-to-digital conversion unit is subjected to the low-pass filtering method in units of samples to obtain a filtered output signal; the blanking difference between the blanking level value of each line of the filtered output signal and the target blanking value is calculated as the clamping error.

[0057] The analog clamping control parameter and the digital clamping control parameter in the analog-digital hybrid automatic clamping control method may be a parameter set manually, and preferably may be an adaptive clamping control parameter. The adaptive clamping control parameter is calculated as follows:

[0058] The method for adaptively adjusting analog clamping parameters and digital clamping control parameters includes:

[0059] Firstly, similar to the first embodiment, the analog clamping control parameter and the digital clamping control parameter are initialized to determine an initial value.

[0060] Then, the blanking difference between the blanking level value of each line of the video signal and the target blanking value is calculated as the clamping error. If the absolute value of the current line clamping error is greater than the analog clamping threshold, the analog clamping control parameter is updated according to the relationship between the current line clamping error and the error tolerance threshold, and the updated analog control parameter is returned to the analog clamping unit, and the signal is adjusted using the analog clamping method;

[0061] If the absolute value of the current row clamp error is greater than the analog clamp threshold, but the analog clamp control parameter has been adjusted to the boundary value and cannot be adjusted further, the digital clamp control parameter is updated according to the relationship between the current row clamp error and the error tolerance threshold, and the digital clamp method is used to adjust the signal.

[0062] If the absolute value of the current row clamp error is less than or equal to the analog clamp threshold, the digital clamp control parameter is updated according to the relationship between the current row clamp error and the error tolerance threshold, and the digital clamp method is used to perform signal adjustment.

[0063] The analog clamping parameters include charging control parameters and discharging control parameters. The method for updating the analog clamping parameters is as follows:

[0064] Generally speaking, when the actual blanking level value is lower than the target blanking level value (the clamping error is a negative number), and the absolute value of the error exceeds the analog clamping threshold, the clamping circuit will start the charging operation to increase the actual blanking level to make it close to the target level.

[0065] When the actual blanking level value is higher than the target blanking level value (the clamping error is a positive number) and the error exceeds the analog clamping threshold, the clamping circuit will initiate the operation of discharging or reducing the charge level to reduce the actual blanking level to close to the target level.

[0066] Since each row needs to be adaptively adjusted, it is necessary to further adjust the parameters of the previous row according to the clamping error to achieve a better control level. The better control logic is shown in Formula 6 and Formula 7:

[0067] Formula 6

[0068] Formula 7

[0069] Among them, the charging control parameter and the discharging control parameter are represented by A_up and A_down respectively, and their initial values ​​are both 0, indicating no charging and no discharging; the larger the A_up, the greater the charging, and the larger the A_down, the greater the discharging. prev and A_up prev They represent A_down and A_up of the previous line respectively, and A_clamp_TH represents the analog clamping threshold.

[0070] The explanation of formula 6 and formula 7 is as follows: When the clamp is locked, the analog clamp parameters remain unchanged, that is, blk_ok=1;

[0071] When clamping is used for control, if the absolute value of the clamping error exceeds the analog clamping threshold value A_clamp_TH, analog clamping is used for processing, otherwise the analog clamping parameters remain unchanged;

[0072] If the clamping error is negative, charging is performed without discharging;

[0073] If the clamp error is positive, discharge is performed first. If the discharge has reached the maximum (or the discharge parameter has reached the maximum), the charge level is reduced.

[0074] In the formula, A_down prev +1 indicates increasing the discharge level or grade, A_up prev +1 means increase the charge level or grade, A_down prev -1 means lower discharge level or grade, A_up prev -1 means decreasing the discharge level or grade.

[0075] In principle, when the clamp is controlled, when the absolute value of the clamp error is greater than the analog clamp threshold A_clamp_TH, it means that the actual signal range is still quite different from the target range, and analog clamping needs to be used for processing, otherwise the analog clamp parameters remain unchanged; if the clamp error is a negative value, it means that the actual blanking level is less than the target level, and charging is performed without discharging; if the clamp error is a positive value, it means that the actual blanking level is greater than the target level, and discharge is performed first. If the discharge has reached the maximum, the charging level is reduced.

[0076] As a preferred solution, the digital clamp control parameter increment is calculated through the following process, which is recorded as blk_err';

[0077] Formula 8

[0078] Wherein, max_up represents the maximum value of A_up, and max_down represents the maximum value of A_down. The maximum value is determined by the specific analog clamp circuit.

[0079] When the clamp is controlled, when the absolute value of the clamp error is less than or equal to the analog clamp threshold A_clamp_TH, it means that the actual signal range is close to the target range and a more precise digital clamp is needed for processing; at the same time, if the analog clamp has been adjusted to the boundary value and the absolute value of the clamp error is still greater than the analog clamp threshold A_clamp_TH, digital clamping is also used for processing.

[0080] According to blk_err', the digital clamp control parameter clamp_d is calculated in the following manner. The larger the clamp_d value is, the greater the amplitude of the signal reduction is.

[0081]

[0082] Among them, clamp_d prev Indicates the clamp_d of the previous row; that is, the current digital clamp control parameter is the clamp control parameter of the previous row plus the digital clamp control parameter increment. The calculation method of the digital clamp control parameter increment includes:

[0083] If the absolute value of the clamping error is greater than the analog clamping threshold, but the analog clamping parameters including the charging control parameter and the discharging control parameter have reached the boundary value, such as the charging control parameter in the previous row is the largest and the discharging control parameter is the smallest, or the charging control parameter is the smallest and the discharging control parameter is the largest, then the digital clamping control parameter increment is the analog clamping threshold. Otherwise, the digital clamping control parameter increment is the clamping error. The boundary value described in the present disclosure can be understood as the maximum or minimum, and cannot be further adjusted in the corresponding direction.

[0084] The updated analog clamping control parameters A_up, A_down and digital clamping control parameter clamp_d of the current row are sent to the analog clamping unit and the digital clamping unit respectively, and then return to the second step to perform the clamping process of the next row until the clamping is completed.

[0085] The clamp control parameters are updated in line units, and clamping is performed during the line blanking period of each line so that valid video content in the line will not be affected by clamping.

[0086] As a preferred solution, a clamp lock marking method is also included to control the calculation of the clamp control parameters of the next row.

[0087] Set the counter, initialize the counter initial parameters, and limit the counter value to a range. Usually, the initial parameter is the minimum value of the range.

[0088] If the absolute value of the clamp error is greater than or equal to the error tolerance threshold, and the counter value of the previous row is not the minimum value, the counter value is reduced by 1. If the counter value of the previous row is the minimum value, the current counter value is counted as the minimum value.

[0089] If the absolute value of the clamp error is less than the error tolerance threshold, and the counter value of the previous row is the maximum value, the counter value of the current row is recorded as the maximum value;

[0090] If the absolute value of the blanking difference is less than the error tolerance value, and the counter value of the previous line is not the maximum value, the counter value is increased by 1;

[0091] If the counter value is greater than or equal to 0, the clamp lock indicator is marked as clamp locked, if not, the clamp is not reached; if the clamp is not reached, the clamp parameter control logic is performed, such as the method of adaptively adjusting the analog clamp parameters and the digital clamp control parameters proposed above. When the clamp is locked, the analog clamp parameters and the digital clamp control parameters remain unchanged.

[0092] The specific process and examples include: illustratively, the initial value of the counter is -cnt_lmt, denoted as cnt.

[0093] In this disclosure, it is assumed that the default value of cnt_lmt is 16, then:

[0094] The initial value cnt = -cnt_lmt, that is, cnt = -16.

[0095] In the present disclosure, the clamp lock flag is controlled by the counter parameter. The larger the cnt_lmt is, the longer the clamp lock waiting time is, but the more stable the clamp system is; the smaller the cnt_lmt is, the faster the clamp lock speed is, but the clamp system is easily affected by noise and fluctuates. The implementer can adjust the parameter value according to experience, test adjustment and actual application needs.

[0096] The formula for counting cnt is as follows:

[0097] Formula 4

[0098] Among them, cnt prev Indicates the counter value of the previous line, max_clamp_err is the error tolerance threshold of the clamp, and |blk_err| means taking the absolute value of blk_err. The counter value is limited to the interval [-cnt_lmt, cnt_lmt].

[0099] The clamp lock flag blk_ok is obtained through the following expression. Its value 1 indicates that the clamp is completed and the clamp has met the requirements.

[0100] Formula 5

[0101] The clamp lock mark is used to determine whether the clamp is reached. If the counter is greater than or equal to 0, the clamp lock is determined to be completed. If not, the clamp is not reached. This preferred solution uses the value of the counter to be used for the next step of determining the clamp lock mark, making the clamp system more stable and anti-noise. Occasionally, one or several lines of signals affected by noise will not cause clamp fluctuations.

[0102] Since the blanking difference of one or several rows is smaller than the error tolerance value when the clamp is not stable yet, it cannot represent the overall signal level. Only when multiple rows are like this can it be said that the overall signal clamp has reached the target value, cnt is greater than 0, and the clamp is in the locked state; after the clamp is locked, when one or several rows are occasionally affected by the external environment, the blanking difference is greater than the error tolerance value. As long as it does not exceed a certain number of rows and the count value cnt is not less than 0, the clamp control parameters will not change to ensure system stability.

[0103] Embodiment 3: A coaxial video signal automatic clamping control device is disclosed, comprising: A signal receiving unit, used for receiving a coaxial video signal; An analog clamping unit, connected to the signal receiving unit, and used to implement analog clamping according to analog clamping parameters; The analog-to-digital conversion unit is connected to the analog clamping unit and is used to convert the analog signal output by the analog clamping unit into a digital signal and input the digital signal into the digital clamping unit; A digital clamping unit, connected to the analog-to-digital conversion unit, and used to implement digital clamping according to digital clamping control parameters; The main processing unit is connected to the analog-to-digital conversion unit and the digital clamping unit respectively, and is used to calculate the blanking difference between the blanking level value of the coaxial video signal and the target blanking value as the clamping error. If the absolute value of the clamping error is greater than the analog clamping threshold, the analog clamping method is used to adjust the signal. If not, the digital clamping method is used to adjust the signal.

[0104] The main processing unit further includes an adaptive clamping calculation unit, which is used to calculate the blanking difference between the blanking level value of each line of the video signal and the target blanking value as the clamping error. If the absolute value of the current line clamping error is greater than the analog clamping threshold, the analog clamping control parameter is updated according to the relationship between the current line clamping error and the error tolerance threshold, and the updated analog control parameter is returned to the analog clamping unit, and the signal is adjusted using the analog clamping method; If the absolute value of the current row clamp error is less than or equal to the analog clamp threshold, the digital clamp control parameter is updated according to the relationship between the current row clamp error and the error tolerance threshold, and the digital clamp method is used to perform signal adjustment.

[0105] In each unit, please refer to Embodiment 1 and Embodiment 2 for more specific circuit structure and control method, which will not be described in detail.

[0106] It should be noted that the analog clamping method and the digital clamping method disclosed above are respectively known to those skilled in the art, and their structures are not specifically described in the present invention. The exemplary structural diagram can be referred to in Figure 4 and Figure 5 Of course, since the present invention protects a hybrid application method of analog and digital, there is no limitation on the detailed scheme and structure of analog clamping and digital clamping. If there are other known or innovative analog clamping methods and digital clamping methods that are applied or combined with the technical solution of the present invention, they are also included in the protection scope of the present invention.

Claims

1. A digital-analog hybrid automatic clamping control method, characterized in that: It includes the following: Initialize analog clamp parameters and digital clamp control parameters; The coaxial video signal is sequentially input into the analog clamping unit, the analog-to-digital conversion unit and the digital clamping unit; after the analog clamping output signal is converted into a digital signal, the digital clamping output signal is outputted through the digital clamping method; The blanking difference between the blanking level value of the video signal and the target blanking value is calculated as the clamping error. If the absolute value of the clamping error is greater than the analog clamping threshold, the analog clamping method is used to adjust the signal. If not, the digital clamping method is used to adjust the signal.

2. The automatic clamping control method for digital-analog hybrid according to claim 1, characterized in that: Also included is a method for adaptively adjusting analog clamping parameters and digital clamping control parameters, including: Calculate the blanking difference between the blanking level value of each line of the video signal and the target blanking value as the clamping error. If the absolute value of the current line clamping error is greater than the analog clamping threshold, update the analog clamping control parameter according to the relationship between the current line clamping error and the error tolerance threshold, and return the updated analog control parameter to the analog clamping unit, and use the analog clamping method to adjust the signal; If the absolute value of the current row clamp error is less than or equal to the analog clamp threshold, the digital clamp control parameter is updated according to the relationship between the current row clamp error and the error tolerance threshold, and the digital clamp method is used to perform signal adjustment.

3. The automatic clamping control method for digital-analog mixing as claimed in claim 2, characterized in that: The analog clamping parameters include charging control parameters and discharging control parameters, and the method for updating the analog clamping parameters includes: When the absolute value of the clamp error is greater than the analog clamp threshold, analog clamping is used for processing, otherwise the analog clamp parameters remain unchanged; When the clamp error is negative, charging is performed without discharging; When the clamp error is positive, discharge is performed first, and if the discharge has reached the maximum, the charge level is reduced.

4. The automatic clamping control method for digital-analog hybrid according to claim 2, characterized in that: Signal conditions that use digital clamping methods for signal conditioning include: When the absolute value of the clamp error is less than or equal to the analog clamp threshold, or the analog clamp parameter has been adjusted to the boundary value and the absolute value of the clamp error is still greater than the analog clamp threshold, the digital clamp method is used for processing.

5. The automatic clamping control method for digital-analog hybrid according to claim 2, characterized in that: The method for updating the digital clamp control parameters comprises: The current digital clamp control parameter is the previous line clamp control parameter plus the digital clamp control parameter increment. The calculation method of the digital clamp control parameter increment includes: If the absolute value of the clamping error is greater than the analog clamping threshold, the analog clamping parameters include charging control parameters and discharging control parameters. If the charging control parameter of the previous row is the largest and the discharging control parameter is the smallest, or the charging control parameter is the smallest and the discharging control parameter is the largest, then the digital clamping control parameter increment is the analog clamping threshold; otherwise, the digital clamping control parameter increment is the clamping error.

6. The automatic clamping control method for digital-analog hybrid according to any one of claims 2 to 5, characterized in that: Also includes clamp locking method, Set the counter, initialize the initial parameters of the counter, and limit the counter value to a range, counting the minimum and maximum values. The initial parameter is the minimum value of the range; If the absolute value of the clamp error is greater than or equal to the error tolerance threshold, and the counter value of the previous row is not the minimum value, the counter value is reduced by 1. If the counter value of the previous row is the minimum value, the current counter value is counted as the minimum value. If the absolute value of the clamp error is less than the error tolerance threshold, and the counter value of the previous row is the maximum value, the counter value of the current row is recorded as the maximum value; If the absolute value of the clamp error is less than the error tolerance value, and the counter value of the previous row is not the maximum value, the counter value is increased by 1; If the counter value is greater than or equal to 0, the clamp lock indicator is marked as clamp locked, if not, the clamp is not reached; When the clamp is locked, the analog clamp parameters and digital clamp control parameters remain unchanged.

7. The automatic clamping control method for digital-analog hybrid according to claim 1, characterized in that: The method further includes a low-pass filtering method, wherein the digital coaxial video signal outputted by the analog-to-digital conversion unit is subjected to a low-pass filtering method in units of samples to obtain a filtered output signal containing a low-frequency signal component of the blanking level; The blanking difference between the blanking level value of the filtered output signal and the target blanking value is calculated as the clamping error.

8. The automatic clamping control method for digital-analog mixing as claimed in claim 7, characterized in that: The blanking level value calculation method includes: taking the calculated average value of N consecutive sample points of the rear shoulder of the synchronization pulse of each line signal after low-pass filtering, and taking the average value as the current blanking level value.

9. A digital-analog hybrid automatic clamping control device, characterized in that: include: A signal receiving unit, used for receiving a coaxial video signal; An analog clamping unit, connected to the signal receiving unit, and used to implement analog clamping according to analog clamping parameters; The analog-to-digital conversion unit is connected to the analog clamping unit and is used to convert the analog signal output by the analog clamping unit into a digital signal and input the digital signal into the digital clamping unit; A digital clamping unit, connected to the analog-to-digital conversion unit, and used to implement digital clamping according to digital clamping control parameters; The main processing unit is connected to the analog-to-digital conversion unit and the digital clamping unit respectively, and is used to calculate the blanking difference between the blanking level value of the coaxial video signal and the target blanking value as the clamping error. If the absolute value of the clamping error is greater than the analog clamping threshold, the analog clamping method is used to adjust the signal. If not, the digital clamping method is used to adjust the signal.

10. The digital-analog hybrid automatic clamping control device according to claim 9, characterized in that: The main processing unit also includes an adaptive clamping calculation unit, It is used to calculate the blanking difference between the blanking level value of each line of the video signal and the target blanking value as the clamping error. If the absolute value of the current line clamping error is greater than the analog clamping threshold, the analog clamping control parameter is updated according to the relationship between the current line clamping error and the error tolerance threshold, and the updated analog control parameter is returned to the analog clamping unit, and the signal is adjusted using the analog clamping method; If the absolute value of the current row clamp error is less than or equal to the analog clamp threshold, the digital clamp control parameter is updated according to the relationship between the current row clamp error and the error tolerance threshold, and the digital clamp method is used to perform signal adjustment.

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