阅读说明：本技术 一种高稳定性的视频触发方法及数字示波器 (High-stability video triggering method and digital oscilloscope ) 是由 吴乾科 周旭鑫 李振军 于 2019-12-25 设计创作，主要内容包括：一种高稳定性的视频触发方法及数字示波器,其中视频触发方法包括：获取并对视频信号进行低通滤波以滤除视频信号中的高频分量,得到滤波信号；检测滤波信号中各个负脉冲的最小谷值,结合预设的迟滞窗口大小计算得到比较电平；根据比较电平对滤波信号进行数字比较,生成同步信号；根据同步信号进行视频触发处理,得到触发信号；依据触发信号控制存储且显示视频信号上触发位置附近的信号波形。由于结合负脉冲的最小谷值和迟滞窗口大小来计算得到比较电平,那么可以在每个更新周期内对滤波信号进行数字比较,实现比较电平自适应跟随的应用效果,有效避免以往比较电平固定不变的应用局限性,同时可以最大程度上降低滤波信号上叠加噪声的干扰作用。(A high-stability video triggering method and a digital oscilloscope are provided, wherein the video triggering method comprises the following steps: acquiring and performing low-pass filtering on the video signal to filter out high-frequency components in the video signal to obtain a filtered signal; detecting the minimum valley value of each negative pulse in the filtering signal, and calculating by combining the size of a preset hysteresis window to obtain a comparison level; digitally comparing the filtered signal according to the comparison level to generate a synchronous signal; performing video triggering processing according to the synchronous signal to obtain a triggering signal; and controlling to store and display the signal waveform near the trigger position on the video signal according to the trigger signal. Because the comparison level is calculated by combining the minimum valley value of the negative pulse and the size of the hysteresis window, the filtering signal can be digitally compared in each updating period, the application effect of the adaptive following of the comparison level is realized, the application limitation that the comparison level is fixed and unchanged in the past is effectively avoided, and meanwhile, the interference effect of the superposed noise on the filtering signal can be reduced to the maximum extent.)

1. A high-stability video triggering method is characterized by comprising the following steps:

acquiring and performing low-pass filtering on a video signal to filter high-frequency components in the video signal to obtain a filtered signal; the high-frequency component is used for carrying the brightness information and the chrominance information of each display line in each frame of video picture corresponding to the video signal;

detecting the minimum valley value of each negative pulse in the filtering signal, and calculating by combining the size of a preset hysteresis window to obtain a comparison level;

according to the comparison level, the filtering signals are compared digitally to generate synchronous signals; the synchronous signal comprises a plurality of field components and a plurality of line components, wherein the field components and the line components are respectively used for identifying each display field and each display line in each frame of video picture, a plurality of continuous display lines form one display field, and at least two continuous display fields form one frame of video picture;

performing video trigger processing according to the synchronous signal to obtain a trigger signal;

and controlling to store and display the signal waveform near the trigger position on the video signal according to the trigger signal.

2. The video trigger method of claim 1, wherein said obtaining and low-pass filtering a video signal to filter out high frequency components in the video signal to obtain a filtered signal comprises:

adaptively determining cut-off frequency of low-pass filtering according to the format of the video signal, filtering high-frequency components exceeding the cut-off frequency in the video signal, and forming a filtering signal by the video signal after the low-pass filtering; the format of the video signal comprises a signal type, an effective display format, a display scale and a frame frequency.

3. The method as claimed in claim 2, wherein said detecting the minimum valley of each negative pulse in the filtered signal and calculating the comparison level with a preset hysteresis window size comprises:

determining the period of the display line in each frame of video picture according to the system of the video signal, setting integral multiple of the period of the display line as an updating period, and detecting the minimum valley value of each negative pulse on each filtering signal in the updating period;

adding the minimum valley value to one or more preset hysteresis window sizes, and calculating to obtain a comparison level of the filtering signal for the signal in the updating period; recalculating and updating the comparison level in the next update period;

the hysteresis window size is generated by a hysteresis comparator arranged on a channel of the filtering signal and used for reducing the sensitivity of the hysteresis comparator relative to the noise superposed on the filtering signal.

4. The video trigger method of claim 3, wherein said digitally comparing said filtered signal according to said comparison level to generate a synchronization signal comprises:

in each updating period, a signal corresponding to the updating period on the filtering signal is compared with a comparison level aiming at the signal in the updating period in a digital mode, a signal smaller than or equal to the comparison level is set to be a first value, a signal larger than the comparison level is set to be a second value, and the first value is smaller than the second value;

and generating a synchronous signal according to the first value and the second value set in the comparison result, wherein the synchronous signal is a rectangular wave, and each trough of the rectangular wave corresponds to the field component or the line component.

5. The video trigger method of claim 4, wherein said performing video trigger processing according to the synchronization signal to obtain a trigger signal, and said controlling storing and displaying the signal waveform near the trigger position on the video signal according to the trigger signal comprises:

detecting the pulse width of each wave trough in the synchronous signal, determining the continuous wave troughs as the field component when the pulse widths of the continuous wave troughs are equal to a preset first value, and determining the wave trough as the line component when the pulse width of one wave trough is equal to a preset second value;

sequentially marking each determined field component and each determined line component, comparing a marking result with a preset video trigger condition, and generating a trigger signal by using a comparison result;

and determining a trigger position on the video signal according to the field component and the line component corresponding to the trigger signal, and performing digital storage and waveform display on a signal waveform near the trigger position on the video signal.

6. A digital oscilloscope, comprising:

a signal input channel for converting an externally input analog video signal into a digitized video signal;

processing circuitry, coupled to the signal input channel, for controlling storage and display of signal waveforms in the vicinity of a trigger position on the video signal according to the video trigger method of any of claims 1-5;

the memory is connected with the processing circuit and is used for digitally storing the signal waveform which is controlled and stored by the processing circuit;

and the display is connected with the processing circuit and used for displaying the signal waveform which is controlled and displayed by the processing circuit.

7. The digital oscilloscope of claim 6, wherein the processing circuit comprises:

the filter circuit is connected with the signal input channel and used for performing low-pass filtering on the video signal to filter out high-frequency components in the video signal and outputting a filter signal;

the detection circuit is connected with the filter circuit and used for detecting the minimum valley value of each negative pulse in the filter signal and calculating by combining the size of a preset hysteresis window to obtain a comparison level;

the comparison circuit is connected with the filter circuit and the detection circuit and is used for carrying out digital comparison on the filter signal according to the comparison level to generate a synchronous signal;

the video trigger circuit is connected with the comparison circuit and used for carrying out video trigger processing according to the synchronous signal and generating a trigger signal;

and the control circuit is connected with the signal input channel, the video trigger circuit, the memory and the display and is used for controlling and storing and displaying the signal waveform near the trigger position according to the trigger signal.

8. The digital oscilloscope of claim 7, wherein said signal input channel comprises a plurality of sub-channels, said processing circuitry further comprising signal source selection circuitry disposed between said signal input channel and said filtering circuitry;

each sub-channel is respectively used for receiving one path of analog video signal and converting the received analog video signal into a digital video signal;

the signal source selection circuit is used for selecting one path of the video signal output in each sub-channel and transmitting the path of the video signal to the filter circuit.

9. The digital oscilloscope of claim 8, wherein the sub-channel comprises a conditioning circuit and an analog-to-digital conversion circuit, the conditioning circuit configured to perform noise reduction processing on the received analog video signal, and the analog-to-digital conversion circuit configured to convert the noise reduced analog video signal into a digitized video signal.

10. A computer-readable storage medium, characterized by comprising a program executable by a processor to implement the video trigger method according to any one of claims 1 to 5.

Technical Field

The invention relates to the technical field of oscilloscope triggering, in particular to a high-stability video triggering method and a digital oscilloscope.

Background

The analog video signal is an analog electrical signal carrying continuous video pictures, and movies and television programs played by previous radio stations use the analog video signal to transmit video picture contents between devices. Since continuous video pictures are transmitted, analog video signals have the concepts of line, field and frame frequency in time, and contain chrominance and luminance information of video contents in the variation of the amplitude of an electric signal, and some analog video signal transmission types even contain audio information in the signal. Currently, there are three main formats for analog video signals: NTSC, PAL and SECAM. Here, the analog video signal will be described simply by taking NTSC as an example.

The NTSC (National Television System Committee, N System for short) System is a color Television broadcasting standard which is customized by the National Television standards Committee, and the chrominance signal modulation of the System includes two types of balanced modulation and orthogonal modulation, thereby solving the compatibility problem of color black and white Television broadcasting, but having the disadvantages of easy phase distortion and unstable color. The analog video signal of NTSC system can be regarded as a signal similar to periodicity, each period can be regarded as one line content in one frame of video picture, the voltage signal change in each line represents the brightness and chroma information of the line, and each period in the analog video signal contains a synchronous signal (Sync Tip), and the line and field in the video signal can be clearly identified by separating the synchronous signal. The synchronous signal is an important mark for identifying lines and fields in the analog video signal, the video trigger function in the oscilloscope is realized based on Sync Tip, and based on the signal characteristics of the NTSC analog video signal, the trigger condition can be set to trigger the oscilloscope at any line and field of the analog video signal, so that the waveform of the signal at the place can be captured.

At present, a special video signal decoding chip is adopted in a scheme for separating a synchronization signal from an analog video signal, such as LMH1981, and if the video signal decoding chip is applied to an oscilloscope to realize a video triggering function, the hardware cost of the oscilloscope is additionally increased, and the oscilloscope is more suitable for processing an ideal analog video signal, and a situation that a video triggering error often occurs in a non-ideal analog video signal is faced. Although the technical solution provided in patent document (CN 201210378445.4) omits a video signal decoding chip, the method of separating the sync signal based on a digital comparator has some defects, the method of determining the positive and negative pulse widths cannot correctly identify the sync signal, and the fixed comparison level cannot accurately separate the sync signal; because in practical applications the analog video signal will superimpose some low frequency disturbance signals, the separated signals cannot be triggered stably in the presence of low frequency disturbances. Therefore, in the process of carrying out video triggering on NTSC signals by the conventional oscilloscope, a user is required to set a trigger comparison level, the comparison level cannot be automatically identified, and the problem of weak anti-interference capability is caused by the comparison level in a fixed form; and once the trigger voltage is set, if the analog video signal has low-frequency motion, the set trigger comparison level cannot adapt to the current disturbance, and finally the phenomenon of unstable video trigger is caused, even the serious problem of failure in video trigger of the oscilloscope is caused.

Disclosure of Invention

The invention mainly solves the technical problem of how to overcome the problem of unstable video trigger in the conventional oscilloscope. In order to solve the technical problem, the application provides a video triggering method of an oscilloscope and a digital oscilloscope.

According to a first aspect, an embodiment provides a high-stability video triggering method, including: acquiring and performing low-pass filtering on a video signal to filter high-frequency components in the video signal to obtain a filtered signal; the high-frequency component is used for carrying the brightness information and the chrominance information of each display line in each frame of video picture corresponding to the video signal; detecting the minimum valley value of each negative pulse in the filtering signal, and calculating by combining the size of a preset hysteresis window to obtain a comparison level; according to the comparison level, the filtering signals are compared digitally to generate synchronous signals; the synchronous signal comprises a plurality of field components and a plurality of line components, wherein the field components and the line components are respectively used for identifying each display field and each display line in each frame of video picture, a plurality of continuous display lines form one display field, and at least two continuous display fields form one frame of video picture; performing video trigger processing according to the synchronous signal to obtain a trigger signal; and controlling to store and display the signal waveform near the trigger position on the video signal according to the trigger signal.

The obtaining and low-pass filtering the video signal to filter out a high-frequency component in the video signal to obtain a filtered signal includes: adaptively determining cut-off frequency of low-pass filtering according to the format of the video signal, filtering high-frequency components exceeding the cut-off frequency in the video signal, and forming a filtering signal by the video signal after the low-pass filtering; the format of the video signal comprises a signal type, an effective display format, a display scale and a frame frequency.

The detecting the minimum valley value of each negative pulse in the filtering signal and calculating by combining the size of a preset hysteresis window to obtain a comparison level comprises: determining the period of the display line in each frame of video picture according to the system of the video signal, setting integral multiple of the period of the display line as an updating period, and detecting the minimum valley value of each negative pulse on each filtering signal in the updating period; adding the minimum valley value to one or more preset hysteresis window sizes, and calculating to obtain a comparison level of the filtering signal for the signal in the updating period; recalculating and updating the comparison level in the next update period; the hysteresis window size is generated by a hysteresis comparator arranged on a channel of the filtering signal and used for reducing the sensitivity of the hysteresis comparator relative to the noise superposed on the filtering signal.

The digitally comparing the filtered signal according to the comparison level to generate a synchronization signal includes: in each updating period, a signal corresponding to the updating period on the filtering signal is compared with a comparison level aiming at the signal in the updating period in a digital mode, a signal smaller than or equal to the comparison level is set to be a first value, a signal larger than the comparison level is set to be a second value, and the first value is smaller than the second value; and generating a synchronous signal according to the first value and the second value set in the comparison result, wherein the synchronous signal is a rectangular wave, and each trough of the rectangular wave corresponds to the field component or the line component.

The video triggering processing is carried out according to the synchronous signal to obtain a triggering signal, and the signal waveform near the triggering position on the video signal is controlled, stored and displayed according to the triggering signal, and the method comprises the following steps: detecting the pulse width of each wave trough in the synchronous signal, determining the continuous wave troughs as the field component when the pulse widths of the continuous wave troughs are equal to a preset first value, and determining the wave trough as the line component when the pulse width of one wave trough is equal to a preset second value; sequentially marking each determined field component and each determined line component, comparing a marking result with a preset video trigger condition, and generating a trigger signal by using a comparison result; and determining a trigger position on the video signal according to the field component and the line component corresponding to the trigger signal, and performing digital storage and waveform display on a signal waveform near the trigger position on the video signal.

According to a second aspect, there is provided in one embodiment a digital oscilloscope, comprising: a signal input channel for converting an externally input analog video signal into a digitized video signal; a processing circuit, connected to the signal input channel, for controlling to store and display the signal waveform near the trigger position on the video signal according to the video trigger method in the first aspect; the memory is connected with the processing circuit and is used for digitally storing the signal waveform which is controlled and stored by the processing circuit; and the display is connected with the processing circuit and used for displaying the signal waveform which is controlled and displayed by the processing circuit.

The processing circuit includes: the filter circuit is connected with the signal input channel and used for performing low-pass filtering on the video signal to filter out high-frequency components in the video signal and outputting a filter signal; the detection circuit is connected with the filter circuit and used for detecting the minimum valley value of each negative pulse in the filter signal and calculating by combining the size of a preset hysteresis window to obtain a comparison level; the comparison circuit is connected with the filter circuit and the detection circuit and is used for carrying out digital comparison on the filter signal according to the comparison level to generate a synchronous signal; the video trigger circuit is connected with the comparison circuit and used for carrying out video trigger processing according to the synchronous signal and generating a trigger signal; and the control circuit is connected with the signal input channel, the video trigger circuit, the memory and the display and is used for controlling and storing and displaying the signal waveform near the trigger position according to the trigger signal.

The signal input channel comprises a plurality of sub-channels, and the processing circuit further comprises a signal source selection circuit arranged between the signal input channel and the filter circuit; each sub-channel is respectively used for receiving one path of analog video signal and converting the received analog video signal into a digital video signal; the signal source selection circuit is used for selecting one path of the video signal output in each sub-channel and transmitting the path of the video signal to the filter circuit.

The sub-channel comprises a conditioning circuit and an analog-to-digital conversion circuit, wherein the conditioning circuit is used for carrying out noise reduction processing on a received analog video signal, and the analog-to-digital conversion circuit is used for converting the noise-reduced analog video signal into a digital video signal.

According to a third aspect, an embodiment provides a computer-readable storage medium comprising a program executable by a processor to implement the video trigger method described in the first aspect above.

The beneficial effect of this application is:

according to the embodiment, the high-stability video triggering method and the digital oscilloscope are provided, wherein the video triggering method comprises the following steps: acquiring and performing low-pass filtering on the video signal to filter out high-frequency components in the video signal to obtain a filtered signal; detecting the minimum valley value of each negative pulse in the filtering signal, and calculating by combining the size of a preset hysteresis window to obtain a comparison level; according to the comparison level, the filtering signals are compared digitally to generate synchronous signals; performing video triggering processing according to the synchronous signal to obtain a triggering signal; and controlling to store and display the signal waveform near the trigger position on the video signal according to the trigger signal. On the first hand, the high-frequency component in the video signal is filtered by low-pass filtering the video signal, so that the high-frequency component can be attenuated to the extent that the negative pulse is not influenced, and the accuracy and the stability of subsequent video triggering processing are improved; in the second aspect, because the comparison level is calculated by combining the minimum valley value of the negative pulse and the size of the hysteresis window, the filtering signal can be digitally compared in the update period of the comparison level, the application effect of the adaptive following of the comparison level is realized, the application limitation that the comparison level is fixed and unchanged in the past is effectively avoided, and meanwhile, the interference effect of noise superimposed on the filtering signal can be reduced to the maximum extent; in the third aspect, when the comparison level is obtained, the size of one or more hysteresis windows is added to the minimum valley value, so that the self-adaptation of the synchronous signals can be realized aiming at the amplitude range of the synchronous signals, and the synchronous signals do not need to be adjusted artificially when the video trigger processing is carried out, so that the synchronous signals with higher stability and precision and stronger interference resistance are generated; in a fourth aspect, the application separates the synchronous signal from the video signal in a processing circuit such as an FPGA and realizes video trigger processing, so that the whole circuit structure of the digital oscilloscope is simplified, the hardware cost is saved, and the digital oscilloscope has higher practical value; in the fifth aspect, since the comparison level input to the comparison circuit is obtained by the detection circuit, in practical application, when low-frequency disturbance or direct current offset is superimposed on the video signal to be detected, the detection circuit can still output the comparison level capable of being used by the comparison circuit to separate the synchronization signal through dynamic tracking of the level, which is beneficial to enhancing the working stability of the video trigger circuit.

Drawings

FIG. 1 is a flow chart of a high-stability video triggering method in the present application;

FIG. 2 is a flow chart of calculating a comparison level;

FIG. 3 is a flow chart of digital comparison to generate a synchronization signal;

FIG. 4 is a flow chart of video trigger processing to obtain trigger signals and digital storage and waveform display of signal waveforms;

FIG. 5 is a schematic diagram of a video signal synthesized from a luminance channel and a chrominance channel;

FIG. 6 is a diagram illustrating a decomposition of each display line in a video signal;

FIG. 7 is a schematic diagram of a low pass filtering of a video signal;

FIG. 8 is a schematic diagram of generating a synchronization signal based on a digital comparison of comparison levels;

FIG. 9 is a diagram illustrating a waveform structure of a synchronization signal;

FIG. 10 is a schematic diagram of the overall structure of a digital oscilloscope according to the present application;

fig. 11 is a detailed structural diagram of the digital oscilloscope.

Detailed Description

The present invention will be described in further detail with reference to the following detailed description and accompanying drawings. Wherein like elements in different embodiments are numbered with like associated elements. In the following description, numerous details are set forth in order to provide a better understanding of the present application. However, those skilled in the art will readily recognize that some of the features may be omitted or replaced with other elements, materials, methods in different instances. In some instances, certain operations related to the present application have not been shown or described in detail in order to avoid obscuring the core of the present application from excessive description, and it is not necessary for those skilled in the art to describe these operations in detail, so that they may be fully understood from the description in the specification and the general knowledge in the art.

Furthermore, the features, operations, or characteristics described in the specification may be combined in any suitable manner to form various embodiments. Also, the various steps or actions in the method descriptions may be transposed or transposed in order, as will be apparent to one of ordinary skill in the art. Thus, the various sequences in the specification and drawings are for the purpose of describing certain embodiments only and are not intended to imply a required sequence unless otherwise indicated where such sequence must be followed.

The numbering of the components as such, e.g., "first", "second", etc., is used herein only to distinguish the objects as described, and does not have any sequential or technical meaning. The term "connected" and "coupled" when used in this application, unless otherwise indicated, includes both direct and indirect connections (couplings).