CN119814999A - A software analysis method and system for analog television signals - Google Patents
A software analysis method and system for analog television signals Download PDFInfo
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- CN119814999A CN119814999A CN202411826632.3A CN202411826632A CN119814999A CN 119814999 A CN119814999 A CN 119814999A CN 202411826632 A CN202411826632 A CN 202411826632A CN 119814999 A CN119814999 A CN 119814999A
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Abstract
The invention relates to a software analysis method and a system for analog television signals, wherein the method comprises the steps of 1, detecting and collecting wireless analog television signals transmitted in air, 2, carrying out carrier detection, modulation identification and signal demodulation on the collected wireless analog television signals, 3, extracting PAL and NTSC signals through synchronous signals, separating light and color, and analyzing chroma demodulation, and 4, carrying out video playing on the selected analog television signals according to the analysis result of the step 3. The invention demodulates, analyzes parameters and plays the mode by detecting and collecting the wireless analog television signal transmitted in the air, reduces the hardware cost, improves the analysis efficiency, and realizes the high-efficiency and accurate analysis and processing of the analog television signal by a software means.
Description
Technical Field
The invention belongs to the technical field of television signal processing, and particularly relates to a software analysis method and system for analog television signals.
Background
Analog television signals are used as conventional television signal transmission modes and still occupy an important role in the whole television broadcasting system, however, as a continuously-changing voltage or current signal, analog television signals are easy to suffer from various interferences in the transmission process, so that the image quality and the sound quality are reduced, and the viewing experience of audiences is affected. Therefore, it is particularly important to accurately analyze and process analog television signals.
Currently, some detection systems for analog television signals exist in the market, but most of these systems are realized based on hardware, so that the cost is high and the flexibility is insufficient. Meanwhile, when processing complex signals, the systems often have the problems of low processing speed and low accuracy.
Disclosure of Invention
The invention aims to provide a software analysis method and a system for an analog television signal, which aim to efficiently and accurately analyze and process the analog television signal through a software means.
The invention provides a software analysis method for analog television signals, which comprises the following steps:
Step 1, detecting and collecting wireless analog television signals transmitted in the air;
Step 2, carrying out carrier detection, modulation identification and signal demodulation on the acquired wireless analog television signals;
step 3, analyzing PAL and NTSC signals through synchronous signal extraction, brightness and color separation and chroma demodulation;
and 4, playing the video of the selected analog television signal according to the analysis result in the step 3.
Further, the step1 includes sampling, quantizing and encoding the continuous analog television signal, converting the continuous analog television signal into discrete digital signals, and performing panoramic spectrum scanning.
Further, the step 3 specifically includes:
(1) Synchronous signal extraction:
Accurately restoring a row and field synchronous signal from an input signal, identifying an odd field by utilizing the characteristic of interlaced scanning, ending odd field scanning at 312.5 rows, and ending even field scanning at 625 rows;
Judging line and field synchronizing signals by detecting the level at 50% of the rising edge of the line synchronizing signals, correcting the deviation of the synchronizing signals, and recording and storing the accumulated deviation;
for field synchronizing signal extraction, when the line length is greater than 1300, the mark is 1, which represents the whole line, less than 1300, the mark is 0, which represents half line;
(2) And (3) light color separation:
The method comprises the steps of adopting a dressing filter to separate a luminance signal and a chrominance signal in a spectrum separation mode according to the principle of the frequency spectrum staggering of a video signal and the comb tooth filtering characteristic of the dressing filter, wherein:
the image signal in the full television signal is composed of a brightness signal and a color difference signal, the two color difference signals are overlapped with the brightness signal after quadrature balance modulation, and the image signal S in the color full television signal in the NTSC system is expressed as:
S=Y+Vcos21/4fct+Usin21/4fct;
Wherein Y, V, U are respectively a luminance signal and two compression color difference signals, and the composite synchronous signal and the luminance signal are separated by an amplitude separation method;
(3) Chroma demodulation:
the expression for the color signal e c (t) of the NTSC system is:
ec(t)＝Usin(wsct+33°)+Vcos(wsct+33°);
And (3) multiplying the local sine and cosine signals which are 2 times of the same frequency and phase as the received chrominance subcarriers and added with 33-degree offset phase respectively to obtain:
[Usin(wsct+33°)+Vcos(wsct+33°)]*2sin(wsct+33°)
=U-Ucos(2wsct+66°)+Vsin(2wsct+66°);
[Usin(wsct+33°)+Vcos(wsct+33°)]*2cos(wsct+33°)
=V+Vcos(2wsct+66°)+Usin(2wsct+66°);
the obtained signal is passed through a low-pass filter to obtain the required U, V color difference signal;
The expression of the color signal e c (t) of PAL format is:
ec(t)＝U(t)sinwsct+φk(t)V(t)coswsct;
Wherein phi k (t) is a switching function with a value of +1 and-1 row by row, the synchronized local oscillation signals are respectively obtained by adjusting the offset phase and the switching function, 2sinw sc t and 2 phi k(t)coswsc t are respectively multiplied by e c (t), and the required U, V color difference signals are obtained by a low-pass filter.
Further, the step (1) includes:
in a frame, the odd Field starts with an integer number of lines, the even Field starts with a half number of lines, 8 bits are taken when the odd Field is detected, the NTSC Field sync will detect 10000010 or 00000010, the PAL will detect 11000010 or 10000010, if one of them is detected as a Field sync signal, the odd Field is made to represent the signal field0_1=1, if the same is the even Field, and vice versa in the PAL case.
The invention also provides a software analysis system for the analog television signal, which comprises an analysis module, wherein the analysis module executes the software analysis method for the analog television signal.
The invention also provides a non-transitory computer readable storage medium storing computer instructions which, when executed by a processor, implement the software analysis method for analog television signals.
The invention also provides an electronic device, which is characterized by comprising:
The system comprises a memory and a processor, wherein the memory and the processor are in communication connection, the memory stores computer instructions, and the processor executes the computer instructions, so that the software analysis method for the analog television signal is executed.
By means of the scheme, the method and the system for analyzing the software of the analog television signals are used for detecting and collecting the wireless analog television signals transmitted in the air, demodulating the signals, analyzing parameters and playing the signals in a standard analysis mode, hardware cost is reduced, and analysis efficiency is improved.
The foregoing description is only an overview of the present invention, and is intended to provide a better understanding of the present invention, as it is embodied in the following description, with reference to the preferred embodiments of the present invention and the accompanying drawings.
Drawings
FIG. 1 is a flow chart of a software analysis method for an analog television signal according to the present invention;
FIG. 2 is a diagram illustrating the extraction of a row synchronization signal according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of field sync extraction according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of parity field determination in accordance with one embodiment of the present invention;
FIG. 5 is a schematic diagram of a comb filter according to an embodiment of the present invention;
FIG. 6 is a waveform diagram of a color full TV signal according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of signal separation according to an embodiment of the present invention;
Fig. 8 is a schematic diagram of an electronic device according to the present invention.
Detailed Description
The following describes in further detail the embodiments of the present invention with reference to the drawings and examples. The following examples are illustrative of the invention and are not intended to limit the scope of the invention.
The present invention will be described in further detail below.
The invention automatically extracts information such as signal frequency points, signal intensity and the like in a set frequency band by detecting and collecting wireless analog television signals transmitted in the air, outputs time domain waveforms in real time, analyzes according to two modes PAL and NSTC of the analog television signals, and demodulates and plays the selected analog television signals. The flow of analog television signal analysis is shown in fig. 1.
1) Time-frequency monitoring acquisition
The time-frequency monitoring realizes the detection and parameter measurement of signals in a specified frequency band by calling basic functions such as carrier detection analysis, parameter measurement, DDC and the like. And monitoring the signal frequency points and the signal energy parameter information in real time, and accurately acquiring the analog television signal.
And the receiving channel signal is sampled and subjected to FFT operation through acquisition processing, and the transmitted analog signal is acquired, quantized and encoded and then converted into a digital signal. FFT operation of equipment appointed resolution is realized on the channel signal data of panoramic spectrum scanning, DDC signal acquisition can be realized, and spectrum and DDC real-time processing data are sent to a computer.
2) Signal identification analysis demodulation
The signal analysis and demodulation mainly comprises carrier detection, modulation recognition, coding recognition and the like, and the signal recognition analysis is realized through detection recognition at different stages. The main purpose of signal identification demodulation is to detect carrier wave, identify and give out characteristic attribute of signal for frequency band range, and make demodulation treatment.
3) PAL and NTSC system analysis
For signals of two systems, the analysis is carried out mainly through synchronous signal extraction, light color separation and chromaticity demodulation.
(1) The extraction of the synchronous signals mainly comprises the accurate recovery of the line and field synchronous signals from the input signals, the identification of the odd-even fields is realized by utilizing the characteristic of interlacing scanning, the odd-even field scanning is finished at 312.5 lines, namely, the half of 312 lines is finished, and the even-even field scanning is finished at 625 lines. The high level is the start of the odd field scan and the low level is the start of the even field scan. The level at the 50% position of the row sync rising edge is detected as shown to the left in fig. 2.
Since the level at 50% of this sync rising edge is the basis for determining the row, field sync signal, how to extract is very important. Generally, the sampling point is not exactly 50% out, so a deviation of the synchronization signal is generated. By correcting, the accumulated phase deviations need to be recorded and stored. As shown in the right side of fig. 2, a, C are sampling points, and B is the 50% level position of the synchronization pulse.
For field sync signal extraction, when the row length is greater than 1300, labeled 1, representing the entire row, less than 1300, labeled 0, representing half the row. 1300 is taken because NTSC half behavior 858 (PAL half behavior 864), NTSC full behavior 1716 (PAL full behavior 1728), and 1300 is approximately the middle of these two values. After this the sequence of line synchronisation signals is converted into a bit stream, which sequence 010 occurs during the field synchronisation according to the characteristics of the television signal, as shown in figure 3, i.e. once this sequence 010 has been detected, this is indicated as a field synchronisation.
As can be seen from the characteristics of the television signal, during a frame, the odd fields start with integer rows and the even fields start with half rows. To facilitate detection of parity fields, taking 8 bits, NTSC field sync will detect 10000010 or 00000010, while PAL will detect 11000010 or 10000010, so only one is detected as a field sync signal. At this time (let the parity Field represent signal field0_1=1), if the same, the even Field (field0_1=0). The opposite is true in the case of PAL. As shown in fig. 4.
(2) The luminance signal and the chrominance signal are combined together in a staggered manner in the composite television signal, and the decoded output is luminance and two color difference signals which are mutually independent, the two color difference signals are required to be obtained by quadrature demodulation of the chrominance signal, and color crosstalk is required to be avoided, so that the luminance signal and the chrominance signal in the received composite television signal need to be separated before.
In order to improve the accuracy of the Y/C separation, a vanity filter is employed. The luminance signal and the chrominance signal are separated in a spectrally separated manner according to the principle of spectral interleaving of the video signal and the comb filter characteristics of the comb filter. As shown in fig. 5:
If it is assumed that signals of two adjacent lines are correlated, the data of the first line is y+c, and the signals of the adjacent lines are Y-C because the chrominance subcarriers of the two adjacent lines (NTSC system, PAL system are separated by a line) are 180 degrees out of phase. Thus, the two-row signals are added to obtain the luminance signal Y, and the two-row signals are subtracted to obtain the chrominance signal C.
The full television signal waveform is shown in fig. 6. In one scan line, the scan line is composed of a line synchronization pulse, a blanking pulse, a color burst pulse, and an image signal waveform. The line frequency is 15625KHz and the corresponding line period is 64 microseconds. The blanking pulse occupies about 15 microseconds, the relative level is 0.75, the line synchronization pulse is located in the blanking pulse, the width is 4.7 microseconds, the relative level is 1, the color synchronization pulse is located on the back shoulder of the line synchronization pulse, and the color synchronization pulse is composed of about ten subcarriers with a certain phase. The remaining approximately 49 microseconds is used to transfer a row of images, i.e., a row in the image matrix. The relative level of the image signal ranges from 0.125 to 0.75, wherein 0.125 is the white signal level and 0.75 is the black signal level.
The image signal in the all-television signal is composed of a luminance signal and a color difference signal. Wherein, the two color difference signals are overlapped with the brightness signal after quadrature balance modulation. The image signal S in the color full television signal in the NTSC system is expressed as:
S=Y+Vcos21/4fct+Usin21/4fct
Wherein Y, V, U are respectively a luminance signal and two compression color difference signals, the composite synchronous signal and the luminance signal are separated by an amplitude separation method, and the chrominance signal and the color burst signal are separated by a time separation method. As shown in fig. 7.
(3) For chroma demodulation, the expression for the NTSC chroma signal e c (t) is:
ec(t)＝Usin(wsct+33°)+Vcos(wsct+33°)
and (3) multiplying the local sine and cosine signals which are 2 times of the same frequency and phase as the received chrominance subcarriers and added with 33-degree offset phase respectively to obtain:
[Usin(wsct+33°)+Vcos(wsct+33°)]*2sin(wsct+33°)
=U-Ucos(2wsct+66°)+Vsin(2wsct+66°)
[Usin(wsct+33°)+Vcos(wsct+33°)]*2cos(wsct+33°)
=V+Vcos(2wsct+66°)+Usin(2wsct+66°)
obviously, the signal shown above is passed through a low pass filter to obtain the desired U, V color difference signal. Similarly, the expression of the chroma signal e c (t) of PAL format is:
ec(t)＝U(t)sinwsct+φk(t)V(t)coswsct
Wherein phi k (t) is a switching function with values of +1 and-1 row by row. The synchronized local oscillation signals are respectively obtained by adjusting offset phases and switching functions to be 2sinw sc t and 2 phi k(t)coswsc t, and then are multiplied by e c (t), and then pass through a low-pass filter to obtain the required U, V color difference signals.
4) Video playing
Analyzing the selected signals, recovering the image picture of the analog television signals after analyzing, and transmitting the image picture into a playing module for displaying.
The invention detects and analyzes the two system signals through the access of the analog television signal, the frequency spectrum scanning, the carrier wave detection, the modulation identification and the signal demodulation, and realizes the analysis and the playing of the analog television signal in a pure software interpretation mode.
The invention adopts an interlaced scanning mode for analyzing two modes, when a picture is scanned, one field is scanned and is half of pixels of a frame of picture, and two fields are scanned, namely, all odd fields and even fields are scanned, so that the whole frame of picture is realized. For PAL mode, 50 fields are scanned in one second, namely, the scanning line of the television scanning 25 frames is 625 lines, the odd field is in front, and the even field is in back. For NYSC modes, the field frequency is 60 fields per second, the frame frequency is 30 frames per second, the scanning line is 525 lines, and the processing of analog television signals is realized through a software algorithm, so that the limitations of the traditional hardware circuit can be overcome, and the efficiency and the flexibility of signal processing are improved.
The embodiment also provides a software analysis system for the analog television signal, which comprises an analysis module, wherein the analysis module executes the software analysis method for the analog television signal.
The present embodiment also provides a non-transitory computer readable storage medium storing computer instructions which, when executed by a processor, implement the software analysis method for analog television signals.
As shown in fig. 8, this embodiment further provides an electronic device, including:
A memory 201 and a processor 202, said memory 201 and said processor 202 being communicatively connected to each other, said memory 201 having stored therein computer instructions, said processor 202 executing said computer instructions to thereby perform said one software analysis method for analog television signals.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, and it should be noted that it is possible for those skilled in the art to make several improvements and modifications without departing from the technical principle of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.
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Cited By (2)
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| CN120263949A (en) * | 2025-06-05 | 2025-07-04 | 理工全盛(北京)科技有限公司 | Data processing method and device for unmanned aerial vehicle image transmission |
| CN120321377A (en) * | 2025-06-16 | 2025-07-15 | 理工全盛(北京)科技有限公司 | Improved method and system for color synchronization in digital decoding of FPV drones |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN120263949A (en) * | 2025-06-05 | 2025-07-04 | 理工全盛(北京)科技有限公司 | Data processing method and device for unmanned aerial vehicle image transmission |
| CN120263949B (en) * | 2025-06-05 | 2025-12-30 | 理工全盛(北京)科技有限公司 | Data processing method and device for unmanned aerial vehicle image transmission |
| CN120321377A (en) * | 2025-06-16 | 2025-07-15 | 理工全盛(北京)科技有限公司 | Improved method and system for color synchronization in digital decoding of FPV drones |
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