Color synchronization improvement method and system for FPV unmanned aerial vehicle digital decoding

Abstract

The invention belongs to the technical field of unmanned aerial vehicle digital decoding, and particularly relates to a color synchronization improvement method and system for FPV unmanned aerial vehicle digital decoding. The method comprises the following steps: receiving an analog image transmission signal of the FPV unmanned aerial vehicle to obtain a discrete digital composite video signal stream; carrying out bright-color separation on signals in the discrete digital composite video signal stream to obtain a chrominance signal, a brightness signal and a synchronization signal; according to the frame synchronization signal, comparing the chrominance signal with a standard chrominance bar signal, and carrying out cured frame phase difference compensation calibration to obtain a chrominance signal for compensating the frame phase difference; performing accumulated phase difference calculation on each line according to the line synchronization signal to obtain a chrominance signal with line phase compensation; and performing RGB image synthesis according to the chrominance signal, the brightness signal and the synchronizing signal with line phase compensation to obtain an FPV unmanned aerial vehicle shooting image with improved color synchronization. Digital decoding is utilized to realize color synchronization simply, and a complex costa phase-locked loop is not needed.

Description

Technical Field

[0001] This application belongs to the technical field of UAV digital decoding, and particularly relates to a method and system for improving color synchronization in FPV UAV digital decoding. Background Art

[0002] Currently, there is a type of FPV UAV on the market that uses analog video transmission. Such UAVs use unencrypted analog signals to transmit UAV images in real time. For such UAVs, an FPV digital decoding method is used to interpret the analog video transmission signal, and then, according to the image processing method, the transmitted video image is compared with the real-time topographic map to obtain the position of the UAV.

[0003] However, the problem with the current solution is that during the signal transmission process, there is a large interference and serious channel distortion. Summary of the Invention

[0004] Based on this, in order to solve the above technical problems, it is necessary to provide a method and system for improving color synchronization in FPV UAV digital decoding.

[0005] In a first aspect, this application provides a method for improving color synchronization in FPV UAV digital decoding, including: Receiving the analog video transmission signal of the FPV UAV to obtain a discrete digital composite video signal stream; Separating the bright and color signals in the discrete digital composite video signal stream to obtain a chrominance signal, a luminance signal, and a synchronization signal, where the synchronization signal includes a horizontal synchronization signal and a frame synchronization signal; Comparing the chrominance signal with a standard chrominance bar signal according to the frame synchronization signal, and performing fixed-frame phase difference compensation calibration to obtain a chrominance signal with compensated frame phase difference; Calculating the cumulative phase difference for each row according to the horizontal synchronization signal to obtain a chrominance signal with horizontal phase compensation; Performing RGB image synthesis according to the chrominance signal with horizontal phase compensation, the luminance signal, and the synchronization signal to obtain an FPV UAV captured image with improved color synchronization.

[0006] In some implementable ways, the step of receiving the analog video transmission signal of the FPV UAV to obtain a discrete digital composite video signal stream includes: Receiving the analog video transmission signal of the FPV UAV, and using quadrature demodulation to convert the analog video transmission signal into an analog baseband signal; Increasing the sampling rate of the analog baseband signal to obtain a discrete digital composite video signal stream.

[0007] In some implementable ways, the step of separating the luminance and chrominance of the signals in the discrete digital composite video signal stream to obtain a chrominance signal, a luminance signal, and a synchronization signal includes: Using a low-pass filter to filter out the high-frequency chrominance components in the discrete digital composite video signal stream to obtain the luminance signal; Using a band-pass filter to extract the chrominance in the discrete digital composite video signal stream to obtain the chrominance signal; Based on the horizontal synchronization signal and vertical synchronization pulses in the discrete digital composite video signal stream, the horizontal synchronization signal and the frame synchronization signal are correspondingly obtained.

[0008] In some implementable ways, the step of comparing the chrominance signal with a standard chrominance bar signal according to the frame synchronization signal, performing fixed-frame phase difference compensation calibration, and obtaining a chrominance signal with compensated frame phase difference includes: Collecting the chrominance components of the standard chrominance bar signal and introducing a fixed-frame phase difference to obtain the sine term and cosine term of the standard chrominance bar signal; Separating the sine and cosine in the chrominance signal to obtain the sine term and cosine term of the chrominance signal; Comparing the sine term and cosine term of the standard chrominance bar signal with the sine term and cosine term of the chrominance signal to obtain a phase offset; Adjusting the fixed-frame phase difference according to the phase offset to obtain a compensated frame phase difference; Compensating the chrominance signal according to the compensated frame phase difference to obtain the chrominance signal with compensated frame phase difference.

[0009] In some implementable ways, the step of calculating the cumulative phase difference for each row according to the horizontal synchronization signal and obtaining a chrominance signal with row phase compensation includes: Based on the horizontal synchronization signal, identifying the start time of each row of video signals and establishing a row number index; Calculating a fixed row time difference according to the actual duration of a single row sampled by the digital acquisition device and the standard single-row theoretical duration to obtain a phase error; Based on the horizontal synchronization signal, incrementing the row number index for each trigger of the horizontal synchronization signal and compensating the phase of the current row to obtain a carrier signal with compensated phase alignment; Processing the chrominance signal according to the carrier signal with compensated phase alignment to obtain the chrominance signal with row phase compensation.

[0010] In some implementable ways, the step of performing RGB image synthesis based on the chrominance signal, luminance signal, and synchronization signal with line phase compensation to obtain an FPV drone captured image with improved color synchronization includes: Using the synchronization signal to perform line synchronization and frame synchronization to form timing alignment; Performing amplitude scaling on the luminance signal to obtain a scaled luminance signal; Constructing an RGB pixel matrix; Under the condition of the timing alignment, according to the RGB pixel matrix, performing matrix conversion on the chrominance signal with line phase compensation and the scaled luminance signal to obtain an FPV drone captured image with improved color synchronization.

[0011] In a second aspect, the present application provides a color synchronization improvement system for FPV drone digital decoding, which is applied to the color synchronization improvement method for FPV drone digital decoding described above. The system includes: A receiving unit for receiving the analog video transmission signal of the FPV drone to obtain a discrete digital composite video signal stream; A separating unit for separating the signals in the discrete digital composite video signal stream into a chrominance signal, a luminance signal, and a synchronization signal, where the synchronization signal includes a line synchronization signal and a frame synchronization signal; A processing unit for comparing the chrominance signal with a standard chrominance bar signal according to the frame synchronization signal to perform fixed-frame phase difference compensation calibration to obtain a chrominance signal with compensated frame phase difference; An accumulation processing unit for calculating the cumulative phase difference for each row according to the line synchronization signal to obtain a chrominance signal with line phase compensation; A result unit for performing RGB image synthesis based on the chrominance signal with line phase compensation, the luminance signal, and the synchronization signal to obtain an FPV drone captured image with improved color synchronization.

[0012] In a third aspect, the present application provides a computer device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the method described above are implemented.

[0013] In a fourth aspect, the present application provides a computer storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method described above are implemented.

[0014] In a fifth aspect, the present application provides a computer program, characterized in that when the computer program is executed by a processor, the steps of the method described above are implemented.

[0015] Beneficial effects: An improved method for color synchronization in the digital decoding of FPV drones, which includes receiving the analog video transmission signal of the FPV drone to obtain a discrete digital composite video signal stream; separating the signals in the discrete digital composite video signal stream into chrominance signals, luminance signals, and synchronization signals, where the synchronization signals include horizontal synchronization signals and frame synchronization signals; comparing the chrominance signals with standard chrominance bar signals according to the frame synchronization signals to perform fixed-frame phase difference compensation calibration to obtain chrominance signals with compensated frame phase differences; calculating the cumulative phase difference for each row according to the horizontal synchronization signals to obtain chrominance signals with row phase compensation; performing RGB image synthesis according to the chrominance signals with row phase compensation, luminance signals, and synchronization signals to obtain the images captured by the FPV drone with improved color synchronization. This application simplifies the implementation of color synchronization using digital decoding and does not require a complex Costa phase-locked loop. According to the time error between digital decoding and the actual analog signal, the phase of the color synchronization filter is adjusted, and the phase of the color synchronization filter is different for different rows; according to the chrominance difference between digital decoding and the actual analog signal, the initial phase of the color synchronization filter is adjusted, and the initial phase of the filter is the same for all frames. Brief Description of the Drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of the present application or in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0017] Figure 1 It is a flowchart of an improved method for color synchronization in the digital decoding of FPV drones in one embodiment.

[0018] Figure 2 It is a schematic diagram of standard chrominance bars of an improved method for color synchronization in the digital decoding of FPV drones in one embodiment.

[0019] Figure 3 It is a diagram showing the frame phase error performance of an improved method for color synchronization in the digital decoding of FPV drones in one embodiment.

[0020] Figure 4 It is a schematic diagram of chrominance bars after frame phase difference compensation of an improved method for color synchronization in the digital decoding of FPV drones in one embodiment.

[0021] Figure 5 It is a schematic diagram showing different phase errors for each row of an improved method for color synchronization in the digital decoding of FPV drones in one embodiment.

[0022] Figure 6 It is a schematic diagram after compensation improvement for a color synchronization improvement method in the digital decoding of FPV drones in an embodiment. Specific implementation manner

[0023] To facilitate the understanding of this application, the following will describe this application more comprehensively with reference to the relevant attached drawings. Embodiments of this application are shown in the attached drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of this application more thorough and comprehensive.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the specification of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0025] It can be understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element.

[0026] The following explains some terms related to this application to facilitate the understanding of this application: The local oscillator (LO) is the core component used for frequency conversion in a radio system. By generating a highly stable reference signal and mixing it with the input signal, it realizes the up-conversion (transmission) or down-conversion (reception) of the signal.

[0027] As Figure 1 shown, in a first aspect, this application provides a method for improving color synchronization in the digital decoding of FPV drones. The method includes: S100, receiving the analog video transmission signal of the FPV drone to obtain a discrete digital composite video signal stream.

[0028] Among them, the analog radio frequency signal transmitted by the FPV drone is converted into a discrete digital baseband signal, so as to provide a high-precision signal source for subsequent chrominance synchronization compensation.

[0029] Specifically, obtaining the discrete digital composite video signal stream may include the following steps: S101, receiving the analog video transmission signal of the FPV drone and converting the analog video transmission signal into an analog baseband signal by using the method of quadrature demodulation.

[0030] Specifically, after receiving the analog video transmission signal emitted by the FPV drone, its center frequency is a specific frequency point (e.g., 5.8 GHz). This analog video transmission signal consists of a carrier wave superimposed with noise that has been amplitude- and phase-modulated.

[0031] Two orthogonal local oscillator signals (with frequencies close to the center frequency of the radio frequency signal) are used for mixing with the radio frequency signal. Among them, the deviation between the local oscillator frequency and the center frequency of the radio frequency signal needs to be controlled within ±20 kHz to avoid the color synchronization frequency deviation exceeding the subsequent calibration capability. Then, the mixed signal is separated into an in-phase signal (I channel) and a quadrature signal (Q channel) through a low-pass filter. Next, the I channel and the Q channel are combined into a complex-form analog baseband signal, completely retaining the amplitude, phase, and chrominance information of the original signal.

[0032] S102, increase the sampling rate of the analog baseband signal to obtain a discrete digital composite video signal stream.

[0033] Specifically, the analog baseband signal is initially sampled at a sampling rate of at least twice the signal bandwidth (e.g., 12 MHz, corresponding to a 6 MHz bandwidth). Next, the sampling rate is increased to 48 MHz (4 times the initial sampling rate) through an interpolation filter, significantly improving the time domain resolution. Ensure the phase error compensation accuracy for each subsequent line of the signal (e.g., the cumulative error within 64 microseconds of a single line time is controllable). Finally, a discrete digital composite video signal stream is generated. Exemplarily, the interval between each sampling point is 20.83 nanoseconds (corresponding to a 48 MHz sampling rate), providing sufficient time resolution for line-level phase compensation.

[0034] The above steps achieve the fast and stable recovery of the color synchronization signal without relying on a complex phase-locked loop, providing a high-precision signal basis for subsequent frame / line phase compensation. The effects are as follows: Simplified quadrature demodulation. The traditional scheme relies on a phase-locked loop (such as a Costa loop) to track the frequency deviation. This scheme circumvents the complex phase-locked design and reduces the hardware complexity by fixing the local oscillator frequency + frequency deviation constraint (<20 kHz).

[0035] High-precision sampling. The oversampling (48 MHz) and interpolation filtering techniques improve the time resolution of the digital signal by 4 times, avoiding the problem of oblique accumulation of line phase errors caused by insufficient sampling rate in the traditional scheme (e.g., the tilt of the black front shoulder).

[0036] Calibration compatibility. By initially calibrating the device to solidify the frame-level phase difference (such as compensating for the chrominance bar mutation per frame), subsequent dynamic adjustment is not required, adapting to the fixed frequency deviation characteristics of different decoding devices.

[0037] S200, separate the signals in the discrete digital composite video signal stream into chrominance signals, luminance signals, and synchronization signals.

[0038] Among them, the synchronization signal includes a line synchronization signal and a frame synchronization signal. The luminance signal (Y), chrominance signal (C), and synchronization signal (Hsync / Frame Sync) are separated from the discrete digital composite video signal stream.

[0039] Specifically, obtaining the chrominance signal, luminance signal, and synchronization signal may include the following steps: S201, using a low-pass filter to filter out the high-frequency chrominance components in the discrete digital composite video signal stream to obtain the luminance signal.

[0040] Specifically, the cut-off frequency of the low-pass filter parameter can be 4.2 MHz (covering the luminance signal bandwidth of NTSC / PAL systems). Input the composite video signal into the low-pass filter to filter out high-frequency chrominance components (such as NTSC 3.58 MHz, PAL 4.43 MHz) and noise. Output a signal containing only low-frequency luminance components. Next, according to the black level of the synchronization pulse, calibrate the DC component of the luminance signal to eliminate the baseline drift during transmission, thereby obtaining a stable luminance signal.

[0041] S202, using a band-pass filter to extract the chrominance in the discrete digital composite video signal stream to obtain the chrominance signal.

[0042] Specifically, exemplary parameters of the band-pass filter can be a center frequency of NTSC 3.58 MHz, PAL 4.43 MHz, and a bandwidth of ±1 MHz, covering the chrominance subcarrier frequency band.

[0043] For the acquisition of the chrominance signal, the composite video signal can be input into the band-pass filter to retain the chrominance components and color sync pulses (Burst), filter out low-frequency luminance and high-frequency noise, and obtain the chrominance signal. Next, use the line synchronization (Hsync) in the synchronization signal to determine the start time of each line. After triggering at the rising edge of the line synchronization signal, wait for a fixed time interval (such as NTSC 4.7 μs) to locate the start position of the color sync pulse and obtain the phase reference of the color sync pulse. Then, according to the standard amplitude of the color sync pulse (such as 0.3 Vp-p), adjust the chrominance signal gain to the specification range to obtain the chrominance signal.

[0044] S203, corresponding to obtain the line synchronization signal and the frame synchronization signal according to the line synchronization signal and field synchronization pulse in the discrete digital composite video signal stream.

[0045] Specifically, for the composite video signal stream, amplitude threshold detection is performed to identify the sync pulses below the black level (for example, the line sync width is 4.7 μs, and the field sync is a wide pulse sequence), the analog pulses are converted into digital level signals (0 / 1), shaped, and noise interference is eliminated to obtain the horizontal sync signal Hsync (Horizontal Synchronization) and the frame sync signal Frame Sync. Among them, the frame sync signal represents combining the field sync signals of two consecutive fields (odd field + even field) into one frame sync signal.

[0046] It should be noted that after obtaining the sync signals, a time reference is provided for luma / chroma separation to ensure the timing alignment of the luma signal and the chroma signal. In the timing alignment, the line sync marks the start of each line and is used for the timing alignment of luma / chroma separation; the frame sync marks the start of the complete frame to ensure the continuity of cross-frame signal processing.

[0047] S300, according to the frame sync signal, compare the chroma signal with the standard chroma bar signal, perform fixed-frame phase difference compensation calibration, and obtain the chroma signal with compensated frame phase difference.

[0048] Specifically, obtaining the chroma signal with compensated frame phase difference may include the following steps: S301, collect the chroma components of the standard chroma bar signal and introduce a fixed-frame phase difference to obtain the sine term and cosine term of the standard chroma bar signal.

[0049] Specifically, the purpose is to provide a reference signal without phase difference for comparison. The introduced fixed-frame phase difference is the fixed frame phase difference introduced by the device's RF circuit (constant for each frame), and it is set to 0 in the standard chroma bar signal. Among them, the standard chroma bar signal ( ) expression (ideally without phase difference): ; Among them, : the standard color difference reference value, the known color difference component defined by the standard chroma bar (such as 75% color bar); : the color burst frequency.

[0050] Generate through a digital signal generator to ensure that its color burst phase has no deviation ( , that is, the fixed-frame phase difference is 0). It is also necessary to store 's reference waveform for subsequent comparison.

[0051] S302, separate the sine and cosine in the chroma signal to obtain the sine term and cosine term of the chroma signal.

[0052] Specifically, receive the chroma signal ( ) expression: ; Among them, : Chrominance signal component, representing the difference information of the image color; : Chrominance subcarrier frequency, the standard carrier frequency defined by the FPV protocol (such as 4.435e6 hz for PAL and 3.58e6 hz for NTSC); : Fixed frame phase difference, the constant phase deviation per frame caused by the device radio frequency circuit (such as local oscillator frequency offset); : Line cumulative phase difference, the phase deviation of each line caused by the incomplete synchronization between the digital sampling rate and the analog signal line period (subsequent line compensation processing is required, not involved here for the time being); : V signal modulation coefficient, a time-related function in the NTSC system (for anti-color distortion) and a fixed constant in the PAL system.

[0053] Furthermore, a digital filter (such as a matched filter) can be used to separate the chrominance signal, so as to extract the sine term (U component) and cosine term (V component) respectively.

[0054] S303, compare the sine term and cosine term of the standard chrominance bar signal with the sine term and cosine term of the chrominance signal to obtain the phase offset.

[0055] Specifically, detect the fixed frame phase difference introduced by the device through phase difference comparison .

[0056] Comparison method: At the starting point of each frame (triggered by the frame synchronization signal), perform quadrature mixing comparison between the actual signal component and the ideal signal component: Actual signal component:

[0057] Ideal signal component:

[0058] Integrate and after mixing, and calculate through the arctangent operation: ; Among them, : Sine term of the actual signal received by the device (including ); : Frame period, determined by the frame synchronization signal (PAL: 40 ms, NTSC: 33.3 ms); 、 : Ideal reference carrier (without ).

[0059] The phase difference between the actual signal and the ideal signal is extracted by using orthogonal mixing integration.

[0060] S304. Adjust the phase difference of the solidified frame according to the phase offset amount to obtain the phase difference of the solidified frame.

[0061] Specifically, the calculation of the compensation value:

[0062] where : the reverse phase compensation amount, which is used to offset the .

[0063] Exemplarily, write into the non-volatile memory of the device. The frame phase error is caused by the radio frequency of the device and will not change after the device is selected. Therefore, the compensation value (phase difference of the solidified frame) only needs to be calibrated once.

[0064] S305. Compensate the chrominance signal according to the compensated frame phase difference to obtain the chrominance signal with the compensated frame phase difference.

[0065] Specifically, generate the compensated reference carrier: ; Mixing and filtering: Mix the received chrominance signal with the corrected carrier, and extract the compensated UV signal through a low-pass filter: ; where respectively represent U and V after compensating the frame phase difference.

[0066] S400. Calculate the cumulative phase difference for each row according to the line synchronization signal to obtain the chrominance signal with line phase compensation.

[0067] Specifically, obtaining the chrominance signal with line phase compensation may include the following steps: S401. Identify the start time of each row of the video signal according to the line synchronization signal and establish a line number index.

[0068] Specifically, detect the line synchronization signal Hsync from the digitized sampling signal to calibrate the start time of each row, establish a line number counter or a line number index (Hindex), which starts from 0 and increases row by row with the line synchronization pulse.

[0069] S402. Calculate the fixed line time difference according to the actual duration of a single row sampled by the digitized acquisition device and the standard single row theoretical duration to obtain the phase error.

[0070] Specifically, a time difference is calculated between the standard single-line theoretical duration specified by the standard FPV protocol and the actual single-line duration sampled by the digital acquisition device to obtain a fixed-line time difference. Next, the fixed-line time difference is converted into a phase error. , and the calculation formula is: ; where, : fixed-line time difference; : color burst frequency.

[0071] S403. According to the line synchronization signal, the line number index is incremented each time the line synchronization signal is triggered, and the phase of the current line is compensated to obtain a carrier signal with phase alignment after compensation.

[0072] Specifically, the line synchronization pulse in each line synchronization signal generated by dynamic phase compensation triggers the increment of Hindex; in this way, the compensation phase of the current line is calculated The formula is: ; where, : current line number; : fixed phase error / line; : fixed frame phase difference.

[0073] Next, dynamic carrier generation is performed to generate a local quadrature carrier aligned with the current line phase: Sine component: ; Cosine component: ; It should be noted that the compensation phase increases linearly with the line number, canceling the phase accumulation error caused by the fixed sampling rate; the phase of the carrier signal matches the actual phase of the current line signal, avoiding the tracking delay of the traditional phase-locked loop.

[0074] S404. According to the carrier signal with phase alignment after compensation, the chrominance signal is processed to obtain the chrominance signal with line phase compensation.

[0075] Specifically, the chrominance signal is multiplied by the compensated carrier signal: Sine channel: ; Cosine channel: .

[0076] By the phase-compensated carrier, the U / V spectrum of the chrominance difference signal is shifted to the baseband. In this way, by filtering out the high-frequency components, the baseband chrominance difference signal is retained.

[0077] Sine channel output: baseband U signal; Cosine channel output: baseband ktV signal (kt is the modulation coefficient of the V signal, which is a time-related function (for anti-color distortion) in the NTSC system and a fixed constant in the PAL system, same as above). The compensated mixing operation concentrates the chrominance signals U / V in the low-frequency band and retains the interference signals in the high-frequency band; next, a low-pass filter (LPF) is used to eliminate high-frequency interference without the need for complex closed-loop control of a phase-locked loop.

[0078] S500. Based on the chrominance signal with line phase compensation, the luminance signal, and the synchronization signal, perform RGB image synthesis to obtain an FPV drone captured image with improved color synchronization.

[0079] Specifically, the steps to obtain an FPV drone captured image with improved color synchronization may include the following: S501. Use the synchronization signal to perform line synchronization and frame synchronization to form timing alignment.

[0080] Specifically, line synchronization includes line synchronization pulse detection. Extract the line synchronization pulse (Hsync) from the digitized video signal, and the start time of each line can be determined by detecting the level jump. Trigger the line number counter (Hindex) to increment row by row to establish a line-level timing reference. Frame synchronization includes frame synchronization reset. Detect the frame synchronization pulse (Fsync) to mark the start of the frame, reset Hindex = 0, and ensure that the line number of each frame starts counting from 0 to align with Hindex in the chrominance compensation phase formula.

[0081] S502. Perform amplitude scaling on the luminance signal to obtain a scaled luminance signal.

[0082] Linearly scale the luminance signal (Y) according to the standard dynamic range defined by the FPV protocol (such as PAL: 0 - 700mV) and normalize it to the [0, 1] interval. And suppress high-frequency noise in the luminance signal through a low-pass filter, with the cut-off frequency set to 1 / 2 of the chrominance subcarrier frequency (such as PAL: 2.17MHz).

[0083] S503. Construct an RGB pixel matrix.

[0084] Exemplarily, determine the number of lines per frame (such as PAL: 625 lines, 576 valid lines) and the number of valid pixels per line (such as 720 pixels) according to the FPV protocol, and initialize the RGB matrix as .

[0085] S504. Under the condition of the timing alignment, according to the RGB pixel matrix, perform matrix conversion on the chrominance signal with line phase compensation and the scaled luminance signal to obtain an FPV drone captured image with improved color synchronization.

[0086] Specifically, the U / V components of the chrominance signal separated with line phase compensation obtained in the foregoing steps and the normalized luminance signal Y are input into the RGB pixel matrix for conversion: ; Wherein, the numbers in the formula are only for illustrative purposes. Additionally, if there are coefficients (such as NTSC anti-color distortion), then adjust the V channel to be . Fill the RGB matrix in row number order, and the frame synchronization signal triggers the output of the entire frame of data. The clock frequency is consistent with the FPV video transmission protocol (such as PAL: 13.5 MHz).

[0087] Embodiment: In traditional digital decoding, since the input F is mixed with a large amount of interference and channel distortion after passing through the channel, it is difficult to lock using a Costa phase-locked loop ; resulting in difficulty in correctly recovering the chrominance signal in a series of subsequent processes.

[0088] The present application provides an improved method for color synchronization in digital decoding of FPV drones, including the following methods: The frequency points of the digital acquisition device and the FPV drone meet the demodulation requirements, and the error is less than 20 kHz; The FPV signal collected digitally, after a series of conversions, the obtained chrominance signal is as follows: ; Assume , and adopt a standard color bar such as Figure 2 , the frame phase error performance is as Figure 3 , and the color bar information mutates within one frame. Figure 4 is the color bar after frame phase difference compensation.

[0089] Through testing with a standard color bar, solidify the frame phase difference and perform compensation to make ; Since the frame phase error is caused by the radio frequency of the detection device, once the device is selected, the frame phase difference no longer changes, and each device only needs to be calibrated and compensated once; Since the time of each frame of the FPV standard is fixed, but the fixed time and sampling error brought by digital decoding result in the phase error of each row not being 0, and the phase error of each row is different, such as Figure 5 , Figure 5 The arrows in the figure indicate before the phase error correction, and not all the arrows in the figure are shown, only for illustrative purposes.

[0090] Digital sampling can use a single frequency and does not perform line synchronization or calibration for each row. The digital sampling rate and the standard FPV signal generate different phase differences for each row, which will have an accumulative effect; the black front shoulder should be vertical, but the accumulative error makes the black front shoulder a slanted line.

[0091] Due to the fixed sampling rate, the usage time of each row of the standard FPV is fixed, and this fixed time difference is ; a fixed phase error is generated for each row , when making compensation, the line number of each row can be used to compensate each row; use

[0092] to perform spectral shifting on the original UV. After low-pass filtering, UV information is obtained, as Figure 6 shown, Figure 6 as indicated by the arrow in

[0093] In summary, an improved method for color synchronization in the digital decoding of FPV drones in this application has the following beneficial effects: 1: By adopting digital decoding of SDR, color synchronization is easily achieved without the need for a complex Costa phase-locked loop.

[0094] 2: By adopting digital decoding of SDR, according to the time error between the digital decoding and the actual analog signal, the phase of the color synchronization filter is adjusted, and the phase of the color synchronization filter is different for different rows.

[0095] 3: By adopting digital decoding of SDR, according to the chrominance difference between the digital decoding and the actual analog signal, the initial phase of the color synchronization filter is adjusted, and the initial phases of the filters for all frames are the same.

[0096] In the second aspect, this application provides an improved system for color synchronization in the digital decoding of FPV drones, which is applied to the improved method for color synchronization in the digital decoding of FPV drones described above. The system includes: A receiving unit, configured to receive the analog video transmission signal of the FPV drone to obtain a discrete digital composite video signal stream; A separation unit, configured to perform bright-dark separation on the signals in the discrete digital composite video signal stream to obtain a chrominance signal, a luminance signal, and a synchronization signal, where the synchronization signal includes a line synchronization signal and a frame synchronization signal; A processing unit, configured to compare the chrominance signal with a standard chrominance bar signal according to the frame synchronization signal, perform compensation calibration of the fixed frame phase difference, and obtain a chrominance signal with compensated frame phase difference; An accumulation processing unit, configured to calculate the cumulative phase difference for each row according to the line synchronization signal to obtain a chrominance signal with line phase compensation; A result unit, configured to perform RGB image synthesis according to the chrominance signal with line phase compensation, the luminance signal, and the synchronization signal to obtain an FPV drone captured image with improved color synchronization.

[0097] In a third aspect, the present application provides a computer device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the foregoing method are implemented.

[0098] In a fourth aspect, the present application provides a computer storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the foregoing method are implemented.

[0099] In a fifth aspect, the present application provides a computer program, characterized in that when the computer program is executed by a processor, the steps of the foregoing method are implemented.

[0100] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, storage, database, or other medium used in the various embodiments provided by the present application can include non-volatile and / or volatile memories. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory can include random access memory (RAM) or an external cache. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and Rambus dynamic RAM (RDRAM), etc.

[0101] The various embodiments in the present disclosure are described in a progressive manner. For the same or similar parts among the various embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments.

[0102] The protection scope of the present disclosure is not limited to the above embodiments. Obviously, those skilled in the art can make various changes and deformations to the present disclosure without departing from the scope and spirit of the present disclosure. If these changes and deformations belong to the scope of the claims of the present disclosure and their equivalent technologies, the intention of the present disclosure also includes these changes and deformations.

Claims

1. An improved method for color synchronization in the digital decoding of FPV drones, characterized in that the method Including: Receiving the analog video transmission signal of the FPV drone to obtain a discrete digital composite video signal stream; Separating the bright and color signals in the discrete digital composite video signal stream to obtain a chrominance signal, a luminance signal, and a synchronization signal, where the synchronization signal includes a horizontal synchronization signal and a frame synchronization signal; Comparing the chrominance signal with a standard chrominance bar signal according to the frame synchronization signal to perform fixed frame phase difference compensation calibration to obtain a chrominance signal with compensated frame phase difference; Calculating the cumulative phase difference for each row according to the horizontal synchronization signal to obtain a chrominance signal with horizontal phase compensation; Performing RGB image synthesis according to the chrominance signal with horizontal phase compensation, the luminance signal, and the synchronization signal to obtain an FPV drone captured image with improved color synchronization.

2. The method for improving the color synchronization in the digital decoding of FPV drones according to claim 1, wherein The step of receiving the analog video transmission signal of the FPV drone to obtain a discrete digital composite video signal stream includes: Receiving the analog video transmission signal of the FPV drone and converting the analog video transmission signal into an analog baseband signal by using an orthogonal demodulation method; Increasing the sampling rate of the analog baseband signal to obtain a discrete digital composite video signal stream.

3. The method for improving the color synchronization in the digital decoding of FPV drones according to claim 1, wherein The step of separating the bright and color signals in the discrete digital composite video signal stream to obtain a chrominance signal, a luminance signal, and a synchronization signal includes: Using a low-pass filter to filter out the high-frequency chrominance components in the discrete digital composite video signal stream to obtain the luminance signal; Using a band-pass filter to extract the chrominance in the discrete digital composite video signal stream to obtain the chrominance signal; Corresponding to obtain the horizontal synchronization signal and the frame synchronization signal according to the horizontal synchronization signal and the vertical synchronization pulse in the discrete digital composite video signal stream.

4. The method for improving color synchronization in digital decoding of FPV drones according to claim 1, wherein The step of comparing the chrominance signal with a standard chrominance bar signal according to the frame synchronization signal to perform fixed frame phase difference compensation calibration to obtain a chrominance signal with compensated frame phase difference includes: Collecting the chrominance components of the standard chrominance bar signal and introducing a fixed frame phase difference to obtain the sine term and cosine term of the standard chrominance bar signal; Separating the sine and cosine in the chrominance signal to obtain the sine term and cosine term of the chrominance signal; Comparing the sine term and cosine term of the standard chrominance bar signal with the sine term and cosine term of the chrominance signal to obtain a phase offset; Adjusting the fixed frame phase difference according to the phase offset to obtain a compensated frame phase difference; Compensating the chrominance signal according to the compensated frame phase difference to obtain a chrominance signal with compensated frame phase difference.

5. The method for improving the color burst in the digital decoding of FPV drones according to claim 1, characterized in that, The step of calculating the cumulative phase difference for each row according to the horizontal synchronization signal to obtain a chrominance signal with horizontal phase compensation includes: Identifying the start time of each row of video signals according to the horizontal synchronization signal and establishing a row number index; Calculating a fixed row time difference according to the actual single-row duration sampled by the digital acquisition device and the standard single-row theoretical duration to obtain a phase error; Incrementing the row number index for each trigger of the horizontal synchronization signal according to the horizontal synchronization signal and compensating the phase of the current row to obtain a carrier signal with phase alignment after compensation; Process the chrominance signal according to the compensated and phase-aligned carrier signal to obtain the chrominance signal with line phase compensation.

6. The method for improving the color burst in the digital decoding of FPV drones according to claim 1, characterized in that, The step of performing RGB image synthesis based on the chrominance signal with line phase compensation, the luminance signal, and the synchronization signal to obtain the FPV drone captured image with improved color synchronization includes: Use the synchronization signal to perform line synchronization and frame synchronization to form timing alignment. Perform amplitude scaling on the luminance signal to obtain the scaled luminance signal. Construct an RGB pixel matrix. Under the condition of the timing alignment, perform matrix transformation on the chrominance signal with line phase compensation and the scaled luminance signal according to the RGB pixel matrix to obtain the FPV drone captured image with improved color synchronization.

7. A digital decoding chrominance synchronization improvement system for FPV drones, characterized in that, Applied to the method for improving color synchronization in the digital decoding of FPV drones according to any one of claims 1-6, the system includes: A receiving unit for receiving the analog video transmission signal of the FPV drone to obtain a discrete digital composite video signal stream. A separating unit for separating the signals in the discrete digital composite video signal stream into a chrominance signal, a luminance signal, and a synchronization signal, where the synchronization signal includes a line synchronization signal and a frame synchronization signal. A processing unit for comparing the chrominance signal with a standard chrominance bar signal according to the frame synchronization signal, performing fixed-frame phase difference compensation calibration to obtain a chrominance signal with compensated frame phase difference. An accumulation processing unit for calculating the cumulative phase difference for each row according to the line synchronization signal to obtain a chrominance signal with line phase compensation. A result unit for performing RGB image synthesis based on the chrominance signal with line phase compensation, the luminance signal, and the synchronization signal to obtain the FPV drone captured image with improved color synchronization.

8. A computer device, comprising a memory and a processor, the memory storing a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 6.

9. A computer storage medium, on which a computer program is stored, characterized in that, When the computer program is executed by the processor, it implements the steps of the method according to any one of claims 1 to 6.

10. A computer program, characterized in that, When the computer program is executed by the processor, it implements the steps of the method according to any one of claims 1 to 6.

Images