Improved method and system for color synchronization in digital decoding of FPV unmanned aerial vehicle

Abstract

The application belongs to the technical field of digital decoding of unmanned aerial vehicles, and particularly relates to a color synchronization improvement method and system for digital decoding of FPV unmanned aerial vehicles. The method comprises the following steps: receiving an analog image transmission signal of an FPV unmanned aerial vehicle to obtain a discrete digital composite video signal stream; performing brightness and color separation on the signals in the discrete digital composite video signal stream to obtain a chrominance signal, a luminance signal and a synchronization signal; comparing the chrominance signal with a standard chrominance bar signal according to a frame synchronization signal to perform solid frame phase difference compensation calibration and obtain a chrominance signal with compensated frame phase difference; performing cumulative phase difference calculation on each row according to a line synchronization signal to obtain a chrominance signal with line phase compensation; and performing RGB image synthesis according to the chrominance signal with line phase compensation, the luminance signal and the synchronization signal to obtain a color synchronization improved FPV unmanned aerial vehicle shooting image. The color synchronization is simply realized by digital decoding, and a complex costa phase-locked loop is not required.

Description

Technical Field

[0001] This application belongs to the field of digital decoding technology for unmanned aerial vehicles (UAVs), and particularly relates to an improved method and system for color synchronization in digital decoding of FPV UAVs. Background Technology

[0002] Currently, there is an FPV drone on the market that uses analog image transmission. This type of drone uses unencrypted analog signals to transmit drone images in real time. For this type of drone, an FPV digital decoding method is used to interpret the analog image transmission signal. Then, according to image processing methods, the transmitted image is compared with a real-time terrain map to obtain the drone's location.

[0003] However, the current solution has the problem of significant interference and severe channel distortion during signal transmission. Summary of the Invention

[0004] Therefore, it is necessary to provide an improved method and system for color synchronization in digital decoding of FPV drones to address the aforementioned technical problems.

[0005] Firstly, this application provides an improved method for color synchronization in digital decoding of FPV drones, including:

[0006] Receive analog image transmission signals from FPV drones to obtain discrete digitized composite video signal streams;

[0007] The signals in the discrete digitized composite video signal stream are subjected to chroma separation to obtain chroma signals, luminance signals and synchronization signals, wherein the synchronization signals include line synchronization signals and frame synchronization signals;

[0008] Based on the frame synchronization signal, the chromaticity signal is compared with the standard chromaticity bar signal, and the fixed frame phase difference compensation calibration is performed to obtain the chromaticity signal with compensated frame phase difference;

[0009] Based on the line synchronization signal, the cumulative phase difference is calculated for each line to obtain a chroma signal with line phase compensation;

[0010] Based on the chroma signal, luminance signal, and synchronization signal with line phase compensation, RGB image synthesis is performed to obtain an FPV drone-captured image with improved color synchronization.

[0011] In some feasible embodiments, the step of receiving the analog image transmission signal from the FPV drone to obtain a discrete digitized composite video signal stream includes:

[0012] The system receives the analog image transmission signal from the FPV UAV and converts it into an analog baseband signal using quadrature demodulation.

[0013] By increasing the sampling rate of the analog baseband signal, a discrete digitized composite video signal stream can be obtained.

[0014] In some feasible embodiments, the step of performing chroma separation on the signals in the discrete digitized composite video signal stream to obtain chroma signals, luminance signals, and synchronization signals includes:

[0015] The high-frequency chroma components in the discrete digitized composite video signal stream are filtered out using a low-pass filter to obtain the luminance signal;

[0016] The chroma signal is obtained by extracting the chroma from the discrete digitized composite video signal stream using a bandpass filter.

[0017] The line synchronization signal and the frame synchronization signal are obtained based on the line synchronization signal and the field synchronization pulse in the discrete digitized composite video signal stream.

[0018] In some feasible methods, the step of comparing the chroma signal with a standard chroma bar signal based on the frame synchronization signal, performing fixed frame phase difference compensation calibration, and obtaining a chroma signal with compensated frame phase difference includes:

[0019] The chromaticity components of the standard chromaticity bar signal are acquired, and the phase difference of the fixed frame is introduced to obtain the sine and cosine terms of the standard chromaticity bar signal.

[0020] The sine and cosine components of the chrominance signal are separated to obtain the sine and cosine terms of the chrominance signal;

[0021] The phase shift is obtained by comparing the sine and cosine terms of the standard chroma bar signal with the sine and cosine terms of the chroma signal.

[0022] Based on the phase offset, adjust the phase difference of the solidified frame to obtain the phase difference of the compensated frame;

[0023] The chroma signal is compensated based on the phase difference of the compensated frame to obtain the chroma signal of the phase difference of the compensated frame.

[0024] In some implementable methods, the step of calculating the cumulative phase difference for each line based on the line synchronization signal to obtain a chroma signal with line phase compensation includes:

[0025] Based on the line synchronization signal, identify the start time of each line of video signal and establish a line number index;

[0026] Based on the actual duration of a single line sampled by the digital acquisition device and the theoretical duration of a standard single line, the fixed line time difference is calculated to obtain the phase error;

[0027] Based on the row synchronization signal, the row number index is incremented for each row synchronization signal, and the current row phase is compensated to obtain a compensated phase-aligned carrier signal.

[0028] The chroma signal is processed based on the compensated phase-aligned carrier signal to obtain the chroma signal with line phase compensation.

[0029] In some feasible methods, the step of performing RGB image synthesis based on the chroma signal, luminance signal, and synchronization signal with line phase compensation to obtain an FPV drone-captured image with improved color synchronization includes:

[0030] Using the aforementioned synchronization signal, line synchronization and frame synchronization are performed to achieve timing alignment;

[0031] The brightness signal is amplitude scaled to obtain a scaled brightness signal;

[0032] Construct an RGB pixel matrix;

[0033] With the timing aligned, matrix transformation is performed on the chroma signal with row phase compensation and the scaled luminance signal according to the RGB pixel matrix to obtain an FPV drone-captured image with improved color synchronization.

[0034] Secondly, this application provides an improved color synchronization system for digital decoding of FPV drones, applied to the aforementioned improved color synchronization method for digital decoding of FPV drones. The system includes:

[0035] The receiving unit is used to receive the analog image transmission signal from the FPV UAV and obtain a discrete digitized composite video signal stream.

[0036] The separation unit is used to perform luminance-chrominance separation on the signals in the discrete digitized composite video signal stream to obtain chrominance signals, luminance signals and synchronization signals, wherein the synchronization signals include line synchronization signals and frame synchronization signals;

[0037] The processing unit is used to compare the chroma signal with the standard chroma bar signal according to the frame synchronization signal, perform fixed frame phase difference compensation calibration, and obtain a chroma signal with compensated frame phase difference;

[0038] The cumulative processing unit is used to calculate the cumulative phase difference for each line based on the line synchronization signal to obtain a chroma signal with line phase compensation.

[0039] The result unit is used to perform RGB image synthesis based on the chroma signal, luminance signal and synchronization signal with line phase compensation to obtain FPV drone-captured images with improved color synchronization.

[0040] Thirdly, this application provides a computer device including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the aforementioned method.

[0041] Fourthly, this application provides a computer storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the aforementioned method.

[0042] Fifthly, this application provides a computer program, characterized in that, when the computer program is executed by a processor, it implements the steps of the aforementioned method.

[0043] Beneficial Effects: A method for improving color synchronization in digital decoding of FPV drones includes receiving analog image transmission signals from an FPV drone to obtain a discrete digitized composite video signal stream; performing luminance-color separation on the signals in the discrete digitized composite video signal stream to obtain a chrominance signal, a luminance signal, and a synchronization signal, wherein the synchronization signal includes a line synchronization signal and a frame synchronization signal; comparing the chrominance signal with a standard chrominance bar signal based on the frame synchronization signal, performing fixed frame phase difference compensation calibration to obtain a chrominance signal with compensated frame phase difference; calculating the cumulative phase difference for each line based on the line synchronization signal to obtain a chrominance signal with line phase compensation; and 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 image with improved color synchronization. This application utilizes a simple digital decoding color synchronization implementation, eliminating the need for a complex Costa phase-locked loop. The phase of the color synchronization filter is adjusted based on the time error between the digital decoding and the actual analog signal. The phase of the color synchronization filter is different for each line. The initial phase of the color synchronization filter is adjusted based on the chromaticity difference between the digital decoding and the actual analog signal. The initial phase of the filter is the same for all frames. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a flowchart of an improved color synchronization method for digital decoding of FPV drones in one embodiment.

[0046] Figure 2 This is a schematic diagram of a standard chromaticity bar for an improved color synchronization method in digital decoding of an FPV drone, as shown in one embodiment.

[0047] Figure 3 This is a frame phase error representation diagram of an improved color synchronization method for digital decoding of an FPV drone in one embodiment.

[0048] Figure 4 This is a schematic diagram of the chroma bar after frame phase difference compensation, which is an improved method for color synchronization in digital decoding of FPV UAVs in one embodiment.

[0049] Figure 5 This is a schematic diagram illustrating the different phase errors of each line in an improved color synchronization method for digital decoding of an FPV drone, as shown in one embodiment.

[0050] Figure 6 This is a schematic diagram illustrating the improved compensation method for color synchronization improvement in digital decoding of FPV drones in one embodiment. Detailed Implementation

[0051] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all couplings of one or more of the associated listed items.

[0053] It is 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 one element from another.

[0054] The following explanations of some terms used in this application are provided to aid in understanding the application:

[0055] The local oscillator (LO) is a core component in a radio system used for frequency conversion. It generates a highly stable reference signal and mixes it with the input signal to achieve up-conversion (transmission) or down-conversion (reception).

[0056] like Figure 1 As shown, in a first aspect, this application provides an improved method for color synchronization in digital decoding of FPV drones, the method comprising:

[0057] The S100 receives analog image transmission signals from the FPV drone and obtains a discrete digitized composite video signal stream.

[0058] In this process, the analog radio frequency signals emitted by the FPV drone are converted into discrete digital baseband signals, thus providing a high-precision signal source for subsequent chromaticity synchronization compensation.

[0059] Specifically, obtaining a discrete digitized composite video signal stream may include the following steps:

[0060] S101, receive the analog image transmission signal from the FPV UAV, and convert the analog image transmission signal into an analog baseband signal using orthogonal demodulation.

[0061] Specifically, after receiving the analog image transmission signal transmitted by the FPV drone, its center frequency is a specific frequency point (e.g., 5.8 GHz). This analog image transmission signal consists of carrier noise superimposed after amplitude and phase modulation.

[0062] Two orthogonal local oscillator signals (with frequencies close to the center frequency of the RF signal) are mixed with the RF signal. The deviation between the local oscillator frequency and the center frequency of the RF signal must be controlled within ±20 kHz to avoid 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) by a low-pass filter. Next, the I-channel and Q-channel signals are combined into a complex analog baseband signal, fully preserving the amplitude, phase, and chromaticity information of the original signal.

[0063] S102 increases the sampling rate of the analog baseband signal to obtain a discrete digitized composite video signal stream.

[0064] Specifically, the analog baseband signal is initially sampled at a sampling rate at least twice the signal bandwidth (e.g., 12MHz, corresponding to a 6MHz bandwidth). Next, an interpolation filter is used to increase the sampling rate to 48MHz (four times the initial sampling rate), significantly improving the temporal resolution. This ensures accurate phase error compensation for each subsequent line of signal (e.g., controllable cumulative error within a single line's 64 microsecond time). Finally, a discrete digitized composite video signal stream is generated; for example, each sampling point is spaced 20.83 nanoseconds apart (corresponding to a 48MHz sampling rate), providing sufficient temporal resolution for line-level phase compensation.

[0065] The above steps, without relying on complex phase-locked loops, achieve rapid and stable recovery of the color synchronization signal, providing a high-precision signal foundation for subsequent frame / line phase compensation. The effect is as follows:

[0066] Quadrature demodulation simplifies the traditional approach, which relies on phase-locked loops (such as Costa loops) to track frequency offset. This approach avoids complex phase-locked loop designs and reduces hardware complexity by fixing the local oscillator frequency and imposing frequency offset constraints (<20 kHz).

[0067] High-precision sampling, oversampling (48 MHz), and interpolation filtering techniques improve the time resolution of digital signals by 4 times, avoiding the problem of skewed accumulation of line phase errors (e.g., tilted black front shoulder) caused by insufficient sampling rate in traditional solutions.

[0068] Calibration compatibility is achieved by fixing the frame-level phase difference through initial device calibration (such as compensation for abrupt changes in chroma bars per frame), eliminating the need for subsequent dynamic adjustments and adapting to the fixed frequency offset characteristics of different decoding devices.

[0069] S200, perform chroma separation on the signals in the discrete digitized composite video signal stream to obtain chroma signal, luminance signal and synchronization signal.

[0070] 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 digitized composite video signal stream.

[0071] Specifically, obtaining the chroma signal, luminance signal, and synchronization signal may include the following steps:

[0072] S201, using a low-pass filter, the high-frequency chroma components in the discrete digitized composite video signal stream are filtered out to obtain the luminance signal.

[0073] Specifically, the low-pass filter's cutoff frequency can be 4.2 MHz (covering the luminance signal bandwidth of NTSC / PAL standards). The composite video signal is input to the low-pass filter to filter out high-frequency chroma components (such as NTSC 3.58 MHz and PAL 4.43 MHz) and noise. The output signal contains only the low-frequency luminance component. Next, based on the black level of the sync pulse, the DC component of the luminance signal is calibrated to eliminate baseline drift during transmission, thereby obtaining a stable luminance signal.

[0074] S202, using a bandpass filter, the chroma in the discrete digitized composite video signal stream is extracted to obtain the chroma signal.

[0075] Specifically, exemplary parameters for a bandpass filter could be a center frequency of NTSC 3.58 MHz, PAL 4.43 MHz, bandwidth of ±1 MHz, and coverage of the chroma subcarrier band.

[0076] To acquire the chroma signal, the composite video signal can be input into a bandpass filter to retain the chroma components and the color sync pulse (Burst), while filtering out low-frequency luminance and high-frequency noise, thus obtaining the chroma signal. Next, the start time of each line is determined using the horizontal sync (Hsync) signal. After the rising edge of the horizontal sync signal is triggered, a fixed time interval (e.g., 4.7 μs for NTSC) is waited for to locate the start position of the color sync pulse, obtaining the phase reference of the color sync pulse. Then, based on the standard amplitude of the color sync pulse (e.g., 0.3 Vp-p), the chroma signal gain is adjusted to the specified range to obtain the chroma signal.

[0077] S203, based on the horizontal synchronization signal and the vertical synchronization pulse in the discrete digitized composite video signal stream, the horizontal synchronization signal and the frame synchronization signal are obtained accordingly.

[0078] Specifically, amplitude threshold detection is performed on the composite video signal stream to identify synchronization pulses below the black level (e.g., horizontal synchronization width of 4.7μs, and field synchronization as 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 synchronization signal Hsync (Horizontal Synchronization) and the frame synchronization signal Frame Sync. The frame synchronization signal represents the merging of the field synchronization signals of two consecutive fields (odd field + even field) into a single frame synchronization signal.

[0079] It should be noted that after obtaining the synchronization signal, a time reference is provided for luminance-chrominance separation, ensuring the timing alignment of the luminance and chrominance signals. In timing alignment, the line synchronization marker marks the beginning of each line for timing alignment of luminance / chrominance separation; the frame synchronization marker marks the beginning of the entire frame to ensure the continuity of signal processing across frames.

[0080] S300: Based on the frame synchronization signal, compare the chroma signal with the standard chroma bar signal, perform fixed frame phase difference compensation calibration, and obtain a chroma signal with compensated frame phase difference.

[0081] Specifically, obtaining the chroma signal with compensated frame phase difference may include the following steps:

[0082] S301, acquire the chromaticity components of the standard chromaticity bar signal, and introduce the phase difference of the solidified frame to obtain the sine and cosine terms of the standard chromaticity bar signal.

[0083] Specifically, the purpose is to provide a reference signal with no phase difference for comparison, introducing a fixed frame phase difference (constant per frame) introduced by the device's RF circuitry, which is then set to 0 in the standard chroma bar signal. Expression (ideal no phase difference):

[0084] ;

[0085] in, Standard color difference reference value, a known color difference component defined by a standard color bar (such as a 75% color bar); Color synchronization frequency.

[0086] Generated by a digital signal generator To ensure that its color synchronization phase is without deviation ( (That is, the phase difference of the solidified frame is 0). Storage is also required. The reference waveform is used for subsequent comparison.

[0087] S302, the sine and cosine of the chrominance signal are separated to obtain the sine and cosine terms of the chrominance signal.

[0088] Specifically, receiving chroma signals ( )expression:

[0089] ;

[0090] in, Color difference signal components represent color difference information in an image; Color synchronization frequency, a standard carrier frequency defined by the FPV protocol (e.g., 4.435e6Hz for PAL, 3.58e6Hz for NTSC). Fixed frame phase difference: a constant phase deviation per frame caused by the device's radio frequency circuitry (such as local oscillator frequency offset); : Line cumulative phase difference, caused by the incomplete synchronization between the digital sampling rate and the line period of the analog signal, resulting in line-by-line phase deviation (requires subsequent line compensation processing, which is not discussed here). V signal modulation coefficient, which is a time-dependent function in NTSC (used to combat color distortion) and a fixed constant in PAL.

[0091] Furthermore, digital filters (such as matched filters) can be used to separate the color difference signals, thereby extracting the sine (U component) and cosine (V component) terms respectively.

[0092] S303, compare the phase difference between the sine and cosine terms of the standard chroma bar signal and the sine and cosine terms of the chroma signal to obtain the phase offset.

[0093] Specifically, the fixed frame phase difference introduced by the phase difference comparison detection device. .

[0094] Comparison method:

[0095] At the beginning of each frame (triggered by the frame synchronization signal), the actual signal component and the ideal signal component are orthogonally mixed and compared:

[0096] Actual signal components:

[0097] Ideal signal components:

[0098] Will and After mixing, the integral is calculated using the arctangent operation. :

[0099] ;

[0100] in, The actual sine wave term of the signal received by the device (including...) ); Frame period, determined by the frame synchronization signal (PAL: 40 ms, NTSC: 33.3 ms). , Ideal reference carrier (none) ).

[0101] The phase difference between the actual signal and the ideal signal is extracted using quadrature mixing integration.

[0102] S304, adjust the phase difference of the solidified frame according to the phase offset to obtain the phase difference of the solidified frame.

[0103] Specifically, the compensation value is calculated as follows:

[0104]

[0105] in, Reverse phase compensation amount, used to offset the phase introduced by the device. .

[0106] For example, Write to the device's non-volatile memory. The frame phase error is caused by the device's radio frequency and does not change after the device is selected; therefore, the compensation value (fixed frame phase difference) only needs to be calibrated once.

[0107] S305, based on the phase difference of the compensation frame, the chroma signal is compensated to obtain the chroma signal of the phase difference of the compensation frame.

[0108] Specifically, the compensated reference carrier is generated:

[0109] ;

[0110] Mixing and filtering:

[0111] Received chroma signal Mixed with a corrected carrier, the compensated UV signal is extracted through a low-pass filter:

[0112] ;

[0113] in, , representing U and V after compensating for the frame phase difference, respectively.

[0114] S400: For each line, the cumulative phase difference is calculated based on the line synchronization signal to obtain a chroma signal with line phase compensation.

[0115] Specifically, obtaining a chrominance signal with line phase compensation may include the following steps:

[0116] S401, Based on the line synchronization signal, identify the start time of each line of video signal and establish a line number index.

[0117] Specifically, the start time of each line is determined by detecting the line synchronization signal Hsync from the digital sampling signal, and a line number counter or line number index (Hindex) is established, which increments line by line starting from 0 with the line synchronization pulse.

[0118] S402, based on the actual duration of a single line sampled by the digital acquisition device and the theoretical duration of a standard single line, calculate the fixed line time difference to obtain the phase error.

[0119] Specifically, the time difference is calculated based on the theoretical duration of a standard single line as specified in the standard FPV protocol and the actual duration of a single line sampled by the digital acquisition device to obtain the fixed line time difference. Next, the fixed line time difference is converted into phase error. The calculation formula is:

[0120] ;

[0121] in, Fixed row time difference; Color synchronization frequency.

[0122] S403, based on the line synchronization signal, the line number index is incremented for each line synchronization signal, and the current line phase is compensated to obtain a compensated phase-aligned carrier signal.

[0123] Specifically, the dynamic phase compensation generates a line synchronization pulse in each line synchronization signal, which triggers the Hindex to increment; thus, the current line compensation phase is calculated. The formula is:

[0124] ;

[0125] in, : Current line number; Fixed phase error per row; : Fixed frame phase difference.

[0126] Next, dynamic carrier generation is performed to generate local orthogonal carriers that are phase-aligned with the current row:

[0127] Sine component: Cosine component: ;

[0128] It should be noted that the compensation phase The linear increase of the line number offsets 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 traditional phase-locked loops.

[0129] S404, Based on the compensated phase-aligned carrier signal, the chroma signal is processed to obtain the chroma signal with line phase compensation.

[0130] Specifically, the chroma signal Multiply by the compensated carrier signal:

[0131] Sine wave channel: Cosine channel: .

[0132] By using a phase-compensated carrier wave, the U / V spectrum of the color difference signal is shifted to the baseband. In this way, the baseband color difference signal is preserved by filtering out high-frequency components.

[0133] 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 correlation function in NTSC (used to combat color distortion) and a fixed constant in PAL, as before). The compensated mixing operation concentrates the color difference signals U / V in the low-frequency band, while the interference signal remains in the high-frequency band; next, a low-pass filter (LPF) is used to eliminate high-frequency interference, eliminating the need for complex phase-locked loop closed-loop control.

[0134] S500: Based on the chroma signal, luminance signal and synchronization signal with line phase compensation, RGB image synthesis is performed to obtain an FPV drone-captured image with improved color synchronization.

[0135] Specifically, obtaining color-synchronized improved FPV drone-captured images may include the following steps:

[0136] S501, using the synchronization signal, perform line synchronization and frame synchronization to achieve timing alignment.

[0137] Specifically, line synchronization includes line synchronization pulse detection, extracting the line synchronization pulse (Hsync) from the digitized video signal, and determining the start time of each line through level transition detection. The line number counter (Hindex) is triggered to increment line by line, establishing a line-level timing reference. Frame synchronization includes frame synchronization reset, detecting the frame synchronization pulse (Fsync) to mark the start of the frame, resetting Hindex to 0, ensuring that the line number of each frame starts counting from 0, and aligning with the Hindex in the chroma compensation phase formula.

[0138] S502, the brightness signal is amplitude scaled to obtain a scaled brightness signal.

[0139] The luminance signal (Y) is linearly scaled and normalized to the [0,1] range according to the standard dynamic range defined by the FPV protocol (e.g., PAL: 0-700mV). High-frequency noise in the luminance signal is suppressed by a low-pass filter, and the cutoff frequency is set to 1 / 2 of the chroma subcarrier frequency (e.g., PAL: 2.17MHz).

[0140] S503, constructs an RGB pixel matrix.

[0141] For example, the number of lines per frame (e.g., PAL: 625 lines, 576 effective lines) and the number of effective pixels per line (e.g., 720 pixels) are determined according to the FPV protocol, and the RGB matrix is ​​initialized as follows: .

[0142] S504, under the condition of time alignment, according to the RGB pixel matrix, the chroma signal with row phase compensation and the scaled luminance signal are matrix transformed to obtain an FPV drone image with improved color synchronization.

[0143] Specifically, the U / V components of the chroma signal with row phase compensation obtained in the aforementioned steps, along with the normalized luminance signal Y, are input into the RGB pixel matrix for conversion:

[0144] ;

[0145] The numbers in the formula are merely illustrative examples. Additionally, if there are... The coefficient (such as NTSC anti-color distortion) is then adjusted to the V channel. The RGB matrix is ​​filled 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 image transmission protocol (e.g., PAL: 13.5MHz).

[0146] Example:

[0147] Traditional digital decoding suffers from significant interference and channel distortion after passing through the channel, making it difficult to lock onto the signal using a Costa phase-locked loop. This makes it difficult for subsequent processes to correctly recover the chroma signal.

[0148] This application provides an improved method for color synchronization in digital decoding of FPV drones, including the following methods:

[0149] The digital acquisition equipment and FPV drone frequency points meet the demodulation requirements, with an error of less than 20kHz.

[0150] The FPV signal from digital centralized acquisition, after a series of conversions, yields the following chromaticity signal:

[0151] ;

[0152] Assumption Using standard color bars, such as Figure 2 Frame phase error performance is as follows Figure 3 The chroma bar information changes abruptly within a frame. Figure 4 The chroma bar after frame phase difference compensation.

[0153] The phase difference of the cured frames is compensated by testing with standard chromaticity bars, so that... Since the frame phase error is caused by the radio frequency of the detection equipment, once the equipment is selected, the frame phase difference no longer changes, and each equipment only needs to be calibrated and compensated once. Because the FPV standard has a fixed frame time, but the error between the fixed time and sampling caused by digital decoding results in a non-zero phase error for each line, and the phase error is different for each line, such as... Figure 5 , Figure 5 The middle arrow points to the area before phase error correction. The arrows in the figure do not represent all areas and are only illustrative examples.

[0154] Digital sampling uses a single frequency and does not perform line synchronization or line-by-line calibration. The digital sampling rate and the standard FPV signal produce different phase differences for each line, resulting in a cumulative effect; the black front shoulder should be vertical, but the cumulative error makes the black front shoulder appear slanted.

[0155] Because the sampling rate is fixed, the usage time per line in a standard FPV is fixed; this fixed time difference is... Each row produces a fixed phase error. When making compensation, you can use the row number for each row. Compensate each row; use phase-compensated...

[0156] The original UV spectrum is shifted. UV information is then obtained after low-pass filtering, such as... Figure 6 As shown, Figure 6 The middle arrow points to the area after phase error correction. The arrows in the figure do not represent all areas and are only illustrative examples.

[0157] In summary, the improved method for seed and color synchronization in digital decoding of FPV UAVs proposed in this application has the following beneficial effects:

[0158] 1: Using SDR digital decoding, color synchronization is easily achieved without the need for a complex Costa PLL.

[0159] 2: Using SDR digital decoding, the phase of the color synchronization filter is adjusted according to the time error between the digital decoding and the actual analog signal. The phase of the color synchronization filter is different depending on the row.

[0160] 3: Using SDR digital decoding, the initial phase of the color synchronization filter is adjusted according to the chromaticity difference between the digital decoder and the actual analog signal, and the initial phase of the filter is the same for all frames.

[0161] Secondly, this application provides an improved color synchronization system for digital decoding of FPV drones, applied to the aforementioned improved color synchronization method for digital decoding of FPV drones. The system includes:

[0162] The receiving unit is used to receive the analog image transmission signal from the FPV UAV and obtain a discrete digitized composite video signal stream.

[0163] The separation unit is used to perform luminance-chrominance separation on the signals in the discrete digitized composite video signal stream to obtain chrominance signals, luminance signals and synchronization signals, wherein the synchronization signals include line synchronization signals and frame synchronization signals;

[0164] The processing unit is used to compare the chroma signal with the standard chroma bar signal according to the frame synchronization signal, perform fixed frame phase difference compensation calibration, and obtain a chroma signal with compensated frame phase difference;

[0165] The cumulative processing unit is used to calculate the cumulative phase difference for each line based on the line synchronization signal to obtain a chroma signal with line phase compensation.

[0166] The result unit is used to perform RGB image synthesis based on the chroma signal, luminance signal and synchronization signal with line phase compensation to obtain FPV drone-captured images with improved color synchronization.

[0167] Thirdly, this application provides a computer device including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of the aforementioned method.

[0168] Fourthly, this application provides a computer storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the aforementioned method.

[0169] Fifthly, this application provides a computer program, characterized in that, when the computer program is executed by a processor, it implements the steps of the aforementioned method.

[0170] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. 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 external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), Rambus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0171] The various embodiments in this disclosure are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0172] The scope of protection of this disclosure is not limited to the embodiments described above. Obviously, those skilled in the art can make various modifications and variations to this disclosure without departing from its scope and spirit. If such modifications and variations fall within the scope of the claims of this disclosure and their equivalents, then the intent of this disclosure also includes such modifications and variations.

Claims

1. An improved method for color synchronization in digital decoding of FPV unmanned aerial vehicles, characterized in that the method... The method comprises the following steps: receiving an analog image transmission signal of an FPV unmanned aerial vehicle to obtain a discrete digitized composite video signal stream; performing brightness and color separation on the signal in the discrete digitized composite video signal stream to obtain a chrominance signal, a luminance signal, and a synchronization signal, wherein the synchronization signal comprises 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 solidified frame phase difference compensation calibration to obtain a chrominance signal with compensated frame phase difference; identifying the starting time of each line of video signal according to the horizontal synchronization signal to establish a line number index; performing fixed line time difference calculation according to the actual length of a single line sampled by a digitized collection device and the theoretical length of a standard single line to obtain a phase error; increasing the line number index according to the horizontal synchronization signal each time the horizontal synchronization signal is triggered, and compensating the phase of the current line to obtain a carrier signal with compensated and phase-aligned phase; processing the chrominance signal according to the carrier signal with compensated and phase-aligned phase to obtain a chrominance signal with line phase compensation; performing RGB image synthesis according to the chrominance signal with line phase compensation, the luminance signal, and the synchronization signal to obtain an FPV unmanned aerial vehicle shooting image with improved color synchronization.

2. The method for improving color synchronization in digital decoding of FPV drones according to claim 1, characterized in that, The step of receiving an analog image transmission signal of an FPV unmanned aerial vehicle to obtain a discrete digitized composite video signal stream comprises: receiving the analog image transmission signal of the FPV unmanned aerial vehicle, and converting the analog image transmission signal into an analog baseband signal by using a quadrature demodulation method; increasing the sampling rate of the analog baseband signal to obtain a discrete digitized composite video signal stream.

3. The method for improving color synchronization in digital decoding of FPV drones according to claim 1, characterized in that, The step of performing brightness and color separation on the signal in the discrete digitized composite video signal stream to obtain a chrominance signal, a luminance signal, and a synchronization signal comprises: filtering out high-frequency chrominance components in the discrete digitized composite video signal stream by using a low-pass filter to obtain the luminance signal; extracting the chrominance in the discrete digitized composite video signal stream by using a band-pass filter to obtain the chrominance signal; correspondingly obtaining the horizontal synchronization signal and the frame synchronization signal according to the horizontal synchronization signal and the field synchronization pulse in the discrete digitized composite video signal stream.

4. The method for improving color synchronization in digital decoding of FPV drones according to claim 1, characterized in that, The step of comparing the chrominance signal with a standard chrominance bar signal according to the frame synchronization signal to perform solidified frame phase difference compensation calibration to obtain a chrominance signal with compensated frame phase difference comprises: collecting the chrominance components of the standard chrominance bar signal and introducing a solidified frame phase difference to obtain the sine term and the cosine term of the standard chrominance bar signal; separating the sine and the cosine in the chrominance signal to obtain the sine term and the cosine term of the chrominance signal; comparing the phase difference of the sine term and the cosine term of the standard chrominance bar signal with the sine term and the cosine term of the chrominance signal to obtain a phase offset; adjusting the solidified 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.

5. The method for improving color synchronization in digital decoding of FPV drones according to claim 1, characterized in that, The step of performing RGB image synthesis according to the color difference signal with row phase compensation, the luminance signal and the synchronization signal to obtain the color synchronization improved FPV unmanned aerial vehicle shooting image, comprising: Performing line synchronization and frame synchronization using the synchronization signal to form timing alignment; Performing amplitude scaling on the luminance signal to obtain a scaled luminance signal; Constructing an RGB pixel matrix; In the case of timing alignment, performing matrix conversion on the color difference signal with row phase compensation and the scaled luminance signal according to the RGB pixel matrix to obtain the color synchronization improved FPV unmanned aerial vehicle shooting image.

6. An improved system for color synchronization for FPV drone digital decoding, characterized by, The system applied to the color synchronization improvement method for FPV unmanned aerial vehicle digital decoding in any one of claims 1-5, comprising: A receiving unit for receiving analog video transmission signals of an FPV unmanned aerial vehicle to obtain a discrete digitized composite video signal stream; A separation unit for performing luminance and color separation on signals in the discrete digitized composite video signal stream to obtain a color difference signal, a luminance signal and a synchronization signal, wherein the synchronization signal includes a line synchronization signal and a frame synchronization signal; A processing unit for comparing the color difference signal with a standard color bar signal according to the frame synchronization signal to perform fixed frame phase difference compensation calibration to obtain a color difference signal with compensated frame phase difference; An accumulation processing unit for identifying the starting time of each line of video signal according to the line synchronization signal to establish a line number index; According to the actual single-line time length sampled by the digital acquisition device and the standard single-line theoretical time length, performing fixed line time difference calculation to obtain phase error; According to the line synchronization signal, incrementing the line number index for each line synchronization signal, and compensating the phase of the current line to obtain a compensated phase-aligned carrier signal; According to the compensated phase-aligned carrier signal, processing the color difference signal to obtain a color difference signal with row phase compensation; A result unit for performing RGB image synthesis according to the color difference signal with row phase compensation, the luminance signal and the synchronization signal to obtain the color synchronization improved FPV unmanned aerial vehicle shooting image. 7.A computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the computer device is configured to perform the method according to any one of claims 1-6 when the computer program is executed by the processor. The processor executes the computer program to realize the steps of the method in any one of claims 1 to 5.

8. A computer storage medium having stored thereon a computer program, characterized in that The computer program is executed by the processor to realize the steps of the method in any one of claims 1 to 5.

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