A method, apparatus, device, and storage medium for multi-camera time synchronization

Abstract

The present application relates to the technical field of multi-camera system, and discloses a multi-camera time synchronization method, device, equipment and storage medium, comprising: setting the refresh rate of screen display content and the frequency of screen PWM modulation wave, the frequency of PWM modulation wave is less than or equal to half of the refresh rate of screen display content; controlling multiple cameras to shoot dynamic screen, and selecting a group of photos with the same screen display content shot by different cameras; taking one of the cameras as a reference camera, and taking one of the dark lines in the photo shot by the reference camera as a reference position; comparing the dark line positions in the photos shot by other cameras with the reference position to obtain the pixel difference set of each camera; and adjusting the time of each camera to be synchronized with the time of the reference camera according to the pixel difference set of each camera. The present application converts the photo pixels into time statistics by using the dark lines generated on the screen during PWM dimming, has high alignment accuracy and low investment cost.

Description

Technical Field

[0001] This invention relates to the field of multi-camera system technology, and specifically to a multi-camera time synchronization method, apparatus, device, and storage medium. Background Technology

[0002] In order to improve the efficiency of image data acquisition, multiple cameras are usually used to shoot at the same time. However, different cameras have different exposure and shooting times, so it is necessary to take certain measures to standardize the time of different cameras.

[0003] Currently, network time synchronization, hardware synchronization signals, and event synchronization are commonly used methods to unify the time of multiple cameras. In certain specific situations, hardware synchronization solutions (network time synchronization and hardware synchronization signals) are difficult to implement, and event synchronization is the only viable method for time synchronization. The conventional approach for camera time synchronization is "high-frequency real-world events + short camera exposures." Multiple cameras capturing the same high-frequency event during a short exposure are considered to have reached the same time reference for all cameras, with an accuracy equal to the reciprocal of the frequency. The higher the event frequency, the more accurate the synchronization. However, generating high-frequency events in reality is difficult. For example, high-frequency displays are expensive and their frequencies are still not high enough, or specialized hardware is required, resulting in high production costs and relatively low synchronization accuracy. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problems of complexity and high cost of the existing multi-camera time synchronization methods, thereby providing a multi-camera time synchronization method, apparatus, device and storage medium.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a multi-camera time synchronization method, comprising: setting the refresh rate of the screen display content and the frequency of the screen PWM modulation wave, wherein the frequency of the PWM modulation wave is less than or equal to half the refresh rate of the screen display content; controlling multiple cameras to capture dynamic screen images, and selecting a set of photos taken by different cameras that have the same screen display content; using one of the cameras as a reference camera, and using the position of a dark ripple in the photo taken by the reference camera as a reference position; comparing the dark ripple position in the photos taken by other cameras with the reference position to obtain a set of pixel differences for each camera; and adjusting the time of each camera to synchronize with the time of the reference camera according to the set of pixel differences for each camera.

[0007] The multi-camera time synchronization method provided by this invention determines the position of dark stripes generated when adjusting screen brightness using PWM and combines this with low-frequency synchronization events to convert photo pixels into time statistics, thereby synchronizing the time of each camera with the time of a reference camera. The synchronization accuracy between multiple cameras can reach an alignment accuracy of 0.1 milliseconds. The synchronization method is simple and utilizes the side effect of screen flicker caused by bright and dark stripes in PWM brightness adjustment for time measurement. It does not require the use of a high refresh rate screen or customized hardware, resulting in low investment costs.

[0008] In one optional implementation, the process of setting the refresh rate of the screen display content and the frequency of the screen PWM modulation wave includes: setting the screen background to white.

[0009] The multi-camera time synchronization method provided by this invention uses a white screen background, which can clearly identify the stripes generated by PWM and reduce the interpretation error.

[0010] In one alternative implementation, the process of controlling multiple cameras to capture images of a dynamic screen includes: controlling the multiple cameras to maintain the same short exposure parameters to capture the screen in high-speed burst mode.

[0011] The multi-camera time synchronization method provided by this invention enables multiple cameras to accurately capture the same screen content during high-speed continuous shooting, reducing errors in the subsequent time synchronization process and shortening the overall synchronization time.

[0012] In one alternative implementation, the process of using one of the cameras as a reference camera and using the position of one of the dark fringes in the photo taken by the reference camera as a reference position includes: selecting one of the multiple dark fringes in the photo taken by the reference camera as a reference dark fringe; and recording the reference position of the reference dark fringe using a scale on the screen.

[0013] The multi-camera time synchronization method provided by this invention has a built-in ruler on the screen. When the camera captures the content displayed on the screen, the dark patterns generated by PWM and the ruler are displayed on the photo, which makes it easy to read the accurate position of each dark pattern through the photo, and to convert pixel statistics into time statistics, which facilitates time conversion in subsequent steps.

[0014] In one optional implementation, the process of comparing the positions of dark patterns in photos taken by other cameras with reference positions to obtain the pixel difference set of each camera includes: recording the positions of all dark patterns in each photo using a scale on the screen; calculating the difference between the position of each dark pattern in each photo and the reference position, and using all the differences in each photo as the pixel difference set of the camera corresponding to that photo.

[0015] In one optional implementation, the process of adjusting the time of each camera to synchronize with the time of a reference camera based on the pixel difference set of each camera includes: obtaining the pixel difference that meets the preset conditions in the pixel difference set of each camera as the pixel adjustment value of the corresponding camera; calculating the time adjustment value of each camera based on the refresh rate of the screen display content, the wavelength of the PWM modulation wave and the pixel adjustment value of each camera; and adjusting the time of the corresponding camera to synchronize with the time of the reference camera based on the time adjustment value of each camera.

[0016] The multi-camera time synchronization method provided by this invention compares the dark patterns in the photos taken by each camera with the reference position to calculate the pixel difference for each photo. The method then selects the smallest pixel difference from each set as the time adjustment value for the camera corresponding to that photo, thereby quickly and accurately converting pixels to time and reducing computational complexity.

[0017] In one alternative implementation, the time adjustment value Δt for each camera i The calculation formula is:

[0018]

[0019] Where N is the refresh rate of the screen display content, w is the wavelength of the PWM modulation wave, and the unit is pixels, Δw i Δt is the pixel adjustment value for the i-th camera. i The unit is seconds.

[0020] Secondly, the present invention provides a multi-camera time synchronization device, comprising: an initialization module for setting the refresh rate of the screen display content and the frequency of the screen PWM modulation wave, wherein the frequency of the PWM modulation wave is less than or equal to half the refresh rate of the screen display content; an acquisition module for controlling multiple cameras to capture dynamic screen images and selecting a set of photos taken by different cameras that have the same screen display content; a reference module for using one of the cameras as a reference camera and using one of the dark ripple positions in the photos taken by the reference camera as a reference position; a comparison module for comparing the dark ripple positions in the photos taken by other cameras with the reference position to obtain a set of pixel differences for each camera; and an adjustment module for adjusting the time of each camera to synchronize with the time of the reference camera based on the set of pixel differences for each camera.

[0021] Thirdly, the present invention provides a computer device, comprising: a memory and a processor, wherein the memory and the processor are communicatively connected to each other, the memory stores computer instructions, and the processor executes the computer instructions to perform the multi-camera time synchronization method described in the first aspect or any corresponding embodiment thereof.

[0022] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to perform the multi-camera time synchronization method described in the first aspect or any corresponding embodiment thereof. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a flowchart illustrating a multi-camera time synchronization method according to an embodiment of the present invention;

[0025] Figure 2 This is a waveform diagram of PWM modulation according to an embodiment of the present invention;

[0026] Figure 3 This is another flowchart illustrating a multi-camera time synchronization method according to an embodiment of the present invention;

[0027] Figure 4 These are screen display images captured simultaneously by different cameras according to embodiments of the present invention;

[0028] Figure 5 This is another flowchart illustrating a multi-camera time synchronization method according to an embodiment of the present invention;

[0029] Figure 6 This is another flowchart illustrating a multi-camera time synchronization method according to an embodiment of the present invention;

[0030] Figure 7 This is a structural block diagram of a multi-camera time synchronization device according to an embodiment of the present invention;

[0031] Figure 8 This is a schematic diagram of the hardware structure of a computer device according to an embodiment of the present invention. Detailed Implementation

[0032] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] This embodiment provides a multi-camera time synchronization method, such as... Figure 1 As shown, it includes:

[0036] Step S1: Set the refresh rate of the screen display content and the frequency of the screen PWM modulation wave. The frequency of the PWM modulation wave is less than or equal to half of the refresh rate of the screen display content.

[0037] like Figure 2 As shown, because the independently controlled three-color light effects change at different rates with voltage, changing the screen input voltage to adjust screen brightness will cause color distortion in the screen display. Therefore, when adjusting screen brightness, 5V and 0V are usually used alternately to reduce the overall brightness. The time ratio of 5V and 0V is the duty cycle. Due to the persistence of vision, people usually do not perceive the sudden changes in brightness, but rather feel that the screen becomes darker overall. When using a camera for short-exposure high-speed continuous shooting, due to the propagation of the PWM signal, pixels at different positions on the screen will periodically experience a voltage of "high-low-high-low". When a high voltage passes through a certain screen position, that position becomes brighter. In the next time period, the same position passes through a low voltage, and that position becomes darker. When viewed continuously, this results in alternating bright and dark stripes, that is, you can clearly see alternating bright and dark stripes moving.

[0038] For example, the movement of bright and dark stripes will form different phases, which can be accurate to the pixel level. For example, a 240Hz square wave with a 2K pixel phase resolution, the screen occupies about 5 stripes, each stripe is 400 pixels, then it is 100 pixels moved in 1ms, each pixel corresponds to 1 / 100ms, the theoretical time resolution is 1 / 100ms, this resolution is much higher than the 2ms accuracy of a 500Hz refresh rate display.

[0039] Specifically, if the refresh rate of the screen display content is set to N, the screen will refresh the display content once every 1 / N seconds; if the frequency of the screen PWM modulation wave is set to M, and M≤N / 2 is guaranteed; if the total width of the adjacent bright and dark lines generated by the PWM modulation wave on the screen is one cycle, then after setting, the PWM modulation wave will move one cycle every 1 / M seconds.

[0040] Step S2: Control multiple cameras to capture images of the dynamic screen, and select a set of photos taken by different cameras that have the same screen display content.

[0041] Specifically, after controlling multiple cameras to be synchronized to take pictures of the dynamic screen, a set of photos taken by different cameras with the same screen display content is compiled.

[0042] Step S3: Use one of the cameras as the reference camera, and use the position of one of the dark lines in the photo taken by the reference camera as the reference position.

[0043] Step S4: Compare the dark texture positions in photos taken by other cameras with the reference positions to obtain the pixel difference set for each camera.

[0044] Specifically, after selecting a camera as the reference camera, one of the dark lines in the photos taken by the camera is used as the reference position. The dark line positions in photos taken by other cameras are compared to obtain the pixel difference set of each camera.

[0045] Step S5: Adjust the time of each camera to synchronize with the time of the reference camera based on the pixel difference set of each camera.

[0046] Specifically, the pixel difference set of each camera is converted into the corresponding time parameter of that camera, and the time of each camera is adjusted according to the time parameter so that the time of each camera is synchronized with the time of the reference camera.

[0047] The multi-camera time synchronization method provided in this embodiment determines the position of dark lines generated when adjusting screen brightness using PWM and combines this with low-frequency synchronization events to convert photo pixels into time statistics, thereby synchronizing the time of each camera with the time of the reference camera. The synchronization accuracy between multiple cameras can reach an alignment accuracy of 0.1 milliseconds. The synchronization method is simple and utilizes the side effects of PWM brightness adjustment for time measurement. It does not require the use of a high refresh rate screen or hardware customization, resulting in low investment costs.

[0048] In some alternative implementations, the process of setting the refresh rate of the screen display content and the frequency of the screen PWM modulation wave includes setting the screen background to white.

[0049] It should be noted that the screen background can also be any other color that creates a noticeable color difference between the background and the PWM modulated wave pattern.

[0050] In some alternative implementations, the process of controlling multiple cameras to capture images of a dynamic screen includes controlling multiple cameras to maintain the same short exposure parameters to capture the screen in high-speed burst mode.

[0051] Specifically, multiple cameras to be synchronized are controlled to capture images of a dynamic screen with the same short exposure parameters in order to reduce the error between different cameras.

[0052] In some alternative implementations, such as Figure 3 Figure 2 As shown, the process of using one of the cameras as a reference camera and taking the position of one of the dark lines in the photo taken by the reference camera as the reference position includes:

[0053] Step S31: Select one of the multiple dark lines in the photo taken by the reference camera as the reference dark line.

[0054] Step S32: Record the reference position of the reference dark pattern using the ruler on the screen.

[0055] For example, such as Figure 4 As shown, when camera A and camera B simultaneously capture the number 4, these two photos are considered as a set of photos taken by different cameras but with the same screen display content. Camera A is used as the reference camera, and the second dark fringe 'a' in the photo taken by camera A is used as the reference dark fringe. The reference position of the reference dark fringe is read as w1 using the scale on the screen. The total width of the adjacent dark and bright fringes of the PWM modulation wave is one wavelength, and the wavelength of the PWM modulation wave is read as w using the scale.

[0056] In some alternative implementations, such as Figure 5 As shown, the process of comparing the locations of dark lines in photos taken by other cameras with a reference location to obtain the pixel difference set for each camera includes:

[0057] Step S41: Use the ruler on the screen to record the location of all dark lines in each photo.

[0058] Step S42: Calculate the difference between the location of each dark freckle in each photo and the reference position, and use all the differences in each photo as the set of pixel differences of the corresponding camera.

[0059] For example, such as Figure 4 As shown, after reading the positions of each dark fringe in the photo taken by camera B as 0, w2, w3 and w4 respectively through the scale, the difference between the position of each dark fringe in the photo taken by camera B and the reference position w1 is calculated to obtain the pixel difference Δw1, Δw2, Δw3 and Δw4 corresponding to each dark fringe. Δw1, Δw2, Δw3 and Δw4 are used as the pixel difference set of camera B.

[0060] In some alternative implementations, the process of adjusting the time of each camera to synchronize with the time of a reference camera based on the pixel difference set of each camera is as follows: Figure 6 As shown, it includes:

[0061] Step S51: Obtain the pixel difference that meets the preset conditions from the pixel difference set of each camera as the pixel adjustment value of the corresponding camera.

[0062] Specifically, since the screen refreshes the displayed content every 1 / N seconds, the frequency of the screen PWM modulation wave is set to M, and M≤N / 2. Therefore, within every 1 / N seconds, the dark ripple value of the PWM modulation wave can only move a distance less than half its own wavelength. Thus, the pixel difference less than half a wavelength in each camera pixel difference set is selected as the pixel adjustment value of the corresponding camera.

[0063] For example, such as Figure 4 As shown, all pixel differences in the pixel difference set of camera B are compared with half of the PWM modulation wavelength w. Only Δw2 is less than w / 2, and Δw2 is taken as the pixel adjustment value Δw of camera B. B .

[0064] Step S52: Calculate the time adjustment value for each camera based on the refresh rate of the screen display content, the wavelength of the PWM modulation wave, and the pixel adjustment value of each camera.

[0065] Specifically, the time adjustment value Δt for each camera i The calculation formula is:

[0066]

[0067] Where N is the refresh rate of the screen display content, w is the wavelength of the PWM modulation wave, and the unit is pixels, Δw i Δt is the pixel adjustment value for the i-th camera. i The unit is seconds.

[0068] For example, such as Figure 4 As shown, assuming the PWM-modulated dark stripe's direction of movement is from the left side of the screen to the right side, it can be determined that within 1 / N seconds, the movement of the black stripe is less than half a wavelength w. Therefore, it can be determined that camera B's shooting time is earlier than camera A's shooting time, and the time difference (i.e., the time adjustment value) Δt B for:

[0069]

[0070] Step S53: Adjust the time of the corresponding camera to be synchronized with the time of the reference camera based on the time adjustment value of each camera.

[0071] For example, such as Figure 4 As shown, if camera A records its own time as T1 and camera B records its own shooting time as T2, then Δt should be added to camera B's own time T2. BThen, complete the step of synchronizing the time of camera B with the time of camera A.

[0072] This embodiment also provides a multi-camera time synchronization device, which is used to implement the above embodiments and any optional implementation methods, and will not be repeated as already described. As used below, the term "module" can be a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0073] This embodiment provides a multi-camera time synchronization device, such as... Figure 7 As shown, it includes:

[0074] The initialization module 801 is used to set the refresh rate of the screen display content and the frequency of the screen PWM modulation wave. The frequency of the PWM modulation wave is less than or equal to half of the refresh rate of the screen display content.

[0075] The acquisition module 802 is used to control multiple cameras to capture images of a dynamic screen and select a set of photos taken by different cameras that have the same screen display content.

[0076] The reference module 803 is used to use one of the cameras as a reference camera and to use the position of one of the dark lines in the photo taken by the reference camera as the reference position.

[0077] The comparison module 804 is used to compare the positions of dark lines in photos taken by other cameras with the reference positions to obtain the pixel difference set of each camera.

[0078] The adjustment module 805 is used to adjust the time of the camera to synchronize with the time of the reference camera based on the pixel difference set of each camera.

[0079] In this embodiment, the hardware-based logic mapping device is presented in the form of a functional unit. Here, a unit refers to an ASIC circuit, a processor and memory that execute one or more software or fixed programs, and / or other devices that can provide the above functions.

[0080] Further functional descriptions of the above modules and units are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0081] This invention also provides a computer device having the above-described features. Figure 7 The multi-camera time synchronization device shown.

[0082] like Figure 8As shown, the computer device includes one or more processors 10, memory 20, and interfaces for connecting the components, including high-speed interfaces and low-speed interfaces. The components communicate with each other via different buses and can be mounted on a common motherboard or otherwise installed as needed. The processors can process instructions executed within the computer device, including instructions stored in or on memory to display graphical information of a GUI on external input / output devices (such as display devices coupled to the interfaces). In some alternative implementations, multiple processors and / or multiple buses can be used with multiple memories and multiple memory modules, if desired. Similarly, multiple computer devices can be connected, each providing some of the necessary operations (e.g., as a server array, a group of blade servers, or a multiprocessor system). Figure 8 Take a processor 10 as an example.

[0083] Processor 10 may be a central processing unit, a network processor, or a combination thereof. Processor 10 may further include a hardware chip. The hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The programmable logic device may be a complex programmable logic device (CAMP), a field-programmable gate array (FPGA), a general-purpose array logic (GDA), or any combination thereof.

[0084] The memory 20 stores instructions executable by at least one processor 10 to cause at least one processor 10 to perform the method shown in the above embodiments.

[0085] The memory 20 may include a program storage area and a data storage area. The program storage area may store the operating system and applications required for at least one function; the data storage area may store data created based on the use of the computer device as shown by a landing page for an app. Furthermore, the memory 20 may include high-speed random access memory and may also include non-transitory memory, such as at least one disk storage device, flash memory device, or other non-transitory solid-state storage device. In some alternative embodiments, the memory 20 may optionally include memory remotely located relative to the processor 10, which can be connected to the computer device via a network. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks, mobile communication networks, and combinations thereof.

[0086] The memory 20 may include volatile memory, such as random access memory; the memory may also include non-volatile memory, such as flash memory, hard disk or solid-state drive; the memory 20 may also include a combination of the above types of memory.

[0087] The computer device also includes a communication interface 30 for communicating with other devices or communication networks.

[0088] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as computer code that can be recorded on a storage medium, or implemented as computer code downloaded over a network and originally stored on a remote storage medium or a non-transitory machine-readable storage medium and then stored on a local storage medium. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code, which, when accessed and executed by the computer, processor, or hardware, implements the methods shown in the above embodiments.

[0089] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0090] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A multi-camera time synchronization method, characterized by, The method comprises the following steps: setting a refresh rate of screen display content and a frequency of a screen PWM modulation wave, wherein the frequency of the screen PWM modulation wave is less than or equal to half of the refresh rate of the screen display content; controlling multiple cameras to take photos of a dynamic screen, and selecting a group of photos taken by different cameras and having the same screen display content; taking one of the cameras as a reference camera, and taking one of the dark line positions in the photo taken by the reference camera as a reference position; comparing the dark line positions in the photos taken by other cameras with the reference position, and obtaining a pixel difference set of each camera; adjusting the time of each camera to be synchronized with the time of the reference camera according to the pixel difference set of each camera; the process of adjusting the time of each camera to be synchronized with the time of the reference camera according to the pixel difference set of each camera comprises: respectively taking the pixel differences in the pixel difference set of each camera that meet a preset condition as pixel adjustment values of the corresponding camera; calculating a time adjustment value of each camera according to the refresh rate of the screen display content, the wavelength of the PWM modulation wave and the pixel adjustment value of each camera; adjusting the time of the corresponding camera to be synchronized with the time of the reference camera based on the time adjustment value of each camera.

2. The multi-camera time synchronization method of claim 1, wherein, the process of setting the refresh rate of screen display content and the frequency of a screen PWM modulation wave comprises: setting the screen background to white.

3. The multi-camera time synchronization method of claim 2, wherein, the process of controlling multiple cameras to take photos of a dynamic screen comprises: controlling the multiple cameras to keep the same short exposure parameter to take high-speed continuous photos of the screen.

4. The multi-camera time synchronization method of claim 3, wherein, the process of taking one of the cameras as a reference camera, and taking one of the dark line positions in the photo taken by the reference camera as a reference position comprises: taking one of the multiple dark lines in the photo taken by the reference camera as a reference dark line; recording the reference position of the reference dark line through a ruler on the screen.

5. The multi-camera time synchronization method of claim 4, wherein, the process of comparing the dark line positions in the photos taken by other cameras with the reference position, and obtaining a pixel difference set of each camera comprises: recording the positions of all the dark lines in each photo through a ruler on the screen; respectively calculating the difference between the position of each dark line in each photo and the reference position, and taking all the difference values in each photo as a pixel difference set of the corresponding camera.

6. The multi-camera time synchronization method of claim 1, wherein, a time adjustment value of each camera t i The calculation formula is: wherein, N is a refresh rate of a screen display content, w is a wavelength of a PWM modulation wave, w i is a pixel adjustment value of the i th camera.

7. A multi-camera time synchronization apparatus, characterized by, The method comprises the following steps: an initialization module is configured to set a refresh rate of screen display content and a frequency of a screen PWM modulation wave, wherein the frequency of the screen PWM modulation wave is less than or equal to half of the refresh rate of the screen display content; an acquisition module is configured to control multiple cameras to take photos of a dynamic screen, and select a group of photos taken by different cameras and having the same screen display content; a reference module is configured to take one of the cameras as a reference camera, and take one of the dark line positions in the photo taken by the reference camera as a reference position; a comparison module is configured to compare the dark line positions in the photos taken by other cameras with the reference position, and obtain a pixel difference set of each camera; an adjustment module is configured to adjust the time of each camera to be synchronized with the time of the reference camera according to the pixel difference set of each camera. The process of adjusting the time of each camera to be synchronized with the time of the reference camera according to the pixel difference set of each camera comprises: acquiring pixel differences meeting preset conditions in the pixel difference set of each camera as pixel adjustment values of the corresponding camera respectively; According to the refresh rate of the screen display content, the wavelength of the PWM modulation wave and the pixel adjustment value of each camera, the time adjustment value of each camera is calculated; and the time of the corresponding camera is adjusted to be synchronized with the time of the reference camera based on the time adjustment value of each camera.

8. A computer device, comprising: Comprise: A memory and a processor, which are connected in communication with each other, the memory stores computer instructions, and the processor executes the computer instructions to perform the multi-camera time synchronization method in any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that, The computer readable storage medium stores computer instructions, and the computer instructions are used to make the computer execute the multi-camera time synchronization method in any one of claims 1 to 6.

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