CN117939134A - Wireless video communication method and system - Google Patents
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
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- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
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- H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
- H04N19/146—Data rate or code amount at the encoder output
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Abstract
The invention discloses a wireless video communication method which comprises the steps of data acquisition, coding processing, signal transmission, decoding and restoring. Firstly, video data are collected through cameras arranged around a vehicle and are converted into electric signals, and then the electric signals are encoded by using an average code rate algorithm of an H.264 open source encoder X264. And then, signal transmission is carried out by utilizing a wireless transmission technology, and finally, the received wireless signal is decoded at a receiving end to recover the original video data. In addition, the invention also adopts an optimized quantization parameter QP and buffer size setting method to improve the coding efficiency and the transmission quality. Wi-Fi, 4G/5G mobile communication technology, bluetooth or NFC can be used for transmission of wireless signals, and flexibility and reliability of transmission are guaranteed.
Description
Technical Field
The invention belongs to the field of communication, and particularly relates to a wireless video communication method and system.
Background
With the rapid development of the automobile industry and the improvement of the life quality of people, automobiles have become main transportation means for traveling. Accordingly, driving safety factors are becoming more important, and thus, vehicle-mounted 360-degree looking around systems have been developed as important driving assisting tools. The vehicle-mounted 360-degree looking-around system is used for collecting image information around a vehicle in real time through cameras arranged around the vehicle, and fusing the image information into a panoramic image of a top view of the vehicle through an image processing technology, so that the panoramic image is used for a driver to refer to, and accidents caused by blind areas of vision are avoided.
To achieve this goal, video communication technology is a critical loop. Generally, video data is transmitted in a wireless manner, and is required to be firstly encoded and converted into an electrical signal, then transmitted through a signal transmission technology, and then decoded and restored into original video data at a receiving end.
However, existing wireless video communication technologies have some problems in vehicle-mounted look-around systems:
The transmission efficiency is low: in general, performance parameters such as bandwidth, delay, jitter, and packet loss rate of a wireless network have a certain influence on video transmission efficiency. However, when the existing coding algorithm processes data, these factors are often not considered, so that the coded data cannot fully utilize network resources, and the transmission efficiency is reduced.
Image quality is unstable: when the camera collects video data, the video data is carried out according to a set frame rate and a set code rate, but the change of the network environment and the instability of the network quality can cause the change of the frame rate and the code rate in the transmission process, thereby influencing the quality of the decoded image.
The environmental change cannot be reflected in time: the vehicle-mounted surrounding system needs to acquire surrounding environment information in real time so that a driver can make accurate judgment. However, the existing wireless video communication method may cause environmental information fed back to the driver to be delayed due to delay in encoding, transmission and decoding, thereby affecting driving decisions.
Disclosure of Invention
The invention mainly solves a series of technical problems faced by wireless video communication in the existing vehicle-mounted wireless 360-degree looking-around system: firstly, how to integrate network performance parameters such as bandwidth, delay, jitter, packet loss rate and the like into coding processing steps by improving a coding processing algorithm, so that coded data can be better adapted to a network environment, and the data transmission efficiency is improved.
In order to achieve the above purpose, the present invention is realized by adopting the following technical scheme: the communication method comprises the following steps:
S1, data acquisition: after video data is collected by cameras arranged at various positions of the vehicle, the video data is converted into electric signals;
S2, coding: encoding the acquired electric signals and converting the acquired electric signals into transmittable wireless data;
S3, signal transmission: using wireless transmission technology to transmit data;
s4, decoding and restoring: and decoding and restoring the received wireless signals to restore the original video data.
In one scheme, the coding process is improved in 2 aspects of frame layer quantization parameter QP and buffer size setting of the ABR algorithm by combining wireless network parameters on the basis of the average code rate algorithm ABR of the H.264 open source encoder X264.
In one scheme, the data acquisition is carried out by installing cameras in the front, back, left and right directions of the vehicle to obtain real-time video information around the vehicle.
In one scheme, the improvement of the ABR algorithm quantization parameter QP at the frame layer in combination with the wireless network parameters is as follows:
(1) Acquiring performance parameters of a current wireless channel, such as bandwidth, delay, jitter and packet loss rate;
(2) Taking the returned bandwidth value in the wireless network as a target code rate in an X264 code rate control algorithm, and solving a quantization parameter QP according to an ABR code rate control algorithm in X264;
(3) Adding a compensation algorithm to optimize the quantization parameter QP calculated by the ABR code rate control algorithm in the step (2);
the calculation process of the compensation algorithm is as follows:
1) After calculating the quantization parameter QP for each frame, the average quantization parameter for the encoded frame is calculated A ratio of a sum of coded frame quantization parameters QP to a number of coded frames;
Wherein the method comprises the steps of Representing the current coding frame number,/>A quantization parameter QP value representing an i-th frame;
2) Meanwhile, calculating the difference value between the real_bit of the actual output code rate and the target_bit of the target code rate;
If the difference diff_bit is smaller than a preset value-R, and The quantization parameter QP is reduced; if the difference diff_bit is larger than a preset value R and/>Then the quantization parameter QP is increased; wherein R is selected according to the deviation percentage from the target code rate, and 1% is selected;
3) When the code rate difference and the average quantization parameter do not meet the condition of 2), the quantization parameter in 3) is kept unchanged,
4) And taking the quantization parameter QP after the optimization of the 3) as a quantization value of the current frame coding to carry out X264 coding.
In one aspect, the buffer size is set to: defining an average rate control rate to describe the approach of the current output rate to the set target rate, and setting the average rate control rate asThe calculation formula is as follows:
，
wherein, For the set average target code rate,/>For the average bit rate of the currently encoded frame, the method in the program is:
wherein, For the number of frames currently encoded,/>For a set frame rate,/>Multiplying 8 for the current coded total byte number and converting into bit; correcting the size of the buffer area by using the average code rate control rate parameter;
For new code buffer Expressed by/>The calculation formula is as follows:
When the average code rate control rate is greater than 1, the current average code rate is greater than the target code rate, and QP is increased, so that the output code rate is reduced; when the average rate control rate is less than 1, the situation is reversed. In one scheme, wi-Fi, mobile communication technology 4G/5G, bluetooth and NFC are adopted for signal transmission.
In one scheme, the decoding reduction process is as follows:
s401, receiving a wireless signal: receiving encoded video data from a sender;
s402, buffer processing: storing the received data in a buffer to provide a continuous data input for the decoding process;
s403, data decoding: decoding the received data using a decoding algorithm corresponding to the encoding process, the decoding algorithm employing a DCT discrete cosine transform, the specific formula being as follows:
wherein, Is a transformed coefficient, and is also commonly referred to as a frequency domain representation;
refers to the image pixel values in the spatial domain;
u and v are transformed frequency variations, corresponding to the horizontal and vertical axes in the frequency domain;
x and y are spatial coordinates, corresponding to the rows and columns of the image;
N is the size of the input image, i.e. the number of rows or columns;
And/> Is a normalized coefficient for ensuring energy conservation of the transformation, in general,/>, when u or v is equal to 0Or/>Take the value of/>Otherwise, the value is 1.
In another aspect, a wireless video communication system, said system adapted for use in said method, said system comprising:
Data acquisition equipment: comprises one or more cameras which are arranged in the front, back, left and right directions of the automobile;
Encoding device: converting input from a data acquisition device into transmittable electrical signals, comprising one or more encoders;
Wireless transmission device: including one or more transmitters, and corresponding wireless network hardware;
Decoding device: comprising one or more decoders;
the output end of the data acquisition equipment is connected with the encoding equipment, the encoding equipment is connected with the decoding equipment through the wireless transmission equipment, and the decoding equipment decodes the video and sends the decoded video to the display for displaying.
The invention has the beneficial effects that:
The invention has the advantages of improving the transmission efficiency, the image quality stability and the real-time performance of the wireless video communication. Through a well-designed coding processing algorithm and by combining wireless network parameters, the coded data can fully consider the characteristics of a wireless network and fully utilize network resources, thereby remarkably improving the data transmission efficiency. Meanwhile, the optimized decoding algorithm and the buffer processing strategy are applied, so that the stability of the frame rate and the code rate of video data can be kept under the condition of network environment change, and the stability of the decoded image quality is further ensured. In addition, the invention shortens the delay of encoding, transmission and decoding, so that the vehicle-mounted 360-degree looking-around system can timely reflect the environmental change around the vehicle, provide instant and accurate looking-around information, and provide effective support for a driver to make accurate judgment, thereby greatly improving driving safety and convenience.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
FIG. 2 is a flowchart of an ABR rate control algorithm for improving a frame layer quantization parameter QP according to the present invention;
FIG. 3 is a flowchart of the ABR algorithm for improving buffers according to the present invention;
Fig. 4 is a decoding flow chart of the present invention.
Detailed Description
In order that the invention may be readily understood, a more complete description of the invention will be rendered by reference to the appended drawings. Exemplary embodiments of the present invention are illustrated in the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, 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 invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
As shown in fig. 1, the communication method includes:
S1, data acquisition: first, a camera is installed in each of the four directions of the front, rear, left and right of the vehicle. The four cameras are used for acquiring real-time video information of the vehicle in four directions, so that drivers can better know the traffic conditions of surrounding environments.
Firstly, four cameras respectively monitor the front direction, the rear direction, the left direction and the right direction of the vehicle in real time. The camera converts video data acquired in real time into image signals.
The image signals are then passed into an in-vehicle imaging system, which will convert these signals into digital signals. The digital signal needs to be subjected to preprocessing before being subjected to the next encoding process, including stabilization processing of the original image for image quality enhancement, noise cancellation, and the like.
Finally, the preprocessed digital signal is stored, awaiting the encoding process and the appropriate transmission.
Therefore, the video signals in the front, back, left and right directions are completely collected, preparation can be made for the next coding processing and transmission, a 360-degree blind-angle-free looking-around view can be obtained by a driver, and the view can be accurate to be real-time, so that the driver can be assisted to the greatest extent.
S2, coding: encoding the acquired electric signals and converting the acquired electric signals into transmittable wireless data;
The coding process is improved in 2 aspects of frame layer quantization parameter QP and buffer size setting by combining wireless network parameters on the basis of an average code rate algorithm ABR of an H.264 open source coder X264.
An X264 average code rate control algorithm;
the code rate control algorithm of X264 is based on libavcodec library and is only carried out at the frame layer, and is derived from practical experience, and the flexibility, instantaneity and high efficiency of code rate control are emphasized. Code rate control characteristics of an X264 coder:
(1) The constant quality is not equal to the constant peak signal-to-noise ratio PSNR and the quantization parameter QP.
(2) Different frames use different QP values, such as an I-frame QP value that is small and a B-frame QP value that is large.
(3) More bit allocation strategies affect the motion compensation effect.
There are 2 kinds of code rate control of X264
(1) Single-pass encoding. Mainly comprises a fixed parameter quantization parameter CQP, a fixed code rate control factor CRF, an average bit rate ABR and the like. CQP, CRF and ABR rate control at the frame layer level, and X264 has no macroblock level rate control algorithm.
(2) And (5) encoding for a plurality of times. The best compression effect is achieved for multiple times of compression of the video when the video is coded for multiple times, but the time consumption is high. Generally, two encodings are used, and the algorithm generates statistical information for each frame on the basis of the first encoding, i.e. the single encoding, and in the second encoding, the statistical information of the first encoding is used for optimization, so as to obtain better quantization parameters.
In practical application, the real-time requirement is high, and the network bandwidth is unstable, so that the ABR mode of single coding is selected, and the ABR algorithm only needs to control the code rate by means of the reference information of the coded frame without considering the uncoded frame. Allowing an error of about 10% of the output code rate.
The basic flow of the ABR algorithm is:
(1) And calculating the residual transformation absolute value SATD of the current frame of the image. The h.264 standard performs coding control based on Lagrangian cost function, and the code rate distortion cost J is expressed as:
（1）
Where SAD is the sum of absolute values of the difference between the predicted reconstructed block and the encoded block, R represents the minimum number of encoded bits, Is a frame rate distortion cost coefficient. The sum of absolute values of image residual transform SATD is utilized in the X264 rate control algorithm instead of SAD. SATD is a value obtained by accumulating residual errors through Hadamard transformation, and the formula (1) is modified as follows:
（2）
The difference between the absolute error and the time domain residual value reflected by SAD cannot represent the size of the code stream, and the residual error can reflect the size of the code stream to a certain extent after transformation. SATD is therefore more suitable for rate-distortion optimized reference.
(2) Calculating the fuzzy complexity of the current image according to the SATD value of the current frame. The SATD value of the current frame is noted as/>The cumulative complexity is calculated by the method and is recorded as/>. The cumulative complexity is weighted by the previous frame complexity weighted cumulative sum/>The values are jointly calculated:
（3）
the blur complexity is recalculated. The fuzzy complexity of the ith frame is recorded as The calculation formula is as follows:
（4）
Wherein the method comprises the steps of Represents the weighted accumulated frame number, and the calculation formula is as follows:
（5）
as can be seen from formulas (4) and (5), the iteration relation exists in the calculation of the fuzzy complexity, so that the stability of the internalization parameters of adjacent frames is ensured; the complexity is estimated more accurately by considering the previous frame information in combination with the current frame SATD.
(3) And calculating a quantization level qscale according to the blurring complexity of the current image, and correcting the quantization level qscale. The original quantization parameter is calculated by fuzzy complexity, and the calculation formula is as follows:
（6）
Wherein the method comprises the steps of For compression control parameters, the fixed bit rate mode is set to 0, and the fixed quantization value is set to 1, and the default value is 0.6 in the ABR bit rate control algorithm.
(4) From the following componentsCalculating a quantization parameter QP;
（7）
Wherein the method comprises the steps of All are empirical values.
(5) Encoding a current frame according to QP
The average code rate control algorithm in X264 is obtained by time experience, and has some defects, for example, the ABR algorithm considers the information of the coded frames, does not consider the information of the uncoded frames, is inaccurate in calculation, and has about 10% of errors in output code rate; the adjustment of the size of the buffer area is only related to the initial value, the current frame number, the frame rate and the like of the buffer area, and the adjustment strategy is not exact and is not beneficial to code rate control.
The invention improves a video self-adaptive code rate control method combining the current wireless network state on the basis of an X264 average code rate control algorithm ABR, and mainly performs two aspects of frame layer quantization parameter QP optimization calculation and coding buffer size setting.
As shown in fig. 2, the quantization parameter QP at the frame layer for the ABR algorithm in combination with the wireless network parameters is improved as follows:
(1) Acquiring performance parameters of a current wireless channel, such as bandwidth, delay, jitter and packet loss rate;
Ping test: the time for a packet to travel from the source to the destination (round trip) is measured by sending an ICMP request to the destination and then waiting for a reply. This time is the delay. The following equation can be generally used to calculate: delay = time of a packet from source to destination + time of a packet from destination back to source. Typically in milliseconds (ms). The Ping test can also detect packet loss. If the request does not return a reply, the packet is deemed lost.
Bandwidth testing: the bandwidth is obtained by downloading or uploading a file of known size over a period of time and then dividing by the time spent. The formula is: bandwidth (Mbps or Kbps) =file size (Mb or Kb)/time (seconds).
Jitter test: jitter refers to the fluctuation in delay between successive packet transmissions. And sending a series of data packets through a network, analyzing the delay of each data packet, and calculating the difference between the data packets. The jitter calculation formula is: jitter = maximum delay-minimum delay.
The above steps may use tool libraries, which and network libraries can generally provide interfaces to directly derive parameters such as bandwidth, delay, jitter, and packet loss rate.
(2) Taking the returned bandwidth value in the wireless network as the target code rate in the X264 code rate control algorithm, solving a quantization parameter QP according to the ABR code rate control algorithm in X264, and describing in the formulas (1) - (7).
(3) Adding the following compensation algorithm to optimize the quantization parameter QP calculated by the original algorithm in the step (2);
1) After calculating the quantization parameter QP for each frame, the average quantization parameter for the encoded frame is calculated A ratio of a sum of coded frame quantization parameters QP to a number of coded frames;
（8）
Wherein the method comprises the steps of Representing the current coding frame number,/>A quantization parameter QP value representing an i-th frame;
2) Meanwhile, calculating the difference value between the real_bit of the actual output code rate and the target_bit of the target code rate;
（9）
If the difference diff_bit is smaller than a preset value-R, and The quantization parameter QP is reduced; if the difference diff_bit is larger than a preset value R and/>Then the quantization parameter QP is increased; wherein R is selected according to the deviation percentage from the target code rate, and 1% is selected;
3) When the code rate difference and the average quantization parameter do not meet the condition of 2), the quantization parameter in 3) is kept unchanged,
4) And taking the quantization parameter QP after the optimization of the 3) as a quantization value of the current frame coding to carry out X264 coding.
As shown in fig. 3, the buffer size is set as follows: defining an average rate control rate to describe the approach of the current output rate to the set target rate, and setting the average rate control rate asThe calculation formula is as follows:
（10）
wherein, For the set average target code rate,/>For the average bit rate of the currently encoded frame, the method in the program is:
（11）
wherein, For the number of frames currently encoded,/>For a set frame rate,/>Multiplying 8 for the current coded total byte number and converting into bit; correcting the size of the buffer area by using the average code rate control rate parameter;
For new code buffer Expressed by/>The calculation formula is as follows:
（12）
when the average code rate control rate is greater than 1, the current average code rate is greater than the target code rate, and QP is increased, so that the output code rate is reduced; when the average rate control rate is less than 1, the situation is reversed.
S3, signal transmission: using wireless transmission technology to transmit data;
the signal transmission adopts Wi-Fi, mobile communication technology 4G/5G, bluetooth and NFC.
And selecting a proper wireless transmission technology according to the actual situation of the wireless network and the data transmission requirement. For example, if the vehicle-mounted looking-around system is closer to the receiving device, bluetooth or NFC may be selected for transmission; wi-Fi or 4G/5G communication technologies can be selected if long-range transmission is required.
The encoded data is then transmitted via the selected wireless transmission technology. In the transmitting process, the transmitting power and frequency can be continuously adjusted to adapt to the change of the network condition, so that the reliable transmission of the data is ensured.
Next, the reception process of the data is entered, and the reception apparatus receives the transmission data using the same wireless communication technology as the transmission. To enhance the stability of the transmission, a signal strength threshold may be set, and when the received signal strength is below the threshold, transmission may be re-requested.
As shown in fig. 4, S4, decoding reduction: and decoding and restoring the received wireless signals to restore the original video data.
The decoding and restoring process is as follows:
s401, receiving a wireless signal: receiving encoded video data from a sender;
s402, buffer processing: storing the received data in a buffer to provide a continuous data input for the decoding process;
s403, data decoding: decoding the received data using a decoding algorithm corresponding to the encoding process, the decoding algorithm employing a DCT discrete cosine transform, the specific formula being as follows:
（13）
wherein, Is a transformed coefficient, and is also commonly referred to as a frequency domain representation;
refers to the image pixel values in the spatial domain;
u and v are transformed frequency variations, corresponding to the horizontal and vertical axes in the frequency domain;
x and y are spatial coordinates, corresponding to the rows and columns of the image;
N is the size of the input image, i.e. the number of rows or columns;
And/> Is a normalized coefficient for ensuring energy conservation of the transformation, in general,/>, when u or v is equal to 0Or/>Take the value of/>Otherwise, the value is 1.
Example two
A wireless video communication system, said system being adapted for use in said method, data acquisition device: is mainly responsible for capturing video data in the environment. Generally comprises one or more high-definition cameras, and can be arranged in all directions of the front, the back, the left, the right and the like of an automobile. The purpose of doing so is in order to acquire the all-round video information around the vehicle, has further strengthened the security of driving, has avoided the existence of blind area.
Encoding device: and is mainly responsible for converting the acquired video data into electrical signals. The collected video data is typically an analog signal that needs to be encoded and converted to a digital electrical signal before transmission. The process is mainly completed through the encoder, and various complex video compression algorithms can be performed, so that the bandwidth of data transmission is greatly reduced, and the transmission efficiency is improved.
Wireless transmission device: mainly responsible for wireless transmission of encoded video data. It includes one or more wireless signal transmitters and corresponding wireless network hardware to wirelessly transmit encoded video data to a designated location. Such as a 4G/5G data network, wiFi wireless network, bluetooth, etc.
Decoding device: is mainly responsible for restoring the received electrical signals to video data. After the video data sent by the wireless transmission device reaches the destination, the video data needs to be decoded and restored into the original video data through one or more decoders, so that the original video data becomes a video which can be played.
The video data collected by the camera is encoded by the encoding equipment, transmitted by the wireless transmission equipment, finally decoded by the decoding equipment and displayed on the display, thereby realizing video communication of wireless transmission, greatly improving the transmission efficiency of the video data and having important benefits for applications such as real-time monitoring, safe driving and the like.
Those skilled in the art will appreciate that implementing all or part of the above-described methods in accordance with the embodiments may be accomplished by way of a computer program stored on a computer readable storage medium, which when executed may comprise the steps of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a read-only memory (ReadOnlyMemory, ROM), a random access memory (RandomAccessMemory, RAM), or the like.
It should be understood that the detailed description of the technical solution of the present invention, given by way of preferred embodiments, is illustrative and not restrictive. Modifications of the technical solutions described in the embodiments or equivalent substitutions of some technical features thereof may be performed by those skilled in the art on the basis of the present description; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. A method of wireless video communication, characterized by: the communication method comprises the following steps:
s1, data acquisition: after video data is collected by cameras arranged at various positions of the vehicle, the video data is converted into electric signals;
s2, coding: encoding the collected video signals;
S3, signal transmission: using wireless transmission technology to transmit data;
s4, decoding and restoring: and decoding and restoring the received wireless signals to restore the original video data.
2. A method of wireless video communication according to claim 1, wherein: the coding process is improved in 2 aspects of frame layer quantization parameter QP and buffer size setting by combining wireless network parameters on the basis of an average code rate algorithm ABR of an H.264 open source coder X264.
3. A method of wireless video communication according to claim 1, wherein: and the data acquisition is carried out, cameras are arranged in the front, rear, left and right directions of the vehicle, and real-time video information around the vehicle is obtained.
4. A method of wireless video communication according to claim 2, wherein: the improvement of the quantization parameter QP of the ABR algorithm at the frame layer by combining the wireless network parameters is as follows:
(1) Acquiring performance parameters of a current wireless channel, bandwidth, delay, jitter and packet loss rate;
(2) Taking the returned bandwidth value in the wireless network as a target code rate in an X264 code rate control algorithm, and solving a quantization parameter QP according to an ABR code rate control algorithm in X264;
(3) Adding a compensation algorithm to optimize the quantization parameter QP calculated by the ABR code rate control algorithm in the step (2);
the calculation process of the compensation algorithm is as follows:
1) After calculating the quantization parameter QP for each frame, the average quantization parameter for the encoded frame is calculated A ratio of a sum of coded frame quantization parameters QP to a number of coded frames;
；
Wherein the method comprises the steps of Representing the current coding frame number,/>A quantization parameter QP value representing an i-th frame;
2) Meanwhile, calculating the difference value between the actual output code rate real_bit and the target code rate target_bit;
；
If the difference diff_bit is smaller than a preset value-R, and The quantization parameter QP is reduced; if the difference diff_bit is larger than a preset value R and/>Then the quantization parameter QP is increased; wherein R is selected according to the deviation percentage from the target code rate and is 1%;
3) When the code rate difference and the average quantization parameter do not meet the condition of 2), the quantization parameter in 3) is kept unchanged,
4) And taking the quantization parameter QP after the optimization of the 3) as a quantization value of the current frame coding to carry out X264 coding.
5. A method of wireless video communication according to claim 2, wherein: the buffer area is set as follows: defining an average rate control rate to describe the approach of the current output rate to the set target rate, and setting the average rate control rate asThe calculation formula is as follows:
；
wherein, For the set average target code rate,/>For the average bit rate of the current encoded frame, the calculation method is as follows:
；
wherein, For the number of frames currently encoded,/>For a set frame rate,/>Multiplying 8 for the current coded total byte number and converting into bit; correcting the size of the buffer area by using the average code rate control rate parameter;
For new code buffer Expressed by/>The calculation formula is as follows:
；
when the average code rate control rate is greater than 1, the current average code rate is greater than the target code rate, and QP is increased, so that the output code rate is reduced; when the average rate control rate is less than 1, the situation is reversed.
6. A method of wireless video communication according to claim 2, wherein: the signal transmission adopts Wi-Fi, mobile communication technology 4G/5G, bluetooth and NFC.
7. A method of wireless video communication according to claim 2, wherein: the decoding and restoring process is as follows:
s401, receiving a wireless signal: receiving encoded video data from a sender;
s402, buffer processing: storing the received data in a buffer to provide a continuous data input for the decoding process;
s403, data decoding: decoding the received data using a decoding algorithm corresponding to the encoding process, the decoding algorithm employing a DCT discrete cosine transform, the specific formula being as follows:
；
wherein, Is a transformed coefficient, and is also commonly referred to as a frequency domain representation;
refers to the image pixel values in the spatial domain;
u and v are transformed frequency variations, corresponding to the horizontal and vertical axes in the frequency domain;
x and y are spatial coordinates, corresponding to the rows and columns of the image;
N is the size of the input image, i.e. the number of rows or columns;
And/> Is a normalized coefficient used to ensure energy conservation of the transformation, and in general, when u or v is equal to 0,Or/>Take the value of/>Otherwise, the value is 1.
8. A wireless video communication system, said system being adapted for use in a method as claimed in any one of claims 1 to 7, wherein: the system comprises:
data acquisition equipment: the camera comprises a plurality of cameras which are arranged in the front, rear, left and right directions of the automobile;
encoding device: converting an input from a data acquisition device into a transmissible electrical signal comprising at least one encoder;
Wireless transmission device: comprising at least one transmitter, and corresponding wireless network hardware;
decoding device: comprising at least one decoder;
the output end of the data acquisition equipment is connected with the encoding equipment, the encoding equipment is connected with the decoding equipment through the wireless transmission equipment, and the decoding equipment decodes the video and sends the decoded video to the display for displaying.
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