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CN-121985128-A - Wiring-free wireless transmission method and system for car backing image

CN121985128ACN 121985128 ACN121985128 ACN 121985128ACN-121985128-A

Abstract

The invention discloses a wiring-free wireless transmission method and a wiring-free wireless transmission system for a back image, which belong to the technical field of video coding, and are characterized in that when a back mode is started, a wireless transmission link monitoring thread is started, wireless transmission link performance indexes are acquired, an acceptable target code rate of a current back image frame is given, after each frame image is acquired, back image acquisition equipment analyzes to obtain an initial block-level coding precision matrix, inter-frame smoothing and variation amplitude constraint is carried out on coding precision of each spatial position in the matrix, differential coding is carried out on each spatial coding block according to a final block-level coding precision matrix, a coding data stream adapting to the bearing capacity of a current link is generated, the coding data stream is transmitted to a CarPlay terminal through a wireless transmission link, a monitoring result is acquired in the transmission process, the target code rate and block-level precision allocation of a subsequent frame are dynamically adjusted, and impact on the real-time property and accuracy of the back image caused by queue backtracking and frame-level loss is reduced from the source.

Inventors

  • XIONG LIJUN

Assignees

  • 惠州市欣相荣科技有限公司

Dates

Publication Date
20260505
Application Date
20260130

Claims (10)

  1. 1. The wiring-free wireless transmission method for the back image of the car is characterized by comprising the following steps of: Step one, after a wiring-free Carplay system starts a reversing mode, starting a wireless transmission link monitoring thread, acquiring a wireless transmission link performance index, and analyzing a target code rate of a reversing image frame; step two, the reversing image acquisition equipment acquires reversing image frames, performs space division to obtain a plurality of independent space coding blocks, analyzes an initial block-level coding precision matrix corresponding to the reversing image frames based on the target code rate of the reversing image frames, and performs inter-frame smoothing operation on the coding precision of each space position on the initial block-level coding precision matrix to form a final block-level coding precision matrix; and thirdly, performing differential coding processing on each space coding block based on a final block-level coding precision matrix to generate a coding data stream adapting to the performance of a current wireless transmission link, transmitting a reverse image frame to a carrlay terminal through the wireless transmission link, monitoring the transmission state of the coding data stream in real time in the transmission process, acquiring a monitoring result, dynamically adjusting coding parameters according to the monitoring result, and realizing self-adaptive dynamic optimization of the coding process in a reverse image wireless transmission scene.
  2. 2. The wireless transmission method of the wiring-free car backing image of claim 1, wherein the target code rate of the car backing image frame is analyzed, and the specific analysis process is as follows: After the performance index of the wireless transmission link is subjected to smoothing treatment through an exponential weighting algorithm, the treatment result is marked as a link transmission quality coefficient; The link transmission quality coefficient represents real-time transmission performance of the wireless transmission link in a wiring-free Carplay reverse image wireless transmission scene; mapping available bandwidth of the wireless transmission link from a database by taking the link transmission quality coefficient as an index; and mapping the target code rate of the reverse image frame through a piecewise linear function based on the available bandwidth of the wireless transmission link, and limiting the change amplitude of the target code rate of the adjacent frame.
  3. 3. The wireless transmission method of the wiring-free Carplay reverse image of claim 1, wherein the analysis of the initial block-level coding precision matrix corresponding to the reverse image frame comprises the following specific analysis processes: acquiring the total bit budget of a wireless transmission link; dividing the current reversing image frame into a plurality of space coding blocks; Analyzing the content complexity of each space coding block, giving importance weight corresponding to each space coding block, and weighting and summarizing the regional priority scores of each space coding block; based on the regional priority scores of the space coding blocks, distributing the total bit budget of the current wireless transmission link to obtain block-level bit budget of each space coding block; Mapping the block level bit budget of each space coding block into a preset matrix level index set to determine the block level coding precision adopted by each space coding block; And filling the corresponding original matrix level into a two-dimensional grid consistent with the division of the coding blocks according to the spatial position of each spatial coding block in the current reversing image frame to obtain an initial block-level coding precision matrix reflecting the block-level coding precision of each spatial coding block on spatial distribution.
  4. 4. The wireless transmission method of the wiring-free carrier reverse image of claim 1, wherein the method is characterized in that the method comprises the following steps of: Aiming at a certain space position on the initial block-level coding precision matrix, reading the block-level coding precision actually adopted by the space position in the previous frame as historical precision; weighting the block-level coding precision corresponding to the current reversing image frame at the space position and the historical precision according to a preset smoothing coefficient, and marking the weighting result as the temporary block-level coding precision of the space position; the smoothing coefficient is used for controlling the duty ratio of the current frame block level coding precision and the previous frame historical precision in the weighting result; Acquiring a precision deviation value between the temporary block level coding precision and the history precision; Extracting a first defined accuracy deviation value from a database; and limiting the precision deviation value between the temporary block level coding precision and the historical precision based on the first defined precision deviation value, and sequentially updating the temporary block level coding precision of each spatial position to obtain an initial block level coding precision matrix meeting the time continuity constraint.
  5. 5. The method for wireless transmission of wiring-free Carplay reverse image of claim 4, wherein forming a final block-level coding precision matrix further comprises performing neighborhood spatial smoothing operation on coding precision of each spatial position on an initial block-level coding precision matrix, and the specific operation process is as follows: Defining a second precision deviation value from the database; On the initial block level coding precision matrix, analyzing a precision deviation value between the temporary block level coding precision of a certain space position and the temporary block level coding precision of an adjacent space position; if the precision deviation value between the temporary block level coding precision of the space position and the temporary block level coding precision of the adjacent space position is higher than the second definition precision deviation value, correcting the temporary block level coding precision grade of the space position so as to enable the average value of the adjacent temporary block level coding precision to be converged, and updating the temporary block level coding precision grade of the space position; and sequentially updating the temporary block level coding precision grades of the spatial positions to form an initial block level coding precision matrix which simultaneously meets the spatial continuity constraint.
  6. 6. The method for wireless transmission of wiring-free Carplay reverse image of claim 4, wherein the forming of the final block-level coding precision matrix comprises the following steps: performing inter-frame smoothing operation on the coding precision of each spatial position on the initial block-level coding precision matrix; After the inter-frame smoothing operation is completed, updating an initial block-level coding precision matrix; Carrying out neighborhood space smoothing operation on the coding precision of each space position on the updated initial block-level coding precision matrix; After the neighborhood space smoothing operation is completed, the initial block level coding precision matrix is updated, and the updated initial block level coding precision matrix is marked as a final block level coding precision matrix.
  7. 7. The method for wireless transmission of wiring-free Carplay reverse image of claim 1, wherein the dynamic adjustment of the coding parameters according to the monitoring result comprises the following specific adjustment processes: the coding parameters comprise piecewise linear functions, first defined precision deviation values and second defined precision deviation values; Extracting the actual output delay time length of the current reversing image frame from the monitoring result, and extracting the defined output delay time length from the database; comparing the actual output delay time length of the current reversing image frame with the defined output delay time length; If the actual output delay time of the current reversing image frame is not longer than the defined output delay time, continuously monitoring the reversing image coding process; if the actual output delay time length of the current reversing image frame is longer than the defined output delay time length, increasing a loss value in the piecewise linear function, so that the correction target code rate is reduced; Continuously monitoring the reversing image coding process, acquiring the duration of inter-frame smoothing operation and the total duration of neighborhood space smoothing operation in a preset monitoring window, accumulating and summarizing, and marking the summarizing result as the total loss duration; The coding parameters are depth adjusted based on the total loss duration.
  8. 8. The wireless transmission method of the wiring-free display reverse image of claim 7, wherein the depth adjustment of the coding parameters based on the total loss time length is as follows: comparing the total loss time length with defined loss time lengths stored in a database; if the total loss time is not higher than the defined loss time, continuously monitoring the reversing image coding process; If the total loss time is longer than the definition loss time, the first definition precision deviation value and the second definition precision deviation value are increased and corrected.
  9. 9. The method for wireless transmission of a wiring-free Carplay reverse image of claim 1, wherein the method is characterized in that the method further comprises the steps of determining whether to update coding parameters or not, and the specific determination process is as follows: if the coding parameters are in a non-updatable state, judging that the coding parameters are not updated; If the coding parameters are in an updatable state, acquiring the code rate total deviation value of the current reverse image wireless transmission; Extracting a defined code rate total deviation value from a database, and comparing the code rate total deviation value with the code rate total deviation value of the current reversing image wireless transmission; if the code rate total deviation value of the current reversing image wireless transmission is higher than the defined code rate total deviation value, judging that the coding parameters are not updated; If the code rate total deviation value of the current reverse image wireless transmission is not higher than the defined code rate total deviation value, the code parameters are judged to be updated, and the finally solidified code parameters in the current reverse image wireless transmission process are covered with the historical code parameters in the database.
  10. 10. A wiring-free wireless transmission system for a car backing image, which is characterized by comprising the following components: The system comprises a target code rate analysis module, a coding precision smoothing module and a coding parameter adjustment module; The target code rate analysis module is used for starting a wireless transmission link monitoring thread after the wiring-free Carplay system starts a reversing mode, collecting wireless transmission link performance indexes and analyzing the target code rate of a reversing image frame; The coding precision smoothing module is used for acquiring a reversing image frame by the reversing image acquisition equipment, carrying out space division to obtain a plurality of independent space coding blocks, analyzing an initial block level coding precision matrix corresponding to the reversing image frame based on a target code rate of the reversing image frame, and carrying out inter-frame smoothing operation on coding precision of each space position on the initial block level coding precision matrix to form a final block level coding precision matrix; The coding parameter adjustment module is used for carrying out differential coding processing on each space coding block based on the final block-level coding precision matrix, generating a coding data stream adapting to the performance of the current wireless transmission link, transmitting the reverse image frame to the Carplay terminal through the wireless transmission link, monitoring the transmission state of the coding data stream in real time in the transmission process, obtaining a monitoring result, dynamically adjusting the coding parameters according to the monitoring result, and realizing the self-adaptive dynamic optimization of the coding process in the reverse image wireless transmission scene.

Description

Wiring-free wireless transmission method and system for car backing image Technical Field The invention relates to the technical field of video coding, in particular to a wiring-free wireless transmission method and system for a back image of a carrlay. Background With the development of vehicle-mounted wireless communication technology, in order to reduce the cost of wire harness, simplify the loading process and improve the installation convenience of the post-loading system, in recent years, a product form of transmitting a reversing image signal to a vehicle or a CarPlay display interface in a wireless manner has appeared, wherein the CarPlay is essentially a vehicle-mounted interconnection system and comprises a display interface adapted to a vehicle-mounted scene. For example, part of the scheme adopts wireless transmission links such as 2.4GHz/5GHz WiFi and a special 5.8GHz digital image transmission module, video signals collected by a vehicle tail camera are coded and compressed and then are sent to a decoding terminal of a front cabin in a wireless mode, and then the decoding terminal is connected to a vehicle machine or a CarPlay box in a high-definition multimedia interface, a low-voltage differential signal interface or a USB video input mode. However, in the radio environment in the car, there are often multiple wireless services such as WiFi hotspots, mobile phone hotspots, bluetooth audio, tire pressure monitoring systems, keyless entry, etc. of the car machine at the same time, and interference and competition in the shared frequency band can directly affect stable transmission of the reversing video. In the existing reversing image wireless transmission scheme, in order to ensure basic image quality and real-time performance under a limited bandwidth, a video encoder based on advanced video coding standards, high-efficiency video coding standards or motion joint image expert group coding standards and other standards is generally adopted, and a frame-by-frame image sequence acquired by a camera is compressed into a code stream and then transmitted through a wireless transmission link. The typical process comprises the steps of outputting an original image by a camera, preprocessing the original image by an image signal processor, inputting the original image into a coding chip or a system-level chip, executing the steps of block division, time domain/space domain prediction, transformation quantization, entropy coding and the like by an encoder to generate a compressed code stream, packaging the code stream slice at a network layer or a link layer by a transmitting end, transmitting the code stream slice to a receiving end in a user datagram protocol/real-time transmission protocol, a proprietary wireless protocol and the like, de-packaging, decoding and restoring the code stream by the receiving end, and finally transmitting the decoded image frame to a vehicle display pipeline or a CarPlay display interface. In this process, the encoder typically configures the encoding parameters according to a preset target code rate, resolution, and frame rate to satisfy the code rate constraint in an average sense. However, in most post-loading or low-cost vehicle-mounted scenes, the sensing capability of the coding end to the wireless channel is limited, and the code rate control is mostly adjusted according to the complexity of the current frame content and the fixed target code rate, so that the depth linkage with the actual available bandwidth, time delay and packet loss conditions of the wireless transmission link is lacked. The prior art has the following technical problems: In the actual use environment of the vehicle, the reversing action often occurs in complex scenes such as underground garages, narrow streets, rains and nights, backlight or strong reflection, and meanwhile, strong brightness contrast, local high light spots, raindrops and noise textures, ground fine crushing textures, edges of the vehicle and pedestrians and other high-frequency information exist in the pictures acquired by the reversing camera, so that the statistical characteristics of the images show severe fluctuation in time and space. The conventional code rate control mechanism based on H.264/H.265 is generally adopted in the existing vehicle-mounted wireless reversing image scheme, a coding end dynamically adjusts quantization parameters according to content complexity estimation (such as residual energy, motion vector distribution, texture intensity and the like) of a current frame or a plurality of frames and a preset target code rate, when local library light flickers, a front-facing car light enters a picture and rain and night noise is increased, a complexity estimation module judges the picture as a difficult-to-code scene, a code rate controller is used for avoiding serious mosaic and stripe artifact, quantization parameters are often obviously reduced and output code rate is raised in a very short time, at