CN103428493A - Light wireless transmission system for high-definition videos - Google Patents

Abstract

The invention discloses a lightweight high-definition video wireless transmission system, which includes a video server end and a video browser end, and the video server end and the video browser end perform wireless data transmission through a Mesh network; the video server end includes a core processing chip and a core The wireless transmitting module connected to the processing chip, the core processing chip is provided with an image acquisition interface; the video browser end adopts a computer and client video browsing software based on Windows platform. The system realizes the long-distance transmission of 720P high-definition images under the condition of limited wireless bandwidth, and the transmitter device has the characteristics of light weight and low power consumption, which is convenient for extended application on mobile devices with limited load, and assists in solving problems such as major natural Disaster sites, large-scale mass gatherings, and important security sites, etc., rear commanders need to keep abreast of real-time information issues in order to improve the accuracy and timeliness of response decisions and improve work efficiency.

Description

Lightweight high-definition video wireless transmission system

This invention is supported by Tianjin Natural Science Foundation, the fund number is 13JCYBJC15800.

technical field

The invention belongs to the technical field of video image processing and wireless network communication, and relates to a high-definition video signal collection and long-distance transmission device.

Background technique

In the production and life of modern society, the application demand for wireless video transmission is growing rapidly. The wireless video transmission system compresses and encodes the video information collected by the image sensor on site, and then transmits it to the rear client through wireless means. Make decisions and effectively shorten response time.

The wireless video transmission system can be used for reconnaissance, surveillance, etc. in the military, and can be used in planning and measurement, remote sensing imaging, engineering rescue and other fields in civilian use. For the image transmission system of some emergency command centers, it is often required to transmit the real-time image information of the emergency scene to the command center, such as the scene of major natural disasters, large-scale mass gatherings and important security sites, so as to improve the accuracy and timely response to decision-making. performance, improve work efficiency.

Wireless image transmission is real-time video transmission, and there are two key technologies: one is high-definition video compression processing, that is, video compression; the other is wireless data transmission in motion, that is, wireless data communication. Therefore, to develop a wireless image transmission system that can stably transmit high-definition video signals with a wide frequency band during high-speed movement, two main problems must be solved: one is to achieve high-resolution video with as high a compression ratio as possible. Compression algorithm; the second is high stability real-time high-speed data communication.

The image resolution of the current wireless video image transmission system is low, subject to the video compression algorithm, its bit rate is high, and the effective transmission rate of the existing wireless communication link is low, it is difficult to transmit high-definition video signals with low compression ratio.

With the development of computer hardware and software and wireless communication technology, wireless video transmission technology has also achieved rapid development, and the application field of wireless video transmission technology is becoming more and more extensive. Sexuality puts forward higher demands. In the existing wireless video transmission applications, video compression coding is mainly based on MPEG2/4, H.261/263 and so on. Among them, high-quality images (standard PAL/NTSC resolution not less than 720×576) are generally encoded and decoded by MPEG2, and the average bit rate of high-definition video is above 10Mbps, which requires a higher data transmission rate. The development direction of the wireless high-definition video transmission system is increasingly tending to high-definition video resolution, intelligent transmission links, and system function integration.

Contents of the invention

The purpose of the present invention is to solve the problems of compression processing and wireless transmission of high-definition video information in the above-mentioned prior art, and provide a lightweight high-definition video wireless transmission system.

The present invention is realized according to the following technical solutions:

The lightweight high-definition video wireless transmission system of the present invention includes a video server end and a video browser end, and the video server end and the video browser end perform wireless data transmission through a Mesh network; the video server end includes a core processing chip and is connected to the core processing chip The wireless transmission module is equipped with an image acquisition interface on the core processing chip; the video browser uses a computer and Windows-based client video browsing software.

The image acquisition interface is connected with CCD image sensor, CMOS image sensor or DV camera equipment.

The video server uses the H.264/AVC compression standard to compress the collected video data with a high compression ratio.

When the video server side compresses the video data, it adopts inter-frame prediction and intra-frame prediction coding to remove redundant information, so as to improve video compression efficiency; the decoding end will not be distorted by integer DCT transformation, and no mismatch will occur. Addition and shift operations replace multiplication, which reduces the computational load of the entire algorithm; entropy coding further compresses the zero values that appear after quantization, and encodes the quantized coefficients of the residual block to remove statistical redundancy.

The wireless transmission module of the video server end is a low-power directional Wi-Fi antenna, and the data is encoded by the RTSP protocol for transmission, and the video browser end is in the form of a computer using a Wi-Fi access point to access the server end through the RTSP protocol To realize the reception of wireless video data.

The advantages and positive effects that the present invention has are:

The system realizes the long-distance transmission of 720P high-definition images under the condition of limited wireless bandwidth, and the transmitter device has the characteristics of light weight and low power consumption, which is convenient for extended application on mobile devices with limited load, and assists in solving problems such as major natural Disaster sites, large-scale mass gatherings, and important security sites, etc., rear commanders need to keep abreast of real-time information issues in order to improve the accuracy and timeliness of response decisions and improve work efficiency. The system is mainly used in long-distance wireless transmission of high-definition video in many industries and fields.

Description of drawings

Fig. 1 is the structural diagram of the video server end of the lightweight high-definition video wireless transmission system of the present invention;

Fig. 2 is the functional block diagram of H.264 video transmission based on RTP/UDP of the lightweight high-definition video wireless transmission system of the present invention;

Fig. 3 is a single-frequency wireless Mesh structural diagram of the present invention;

Fig. 4 is a functional diagram of information interaction between the video browser end and the video server end of the present invention.

Detailed ways

The lightweight high-definition video wireless transmission system of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

The lightweight high-definition video wireless transmission system of the present invention includes a video server end and a video browser end, and the video server end and the video browser end perform wireless data transmission through a Mesh network (multi-hop network) to complete high-resolution video collection , encoding, wireless transmission, decoding, real-time playback and other processes. The video server end includes a core processing chip and a wireless transmitting module connected with the core processing chip, and the core processing chip is provided with an image acquisition interface; the video browser end adopts a computer and client video browsing software based on Windows platform.

The image acquisition interface is a high-definition video signal input interface, which is used to connect equipment such as CCD image sensor, CMOS image sensor or DV camera.

Fig. 1 is a structural diagram of the video server end of the lightweight high-definition video wireless transmission system of the present invention. As shown in Figure 1, the video server side uses the TMS320DM368 processor as the core processing chip, uses the video processing subsystem of the chip to collect and preprocess the original video signal from the signal input by the image acquisition interface, and uses the internal integrated video encoder The decoding coprocessor does most of the video compression processing. Use the H.264/AVC compression standard to compress the collected video with a high compression ratio, and improve the open source H.264 algorithm. It has good network adaptability, anti-packet loss performance and anti-bit error, making it meet the requirements of wireless Video transmission requires low latency and low bit rate for video streams.

The wireless transmitter module on the video server side is a low-power directional Wi-Fi antenna. In view of the fact that wireless video transmission is sensitive to picture lag, the video server side uses RTSP (Real-time Streaming Protocol) to package the compressed video stream with RTP. Ensure the real-time and stability of high-definition video, and use the EMAC module of the TMS320DM368 core processing chip to cooperate with the Mesh network composed of multiple Wi-Fi APs to better adapt to the bit error interference of the transmission channel in a complex electromagnetic environment and improve The robustness of the system enhances the stability of the system image quality and realizes the wireless transmission of 720P high-definition video data.

In H.264, inter-frame prediction and intra-frame prediction coding are used to remove redundant information to improve video compression efficiency; the use of integer DCT transforms the decoding end without distortion and mismatches, and the use of addition and shift operations instead of multiplication reduces The computational load of the entire algorithm is reduced; the entropy coding further compresses the zero value that appears after quantization, and encodes the quantized coefficient of the residual block to remove statistical redundancy.

The working process of the video server is as follows:

The STM320DM368 chip collects data from the connected camera or CCD chip to obtain a 720P video stream, uses the video processing in the VPSS (Video Processing Subsystem, video processing subsystem), and the VPFE (video processing front end) in the VPSS uses the ISIF (image sensor interface) to preprocess the video stream obtained by the sensor, such as control and parameter setting, and then the programmable image channel (IPIPE) converts the raw data from CCD/CMOS to YCbCr-4:2:2 or YCbCr-4:2: 0 data conversion. The converted data is stored in SDRAM (Synchronous Dynamic Random Access Memory) through DMA (Direct Memory Access) channel, and then HDVICP (High Definition Codec Coprocessor) transmits video data through DMA for encoding processing .

The HDVICP in DM368 compresses the video signal in YUV format, and the compression algorithm uses the H.264 standard. In H.264, predictive transformation, quantization coding and statistical coding are used to eliminate redundant information in the video information collected by the front end: first, motion estimation and motion compensation are performed to eliminate temporal redundancy between adjacent frames. Then integer transformation is performed on the residual after motion compensation to eliminate spatial redundancy. Next, quantize the transform coefficients to eliminate visual redundancy, and finally perform entropy coding on the quantized coefficients and motion vectors to eliminate statistical redundancy, and finally obtain a standard compressed code stream.

The obtained standard video stream is transferred to the full-duplex SPI interface (Serial Peripheral Interface, Serial Peripheral Interface) through the DMA controller, and the SPI interface and COFDM (Coded Orthogonal Frequency Division Multiplexing, that is, coded orthogonal frequency division multiplexing) module The corresponding SPI interface of the DM368SPI interface is connected, and the maximum working frequency of the CLK line of the DM368SPI interface is set to 20MHz to meet the transmission rate adjustment requirements of the video stream. The video stream packet length is 188 bytes.

Fig. 2 is a functional block diagram of H.264 video transmission based on RTP/UDP of the lightweight high-definition video wireless transmission system of the present invention. As shown in Figure 2, in the process of using RTSP (Real Time Streaming Protocol, real-time streaming protocol) to transmit H.264 video: the RTP encapsulation module mainly encapsulates the compressed H.264 video stream; RTCP (Real-time Control Protocol, real-time transmission control protocol) analysis module is responsible for generating and sending RTCP packets, and analyzing the received RTCP packets; QoS (Quality of Service, service quality) feedback control module is based on the received RR message feedback information , to dynamically adjust the sending rate of RTCP packets; the sending buffer module sets the port to send RTP (Real-time Transport Protocol, Real-time Transport Protocol) packets and RTCP packets; UDP (User Datagram Protocol, User Datagram Protocol) directly Communicate with the Ethernet physical layer for video RTP packet transmission. The encoded video stream continues to be transmitted to the Ethernet media access controller EMAC through the DMA (Direct Memory Access) bus.

Fig. 3 is a structural diagram of the single-frequency wireless Mesh of the present invention. As shown in Figure 3, the single-frequency wireless Mesh structure diagram, the wireless transmission principle of the Mesh network is as follows: the currently commonly used Wi-Fi standard is IEEE802.11n, including the 2.4GHz and 5.8GHz frequency bands, and maintains the compatibility with 802.11b/g/a It is backward compatible. At present, the transmission speed of 320~600Mbps can be achieved through technologies such as MIMO (Multiple-Input Multiple-Output), OFDM (Orthogonal Frequency Division Multiplexing, Orthogonal Frequency Division Multiplexing).

On the video browser side, the computer uses the Wi-Fi access point to access the server side through the RTSP protocol to receive wireless video data. On the PC platform of the client, use VS2008 to develop a video browser software including transmission rate detection, use the IE browser kernel and video decoding plug-in that comes with the Windows system, and use the H.264/AVC compression standard to receive data from the communication module. The image code stream is decoded, and finally a YCbCr-4:2:0 standard 720P digital video sequence is generated to realize the decoding and real-time display of the compressed video stream.

In this system, the Wi-Fi AP (Wi-Fi Access Point, wireless access point) is used to transmit the RTP packet of the video data to the wireless channel of the 5.8GHz frequency band. The AP is one of the parts of the wireless network. The AP broadcasts the SSID (Service Set Identifier) via the beacons (signal station) packet every 0.1s. The transmission rate of the beacons packet is 1Mbps, and the packet length is relatively short. The PC's Wi-Fi network card can receive the broadcast packets of this SSID. After the connection is established, a temporary non-central distributed control network is formed between the server and the client PC in the wireless video transmission system, and the transmission of video data packets starts under the command of the PC.

When the wireless video transmission system is carried to a long distance, that is, the video server is out of the communication range with the PC client, other APs can be used as relay points to forward video streams to complete multi-hop communication. This transmission form is called Mesh network (multi-hop network). In the process of data transmission, when a Wi-Fi AP node fails, the system can select a nearby node to continue communication, and because of the existence of Wi-Fi AP, it also acts as a relay amplifier for wireless signals. Therefore, the Mesh network has the advantages of robustness, non-line-of-sight transmission, easy deployment, flexible structure, and high bandwidth.

In conventional wireless video transmission, in order to reduce the application cost, the wireless Mesh network used in the system usually arranges multiple single-frequency APs in a straight line as much as possible, and sets it as a single-frequency Mesh structure. A is the Wi-Fi AP node on the video server side, and H is the Wi-Fi AP node on the video browsing software side. The fastest communication flow is shown in Figure 3.

Fig. 4 is a functional diagram of information interaction between the video browser end and the video server end of the present invention. As shown in Figure 4, in order to realize the wireless transmission of high-definition video, the video server needs to transmit the H.264 video stream to the video browser through the Wi-Fi network. The information interaction process between the video server and the browser software in the RTSP protocol is as follows :

The video browser software initiates an RTSP OPTION request through the PC to obtain the provision method of the video server, and the server returns the corresponding support method after receiving it. Five methods are used in the system: DESCRIBE, SETUP, TEARDOWN, PLAY, etc.

The browser software initiates an RTSP DESCIBE request and sends session description information. The information received by the video server mainly includes: media name, decoder type, video resolution, user's decoding ability, etc., and returns information including media name, frame rate, and sampling rate. , encoding type, transmission protocol and other necessary media parameters to the browser software.

The browser software initiates an RTSP SETUP request to request session establishment and prepare for transmission. After the video server receives it, it creates a UDP socket for RTP/RTCP, and responds with a port number and a session identifier.

The browser software initiates an RTSP PLAY request to request real-time video playback. The video server immediately makes corresponding information including the session identifier, RTP packet serial number, time stamp, etc., and then performs RTP encapsulation on the H.264 video stream, and sets the current state as Playing, and the rtp thread thread of the video server program checks the Playing state Then start the transmission of RTP data packets.

The browser software initiates a TEARDOWN request to stop the RTSP protocol. After receiving the message, the server will close the current connection, stop the transmission of the RTP data packet, and delete the IP address of the PC on which the browser software runs and other information from the maintenance list.

The invention abandons the traditional single-hop network wireless transmission mode that causes system paralysis due to node failure, and adopts wireless mesh network transmission, which has the advantages of good robustness, flexible structure, high bandwidth, and non-line-of-sight transmission.

Claims (5)

1. A lightweight high-definition video wireless transmission system, characterized in that: the transmission system includes a video server end and a video browser end, and the video server end and the video browser end carry out wireless data transmission through a Mesh network; the video server end includes a core A processing chip and a wireless transmitting module connected to the core processing chip, the core processing chip is provided with an image acquisition interface; the video browser end adopts a computer and client video browsing software based on Windows platform. 2. The lightweight high-definition video wireless transmission system according to claim 1, characterized in that: the image acquisition interface is connected to a CCD image sensor, a CMOS image sensor or a DV camera device. 3. The lightweight high-definition video wireless transmission system according to claim 1, wherein the video server uses the H.264/AVC compression standard to compress the collected video data with a high compression ratio. 4. The lightweight high-definition video wireless transmission system according to claim 3, characterized in that: when the video server compresses the video data, inter-frame prediction and intra-frame prediction coding are used to remove redundant information, so as to improve video compression efficiency ;The integer DCT transformation is used to transform the decoding end without distortion and mismatch, and the addition and shift operations are used to replace the multiplication, which reduces the amount of calculation of the entire algorithm; the entropy coding further compresses the zero value that appears after quantization, and the residual block The quantized coefficients are coded to remove statistical redundancy. 5. The light-duty high-definition video wireless transmission system according to claim 1, characterized in that: the wireless transmitting module at the video server end is a low-power directional Wi-Fi antenna, and the RTSP protocol is used to encode the data before transmission, and the video browsing On the server side, the computer uses the Wi-Fi access point to access the server side through the RTSP protocol to receive wireless video data.

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