The video system composed of video hardware such as video acquisition card and interactive electronic whiteboard is often used for image acquisition/image analysis and processing/video conference/digital monitoring.
Government: telecommuting meetings, government procurement meetings, remote statistics and collaboration, government bidding meetings, personnel recruitment and assessment, public consultation, letters and visits, and public health command.
Finance: financial work conference, remote customer service, office meeting, e-commerce, remote consultation, operation guidance, roadshow, remote recruitment and training.
Enterprises: regular meetings, remote business negotiations, collaborative work, remote recruitment, remote training for agents and distributors, technical seminars, administrative work, internal training and learning, branch meetings, remote customer service and remote monitoring.
Medical treatment: remote consultation, remote medical consultation and remote medical communication.
Education: multimedia teaching video live recording, online education and training, remote tutoring, examination room monitoring, parent-teacher conferences, academic exchanges in different places, and distance teaching observation classes.
Public security law, army: teleconference, long-distance coordinated combat command, long-distance police command, long-distance interrogation, long-distance prison visit, court live broadcast, emergency command.
Operation: Telecom-level network conference service, instant messaging service, VOIP, PSTN.
Information and media: TV interaction, remote interview, remote consultation and remote commerce.
Application of Video Capture Card
Electronic equipment has entered people's daily life from obscurity. Faced with the ever-changing monitoring products and constantly updated monitoring card quotations in the market, people are always at a loss. Only by constantly understanding the monitoring market and monitoring technology can we be in an invincible position.
With the continuous development of information technology, computer technology has been introduced into the field of video acquisition and video processing. Computer processing of video information and digital transmission of video data have been widely used in many fields, as well as in our flight tests.
The image acquisition chipset is used to complete image acquisition, frame storage address generation and image data refresh; Except for setting the acquisition mode, the main processor does not participate in the acquisition process, and we can get the corresponding video data by fetching the acquired video data at the corresponding frame memory address. This method has obviously improved in function, performance, reliability and speed, but the cost is higher. The latter adopts general video A/D converter to realize image acquisition, which is characterized by high speed requirement for the processor, low cost and easy implementation, and can meet the needs of some image acquisition systems.
The system requires a maximum of 25 frames per second (set to be adjustable), and the client displays a maximum of 25 frames in real time (set to be adjustable) and saves them in MPEG4-4 format. The maximum screen resolution is 1024X768. Multi-channel video real-time acquisition adopts VisionRGB-PRO card (Datapath Company, UK), which can acquire two channels of video data in real time at the same time, basically meeting the requirements of this system, and then use a VGA matrix switch to manually switch and collect four channels of video data from the front-end data source.
Hardware environment construction
The acquisition system mainly realizes the manual switching and real-time acquisition of four front-end video data. On the server side, two video data can be collected and stored at the same time (only one video acquisition card is used here), or only one video data can be collected at a time, and then transmitted to the client for real-time display through the network, and the server side also displays the collected videos in real time. In the aspect of video switching, the server or the client can switch by itself, the server can switch the corresponding video input/output port by operating VGA matrix switching through serial port, and the client can switch the corresponding video input/output port through network-server program corresponding module-serial port -VGA matrix switching.
The large amount of video data requires the video data processing system to have the characteristics of real-time acquisition, large-capacity storage and real-time processing. The software should realize real-time video data acquisition (at most two channels), video interface control, real-time video data encoding and saving and sending to multiple clients. The realization of the server is the key of the whole system, and a lot of work is undertaken here, so it is inevitable to have high requirements for software and hardware. These are the main functions to be implemented on the server.
The most important thing in acquisition is real-time. In this paper, the event-driven method is used to obtain data from the port, display the collected video data stream on the desktop, and then encode and save it. The data collected by the video should be set as bitmap video frames through the corresponding modules of the software, so as to facilitate the display and coding and storage on the server side. Divx coding is adopted here, and the MPEG4-4 stream in frame format is formed after Divx coding.
Server side implementation
Divx decoding is also decompressed in frame format, so when sending data to the client, it is beneficial to send the video data stream in frame units. Media streams are divided into four streams: video stream, audio stream, text stream and MIDI stream. The graphics card collects two video streams, and each video stream is saved with an additional text stream. The text stream is mainly based on the server time and some manually input text information required by customers. When recording two media streams, there are usually two recording methods. Here, the video stream and the text stream are recorded in a file, which is beneficial to the future storage and reference of the file. In the aspect of acquisition software implementation, the corresponding SDK (Software Development Toolkit) and API (Application Programming Interface) are mainly used, and VFW(VideoforWindows) can also be used. However, the latter method can realize a simple single-channel video acquisition card, and the first method is more flexible for multi-channel video acquisition, but the implementation is much more complicated than the second one.
The coordination of all aspects of the server is the key. When the program starts, it defaults to the video capture card channel set last time. If there is video data, it will be displayed and saved. If there is no video data, wait. If you want to adjust the video capture card channel, you can use the serial port to send the corresponding command to the VGA matrix switch, so that the VGA matrix switch can switch the corresponding input and output channels. You can also switch the input and output channels corresponding to the VGA matrix switch from the client to the server serial port through the network (which will be introduced later when introducing the client). The original video file will be automatically saved after each switch. If there is video data after switching, a new video file will be automatically regenerated.
Real-time transmission of video data by local area network has been widely used in some fields, and wired local area network accounts for the majority, because wired local area network technology is mature and transmission speed is fast. However, when transmitting a large amount of video data for a long time, it will also lead to unstable transmission speed, data congestion, and greatly reduced video transmission quality, which will easily lead to ghosting, jitter, scattered screen, delay and other phenomena. The picture displayed on the server desktop is not encoded, but the video data stored in the network transmission is encoded by Divx, which effectively reduces the transmission burden between the network and the server.
In order to transmit media streams efficiently, in real time and with high quality on LAN, it needs the support of many technologies, including the selection of network transport layer protocol, coding (decoding) technology, network transport layer quality control technology and so on.