Learn about video capture card to identify the main features and techniques (1)

The purpose of purchasing card is nothing can be easier and more effective monitoring, the security field (video acquisition card), and a variety of fabulous DVR card, let a lot of contractors and consumers in particular just entrants have, you should need to look at several large areas.

Video acquisition card key features and technologies

Interface: the market for video acquisition card interface can be divided into several types, video acquisition card interfaces including video and PC interfaces and analog video device interface.

Current PC video capture card usually uses the 32-bit PCI bus interface, it is inserted into the PC motherboard expansion slot for acquisition card and PC communication and data transfer. Acquisition card with at least one composite video interface (VideoIn) to analog video device connected. High performance capture card generally has a composite video interface and a S-Video interface. General acquisition card supports PAL and NTSC two DTT.

Note that video acquisition card generally do not have TV antenna connector and an audio input port, you cannot use video capture card direct acquisition television RF signal, while not directly capture the sound of analog video signal.

To capture sound, the PC must have a sound card, video capture card through the PC's sound card gets digitized sound and sound and collected together digital video synchronization.

Features: the main video capture cards? what are the functions on your PC video capture card can receive from the video input terminal of analog video signal, the signal acquisition, quantify into a digital signal and then coding into digital video sequences.

Most video capture cards are equipped with hardware compression features in collecting video signal on the card first when the video signal is compressed, and then only through the PCI interface to compressed video data to the host. General PC video acquisition card use intra compression algorithm to store digital video into AVI files, upscale some video acquisition card also can directly collected digital video data real-time compressed into MPEG-1 format file.

Due to the analog video input can provide continuous information source, a video capture card to capture analog video sequences in each frame the image, and in collecting the next frame image before these data into PC system.

Therefore, the key to achieving real-time acquisition is every frame processing time required. If every frame of video image processing time over the adjacent frame intervals between, to a loss of data, which dropped frames. Acquisition cards is to get the video sequences before compression, and then into the hard drive, i.e. video sequences of the acquisition and compression is done together, and you do not have to compress again. Different grades of acquisition card has a different quality of acquisition compression performance.

Drivers and applications: video acquisition card there is the need to drive to work properly, video capture cards are equipped with a hardware driver for PC control of the acquisition card and data communications.

Depending on the capture card requires the operating system environment, each has a different driver. Only the acquisition card plugged into the PC motherboard expansion slot and proper installation of the driver to work properly. Acquisition cards are equipped with a capture application to control and manipulate the acquisition process. There are also some generic collection procedures, digital video editing software such as AdobePremiere also has a collection of features, but these application software must be used with a capture card hardware. That is, only the acquisition card hardware after normal installation and driver to use.

Application of video acquisition card

Electronic equipment have been unknown to walk into people's everyday life, the changing face of market monitoring products, as well as continuously updated monitoring card offer, people always confused, so we had to constantly monitor the market to understand, and monitor and control technology to be invincible.

With the continuous development of information technology, computer technology into the video collection, video processing, computer processing of video information and the use of digital transmission of video data in many areas have a wide range of applications, in our airplanes flight test has also been a large number of applications.

Video image acquisition more, basic can be divided into 2 main categories: digital signal acquisition and analog data acquisition.

Complete with image acquisition and image acquisition chipset, frame memory address generation and image data refresh; in addition to the acquisition mode setting, the primary processor is not involved in the acquisition process, as long as the corresponding frame memory address remove collected video data to get the corresponding video data, this approach in terms of functionality, performance, reliability, speed, etc. have been significantly improved, but the cost is high.

The latter uses the generic video A/D converter for image acquisition, it features data acquisition CPU time requirements for processor speed, low cost, easy to implement to meet a certain image acquisition system needs.

This system requires the collecting maximum per second and 25 frames (as adjusted), clients real-time display of maximum 25 frames (as adjusted), saved as MPEG4 format, the screen for maximum resolution of 1024 x 768.

Multi-channel video real-time acquisition using VisionRGB-PRO cards (United Kingdom Datapath Inc.), this card can be real-time acquisition two channel video data, the basic met the requirements of the system, then uses a VGA matrix switcher to front-end data source four channel video data for people to switch collection.

Construction of the hardware environment

This acquisition system main realization on front-end quad video data of people switched real-time collection, the server may also collect and store two channel video data (here only one video acquisition card) or a collection of only one channel video data, and then by network real-time transmission to the client, the server-side also real-time display of the acquisition of video.

In terms of video switch can be used in server-side or client-to-switch, the server can operate over a serial port VGA matrix switch accordinglyVideo input switching output, in client server program over the network-the corresponding module-serial port-VGA matrix switch to the appropriate video input output port of the switch.

Video data volume is large, this requires video data processing system with real-time acquisition, mass storage, and real-time processing characteristics.

Software to achieve the real-time collection of video data (up to two-channel), control video interface, the video data real-time encoding to save and send to multiple clients. In the server-side implementation is key to the entire system, in which also bear a great deal of work on the software and hardware requirements are high becomes inevitable. The above is to be implemented on the server key features.

In the collection is most important is to have real time, to event-driven method to get data from the port, the acquisition to the video streaming in the desktop display at the same time and then save the encoding, video acquisition of data corresponding to the software module to set the bitmap type of video frames in order to facilitate the display of server-side and save with encoding, in the use of Divx codec, Divx encoded form to frames format MPEG4 stream.

Server-side implementation

Divx decoding is to extract frame format, so to send data to the client to frames when you send video data streams.

Media stream is divided into four streams: video streams, audio streams, text flow, MIDI stream, using the video card acquisition two channel video stream on save each video stream with a text stream, the main text flow should the customer asked to join the server time and some human-entered text information in the records of the two media stream in general there are two logging methods, here is the video stream and write the text stream to a file so conducive to file future preservation and access. In the capture software implementations of the main application of the corresponding SDK (Softwaredevelopmentkit) and API (application programming interface), also available VFW (VideoforWindows). But the latter approach for simple single video capture card, for multi-channel video collection with the first approach is more flexible, than the second complex number.

In the server-side aspects of coordination is the key, the program starts first default last set of video acquisition card channel, such as video data display, save, if there is no video data is waiting, if you want to adjust the video capture card channel available serial port to VGA matrix switch sends the appropriate commands to VGA matrix switcher to switch input and output channel.

Can the client via the network to the server port to VGA matrix switch VGA matrix switch corresponding input and output channel switching (behind describes client then introduction). After each switch will automatically save the original video files, such as the switch is followed by video data will be automatically rebuilt a new video file.

Use LAN real-time transmission of video data has been in some areas, a large number of applications, LAN to a wired local area network, since wired LAN technology is mature, transmission speed, however long the transfer large amounts of video data can also cause the transfer rate instability, causing data plug, can cause video transmission quality, easily lead to a significant reduction of ghosting, jitter, corruption, delay, etc.

In the server desktop display screens are not handled by any coding, network transmission and video data is saved by Divx encoded, this powerful reduces network transmission and server load.

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