2, easy to carry. USB devices are mostly “small, light, thin,” known to the user, the same 20G hard drive, USB hard drives than IDE hard to light half of the weight you want to carry large amounts of data, of course, is the first of the USB hard drive elected.
USB Interface
RS232C serial port: RS-232C standard (protocol) the full name is the EIA-RS-232C standard, which EIA (Electronic Industry Association) on behalf of the U.S. Electronics Industry Association, RS (ecommeded standard) represent recommended standards, identification number 232 is, C is the latest in a modified RS232 (1969), before that, there RS232B, RS232A. It provides cable and mechanical, electrical characteristics, function and signal transmission process. There is another common physical standard EIA RS-232-C, EIA RS-422-A, EIA RS-423A, EIA RS-485. Here only EIA RS -232-C (referred to as 232, RS232). Computer input and output interfaces, is the most common serial interface, RS-232C standard interface rules, 25 lines, the four data lines, control lines 11, three time lines, seven reserve and undefined line, used only 9, commonly used with 25-pin D-sub ports together with a maximum transmission rate of 20kbps, cables up to 15 meters. RS232C port is used for computer input control signal LED display.
as the AV output is still a mixture of video luminance and chrominance signals, so still need to display device brightness and color separation, and decoding can be imaged. Such an approach is bound to result in quality loss, so the AV interface quality is still unsatisfactory. The connection is very simple, just three colors AV cable and TV end of the three colors of the interface corresponding to the connection.
In recent years, with a large number of USB-enabled PC penetration, USB and gradually became the PC standard interface is the general trend. The host (host) side, the latest PC, almost 100% support USB; and in the peripheral (device) terminal, a device using the USB interface is also growing, such as digital cameras, scanners, joysticks, tape and floppy drives, video equipment , printer, keyboard, mouse and so on.
1, hot-pluggable. This allows users to use an external device, do not need to repeat the “shutdown à the parallel or serial cable connected to the à re-boot” this kind of action, but directly on the PC boot, you can plug the USB cable to use.
VGA input interface: VGA interface asymmetric distribution 15pin connection, it works: the memory is stored in digital format within the image (frame) signal has gone through in the RAMDAC analog modulated high-frequency analog signals, and then output to the plasma imaging, so the input VGA signal (LED display inside), you do not like the other video signal decoding circuit as the matrix to go through the conversion. From the front VGA video imaging principle we can see the video transfer process is the shortest, so the VGA interface has many advantages, such as crosstalk-free separation circuit synthesis without wear and tear.
BNC port: coaxial cable typically used in workstations and connectors, standard professional video device input and output ports. BNC cable has five connectors for receiving red, green, blue, horizontal sync and vertical sync signals. BNC connector is different from the ordinary standard 15-pin D-SUB connector of the special display interface. By the R, G, B primary color signals and horizontal sync, vertical sync signal connector of five independent components. Mainly used to connect workstations and other high frequency requirements of the scanning system. BNC connectors can be isolated from the video input signal to reduce interference between the signal and the signal bandwidth larger than the ordinary D-SUB, can achieve the best signal response effect.
3, the standard uniform. We commonly IDE interface hard disk, keyboard, mouse, serial port, parallel port printer scanner, but with USB, these applications were all peripherals can be connected to the PC the same standards, then there is a USB hard drive, USB mouse , USB printer, and so on.
AV interface, the standard video input (RCA) interface: also known as AV interface, usually a pair of white and yellow audio interface, video interface, it is usually RCA (commonly known as RCA) to connect , only need to use the standard with RCA AV cable connects to the corresponding interfaces. AV interface to allow the separation of audio and video transmission, which is avoided because the audio / video mixing interference caused decline in image quality, but because of transmission AV interface is still a luminance / chrominance (Y / C) a mixture of video signal, the device still needs to show its bright / color separation and chroma decoding to imaging, the first mixed and then the color separation process will inevitably result in the loss of signal, chrominance signal and luminance signal will be a great opportunity to mutually interference and thus affect the final output image quality. AV also has a certain vitality, but because of its own Y / C blend that can not overcome the shortcomings can not limit the number of occasions in the pursuit of visual use.
USB is the abbreviation for Universal Serial Bus, English, Chinese meaning is “Universal Serial Bus.” It is a new field of application in the PC interface technology. As early as 1995, it has a PC with a USB interface, but the lack of software and hardware support, these PC USB port are idle unused. After 1998, with Microsoft Windows 98, built-in USB interface, support for modules, coupled with the increasing number of USB devices, USB interface, it getting into the practical stage.
Overall, AV interface to allow the separation of audio and video transmission, the audio and video imaging to avoid interference caused by the picture quality. AV interface to connect a TV and DVD more widely used, is one of the interfaces necessary for each TV.
4, you can connect multiple devices. USB on the PC tend to have multiple interfaces, you can also connect several devices, if connected to a 4-port USB HUB, you can then connect 4 USB devices, and so on, he can not even go to devices in your house while even on a PC without any problems (Note: up to 127 devices can be connected).
USB device will be the reason why a large number of applications, mainly has the following advantages:
component video inputs: the current level in a number of professional video workstation / professional video editing card or device on a high-end DVD players and other appliances see YUV YCbCr Y / BY / BY and other identification marks of the interface, although the shape of different labeling methods and joints but they are color refers to the same interface port (also known as component video interface). It is usually YPbPr and YCbCr two kinds of identification, the former said progressive scan component output, which represents the interlaced component output. We can see from the above relations, we need to know the value of Y Cr Cb value of G can be (ie, the fourth equation is not necessary), so the video output and color processing to ignore the green uniform and keep only difference Cg Y Cr Cb, which is the basic definition component output. S-Video as the advanced products the S-Video Component output chrominance signal C transmitted broken down into component Cr and Cb, thus avoiding the two color decoding and re-mixing process of separation, but also to maintain the color the maximum channel bandwidth, only after the anti-matrix decoding circuit can be reduced to RGB RGB signal imaging, which minimizes the video source to display the video signal path between the imaging, avoiding the cumbersome transfer process image distortion caused by, so color output interface mode is the best variety of video output interface of a.
DVI digital terminal is better than the standard VGA terminal signal, the entire contents of the digital interface ensures a digital format for transmission to ensure that the host to monitor the integrity of the data transfer process (introduction of non-interference signal), can be more clearly the images.
S Video Input: S-Video specific English name called Separate Video, the video in order to achieve better results, people began to explore a more efficient and higher quality HD video transmission, which is the current flourishing of S- Video (also known as two component video interface), Separate Video Video signal meaning is to separate the transmission, which is based in the AV interface will chrominance signal C and luminance signal Y separation, and then were transferred to a different channel, It emerged and developed in the late 1990s, usually a standard 4-pin (no sound) or extended 7-pin (with sound). S-Video interface with graphics and video equipment (such as analog video capture / editing card, TV and para-professional level monitor TV card / TV box and video projection equipment, etc.) currently has more common, compared with AV interface because it does not then Y / C hybrid transmission therefore no need for bright separation and decoding, and the use of separate transmission channel video equipment in large part to avoid the crosstalk signal generated within the image distortion, greatly enhance the image clarity, but the S-Video still be two color difference signals (Cr Cb) all the way color signals mixed as C, for transmission and then decoded within a display device for processing for the Cb and Cr, which will bring some much signal loss and distortion (the distortion is small but in the strict broadcast video equipment under test can still find), and because of the mixed Cr Cb chrominance signal bandwidth lead to certain restrictions, so although the S-Video has been relatively good, but still far from perfect, S-Video, while not the best, but considering the current market conditions and other factors such as overall cost, it is the most common video interface.
AV interface, also known as (RCARCA) can be regarded as TV improved interface, there have been very different appearance. Divided into three lines, namely: audio interface (red with white lines to form the left and right channels) and video interface (yellow).
DVI input: DVI port is mainly used with a digital display output connected to the computer graphics to display the computer RGB signal. DVI (Digital Visual Interface) digital display interface, by September 1998, at the Intel Developer Forum in the Digital Display Working Group (Digital Display Working Group referred to DDWG), developed by digital display interface standard.
HDMI Interface: HDMI is based on the DVI (Digital Visual Interface) developed, can be seen as the strengthening and extension of DVI, the two can be compatible. Maintain a high quality HDMI in the case of transfer to digital format high-definition video and uncompressed multi-channel audio data, the maximum data transmission speed of 5Gbps. HDMI can support all ATSC HDTV standards, not only to meet the highest quality 1080p resolution, but also support DVD Audio as the most advanced digital audio formats, support for 8-channel 96kHz or stereo 192kHz digital audio transmission, and only one HDMI cable, eliminating the digital audio connection. HDMI also have the extra space standards can be applied to future upgrades of audio and video formats. Compared to HDMI and DVI interfaces are smaller and can transmit audio and video signals. DVI cable length can not exceed 8 meters otherwise it will affect the picture quality, but basically there is no HDMI cable length limit. As long as an HDMI cable, you can replace up to 13 analog transmission line, can effectively solve the connected home entertainment system behind the tangled mess of problems. HDMI can be used with broadband digital content protection (High-bandwidth Digital Content Protection; HDCP), in order to prevent a copyrighted audio and video content from unauthorized copying. Because HDMI embedded HDCP content protection mechanism, so Hollywood has a special appeal. HDMI specifications include use for the consumer electronics and PC Type A connector Type B connector with the two, I believe HDMI will soon be using the PC industry.
