Introduction to 1394
I. Concept
The full name of 1394 card is IEEE 1394 interface card. This interface technology was first founded by Apple, an old computer manufacturer. Apple calls it Firewire, so many people are used to calling 1394 card firewire card. Its original intention is to use it as a high-speed data transmission interface. 1995 The American Institute of Electrical and Electronics Engineers (IEEE) adopted it as the official new standard with the number 1394, which is also the origin of the name IEEE 1394. Different companies have different names for 1394 interface technology because their registered trademarks are different. For example, Sony calls it i.Link, Texas Instruments calls it Lynx and so on. It's actually the same thing.
To sum up, we can know that IEEE 1394 is an external serial bus standard, which can achieve a data transmission rate of 400MB/s and is very suitable for video image transmission. As an open data transmission technology standard, IEEE- 1394 has been applied in many fields, including digital cameras, high-speed external hard disks, printers and scanners. The standard 1394 interface can simultaneously transmit digital video signals and digital audio signals. Compared with analog video interface, 1394 technology has no signal loss in the process of acquisition, recording and playback. It is precisely because of this advantage that 1394 card is more used as a video capture card, ignoring its other functions. The original 1394 card cost thousands of dollars each time. In recent years, with the decline of production cost, the cheapest card is only tens of yuan, and 1394 card is rapidly spreading to more ordinary families.
Second, the classification of 1394 card
At present, 1394 cards on the market can be basically divided into two categories: 1394 cards with hard decoding function and 1394 cards with software compression coding. The former is more expensive and the latter is very cheap, only about 100 yuan. Tiger's 1394 card was only 70 yuan, and it has been used well:) Let me talk about these two cards slowly.
The first is a 1394 card with hard decoding function, such as EZDV acquisition card, which can not only transmit the video signal of TV or video recorder to the computer, but also have hardware compression function, and can compress the video data into a video stream in MPEG- 1 format in real time and save it as. MPEG files or DAT file, so that it is convenient to make video discs. Well-known brands include Pinnacle and Snazzi. The performance of these products is generally good, the supporting software is more professional and functional, and the use effect is ideal, but the price is relatively expensive, ranging from several hundred to more than one thousand yuan, and the most expensive one is ten thousand yuan!
Another cheap card 1394, which uses software to realize compression coding, has the function of inputting video signals into a computer, turning them into digital signals that can be recognized by the computer, and then editing the video in the computer with software. Generally speaking, the function of 1394 card is to transfer the video content in the digital video tape to the hard disk. 1394 card is just a data transmission interface, unlike video capture card which needs video compression hardware. AVI files transmitted to hard disk through 1394 card are edited and post-processed by software. In fact, even if there is compression coding hardware on the 1394 card, it only works when editing and generating MPEG files, but not when transmitting data. The biggest feature of this 1394 card is its low price, which is suitable for beginners. The disadvantage is that 1394 card is edited by software, and the data volume is huge (1 hour video 13- 17GB, which means that a 60-minute DV tape takes up 13- 17GB of hard disk space). If you want to do video editing again:) If you don't want to upgrade your computer, you can choose the first card with hardware coding function, 1394, because it is a way of collecting and compressing, so it takes up less hard disk space (1 hour video takes up about 650-700MB of hard disk space), and the compressed image quality is still better, but the price is a little expensive.
Because the 1394 card with hardware codec function uses the hardware on its card to generate digital video, different brands of cards will have different coding effects, so Tiger suggested that if you want to buy this card, it is best to be within the financial range-the more expensive the better!
Tiger thinks ordinary 1394 cards can be used in general households. The basic process is as follows: transfer the video content to the computer hard disk through 1394 card, and generate it as an AVI file, then edit it with software to generate a new AVI file, and generate the edited material as an MPEG 1 or MPEG2 file, and carve it into a VCD or DVD for permanent storage.
Introduction to Usb
USB(Universal Serial Bus), commonly known as Universal Serial Bus, aims to solve the problems of fragmented connection mode and ease of use of interface devices. Many computer users may have no problem using it in front of the computer, because out of sight, they can only see the connecting line between the mouse and the keyboard at most. But once you get behind the computer, you may be dumbfounded to see so many kinds of wires, including at least power cord, monitor signal cable, printer connection cable, modem and speaker. In addition to taking some time to distinguish when connecting, it is also very tiring to sort out these jumbled wires behind the computer. No matter how you organize it, it's still ugly. Sometimes you think, if you have a power cord, just switch to wireless mode! Of course, that will be the best in the future. At present, the best way is to simplify all the connecting lines for the convenience of users.
Therefore, a few years ago, Compaq, DEC, IBM, Intel, Microsoft, NEC and Nortel * * * jointly launched the USB specification, aiming at reducing the number of connecting wires behind the computer as much as possible, making it convenient for users to use, making many different interface devices use the same connecting wires, thus simplifying the cables of various connections. Take a closer look at their specifications. If all these peripherals use USB, it seems that the above purpose can really be achieved.
In order to connect various interface devices, USB can connect 127 devices at most, which is quite scary. For ordinary users, this number is unnecessary, and the equipment of 10 is rarely used. But has anyone ever thought that if there are so many connections, it will be enough. In the specification design of USB, when you want to connect so many interface devices, you must have the design of USB HUB, which can easily connect the periphery. The so-called HUB, similar to the hub function of the network, can be called hub, which can be connected in series to facilitate the installation of more devices. In the future, users will most often see the USB hub on the monitor or keyboard to facilitate the connection of devices to the desktop. Of course, there may be a separate hub.
USB was originally designed to connect various interface devices, aiming at medium and low speed interface devices, so the transmission speed of USB is not high. USB has two transmission rates. The first is full-speed mode, with the highest transmission rate reaching 12Mbps. The second is low-speed mode, with the transmission rate of 1.5Mbps. The low-speed mode is only used in a few peripheral areas, and its only advantage is low EMI. Therefore, the full-speed transmission speed of USB is quite high compared with the existing serial port (the standard is 1 15200bps), but when there are many peripheral connections, the overall performance may decline. In addition, USB is also very convenient to use, that is, it supports hot plug. If the device driver has been installed in the operating system, it can be installed or uninstalled directly when the system is running, unlike many devices that have to turn off the system power or restart the operating system before they can be used, which increases the convenience of use.
Support for USB can be divided into hardware and software. On the host computer, the general PC PC started to support from Intel VX chipset, and now almost all system chipsets have the function of supporting USB. The more troublesome part is the operating system, because USB has many functions that need the cooperation of the operating system to play its greatest role. If the operating system doesn't support it, the design of USB is like waste. Take Windows 9X, which has the largest number of users at present, as an example. In fact, USB support can be added to Windows 95 OSR2, but many users don't know whether they can add it. In addition, many interface equipment manufacturers are not fully optimistic about the USB market, so there are not many users and products. However, the newly launched Windows 98 supports USB function, and I believe that a large number of products will appear on the market soon. At present, USB devices include mouse, keyboard, joystick, speaker and display. The display part is used to set the display screen, instead of directly transmitting the display data through USB, and the display may have the function of hub. In addition, USB peripherals, such as digital cameras, scanners, printers and so on. Will also appear one after another. In the foreseeable future, all kinds of low-speed devices will use USB as the transmission interface.
Devices that use USB are very simple. At present, Windows 98 is designed to support USB. As soon as the user plugs in a new device, it will detect it immediately and automatically install the required driver. When installing the driver, you don't need to shut down or reactivate the operating system first, and the new device can be used immediately.