Use 1394
IEEE 1394, alias FireWire interface, is a high-speed transmission interface developed by the development alliance led by Apple, and the data transmission rate is generally 800Mbps. FireWire is a trademark of Apple. Sony products call this interface iLink.
The original design of IEEE 1394 is to allow users to edit electronic image files directly through the IEEE 1394 interface on computers with high transmission rate to save hard disk space. Before IEEE 1394, special hardware must be used to download the film to the hard disk for editing. However, with the price of hard disks getting cheaper and cheaper, the development of USB 2.0 is not too slow. It has replaced IEEE 1394 and become the most commonly used interface for external computer hard disks and other peripheral devices.
In the early days, the dispute over the pricing of manufacturing license within the development alliance caused the delayed adaptation of this technology in the market. At the time of pricing, Apple hopes that the license fee profit of each production joint will be $65,438 +0 to $2. Other alliance companies (such as Intel) think this price is too high. If all the companies in the alliance demand such a high profit, the license fee for an interface will be as high as ten dollars. Many companies in the alliance are also members of USB Developer Forum (USB-IF). Because of this dispute, other companies in the alliance began to pay attention to USB 2.0. Features of IEEE 1394 The features of IEEE 1394 can be summarized as follows:
(1) Expressway
The rate specified in IEEE 1394- 1995 is 100 megabits/second to 400 megabits/second. The higher rate in IEEE 1394b is 800 Mbps to 3.2 Gbps ... In fact, 400Mbps can meet almost all requirements. Now, the usual possible physical stream LSI speed is 200Mbps. In addition, the actual transmitted data is generally compressed, and the original video data is not directly transmitted. So it can be said that 200Mbps is the speed that can meet the actual demand. But for multi-channel digital video signal transmission, the higher the transmission rate, the better, and there is no end.
(2) Real-time
The characteristic of IEEE 1394 is to use isochronous transmission to ensure real-time. At this point, SSA, FiberChannel and Ultra SCSI also have the same performance as IEEE 1394.
(3) Use thin cables for easy installation.
4. The thin cable composed of two signal wires and two power wires makes the installation very simple and the price is relatively cheap. However, the contact distance is only 4.5 meters, which seems to be slightly insufficient. Therefore, some people are also exploring ways to extend the contact distance. The published experimental plastic optical fiber can extend the contact distance to 70 meters.
(4) Bus structure
IEEE 1394 is a bus, not an I/O. When transmitting data to various devices, I/O is not used to transmit data like a network, but the converted space is read and written according to the IEEE 12 12 standard. In short, from the upper level, IEEE 1394 is the same bus as PCI.
The difference between 1394 bus and ordinary USB bus is that 1394 bus is a point-to-point bus. In other words, any device on the bus can actively send requests. It's a bit like a round table. Everyone is equal. On the other hand, devices on the USB bus are waiting for the host to send a request. Then do the corresponding action. Therefore, the 1394 device is smarter, more complicated and more expensive. This characteristic of 1394 bus determines that 1394 can break away from the bondage of desktop host and be more attractive to digital home appliances.
The topology of 1394 bus, like USB, is a tree structure. The tree structure means that all connected devices cannot form a ring (circle), otherwise they may not work normally. However, 1394b proposes a method to avoid the ring structure. Even if the equipment is connected in a circle, it can ensure normal work. Serial buses such as 1394 and USB are different from parallel buses such as PCI. If two devices must pass through the third device, data must also pass through the third device, which means that the third device must also participate in the transmission. Parallel buses such as PCI are like a road leading to various doors. If two devices agree to transmit data and apply for a bus, they can transmit data directly without going through a third device. Of course, the more essential difference is that 1394 is serial, while PCI is parallel.
Between devices on the 1394 bus, some devices will also be selected as bus management to do some extra work, such as
Root node: mainly the final referee in bus arbitration.
Synchronous resource manager: mainly manages bandwidth or provides bus topology and limited power management in synchronous transmission.
Bus manager: you can set the root node, provide bus topology, optimize network response time, and more advanced power management.
(5) Hot plug
It can be plugged and unplugged with electricity. Adding or deleting new devices without turning off the power supply is very simple.
(6) Plug and Play
Adding a new device can be automatically assigned without setting an ID. SCSI users must set the SCSI address, while users of IEEE 1394 don't need any relevant knowledge, and the operation is very simple, so they can use it after connecting.
In fact, whenever a new device accesses a certain 1394 port, the whole bus will have a' welcome ceremony', which is spontaneous and has nothing to do with the PC host. The scientific name is' bus reset'. During this process, all devices will rename themselves (node ID). The new equipment took this opportunity to give itself a name. The naming mechanism of 1394 is simple, starting from 0 to 62 at most. Generally, the id of the leaf node is small and the id of the root is the largest. After the ceremony, everyone went their separate ways. The bus reset of 1394 is very common, as long as it is 1us. Long 160us, but under USB, it is as grand and lengthy as the phoenix nirvana. At least under USB2, it takes 150ms to reset one port, and a bus reset will reset all the ports of connected devices, so it definitely takes more than 600ms+ to connect four devices. There is no difference between good and bad, but their working methods are different.
App application
The application of IEEE 1394 is not limited to a single computer interface field. It has the characteristics of high-speed broadband, especially the ability of isochronous transmission, and can be applied not only to computers, but also to household appliances. At the same time, don't think that IEEE 1394 can only be applied to small areas like home LAN. Research on bridging with ATM is under way, and long-distance broadband application has also been envisaged. The idea of connecting microcomputer and household appliances with IEEE 1394 is shown in the following figure. As can be seen from the figure, the application of IEEE 1394 can be roughly divided into three parts: first, household appliances such as digital video recorders and camcorders; second, computer peripherals such as printers and scanners; and third, internal peripherals such as hard disks and DEV-ROM.
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The popularity of IEEE 1394 initially attracted the attention of home appliance manufacturers, because its transmission rate reached 100Mbit/s to 400Mbit/s, and it can transmit uncompressed digital images in real time, and it can not only establish connections with microcomputers, but also directly connect home appliances without microcomputers. 1996, the digital camera forum composed of more than 50 home appliance manufacturers took IEEE 1394 as the standard interface of digital video/audio. That is to say, digital TV receivers corresponding to digital cameras and digital broadcasting also adopt this standard. Sony has launched two NTSC digital cameras with IEEE 1394 standard digital audio and video interfaces, which is the first step for the global application of IEEE 1394. 1997165438+10. After the technical standards for preventing illegal copying are determined, cameras and DVDs with IEEE 1394 interfaces can be listed. The European Digital Television Broadcasting Company decided to adopt the bus of IEEE 1393 standard for remote control devices and other peripheral devices. Sony has fully adopted IEEE 1394 interface in its high-definition multimedia products, realizing digitalization and networking. Other home appliance enterprises have also made progress in using IEEE 1394. For example, Kodak Company produced the first digital camera supporting IEEE 1394. Seiko-Epson's color printer with IEEE 1394 interface can be directly connected to a digital camera or video camera, and color photos can be printed without a computer.
The response of computer manufacturers to IEEE 1394 seems a little late, but some major manufacturers have already started to act. At the end of 1997, Intel decided to integrate the IEEE 1394 circuit into the peripheral chip (logic LSI). Microsoft has supported IEEE 1394 port in Windows 98, and developed device driver software supporting digital video cameras and digital video recorders. Another technology called Device Bay, which is advocated by several companies such as Intel and Microsoft, is also emerging. The equipment cabin will be connected with various devices through USB and IEEE 1394. It can be seen that these new standards are expected to be widely used.
In a word, IEEE 1394 is both a new generation interface and a new generation bus. It is not only a computer peripheral interface standard, but also a home appliance interface standard; As a humanized multimedia connection mode, it can be widely used in home, mobile environment and office. As a low-cost digital audio/video interface, new audio/video products such as digital TV, multimedia and compact disc (MMCD) home network will be the initial market of IEEE 1394. IEEE 1394 will gradually improve the existing SCSI scanning equipment, optical disks, tape drives, printers, etc. So as to fundamentally eliminate the obstacles for families to move towards multimedia. 1394 card classification editing this paragraph 1394 cards currently 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!
For general household use, ordinary card 1394 is enough. The basic process is as follows: the video content is transmitted to the computer hard disk through the 1394 card, and generated as an AVI file; a new AVI file is generated by post-editing with software; the edited material is generated as an MPEG 1 or MPEG-2 file, which is carved into a VCD or DVD for permanent storage.
IEEE 1394 interface is a high-speed serial interface standard initiated by Apple and TI. It is called FireWire by Apple, i.Link by Sony and Lynx by TexasInstruments. Although the registered trademarks of their respective manufacturers have different names, they are essentially a technology, namely IEEE 1394.
IEEE 1394 is an external serial bus standard with high speed of 800Mbps. In recent years, with the decrease of cost, 1394 card is rapidly spreading. Other related devices, such as digital cameras, hard disks, network cameras, etc., are gradually emerging.
1394 interface has the function of broadcasting data from one input information source to multiple output machines, especially suitable for AV (home audio-visual connection). Because the interface has isochronous transmission function, the quality of audio and video data played back by audio-visual AV equipment is guaranteed, and the playback effect is good.
Strictly speaking, IEEE 1394 card is just a universal interface like USB, not a video capture card. For example, we can connect a high-speed external hard disk to the IEEE 1394 card. However, most of the applications of IEEE 1394 card are connected with DV digital cameras to collect digital video signals, so we usually regard it as an acquisition card. At present, the 1394 cards on the market can be simply divided into two categories: DV cards with hardware DV real-time coding function and 1394 cards with software compression coding.
DV cards with hardware coding function are generally several thousand yuan. DV cards with hardware coding can greatly improve the speed of DV editing, and can handle some special effects in real time, and many of these cards have the function of handling MPEG-II video streams.
According to the original standard, there are two types of 1394, namely 1394a(400Mbps) and 1394b(800Mbps). But now most of the interfaces on the market are 1394a, and 1394b is rare.
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