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IEEE-1394

IEEE-1394 is a multimedia communication bus. The 1394 bus is a versatile, high-speed and inexpensive method, of interconnecting a variety of consumer electronics devices and personal computers.

What is a 1394 "bus?"

You can think of a "bus" as a linear electronic path on which several devices share information. As you connect 1394 devices using a common series of cables, you are connecting them to the 1394 bus. (While this kind of bus can actually take you to work ? in a manner of speaking ? it does not require four wheels.)

Why was 1394 created?

1394 was designed to be a global interconnect, eliminating the need for many different input/output connectors. The resulting port integration and consolidation of circuit board space results in an overall reduction in product cost and complexity. The 1394 bus is a versatile, high-speed and inexpensive method of interconnecting a variety of consumer electronics devices and personal computers, while eliminating the frustrating tangle of cables most users encounter today.

How many devices can be connected with 1394?

With 1394 you can connect up to 63 devices together.

When 1394.1 bus bridges become available, it will be possible to connect over 60,000 devices using the 1394 bus standard. Digital camcorders, surround sound processors, scanners, printers, hard disk audio recorders, videoconferencing cameras and disk drives all share a common bus connection, not only to an optional host computer, but to each other as well. Because of this, 1394 is a prime candidate for the "Home Network" standard initiated by VESA (Video Electronic Standards Association) and other industry associations.

How fast is 1394?

The 1394 standard defines three signaling rates which, in precise terms, are: 98.304, 196.608 and 393.216 Mbits/s (megabits per second). These rates are referred to in the 1394 standard as S100, S200 and S400. There are efforts underway to expand the standard to include 800 and 1,200 Mbits/s speeds.

You can mix and match devices of different speeds on the same 1394 bus. Using "isochronous" data transmission, even the S100 implementation supports two simultaneous channels of 30fps (frames per second) broadcast-quality video along with stereo audio.

What software do I need?

All modern personal computer operating systems already support 1394, including Windows 98, Windows 2000, Mac OS 8.6, and Mac OS 9.0.

Can I connect and disconnect devices without turning the power off?

Yes. 1394 is defined as "hot pluggable." That means when you add a new device, the 1394 bus automatically recognizes it. Similarly, when a device is disconnected, the bus automatically reconfigures itself. The standard 1394 cable provides up to 1.5 amps of DC power to keep remote devices "aware," even when they are powered down.

Do I need a computer on the 1394 bus to make it work?

No. You do not need a computer to take advantage of 1394. A VCR, for example, can act as a 1394 bus controller for camcorders, TV sets, stereo receivers, amplifiers and other home theater components.

How does 1394 compare to SCSI?

The SCSI bus requires that devices be serially daisy-chained together, with each device having a non-conflicting, pre-assigned address and that the final SCSI device be terminated. There is a limit of seven devices on a SCSI chain. In contrast, 1394 devices can be connected in multiple configurations. These can include a star or tree pattern with its own daisy chain branches. Device terminators are not required. And 1394 addressing, unlike SCSI, is done dynamically; there is no need for address pre-assignment. Plus, 1394 allows up to 1,023 buses to be bridged together.

How does 1394 compare to Ethernet?

1394 multiplexes (combines) a variety of different types of digital signals, including video, audio, MIDI and device control commands, on two twisted-pair conductors (similar to that of 10base-T Ethernet). This ability to easily multiplex or combine different signal types distinguishes 1394 from other systems which transmit only a single signal type.

Ethernet, for example, is typically used in data networks and requires special protocols (presently implemented only in proprietary multimedia networking systems) to transmit real-time, high-quality audio and video.

In comparison, 1394 is much more flexible in its accommodation of different data types and topologies than Ethernet and other alternative networking systems. 1394 uses a "fairness" arbitration approach to assure that all devices that have information to transmit get a chance to use the bus. 1394 protocols also include device-specific commands to start and stop camcorders, VCRs and other tasks. Standard Ethernet does not provide these important features.

What does a 1394 cable look like?

1394 interconnections are usually made with a 6-conductor cable that contains two separately shielded "twisted" pairs for transmitting data, plus two power conductors and an overall external shield. The two twisted pairs create a transmit/receive connection. The power conductors (8 to 30VDC, 1.5A) supply power to some devices.

Some devices, such as most digital camcorders, and several digital cameras, use a smaller 4-pin connector to save space. The 4-pin 1394 connector is a part of the 1394 standard intended primarily for battery-powered devices.

Casanova's and CGI Computer Wares Inc have a full range of cables available to meet current cabling needs and future demands for 1394 device networking. You can purchase 1394 cables with the 6-pin connector on one end, and the 4-pin connector on the other end. IEEE-1394 networking cables come in 4-pin to 4-pin and 6-pin to 6-pin configurations in several different lengths..

Why do most DV camcorders have 4-pin 1394 connectors?

Sony camcorders have only a single 4-pin 1394 connector. It is smaller than the standard 1394 connector and has only the data signaling pairs (no power conductors). The 4-pin 1394 connector is a part of the 1394 standard intended primarily for battery-powered devices.

What about the 4.5-meter cable length limitation?

1394 cables are limited to 4.5 meters between devices before signal distortion begins to occur. The use of 1394 to implement home networks will require cable hops likely to exceed 10 meters. Restricting the speed of the bus to S200 enables an increase in the distance between nodes to about 14 meters (approximately 45 feet). 1394 transceivers have been announced that are powered by in-wall wiring and extend the distance between active nodes to at least 70 meters using plastic optical fiber (POF).

What is a 1394 card?

A 1394 card (or 1394 expansion card, board, or adapter) is a subsystem circuitry designed to provide 1394 capabilities to a computer that did not originally come with 1394. The 1394 card plugs into one of the available expansion ports found inside a personal computer.

What does peer-to-peer mean?

1394 is a peer-to-peer interface. This allows dubbing from one camcorder to another without the need for a computer. Or, for example, you can stream A/V data off a hard disk in real time, without computer assistance. It also allows multiple computers to share a given peripheral without any special support in the peripheral or the computers. It?s another important reason why 1394 is the digital interface of choice and why its acceptance is growing.

What's the difference between DV and 1394?

DV is the actual format of the video that comes out of your digital video camera. It?s a super high-resolution format that exceeds the quality of S-VHS. It even has many broadcast professionals thinking about scrapping their BetaCam equipment. The images are crisp, bright and have excellent depth and contrast. Best of all, the information is stored on the video tape in digital form, so it can be copied over and over without any loss.

1394 is the jack and protocol that lets you transfer the DV data to your computer. The full 1394 specification includes frame-accurate device control and the ability to read and write the digital video.

What's the difference between DV video over 1394, and video captured using a video capture card?

Most of the high-resolution video capture cards on the market use MJPEG compression. The less you compress the video, the better it looks, but the higher the sustained data rate you need. At compression under 6:1 (over 3000 kilobytes/sec) most people will think the video looks as good as the original, but in reality, it will be slightly lower quality. The video will have very slight artifacts and image loss.

In contrast, the DV spec is a 720x480 image size, at roughly a 5:1 compression. More accurately, it is compressed at a constant throughput of 3,600 kilobytes per second which averages out to 5:1 compression.

Quality in. Quality out. What makes DV so special is that when you capture DV footage to your hard drive via 1394, the DV video on your hard drive is an exact digital copy of the original footage. There is no loss. Every 1394 card delivers the exact same DV-quality output. When choosing a 1394 card, there is no video quality debate regardless of the CODEC (compression method) used.

What is hot swapping?

Hot swapping is the connection and disconnection of computer peripherals or other components while a system is turned on, without interrupting system operation. 1394 enables hot swapping.

What does isochronous mean?

Isochronous data transmission guarantees a certain minimum data rate, such as required for time-dependent data such as video or audio. Think about it. Video and audio occur in continuous streams. If there is a break in the signal for just a moment, the quality of the picture or sound suffers. 1394 is designed to inherently provide isochronous service as required for audio and video communication.

What is the IEEE- Institute of Electrical and Electronics Engineers?

IEEE is the world's largest technical professional society, based in the USA. Founded in 1884 by a handful of practitioners of the new electrical engineering discipline, today's Institute has more than 320,000 members who participate in its activities in 147 countries. The IEEE sponsors technical conferences, symposia and local meetings worldwide, publishes nearly 25% of the world's technical papers in electrical, electronics, and computer engineering and computer science, provides educational programs for its members and promotes standardization. Areas covered include aerospace, computers and communications, biomedical technology, electric power and consumer electronics.

What is the 1394 Trade Association?

The 1394 Trade Association was formed in 1994 to facilitate adoption of 1394 by consumer electronics and personal computer manufacturers. The 1394 Trade Association refers to IEEE 1394 as "The MultiMedia Connection".

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