Tech Tips:
The Truth About Firewire
By Andy DunnAs the world moves from analog to digital, more and more can be demanded from the devices that we use every day. Evolving technology allows us to pack more and more parts and data into smaller and smaller pieces of equipment. New electronic devices, as well as multimedia applications, force us to come up with ways to move large amounts of data quickly between devices and computers. IEEE-1394 was created to make a simple peer-to-peer connection that can carry a great amount of digital information from one device or computer to another.
IEEE-1394, High Performance Serial Bus, is becoming (some would say ‘has become’) the standard for connecting many different types of equipment to a computer or to each other. It was designed to be a universal gateway, eliminating the need for many different input / output connectors. Through a single IEEE-1394 connection, you can transfer video, audio, time code, etc… and can even send digital signals allowing remote control of a device, such as controlling a record deck from an edit station. Computer peripheral devices can be connected to a personal computer through an IEEE-1394 connection allowing the device to be accessed directly by the computer. In some cases, power for a device will come through the Firewire connection as well.
Many different devices can be connected via daisy chain, allowing multiple peripheral devices to be connected together. In fact, up to 63 different devices can be attached with data transfer speeds up to 400Mbps (megabits per second). The result of this is reduced costs and increased functionality for each device by eliminating the need for additional parallel ports, SCSI ports, serial ports etc… 800Mbps (1394b) currently exists but is not yet used by video manufacturers and a 1.2Gbps transfer speed is in the works right now for future IEEE-1394 applications.
IEEE-1394 is recognized more by names trademarked by the large companies utilizing it. Firewire is a registered trademark of Apple Computer while i.Link is a registered trademark of Sony. Both are simply applications of the IEEE-1394 standard in their products. For the rest of this article, let’s just use the term Firewire since it appears to be the more commonly recognized term.
Firewire can be confusing to many people simply because it does so much. It’s hard to believe that it does have limitations. One misunderstanding some people have is that they confuse Firewire with a signal format like DVCPRO or DVCAM. If one machine has a Firewire output and another has a Firewire input, then they should be compatible, right? No, basically, Firewire is nothing more than the connector and a ‘highway’ used to send a signal. Ok, scratch that. Firewire is a lot more than just that, but let’s use that description for just a moment.
A BNC connector (or bnc cable), for example, may carry a standard NTSC analog composite signal. It may carry a standard digital signal as in SD-SDI. It may carry a high definition digital signal as in HD-SDI or it may just carry the red channel of an RGB signal. As long as the receiving device knows that the cable is sending a red channel signal or an HD-SDI signal, you won’t have a problem. If, instead, you send an NTSC signal through BNC into a monitor expecting HD-SDI, the monitor will not understand the signal. You should, for the moment, think of Firewire in the same way. With Firewire, simply having a piece of equipment with a Firewire port does not make it compatible with all other Firewire equipped products since it can carry many different types of signals.
As briefly mentioned earlier, Firewire (IEEE-1394) is a digital video link between HDTV, Digital VCR’s, DVD’s and Digital Camcorders as well as PC’s and high-speed PC peripherals. It is a ‘jack’ AND the protocol that allows you to transfer the digital video from source to destination. More than just it’s connectors, it is a standard to be followed by every manufacturer adding the Firewire, i.Link, or IEEE-1394 port to their product. All products connected via Firewire can communicate with each other as long as they are speaking the same language.
Just because a camera, deck or computer sends out digital signals, it does not mean that the receiving equipment can understand it. The Firewire protocols control how the different types of signals are encoded and decoded for transmitting, but it cannot control whether the receiving equipment will understand the signal once it is decoded.
Some pieces of equipment can handle many different formats or types of signals. For example, when a nonlinear system receives an encoded Firewire signal, part of the information sent tells the system what format is being received. Then, assuming the edit system understood the message, it still must have the correct translation software for receiving that type of signal. Sending DVCPRO HD at 100Mbps through Firewire into a recorder looking for a DV 25 Mbps signal will not provide you with positive results.
So what are particular pieces of equipment sending or expecting through their Firewire ports? I am glad you asked.
DVCAM has been around for quite awhile now so many DVCAM cameras such as the Sony DSR 570 or Ikegami DV7W send a 25Mb DVCAM signal through Firewire and most record decks recognize the signal. The Panasonic AJ-SD930 Player / Recorder can send DV, DVCAM or DVCPRO out of the Firewire port when playing a 25Mb tape (and proper menu settings are made) or it will send a 50Mb DVCPRO signal out of the Firewire port when playing a DVCPRO50 tape. (It will not convert a 50Mbps signal to 25Mbps). Final Cut Pro 4.1 or above will understand either signal, however, Adobe Premier currently does not support the DVCPRO format. Final Cut Pro understands (translates through Firewire) DVCPRO, DVCPRO 50 and with version 4.5, DVCPRO HD because of license arrangements made between Panasonic and Apple. You will, however, need the new Panasonic AJ-1200A DVCPRO HD Recorder / Player to feed 100Mbps HD signals via Firewire to your Final Cut Pro station.
Now, for many reasons, I have focussed on the transfer of DV signals from one audio/video device into another yet this is only one portion of Firewire use today. The Firestore FS-1, for example, can take a camera’s DV Stream through Firewire and send it out to an external Firewire Hard Drive. This means that you can take a Sony PD150, send a DV stream through its i.Link output into the Firestore FS-1 and then send the FS-1 signal into a FireLite 40GB Hard Drive via Firewire. You can now shoot with the PD150 and record on the hard drive instead of (or as well as) in the camera. You can later connect the FireLite to your edit system via Firewire and your footage is already digitized and ready to go. You computer recognizes the external hard drive through Firewire just by plugging it in.
So there you have it, a brief understanding of Firewire, i.Link or IEEE-1394. A rose by any other name would still smell as sweet.
