FireWire (IEEE 1394)

Hardware — FireWire (IEEE 1394)

FireWire is a hardware protocol that you may use to connect devices (cameras, hard drives) to your computer.

It's important to understand that saturating (using up all available bandwidth) your FireWire bus will lead to problems in Wirecast, as the audio and video will appear choppy.

FireWire Saturation

There is an absolute limit to the bandwidth available to your FireWire devices (400 or 800 megabits per second).

If you use a FireWire hub and plug several devices into that hub, you will share the bandwidth on that FireWire bus. Adding a hub does not add any bandwidth to the bus, just more places to plug things in.

If the sum of your devices goes over the speed limit, you "saturate" (use up) the available bandwidth.

If you have a camera attached to the FireWire bus and you saturate the bus, then you will see dropped frames (choppy video).

Devices do not always use all bandwidth

If you have a hard disk connected to a FireWire hub and also have your camera connected to the same hub, it may appear to work. You're using the camera just fine!

Unfortunately, this may not be a good indication of whether the bus will ever become saturated. For example, email could arrive and your email program could access a file on your FireWire drive which causes FireWire saturation.

The lesson to learn is this: Be careful when connecting hardware to your machine. Just because your setup works once when you first put it together in does not mean it will always work. Play with your setup and make sure that you have enough FireWire bandwidth to share all of your devices without experiencing choppy video.

Some Devices, especially cameras, request more bandwidth than actually required

Normally, a camera requires around 25 Megabits/second to deliver audio and video to Wirecast.

Unfortunately some cameras actually allocate 100 megabits / second (or more!).