• Wirecast™ Introduction
• Good presentations
• Usage Patterns
• Hardware
•   Overview
•   FireWire (IEEE 1394)
•   High Definition (HDV)
•   DV Cameras
•   Sleeping
•   S-Video / 2nd Display
•   Configure Devices
•   Device Manager
• Media Capabilities
• Titling Capabilities
• Logo Capabilities
• Broadcasting
• Editing Encoder Presets
• Desktop Presenter
• Media Management
• Menus
• Preferences
• Main Window
• Shot Editing
• Shot Element Panels
• Edit: Scene
• Edit: Title
• Edit: Media
• Edit: Effects
• Edit: Playback
• Edit: Motion
• Edit: Filter
• Edit: Chroma Key
• Acknowledgments

Two Cameras per bus

With one caveat, we recommend a maximum of two cameras per FireWire bus.

This is even if you have an 800 Megabit FireWire bus.

The caveat is that your cameras must have firmware that can handle multiple cameras per bus. The majority of cameras available meet this criteria, but some older cameras, and some cheaper cameras do not. See below for more information regarding having more than one camera per bus.

Note that just running Wirecast once with your cameras may not detect a problem, as some cameras will only randomly fail to work properly with other cameras on the same bus (see notes below).

If you run into this problem, your options are to purchase a second FireWire card (around $30 for a PCI card or a laptop cardbus), or purchase a new camera.

If you only ever use one DV camera per bus, you will not have this problem.

Your Macintosh, by default, has only one bus

Even though you may have a "800" and "400" plugs on your computer, they still share the same internal bus.

The only way to ensure that you use a second bus is to purchase a FireWire card.

But if having more than two cameras won't saturate an 800 mbits/sec, why the 2 camera restriction?

You may be able to get away with more having more cameras per bus.

It mostly depends on the cameras that you use. Some cameras, even relatively recent models, do not behave properly with regard to using multiple cameras on the same bus.

If your cameras behave correctly with regard to the FireWire bus, then you may be able to use more cameras per bus / card. See below for a discussion on "How cameras conflict on 1394".

The upshot is that it may be possible, but due to the hardware limitations, we cannot recommend it.

How cameras conflict on 1394

Although the specific details are more complicated than described herein, the problem is basically this:

Each camera is required to negotiate the channel on the FireWire bus that it will transmit on.

However, some cameras (or more specifically: firmware in those cameras), either do not negotiate at all or ignore the results of the negotiation and transmit on a predetermined channel.

As one might expect, this causes a lot of problems on the receiving end (in Wirecast), as data coming into Wirecast on one channel is actually coming from two devices.

There is nothing Wirecast can do in this situation, and it is widely acknowledged to be a problem with older or very inexpensive cameras.

Sometimes I can use two cameras on the same FireWire bus just fine, sometimes I can't. What's wrong?

The most unfortunate part is that the cameras that fail do not fail consistently.

This has to do with the fact that some cameras appear to "randomly" pick a channel to transmit on. So sometimes it will work and sometimes it will not.