by Pierantonio Boriero and Stephen Albanese, Matrox Imaging

We are starting to see the pieces come together to use IEEE-1394, or Firewire as its known in certain circles, as a medium for some scientific/industrial PC-based vision applications. The first digital video cameras to use it are here, as well as the PC interfaces to move image data from these cameras to PC memory. Application and development software support is still a few steps behind though, due in part to the fact that Windows OS support for 1394 is in its infancy, but things are moving right along. Here's a glimpse at some of today's hardware and software issues surrounding the use of this technology for machine vision applications, with information relevant to the broader spectrum of scientific digital imaging users.

The standard also specifies bidirectional communication for device control and native data, asynchronous (guaranteed delivery) and isosynchronous (guaranteed bandwidth) data streams, peer-to-peer connectivity, plug'n'play operation, hot-plugging, as well as data transmission and power - all on a single cable.

Even in its current implementation, there is enough bandwidth available to handle the video transfer demands of standard resolution monochrome and color imaging applications.

Some video camera considerations at the moment include the fact that they output image data as YUV color streams, and extracting the luminance component for monochrome vision applications or converting YUV color to RGB for color applications takes a toll on CPU bandwidth. This issue will be resolved, however, with the introduction of new cameras offering true monochrome or component RGB output. And for some applications, like off-line analysis, where the delay between acquiring images is long, this might not be a concern at all.

Something that is neither addressed nor on the agenda of the 1394 association is line scan support. Vision applications that must use a line scan camera will still require the use of a frame grabber.

A consideration for real-time imaging like machine vision is the FIFO depths in current 1394-to-PCI bridge chips. Are they deep enough to handle PCI latency issues that could result in the loss of image data? Of course this concern is application specific, but chipmakers are already addressing it with the release of new bridge chips.

The support from Microsoft for 1394 under Windows NT that vision vendors are waiting for to develop these applications will appear with version 5.0, to be renamed Windows 2000 and officially released later this year. Since Windows NT is the platform of choice for machine vision on PCs, this will have an impact on when we see applications.

Presently there is some support for 1394 in Windows 98, although it appears to be focused on areas like video conferencing rather than machine vision. Microsoft provides with Windows 98 a streaming class device driver called DCAM. This interface, however, lacks the frame by frame control necessary for machine vision applications. But for off-line analysis applications, what Microsoft provides may be suitable, since requirements differ.

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