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Monday, February 4, 2008

Firewire Interfaces


The first three modules are part of any digital camera. The interface is the module that characterizes the FireWire camera. It is based on the IEEE 1394 standard, defined by the organization "Institute of Electrical and Electronics Engineers". This standard defines a bus, which transmits:

  1. time critical data, for example a video and
  2. data whose integrity is of critical importance (for example, parameters or files).

It allows the simultaneous use of up to 63 different devices (cameras, scanners, video recorders, hard disks, DVD drives, etc.).

Other standards, called "protocols" define the behavior of these devices. FireWire cameras mostly use one of the following protocols:

AV/C stands for "Audio Video Control" and defines the behavior of DV devices, for example, video cameras and video recorders. It is a standard, defined by the 1394 Trade Association. The Audio/Video Working Group is in charge of it.
DCAM stands for "1394-based Digital Camera Specification" and defines the behavior of cameras that output uncompressed image data without audio. It is a standard, defined by the 1394 Trade Association. The IIDC (Instrumentation and Industrial Control Working Group) is in charge of it.
IIDC is often used synonymously with DCAM.
SBP-2 stands for "Serial Bus Protocol" and defines the behavior of mass storage devices, such as hard disks. It is an ANSI standard maintained by NCITS.

Devices that use the same protocol are able to communicate with each other. A typical example is the connection of a video camera and a video recorder. Thus, in contrast to the USB bus, there is no need to use a controlling computer. If a computer is used, it has to be compatible with the protocols of the device with which it is to communicate (please cf. Exchanging data with computers).

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