FireWire cameras use the

IEEE 1394 IEEE 1394 is an interface standard for a serial bus for high-speed communications and isochronous real-time data transfer. It was developed in the late 1980s and early 1990s by Apple in cooperation with a number of companies, primarily Sony an ...

bus A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...

standard Standard may refer to: Symbols * Colours, standards and guidons, kinds of military signs * Standard (emblem), a type of a large symbol or emblem used for identification Norms, conventions or requirements * Standard (metrology), an object th ...

for the transmission of

audio Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound * Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum * Digital audio, representation of sou ...

video Video is an electronic medium for the recording, copying, playback, broadcasting, and display of moving visual media. Video was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) syst ...

and control data. FireWire is Apple Computer's

trademark A trademark (also written trade mark or trade-mark) is a type of intellectual property consisting of a recognizable sign, design, or expression that identifies products or services from a particular source and distinguishes them from othe ...

for the IEEE 1283 standard. FireWire

camera A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a ...

s are available in the form of

photo camera A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a ...

s and

video camera A video camera is an optical instrument that captures videos (as opposed to a movie camera, which records images on film). Video cameras were initially developed for the television industry but have since become widely used for a variety of oth ...

s, which provide image and

data In the pursuit of knowledge, data (; ) is a collection of discrete Value_(semiotics), values that convey information, describing quantity, qualitative property, quality, fact, statistics, other basic units of meaning, or simply sequences of sy ...

. A special form of video cameras is used in the domains of industry,

medicine Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pr ...

astronomy Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, g ...

, microscopy and

science Science is a systematic endeavor that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earli ...

. These special cameras do not provide audio data. Fwcam overview padding

Structure

The basic structure of FireWire cameras is based on the following six modules:

Optics

FireWire

s are based on CCD or CMOS chips. The light-sensitive area, as well as the

pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device. In most digital display devices, pixels are the ...

s of these chips, are small. In the case of cameras with integrated

optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultrav ...

, we can assume that the optics are adapted to these chips. However, in the domains of

professional A professional is a member of a profession or any person who works in a specified professional activity. The term also describes the standards of education and training that prepare members of the profession with the particular knowledge and ski ...

, and semi-professional

photography Photography is the art, application, and practice of creating durable images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is employe ...

, as well as in the domain of

special Special or specials may refer to: Policing * Specials, Ulster Special Constabulary, the Northern Ireland police force * Specials, Special Constable, an auxiliary, volunteer, or temporary; police worker or police officer Literature * ''Specia ...

cameras, interchangeable optics are often used. In these cases, a system specialist has to adapt the optics and the chip to the application (see System integration). Besides normal lenses, such interchangeable lenses may be

microscope A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisi ...

endoscope An endoscope is an inspection instrument composed of image sensor, optical lens, light source and mechanical device, which is used to look deep into the body by way of openings such as the mouth or anus. A typical endoscope applies several modern t ...

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observ ...

s, etc. With the exception of the standard C-mount and CS-mount, the mounts of interchangeable optics are company-specific.

Signal capture

Since the function of a FireWire camera depends upon electrical signals, the module "signal capture" transforms the incident

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...

, as well as the incident

sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' b ...

into

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no ...

s. In the case of light, this process is performed by a CCD or CMOS chip. The transformation of the sound is performed by a

microphone A microphone, colloquially called a mic or mike (), is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and publ ...

Digitization

The first step of the image's digitization results from the structure of a CCD or CMOS chip. It dissects the image into pixels. If a pixel has collected many photons, it creates a high voltage. Should there only be a few photons, a low voltage is created. "Voltage" is an analog value. Therefore, during the digitization's second step, the voltage has to be transformed into a digital value by an A/D converter. Now the raw digital image is available. A microphone transforms the sound into a voltage. An A/D converter transforms these analog values into digital ones.

Signal enhancement

The creation of

color Color (American English) or colour (British English) is the visual perceptual property deriving from the spectrum of light interacting with the photoreceptor cells of the eyes. Color categories and physical specifications of color are assoc ...

is based on a color filter, which is located in front of the CCD or CMOS chip. It is

red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondar ...

green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a combi ...

blue Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between violet and cyan on the spectrum of visible light. The eye perceives blue when ...

and changes its color from pixel to pixel. Therefore, the filter is called a

color filter array In digital imaging, a color filter array (CFA), or color filter mosaic (CFM), is a mosaic of tiny color filters placed over the pixel sensors of an image sensor to capture color information. The term is also used in reference to e paper devices ...

or, after its inventor,

Bayer filter A Bayer filter mosaic is a color filter array (CFA) for arranging RGB color filters on a square grid of photosensors. Its particular arrangement of color filters is used in most single-chip digital image sensors used in digital cameras, cam ...

. Using these raw digital images, the module "signal enhancement" creates an image, which meets aesthetic

requirement In product development and process optimization, a requirement is a singular documented physical or functional need that a particular design, product or process aims to satisfy. It is commonly used in a formal sense in engineering design, includ ...

s. The same is true for the audio data. In the final step, the module compresses the image and audio data and outputs them - in the case of video cameras - as a DV data stream. In the case of

photo A photograph (also known as a photo, image, or picture) is an image created by light falling on a photosensitive surface, usually photographic film or an electronic image sensor, such as a CCD or a CMOS chip. Most photographs are now crea ...

cameras, single images may be output and, if applicable, voice comments as files. The application domains of industry, medicine, astronomy, microscopy and science often use special

monochrome A monochrome or monochromatic image, object or palette is composed of one color (or values of one color). Images using only shades of grey are called grayscale (typically digital) or black-and-white (typically analog). In physics, monochrom ...

cameras. They forgo any

signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...

enhancement and thus output the digital image

in its raw state. Some special models of color cameras are only capable of outputting raw digital image data. Such cameras are called ColorRAW or Bayer cameras. They are often used in industry, medicine, astronomy, microscopy, and science. In form of photo cameras, they are used by professional photographers. Semi-professional photo cameras often offer an optional RAW mode. The enhancement of the raw digital data takes place outside the camera on a computer and therefore the user is able to adapt it to a particular application.

Interface

The first three modules are part of any digital camera. The

interface Interface or interfacing may refer to: Academic journals * ''Interface'' (journal), by the Electrochemical Society * '' Interface, Journal of Applied Linguistics'', now merged with ''ITL International Journal of Applied Linguistics'' * '' Int ...

is the module that characterizes the FireWire camera. It is based on the IEEE 1283 standard, defined by the organization "Institute of Electrical and Electronics Engineers". This standard defines a

, which transmits: # time critical data, for example, a video and # data whose integrity is of critical importance (for example, parameters or files). It allows the simultaneous use of up to 74 different devices (

s, scanners, video recorders, hard disks,

DVD The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any kind ...

drives, etc.). Other standards, called "

protocols Protocol may refer to: Sociology and politics * Protocol (politics), a formal agreement between nation states * Protocol (diplomacy), the etiquette of diplomacy and affairs of state * Etiquette, a code of personal behavior Science and technology ...

" define the behavior of these devices. FireWire cameras mostly use one of the following protocols: ; AV/C : 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 1348 Trade Association. The Audio/Video Working Group is in charge of it. ; DCAM : 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 : IIDC is often used synonymously with DCAM. ; SBP-2 : SBP-2 stands for "Serial Bus Protocol" and defines the behavior of mass storage devices, such as hard disks. It is an

ANSI The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organi ...

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).

Control

The controlling module coordinates the other ones. The user may specify its behavior by: # switches outside the camera, # the FireWire bus, using

application software Application may refer to: Mathematics and computing * Application software, computer software designed to help the user to perform specific tasks ** Application layer, an abstraction layer that specifies protocols and interface methods used in a ...

or # a hybrid of the first two cases.

Photo cameras

Professional and semi-professional photo cameras, and especially

digital camera back A digital camera back is a device that attaches to the back of a camera in place of the traditional negative film holder and contains an electronic image sensor. This lets cameras that were designed to use film take digital photographs. Thes ...

s, offer FireWire interfaces to transfer image data and to control the camera. The image data's transfer is based on the protocol SBP-2. In this mode, the camera behaves as an external hard disk and thus enables the simple exchange of image files with a computer (please cf. Exchanging data with computers). To increase the work efficiency in a photo studio, additionally photo cameras and digital backs are controllable via the FireWire bus. Usually the camera manufacturer does not publish the protocol used in this mode. Therefore, camera control requires a specialized piece of software provided by the camera manufacturer, which mostly is available for

Macintosh The Mac (known as Macintosh until 1999) is a family of personal computers designed and marketed by Apple Inc. Macs are known for their ease of use and minimalist designs, and are popular among students, creative professionals, and software en ...

and

Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ser ...

computers.

Video cameras

Although compatibility to the FireWire bus is only found in high-end photo cameras, it has usually been present in home-user level video cameras. Video cameras are mostly based on the protocol AV/C. It defines the flow of audio and video data, as well as the camera's control signals. The majority of video cameras only provides the output of audio and video data via the FireWire bus ("DVout"). Additionally, some video cameras are able to record audio and video data ("DVout/DVin"). Video cameras exchange their data with computers and/or video recorders.

Special cameras

In the domains of industry, medicine, astronomy, microscopy and science FireWire cameras are often used not for aesthetic, but rather for analytical purposes. They output uncompressed image data, without audio. These cameras are based on the protocol DCAM (IIDC) or on company specific protocols. Due to their field of application, their behavior is considerably different from photo cameras or video cameras: # Their case is small and built mainly from metal and do not follow aesthetic, but rather functional design constraints. # The vast majority of special cameras does not offer integrated optics, but a standardized lens mount called " C-mount" or "CS-mount". This standard is not only used by lenses, but also by microscopes, telescopes, endoscopes and other optical devices. # Recording aids, such as

autofocus An autofocus (or AF) optical system uses a sensor, a control system and a motor to focus on an automatically or manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system ...

or image stabilization are not available. # Special cameras often utilize monochrome CCD or CMOS chips. # Special cameras often do not apply an infrared cut filter or optical low pass filters, thus avoid affecting the image. # Special cameras output image data streams and single images, which are captured using an external trigger signal. In this way, these cameras can be integrated into industrial processes. #

Mass storage In computing, mass storage refers to the storage of large amounts of data in a persisting and machine-readable fashion. In general, the term is used as large in relation to contemporaneous hard disk drives, but it has been used large in relati ...

devices are not available since the images have to be analyzed more or less immediately by the computer connected to the camera. # The vast majority of special cameras is controlled by application software, installed on a computer. Therefore, the cameras do not have external switches. # Application software is rarely available off-the-shelf. It usually has to be adapted to the specific application. Therefore, camera manufacturers offer programming tools designed for their cameras. If a camera uses the standard protocol DCAM (IIDC), it can also be used with third-party software. A lot of industrial computers and

embedded system An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' ...

s are compatible to the DCAM (IIDC) protocol (please cf. Structure / Interface and Exchanging data with computers). In comparison to photo or video cameras, these special cameras are very complifcated. However, it makes no sense to use them in an isolated manner. They are, like other sensors, only components of a bigger system (please cf. System integration).

Exchanging data with computers

FireWire cameras are able to exchange data with any other FireWire device, as long as both devices use the same protocol (please cf. Structure / Interface). Depending upon the specific camera, these data are: * Image and audio files (protocol: SBP-2) * Image and audio data flows (protocol: AV/C or DCAM (IIDC)) * Parameters to control the camera (protocol: AV/C or DCAM (IIDC)) Fwcam open vs prop padding

If the camera is to communicate with a computer, this computer has to have a FireWire interface and to use the camera's protocol. The old days of FireWire cameras were dominated by company specific solutions. Some specialist offered interface boards and drivers, which were accessible only by their application software. Following this approach, application software is in charge of the protocol. Since this solution utilizes the computing resources in a very efficient manner, it is still used in the context of highly specialized, industrial projects. This strategy often leads to problems, using other FireWire devices, as for instance hard disks. Open systems avoid this disadvantage. Open systems are based on a layer model. The behavior of the single layers (interface board, low level driver, high level driver and

API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...

) follows the constraints of the respective operating system manufacturer. Application software is allowed to access operating system APIs, but never should access any level lower. In the context of FireWire cameras, the high level drivers are responsible for the protocol. The low level drivers and the interface boards put the definitions of the standard IEEE 1394 into effect. The advantage of this strategy is the simple realization of application software, which is independent of hardware and specific manufacturers. Especially in the domains of photo cameras and special cameras hybrids between open and company specific systems are used. The interface boards and the low level drivers typically adhere to the standard, while the levels above are company specific. The basic characteristic of open systems is not to use the APIs of the hardware manufacturers, but those of the operating system. For Apple and Microsoft the subject "image and sound" is of high importance. According to their APIs - QuickTime and DirectX - are very well known. However, in the public perception they are reduced to the reproduction of audio and video. Actually, they are powerful APIs that are also responsible for image acquisition. Under Linux this API is called video4linux. It is less powerful than QuickTime and DirectX and therefore additional APIs exist besides video4linux: Fwcam linux padding

; Photo cameras : Photo cameras usually use Linux' infrastructure for mass storage devices. One of the typical applications i
digiKam
; Video cameras : Video cameras are accessed by various APIs. The image to the right depicts the access of the video editing softwar
Kino
to th
libavc1394
API. Kino also accesses other APIs which are not shown in the image to simplify matters. ; Special cameras : The most important API for special cameras i
libdc1394
The image to the right depicts the access of the application softwar
Coriander
to this API. Coriander controls FireWire cameras that are based on the protocol DCAM (IIDC) and acquires their images. In order to simplify the use of video4linux and the dedicated APIs, the meta AP
unicap
has been developed. It covers their bits and pieces with the aid of a simple programming model.

System integration

Often FireWire cameras are only a cog in a bigger system. Typically, a system specialist uses a number of different components to solve a particular problem. There are two basic approaches to do this: # The problem at hand is interesting enough for a group of users. The typical indicator of this situation is the off-the-shelf availability of application software. Studio photography is an example. # The problem at hand is only of interest to a particular application. In such cases, there is typically no application software available off-the-shelf. Therefore, it has to be written by a system specialist. The gauging of a steel plate is an example. Many aspects of system integration are not directly related to FireWire cameras. For example, illumination has a very strong influence on the quality of the acquired images. This holds true for both aesthetic and analytical applications. However, in the context of the realization of application software, there is a special feature, which is typical for FireWire cameras. It is the availability of standardized protocols, such as AV/C, DCAM, IIDC and SBP-2 (please cf. Structure / Interface and Exchanging data with computers). Using these protocols, the software is written independently from any particular camera and manufacturer. By leaving the realization of the protocol to the operating system, and by enabling access to a set of APIs, software can be developed independently from hardware. If, for instance, under Linux a piece of application software uses the API libdc1394 (please cf. Exchanging data with computers), it can access all FireWire cameras that use the protocol DCAM (IIDC). Using the API unicap additionally permits access to other video sources, such as frame grabbers.