Glossary | apertus° - open source cinema


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This is a very technical project so we thought it's a good idea to have a page explaining all technical terms that are used somewhere on this website.

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ApertusName of this project, stands for: free, open, public
see -> Word Definition
Bayer PatternColor filter mosaic to achieve full color (RGB) image aquisition with an otherwise monochrome image sensor, became the standard for digital single chip camera designs, more details -> Wikipedia
BitdepthAlso called color depth, describes the amount of bits used to represent color in a bitmapped digital image. An RGB image traditionally has 24 bits (8 bits per color channel: red, green, blue) where each color channel can have a value between 0 - 255, resulting in 16,777,216 mixed possible colors (256 × 256 × 256).
When talking about camera specs you commonly refer to single color channel values (8 bit or 10 bit) and not to the RGB value of (24bit or 30 bit). Recording footage at bitdepths higher than 8 is becoming increasingly popular in the last few years and it gives room for additional image adjustments in postproduction (e.g. adjusting exposure, colograding). Most of todays monitors and televisions can display only a part of the full RGB (24bit) spectrum (there is specialized equipment, e.g. medical monitors, that can display 10 or 12bit monochrome images or high end cinema projectors that can work with 12bit DCPs ).
more details -> Wikipedia

Charged Coupled Device, a device that has a photoactive region which converts light into an electrical charge, which is then sent as an analog signal. CCD's are found in most camcorder's. Consumer level camcorders usually have only 1 of these chips while many professional cameras have 3, where each of the three processes a specific color in the RGB scheme.

more details -> Wikipedia

C/CS mount

Cinema lense mount generally found with 16mm film cameras and a variety of digital cameras. C has a larger flange back distance at 17.53mm than CS which is at 12.5mm. Because of this CS mounts are more common as they allow C and CS lenses (with an adapter ring - ships with Elphel cameras) unlike the C mount which only allows C lenses. Aside from that, they are the same.

more details -> C or CS mounts

CF Card

Compact Flash, a form of solid state (flash memory) media that is highly portable and used primarily in still and video cameras.The capacity of currect CF cards ranges from 2 MB up to 128 GB. SD (secure digital) cards are more popular than CF, however CF tends to have higher read/write speeds. Sdhc and sdxc have pushed ahead of CF in terms of speed and capacity.

more details -> Wikipedia

Circular Buffer

(short circbuffer) An algorithm which allows old data to be overwritten. This operation is use in streaming and real-time processing.

more details -> DSP Guide


Complimentary Metal-Oxide Semiconductor, a type of integraget circuit commonly used in a variety of digital and analog devices. They use a combination of Positive and Negative type transistors in order to perform logic functions.

more details -> Wikipedia

CMOS Sensors use this technology to convert light to an electrical charge, where each pixel has its own comversion.

more details -> CCD vs CMOS

Codecdefines how media data (audio, video, metadata, etc.) is stored on a recording media

Central Processing Unit, or the brain of a computer. This is where all the primary logical processes take place in order for a computer to operate.

more details -> Wikipedia

Dirac Pro

An open source video compression tool. It uses arithmetic encoding to efficielntly render high quality, low latency video and audio.

more details -> BBC


Open codec by Avid designed for video post production. Similar but less limiting than Apples ProRes codec. DNxHD is freely available without any platform restrictions and also supported by FFMPEG, etc. (The source code for the Avid DNxHD codec is freely available from Avid for internal evaluation and review, although commercial use requires Avid licensing approval.)

-> Wikipedia Page

DOFDepth of Field. Refers to the area of focus. A narrow DOF allows for the subject of an image to be clear, and the background and foreground to be blurred. -> Wikipedia Definition
DOPDirector Of Photography, is responsible for anything regarding camera work and lighting
DSLR Camera

Digital Single Lense Reflex Camera, is a type of camera that uses one lense that direct light to both the image sensor and the viewfinder. This allows for the photographer to see an accurate representation of the framing and depth of field that will be captured. Modern DSLR's also include HD video recording which captures what is seen on the 'live view' screen and renders it into a video file.

more details -> Wikipedia

ElphelElphel Inc. is the company that builds the core camera module - see Company Website
ElphelVisionName of the Apertus viewfinder software named after the company that builds the core camera module. ElphelVision has it's own dedicated subbpage: here
EthernetIs the most widely used computer networking technology for local area networks (LAN). Normally, all stations on a segment share the total bandwidth, which is either 10 Mbit/s (Ethernet), 100 Mbit/s (Fast Ethernet) or 1000 Mbit/s (Gigabit Ethernet). With switched Ethernet, each sender and receiver pair have the full bandwidth.
The Elphel camera uses Ethernet as primiary communication and transfer method for video streaming or accessing/setting camera parameters/data. In contrast to USB or Firewire which are also popular methods to connect digital video/still cameras, Ethernet cables support a much longer transmission distance and allow a (theoretically) infinite number of connected devices. USB and Firewire protocols only allow single-point-to-single-point connections and can therefore not be considered a "network".
EXIFIs a standard for storing metadata with an image. Widely adopted by digital still cameras.
EXIF MakernoteIs an area of the EXIF metadata that can be filled with custom data by a camera manufacturer in addition to the fields that are available through the EXIF standard. This means that the data can only be interpreted correctly if the structure is known.
Elphel for example stores information about the color mode: RGB, JP4 modes, etc. of the image in the Makernote.
FirmwareThe complete software package which controls the functionality of a hardware device. In most cases it will only work with this particular hardware and is not ment to be run on any other device. In our case the Firmware for the Elphel camera is a complete operating system with installed custom software. If you reflash / overwrite your cameras firmware all modifications you applied to it will be overwritten. This does not affect external media like Elphel camera connected HDDs/SSDs.
FPGAField Programmable Gate Array, used for high performance video processing (in parallel pipelines) in Elphel cameras
more details -> Wikipedia
FPSFrames Per Second defines the framerate either on the recording side: camera or playback side: monitor, television. If the framerate of recording and playback are not the same the term overcranking or undercranking is used describing the resulting slow motion or timelapse footage.
More details -> Wikipedia
Free Software
The most common are software libre, free and open source software (FOSS) and free, libre and open source software (FLOSS).
Examples of Free Software Licenses are the GNU GPL or the BSD License.
More details -> Wikipedia

or Free Software, is a program accessable at no cost. However, this does not mean it is open source, nor does it mean that you get full rights, or usage from the software.

More Details -> Wikipedia


The Relationship between the luminance of a screen/projection, and the color value of each pixel. Gamma curves are the calculation to how these values will be displayed. This is calculated by the power-law...

Input values (Vin) = output values (Vout)gamma

More Details -> Wikipedia

GNUThe GNU Project is a free software, mass collaboration project, announced on September 27, 1983, by Richard Stallman at MIT. -> Wikipedia
H264a codec that became very popular in consumer electronics over the last years for HD video delivery, it is now the standard for Blu-ray Discs and used for video streaming by Youtube, Vimeo or the DVB Standard. There has been some dispute over the licensing terms to end users which would go beyond the scope of this glossary, more details -> Wikipedia
HDDHard Disk Drive
more details -> Wikipedia
JP4 RAWOne of the file types which the Elphel camera records to. It is similar to a RAW file in that most of the light information that the sensor see's is kept, yet it is compressed to keep a faster data rate.
MJPEG AKA Motion-JPEG- A codec which compresses every frame of a video into a jpeg image. It is usually kept in a container file(.mov, .avi...) which shows it as a video and not a sequence of photos. more details -> Wikipedia
not to be confused with MPEG which is a completely different codec
Open sourceSoftware that is released under the GPL (general public license) or other free software license. The source code is free to modify and distribute (freely and under the same terms). more details -> Open Source Initiative
PCBPrinted Circuit Board, with soldered electronic parts and components and routed electronic connections between the parts

An HD codec developed by Apple Inc. for video post production. ProRes is popular for it's high visual image quality and has since it's introduction in 2009 also found it's way into some hardware devices and cameras that record their videos directly in ProRes. This allows to start video editing on any Apple based system right away. Windows and Linux based systems have only limited support or no support at all for this format.

Avid pushed a similar but open approach with their DNxHD codec which sports similar image quality standards but is freely available without any platform restrictions and also supported by FFMPEG, etc.

RAW recordingRAW is a way of recording an image that keeps all of the light information that the sensor sees. This allows for great flexibility in post, with better controls over white balance, exposure, and much more.
-> Wikipedia
ResolutionThe clarity of an image, usually measured by pixels or dots. Can be determined by the number of pixels/dots, eg. 1920x1080, or the physical size of the pixels/dots, eg. 300 dpi (dots per inch)
RMSRichard Matthew Stallman, pioneer of the Free Software movement, founder of the GNU project, more details -> Wikipedia
RodsRods are basically support tubes that are traditionally placed as pair under the lens to allow attachment of accessories (like a follow focus or matte box) to the camera or lens. Some camera/rig designs also use rods for shoulder support or to allow mounting of accessories on top of the camera.
RS232Serial Interface, Elphel cameras have a RS232 port with the optional 10369 board which allows direct root access to the cameras Linux console. For people who are familiar with using SSH to connect to remote Linux computers over a network, RS232 can be described as connecting to remote Linux computer connected over a single serial cable. RS232 can also be tunneled through USB (the Arduino does that)
SATA"Serial Advanced Technology Attachment" is the most comon hard drive interface standard nowadays. There are 2 connectors types, one for data and one for power.
Sensor-Front-End (SFE)Camera module that hosts the image sensor on a PCB
Source CodeThe "blueprint" of software. If you have access to the source code you are able to really understand what a software really does.
SSDSolid State Drive, could be seen as the successor of the Hard Disk Drive (HDD) and relies entirely on flash memory. This allows faster read/write speeds, less power consumption and increased robustness (HDDs are extremly vulnerable to shocks), though still at much higher cost.
StereoscopicThe technique of creating the illusion of 3 dimensional space within an image by molding 2 slightly offset images of the same subject together. The viewer must be able to distinguish the two images separately with each eye for the effect to work (usually done with specialized glasses)
More info->Wikipedia
Subversion (SVN)A server/client based version control system to store code and binary files. Other similar systems are CVS (older) and GIT (newer).
USBUniversal Serial Bus -> see Wikipedia
View FinderHardware on a camera which shows the image that will be recorded, and also playback of video previously captured.
Wi-FiWireless Fidelity, a connection type for two or more devices to communitate/share data with each other without having a physical connection.
XLRA common, professional audio connection type. The standard is 3-pin, but there are also mini, 4-pin, 5-pin, and 6pin XLRs.


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