Glossary of TV Technical Terms

TECHNICAL GLOSSARY

Common Television, Broadcasting and Camera Terms

 

Advanced Television Systems Committee (ATSC)

The ATSC is the committee responsible for developing and establishing Digital-HDTV Standards, as well as all 18 formats of Digital TV.

Artifacts

Unwanted visible effects in the picture created by disturbances in the transmission or image processing, such as edge crawl or hanging dots in analog pictures, or pixilation in digital pictures.

Aspect Ratio

Refers to the width of a picture relative to it’s height.  If an NTSC (National Television System Committee) picture is 4 feet wide, it will be 3 feet high; thus it has a 4:3 aspect ratio.  HDTVB has a 16:9 aspect ratio.

Camera – Depth of Field (DOF) 

The area in front of and behind a focused subject in which the image appears sharp.

  • Increasing magnification decreases the DOF
  • Decreasing magnification increases DOF
  • Increasing the f-number (16) increases the DOF
  • Decreasing the f-number (2) decreases DOF

Dynamic Range

Is the ratio between the darkest and the brightest light intensity.  Larger camera sensors usually have larger pixels and larger pixels have a greater ability at gathering light.  Giving the senor a greater range in the tones it can detect.

Camera – Hyper-focal Distance

The distance which all objects can be brought into an acceptable focus, meaning that objects will appear in focus in both the foreground and background.

IEEE 1394 (FireWire)

A digital interface developed by the IEEE 1394 working group.  Transports data at 100, 200, or 400 Mbps.  Can be used to connect digital television devices together.

Interlaced

The frame/picture is made up of two fields:  The first field has 262.5 odd lines (1,3,5…) and the second field has 262.5 even lines (2,4,6…).  The odd lines are scanned (or painted on the screen) in 1/60th of a second and the even lines follow in the next 1/60th of a second.  This presents an entire frame/picture of 525 lines in 1/30th of a second.

Progressive Scan

Progressive scanning is a method for displaying, storing or transmitting moving images in which all the lines of each frame are captured in sequence.  In Progressive Scanning all the horizontal scan lines are captured at one time.

 

Letterbox Mode

A method of presenting widescreen images on a standard screen television.  In order to preserve the aspect ratio of the original video content, the picture is scaled down so that it fits the available width of the television screen.  Since the picture will not fill the screen vertically, dark bars are displayed above and below the picture.

MPEG

Compression standards for moving images advanced by the “Motion Pictures Expert Group”, the international group of industry experts that set standards for compression of video and audio.

MPEG-2

The basis for ATSC digital television transmission.  MPEG-2: Designed to cover a wide range of requirements for “VHS quality” to HDTV, using a series of algorithms and image resolution levels.  MPEG-2 is the compression used by the ATSC and DVB standards.

RGB

The abbreviation for red, green and blue signals, the primary colors of light.  Cameras and telecines have red, blue and green receptors.  Much of the picture monitoring in a production center is in RGB.  RGB is digitized with 4:4:4 sampling which occupies 50 percent more data than 4:2:2.

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