Glossary of SSTV Terms
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AVT
 
   Amiga Video Transceiver.  (1) Interface and software for 
   use with Amiga computer, developed by Ben Blish-Williams, 
   AA7AS, and manufactured by Advanced Electronics Applications 
   (AEA).  (2) A family of SSTV transmission modes first 
   introduced with the AVT product.

 
Back Porch
 
   The blank part of a scan line immediately following the
   horizontal sync pulse.


Chrominance
 
   Color component of a video signal.  Robot color modes transmit
   pixel values as luminance (brightness, symbol "Y") and 
   chrominance (color differences R-Y and B-Y) rather than RGB 
   (red, green, blue).

 
Demodulator
 
   A device (for SSTV) that extracts the image and sync information
   from the received audio signal.


Frame

   One complete image (top to bottom).  As an example, the 
   Scottie S1 mode has 240 scan lines in a frame.


Frame Sequential
 
   An early color SSTV transmission scheme that sent three separate
   images with the red, green, and blue components.  Now obsolete.


Front Porch
 
   The blank part of a scan line just prior to the horizontal sync.


FSTV
  
   Fast Scan TV, often called ATV (Amateur TeleVision).  Provides
   full motion video at the expense of large bandwidth 
   requirements.  Can not be used on any HF or lower VHF bands.


Interlace
 
   A scan line ordering different than simple top to bottom.
   For example, the NTSC and PAL standards use a field of even 
   scan lines and a field of odd scan lines to make a complete frame.

 
Line Sequential
 
   A method of of color SSTV transmission that sends Red,
   Green & Blue sequentially for each scan line.  This method
   permits viewing the image in color as it is received, line
   by line.

 
Luminance
 
   Brightness component of a video signal.  Usually this is
   computed as Y (luminance) = 0.59 * G (Green) + 0.30 * R (Red) +
   0.11 * B (Blue).


Martin
 
   A family of SSTV transmission modes developed by Martin
   Emmerson, G3OQD, in England.


NTSC
 
   Television standard for North America and Japan.  National
   Television System Committee.


PAL
   
   Television standard used in most of Europe.  Stands for 
   Phase Alternation Line.


Pasokon TV
   
   The most respected name in SSTV.


Pixel
 
   A single picture element on a display.  The dots (or blocks)
   which make up a computer display or printer output.


P7 Monitor
 
   A very long persistence Cathode Ray Tube (CRT) used in
   the very early SSTV displays.


RGB
 
   Red, Green, Blue.  A popular model for representing colors.
   Most colors can be simulated, to the human eye, by mixing 
   different blends of red, green, and blue light.


Robot
 
   Abbreviation for the slow scan equipment from Robot Research.
   A family of SSTV transmission modes introduced with this
   equipment.

 
Scan Converter
 
   Device which converts one video standard to another.  For
   instance, the Robot 1200C converted between NTSC and SSTV.

 
Scottie
 
   A family of SSTV transmission modes developed by Ed Murphy,
   GM3BSC, in Scotland.


SECAM
 
   Color TV standard used in France and the CIS.  Sequential Color
   And Memory.

 
SSTV
 
   Slow Scan Television.  A method of sending still images
   with audio signals.  


VIS
 
   Vertical Interval Signalling.  The vertical sync signal,
   the the beginning of an image, contains digitally encoded
   information about the format of the following image.  Most
   SSTV receiving systems use this to automatically select
   the proper receive mode.  First used in the Robot 1200C modes.


Wraase
 
   A family of SSTV transmission modes used by the Wraase
   SC-1 and SC-2 scan converters developed by Volker Wraase, DL2RZ,
   of Wraase Electronik, Germany.