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Unformatted text preview: Fax Standards Group 3 Fax CCITT Draft Documentation T.4 (1980) • Left to right raster scan starting at top of the page. • Each line has 1728 pel (picture elements - black or white) • Line width : 215 mm, 3:85 lines/mm.(or 7.7 lines/mm for higher density) • On ISO A4 Size paper. Today’s fax machines scan documents many times faster and store them internally. Transmission time: 20 ms/scan line including data, fill bits and end-of-line code (EOL) (000000000001 – 11 0’s followed by 1) Coding Methods There are alternate run lengths of white and black pels. The first run is assumed to be white; if not, it is assumed to be 0 with code of ‘00110101’ Run Length = 64 x m + t 64m = represented by ‘ M ake- U p- C ode’ ( MUC ) t = T erminating C ode ( TC ) Max Run length = 1728 = 64.63+27 Two separate pairs of table for (m, t) – one for white pels and the other black pel ( See Temporary files) For example a white run of 1362=64.21+18 = 1344+18 is encoded by concatenating the code word for 1344 (011011010) and the code word for 18 (0100111). Note MUC and TC are both prefix codes. Also, the MUC and TC in white are “mutually” prefix – no MUC of white is a prefix of TC of white and vice-versa. Blacks runs are similarly encoded by the TC...
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This note was uploaded on 06/09/2011 for the course CAP 5015 taught by Professor Mukherjee during the Spring '11 term at University of Central Florida.
- Spring '11