Presentation is loading. Please wait.

Presentation is loading. Please wait.

Modified Huffman coding is used in fax machines. TIFF also uses this technique. It combines the variable length codes of Huffman coding with the coding.

Similar presentations


Presentation on theme: "Modified Huffman coding is used in fax machines. TIFF also uses this technique. It combines the variable length codes of Huffman coding with the coding."— Presentation transcript:

1 Modified Huffman coding is used in fax machines. TIFF also uses this technique. It combines the variable length codes of Huffman coding with the coding of repetitive data in run length encoding FAX and TIFF

2 Faxes have only white bits and black bits. Each line is coded as a series of alternating runs of white and black bits. Runs of 63 or less are coded with a terminating code. Runs of 64 or greater require that a makeup code prefix the terminating code. The makeup codes are used to describe runs in multiples of 64 from 64 to FAXes 4. 2

3 Terminating codewords 4. 3 Run LengthWhite bitsBlack bitsRun LengthWhite bitsBlack bits

4 Makeup Codewords EOL

5 Studies have shown that most facsimiles are 85 percent white. Faxes assume that any line begins with a run of white bits. If it does not, a run of white bits of 0 length must begin the encoded line. White and Black pixels 4. 5

6 Each scan line ends with a special EOL (end of line) character consisting of eleven zeros and a 1 ( ). There is no code that has more than seven leading zeroes. There is no code that has more than three ending zeros. Error Recovering 4. 6

7 If the decoder sees eleven zeros, it will recognize the end of line and continue scanning for a 1. Upon receiving the 1, it will then start a new line. If a bit in a scanned line gets corrupted, the most that will be lost is the rest of the line. If the EOL code gets corrupted, the most that will get lost is the next line. Error Recovering (Cont.) 4. 7

8 0white black010 4white1011 2black11 1white0111 1black white EOL Example 4. 8


Download ppt "Modified Huffman coding is used in fax machines. TIFF also uses this technique. It combines the variable length codes of Huffman coding with the coding."

Similar presentations


Ads by Google